DNVGL-ST-N001

DNVGLSTN001 Edition September 2018 Amended January 2020 Marine operations and marine warranty The electronic PDF version of this document, available at the DNV GL website dnvgl.com, is the official, binding version. DNV GL AS This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used STANDARD DNV GL standards contain requirements, principles and acceptance criteria for objects, personnel, organisations and/or operations. © DNV GL AS September 2018 Any comments may be sent by email to rules@dnvgl.com This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this document. The use of this document by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibility for loss or damages resulting from any use of this document. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used FOREWORD Changes current This document supersedes the June 2016 edition of DNVGLSTN001. Changes in this document are highlighted in red colour. However, if the changes involve a whole chapter, section or subsection, normally only the title will be in red colour. Amendments January 2020 Topic Correction Reference Description [5.6.15.4] Second equation in item c) corrected. Table 112 Equation terms corrected. Figure 116 Figure revised. [11.13.6.2] and [11.13.6.3] Clause split into two clauses (as per 2016 edition). [11.31.5.3] PCP removed (not used elsewhere). [P.2.2] Title changed from Element analysis to Finite element analysis. [P.2.5.1] and [P.2.6.1] FSD changed to FSD for consistency with elsewhere. Changes September 2018 Historic changes are shown in App.A. Sec.1 Introduction The following changes have been made: — Table 11: Table modified to update the normative references. — Table 13: Table modified to include new definitions and revise others. — Table 14: Table modified to include new acronyms/abbreviations/symbols and revise others. Sec.2 Planning and execution The following changes have been made: — — — — — — — — — — — — — General: Editorial changes to improve clarity. [2.2.5.3]: New clause with planning and design sequence diagram included. [2.2.5.4]: New clause added. [2.2.5.5]: New clause added. [2.6.5.2]: New guidance note added. [2.6.6.2]: Clause modified. [2.6.9.5]: New guidance note about wave period uncertainty added. [2.6.10.4]: Clause modified to clarify use of provided alpha factors. [2.6.12.1]: Clause modified to allow option to use LRFD alpha factors where not limited by strength considerations. [2.9.2.2]: Guidance note modified to reference [3.4.15.3]. [2.11.1.4]: Clause modified to shall from should. [2.11.6]: Title modified. [2.11.6.1]: Clause modified. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used CHANGES – CURRENT Page 3 — General: Editorial changes to improve clarity. — Table 31: Table modified to remove unrequired note. — Table 32: Table modified to revise return periods for quayside mooring. Sec.4 Ballast and other systems No main changes have been made to this section. Editorial corrections may have been made in this section Sec.5 Loading and structural strength The following changes have been made to this section: — — — — — — — — — — — — — — — — — — — — General: Editorial changes to improve clarity. [5.4.4.3] g): Guidance note modified. [5.4.4.4]: New clause for when fullscale tests are not viable. [5.6.2.3] e): Clause modified to account for equipment accuracy being considered when determining CoG envelope. [5.6.5.4] c): New clause related to the effects of vibration included. [5.6.5.5] a): New guidance note about when green water may normally be ignored. [5.6.9.5]: Clause modified to make calculation of upper bound friction consistent with other sections. [5.6.15]: Section modified to cover ballasting for counteracting of wind heel. [5.6.15.4]: Clause modified for motions derived from DNV GL and DNV rules for classification of ships. [5.6.16.3]: Clause and guidance note modified to clarify requirements for quartering sea cases. [5.9.2.1]: Clause modified for load cases for motions derived from DNV GL and DNV rules for classification of ships. [5.9.7]: Title modified. [5.9.7]: Section modified to include load factors for motions derived from DNV GL and DNV ship rules, permissible utilisations for welds and slip critical bolted connections and updated Table 58 and Table 59. [5.9.8]: Title modified. [5.9.8.4] 3): New guidance note added to cover use of plastic design provisions in Eurocode 3, /61/. [5.9.8.4] 5): Clause modified to include weld in good shop conditions. Guidance note updated to clarify requirements related to welds on board. [5.9.8.5] 2): Clause modified to include webbing straps. [5.9.8.5] 3): New clause covering material factor for shackles, turnbuckles and complete web lashing assemblies. [5.9.9]: New guidance note added regarding less conservative material factors for friction. [5.10.2.3] 8): Clause modified to clarify waiting time requirements. Sec.6 Gravity based structure (GBS) The following changes have been made to this section: — General: Editorial changes to improve clarity. — [6.2.1]: Former clause [6.2.1.7] moved to [11.10.4.3]. Sec.7 Cables, pipelines, risers and umbilicals This section replaces the applicable sections of the following documents: — GL Noble Denton, Guidelines for Submarine Pipeline Installation, 0029/ND, — GL Noble Denton, Guidelines for Offshore Wind Farm Infrastructure Installation, 0035/ND, and — DNV offshore standard, Loadout, transport and installation of subsea objects (VMO Standard Part 26), DNVOSH206. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 4 Changes current The following changes have been made to this section: This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Sec.3 Environmental conditions and criteria Sec.9 Road transport No main changes have been made to this section. Editorial corrections may have been made in this section. Sec.10 Loadout No main changes have been made to this section. Editorial corrections may have been made in this section. Sec.11 Sea voyages The following changes have been made to this section: — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — General: Editorial changes to improve clarity. [11.6]: Section modified for both DNV GL and DNV ship motions. [11.7.1.2]: New clause to clarify checks for green water loads. [11.7.2.1]: New clause including new guidance note for using LRFD approach with ASD/WSD default motions added. Table 114: Table modified to allow linear interpolation for case 14. [11.7.3.1]: New clause stating load and resistance factors to be applied. [11.7.3.2]: Clause modified to clarify requirements for selfweight. [11.7.3.2]: New guidance note for using ASD/WSD approach with LRFD default motions added. [11.9.2.4]: Clause modified to clarify requirement related to effect of vibrations on friction including new guidance note. [11.9.2.8]: New clause for minimum seafastening for sheltered waters included. [11.9.5.15]: Guidance note modified for clarity. [11.9.5]: Section modified to update requirements for lashing seafastenings. [11.9.5.33]: Clause modified to clarify acceptable conditions for welding. [11.9.9.6]: Clause modified to include requirement to provide safe access. [11.10.1.1]: Clause modified to clarify calculations related to stability. [11.10.1.2]: New clause to clarify calculation of metacentric height. [11.10.1.5]: New clause related to air cushion. [11.10.1.6]: New clause related to loose solid ballast. [11.10.4.3]: Clause modified to include text related to air escape that was previously in [6.2.1]. [11.12.1.7]: Clause modified to account for high density traffic zones. [11.12.2]: Section modified for bollard pull requirements. [11.12.2.14]: New clause for short towlines. [11.12.2.15]: New clause for shallow water included. [11.12.11.2]: Clause modified to clarify burning and weld gear requirements. [11.13.4]: Section modified as previous [11.13.4.4] now [11.13.4.1]. Acroymns used updated for consistency with the rest of the document. [11.13.6]: Section modified to clarify the use of Kenter shackles. [11.13.13.1]: Clause modified to include text related to retrival of towing gear. [11.13.14]: Section modified to make inspection terminology consistent with lifting section. [11.13.14.3]: Clause modified to include text related to equipment in the splash zone. [11.13.14.4]: Clause modified including new guidance note. [11.13.14.6]: New clause to clarify nonsocket terminations. [11.13.14.7]: Clause modified to change requirement for resocketing to 2.5 (two and a half) years. [11.14.1.2]: Clause modified as references updated (definition remains the same) and new guidance note included. [11.17.4.1]: Clause modified to change GMDSS radio to DSC VHF radio. [11.17.5.1]: Clause modified to include requirement to sound signals. [11.20.3.3]: Clause modified to make acroymns used consistent with the rest of the document. [11.21]: New section on specifics for inland waterways. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 5 Changes current No main changes have been made to this section. Editorial corrections may have been made in this section. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Sec.8 Offshore wind farm (OWF) installation operations Sec.12 Tow out of drydock or building basin No main changes have been made to this section. Editorial corrections may have been made in this section. Sec.13 Jacket installation operations The following changes have been to this section: — — — — — — — General: Editorial changes to improve clarity. [13.1.1]: Former clause [13.1.1.5] deleted as modified text included in [13.1.1.4]. [13.1.1.4]: Clause modified to simplify text. [13.3.2.1]: New guidance note on overstress during launch added. Table 132: Table modified to clarify case. [13.6.9.2]: New clause to ensure adequate clearances during launch included. [13.10.1]: Section modified to clarify requirements for onbottom stability. Sec.14 Construction afloat The following changes have been to this section: — General: Editorial changes to improve clarity. — [14.3.1]: Clause modified to include requirements for nonGBS type structures. Sec.15 Liftoff, mating and floatover operations The following changes have been to this section: — General: Editorial changes to improve clarity. — [15.1.1.6]: Clause modified to make terminology consistent. Sec.16 Lifting operations The following changes have been made to this section: — — — — — — — General: Editorial changes to improve clarity. [16.2.3.3]: Clause modified to clarify that fabrication tolerance is to be included in sling length. [16.2.5.6]: Guidance note modified to clarify vessel length and wave heights for DAFs. [16.2.6]: Section modified for skew load factor application. [16.3.4.2]: Clause modified to clarify sling loads. [16.3.4.3]: Clause modified to clarify sling loads. [16.4.3]: Section modified to use γh for lifting factor. — [16.4.4]: Section modified to use γh for lifting factor. — [16.4.7]: Section modified to clarify types of slings and updated definitions of termination types. — [16.4.8.1]: New guidance note to reflect latest version of IMCA M 179, /81/. — [16.4.8.5]: New guidance note added. — [16.5.2.5]: New clause to clarify shackle requirements. — [16.5.2.6]: Clause [16.5.2.5] modified and expanded to clarify shackle requirements. — [16.7.2.4]: New clause included for hook loading with sling angles greater than 90°. — Figure 163: New figure included for hook loading with sling angles greater than 90°. — [16.8.4.1]: Clause modified to include link to consequence factor. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 6 Changes current [11.26.2.7]: Clause modified to cover all potential situations. [11.26.2.11]: Clause modified to remove requirement for qualification testing [11.26.3.1]: Clause modified to clarify monitoring requirements. Table 1120: Table modified to make friction coefficients consistent with elsewhere in document. [11.26.3.13]: Clause modified for consistency with elsewhere in document. [11.26.4.2]: Clause modified to ensure tow route is clear. [11.26.4.4]: New guidance note to clarify loss of buoyancy requirement. [11.26.8.2]: Clause modified to clarify survey package requirements. [11.27.2]: Section renamed. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — — — — — — — — — Sec.17 Mooring and dynamic positioning systems The following changes have been made to this section: — — — — — — — — — — — — — — — General: Editorial changes to improve clarity. Table 172: Table modified by changing Y to A in time column for quayside/inshore row. [17.6.4.6]: Clause modified to clarify applicability of Table 173. [17.6.5.2]: Clause modified to include description of vertical and horizontal loading. Table 175: Table modified to make column titles consistent with [17.6.5.2]. Table 176: Table modified to make column titles consistent with [17.6.5.2]. [17.1.1.1]: Clause modified to clarify requirement. [17.8.9.2]: New guidance note added to clarify philosophy. [17.10.1.2]: Clause modified to link return periods to [3.4.4]. [17.10.1.5]: Clause modified. [17.10.2.1]: Clause modified to clarify analyses requirements. [17.10.3.5]: New guidance note added for redundancy requirements. [17.10.9]: Section modified to reflect use of WLL when specifying capacity. [17.11.2]: New clause added to clarify assessment requirements for weather restricted operations. [17.13]: Section modified to reflect latest reference documents. Sec.18 Decommissioning and removal of offshore installations No main changes have been made to this section. Editorial corrections may have been made in this section. APPENDIX A Changes historic App.A: This section has been updated with the changes noted in the June 2016 edition. APPENDIX B Planning and execution The following changes have been made to this section: — — — — Editorial changes to improve clarity. [B.2.1]: Clause modified to clarify that text else governs in case of discrepancies. [B.2.2]: New clause. Table B3: Table modified to reflect changes elsewhere. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 7 Changes current [16.8.5.2]: Clause modified to clarify that requirement applies for spreader bars as ancillary equipment. [16.9.3.1]: Clause modified to clarify relative deviations and two new guidance notes. [16.9.5.2]: Clause modified to clarify pin hole requirements and new guidance note added. [16.9.5]: Deleted clause [16.9.5.3]. [16.9.7.1]: New guidance note to clarify timing of NDT. [16.9.7.2]: Clause modified to clarify reusing of lift points. [16.9.7]: Deleted clause [16.9.7.6]. [16.10.8.1]: Clause modified to include example list of effects. [16.11.2.5]: New guidance note to explain changes in latest version of IMCA M 179, /81/. [16.11.7.1]: New clause linking section to definition of ancillary lifting equipment. [16.11.7.2]: New guidance note related to WLL an SWL. [16.12]: Section modified for clarity and consistency. [16.12.5]: Section modified to clarify requirements for spreader bars when considered as structure. [16.13.2.1]: New guidance note added for inshore lifts clearances. [16.17.2.7]: Clause modified to clarify slack sling requirements. [16.17.2.8]: New guidance note added for light or close to neutrally buoyant objects. [16.17.3.1]: Clause modified to replace equation for boom tip motions with link to DNVGLRPN103, /56/. [16.18.2.3]: Clause modified to clarify requirements for spreader bars when considered as structure. [16.18.3]: Section modified to reflect changes elsewhere in the document. [16.18.3.3]: Clause modified to clarify requirements for spreader bars when considered as structure. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — — — — — — — — — — — — — — — — — — — — This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Changes current APPENDIX C Environmental conditions and criteria The following changes have been made to this section: — Editorial changes to improve clarity. — [C.2.1.1]: Equation has been corrected. APPENDIX D Ballasting and other systems INTENTIONALLY LEFT BLANK APPENDIX E Structural strength The following changes have been made to this section: — — — — Editorial changes to improve clarity. [E.1.1.6]: Clause modified for consistency of symbols with rest of document. [E.1.1.6]: New guidance note added. [E.2]: Section modified to reflect changes made in Sec.5. APPENDIX F Gravity based structure (GBS) INTENTIONALLY LEFT BLANK APPENDIX G Cables, pipelines, risers and umbilicals INTENTIONALLY LEFT BLANK APPENDIX H Offshore wind farm installations informative No main changes have been made to this appendix. Editorial corrections may have been made in this Appendix. APPENDIX I Land transport INTENTIONALLY LEFT BLANK APPENDIX J Loadout INTENTIONALLY LEFT BLANK APPENDIX K Sea voyages App.K: Appendix title changed for consistency with Sec.5. No main changes have been made to this appendix. Editorial corrections may have been made in this appendix. APPENDIX L Tow out of drydock or construction basin INTENTIONALLY LEFT BLANK APPENDIX M Jacket Installation INTENTIONALLY LEFT BLANK APPENDIX N Construction afloat INTENTIONALLY LEFT BLANK APPENDIX O Floatover, mating and floatoff operations INTENTIONALLY LEFT BLANK APPENDIX P Lifting operations informative The following changes have been made to this section: — Editorial changes to improve clarity. — [P.2.5] and [P.2.6]: Sections modified to reflect changes to [16.3.4]. APPENDIX Q Mooring and dynamic positioning systems The following changes have been made to this section: — Table Q1: Table modified to include additional items. — [Q.2]: Section modified for clarity and to align with current practices. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 8 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Changes current APPENDIX R Decommissioning and removal of offshore installations INTENTIONALLY LEFT BLANK Editorial corrections In addition to the above stated changes, editorial corrections may have been made. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 9 Section 1 Introduction.......................................................................................... 18 1.1 General........................................................................................... 18 1.2 Objective.........................................................................................19 1.3 Scope.............................................................................................. 20 1.4 References...................................................................................... 20 1.5 Definitions.......................................................................................21 1.6 Acronyms, abbreviations and symbols............................................ 40 Section 2 Planning and execution......................................................................... 49 2.1 Introduction.................................................................................... 49 2.2 General project requirements......................................................... 49 2.3 Technical documentation................................................................ 52 2.4 Risk management........................................................................... 58 2.5 Planning of marine operations........................................................61 2.6 Operation and design criteria......................................................... 62 2.7 Weather forecast............................................................................ 74 2.8 Organization of marine operations................................................. 77 2.9 Monitoring.......................................................................................79 2.10 Inspections and testing................................................................ 81 2.11 Vessels.......................................................................................... 83 Section 3 Environmental conditions and criteria................................................... 86 3.1 Introduction.................................................................................... 86 3.2 Design environmental condition..................................................... 86 3.3 Design environmental criteria for weather restricted operations.... 87 3.4 Design criteria for weather unrestricted operations....................... 88 3.5 Weather/metocean forecast requirements................................... 102 3.6 Benign weather areas................................................................... 102 Section 4 Ballast and other systems................................................................... 105 4.1 Introduction.................................................................................. 105 4.2 System and equipment design...................................................... 105 4.3 Ballasting systems........................................................................ 107 4.4 Guiding and positioning systems.................................................. 113 4.5 ROV systems.................................................................................115 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 10 Contents Changes – current.................................................................................................. 3 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used CONTENTS 5.2 Design principles.......................................................................... 121 5.3 Specific design considerations...................................................... 121 5.4 Testing.......................................................................................... 124 5.5 Load categorisation...................................................................... 126 5.6 Loads and load effects (responses).............................................. 129 5.7 Failure modes............................................................................... 142 5.8 Analytical models..........................................................................143 5.9 Strength assessment.................................................................... 143 5.10 Materials and fabrication............................................................ 153 Section 6 Gravity based structure (GBS)............................................................ 158 6.1 Introduction.................................................................................. 158 6.2 Floating GBS stability and freeboard............................................ 158 6.3 Structural strength....................................................................... 162 6.4 Instrumentation............................................................................ 163 6.5 GBS installation............................................................................ 163 Section 7 Cables, pipelines, risers and umbilicals............................................... 167 7.1 Introduction.................................................................................. 167 7.2 Design philosophy.........................................................................169 7.3 Installation engineering................................................................172 7.4 Vessel and installation equipment................................................ 182 7.5 Loadout and offshore transfer..................................................... 191 7.6 Transport...................................................................................... 197 7.7 Route............................................................................................ 198 7.8 Surveys......................................................................................... 199 7.9 Lay operations.............................................................................. 201 7.10 Other installation activities.........................................................221 7.11 Protection and postlay intervention...........................................226 7.12 Product testing and precommissioning......................................230 7.13 Documentation requirements......................................................231 Section 8 Offshore wind farm (OWF) installation operations.............................. 239 8.1 Introduction.................................................................................. 239 8.2 Planning........................................................................................ 239 8.3 OWF installation vessels............................................................... 241 8.4 Planning and execution................................................................ 243 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 11 Contents 5.1 Introduction.................................................................................. 120 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Section 5 Loading and structural strength.......................................................... 120 8.7 Installation of OWF components...................................................247 8.8 Lifting operations and lifting tools................................................249 8.9 Information required for MWS approval....................................... 249 Section 9 Road transport.................................................................................... 250 9.1 Introduction.................................................................................. 250 9.2 Requirements................................................................................250 9.3 Information required.................................................................... 251 Section 10 Loadout............................................................................................ 253 10.1 Introduction................................................................................ 253 10.2 General....................................................................................... 253 10.3 Loads.......................................................................................... 255 10.4 Design calculations..................................................................... 258 10.5 Systems and equipment..............................................................260 10.6 Vessels........................................................................................ 268 10.7 Operational aspects.................................................................... 271 10.8 Special cases...............................................................................275 10.9 Information required.................................................................. 278 Section 11 Sea voyages...................................................................................... 282 11.1 Introduction................................................................................ 282 11.2 Towage or transport design/approval flow chart........................283 11.3 Motion response......................................................................... 284 11.4 Default motion criteria – general................................................286 11.5 Default motion criteria – IMO..................................................... 286 11.6 Default motion criteria – ships................................................... 287 11.7 Default motion criteria – specific cases...................................... 290 11.8 Directionality and heading control.............................................. 294 11.9 Design and strength................................................................... 296 11.10 Floating stability....................................................................... 311 11.11 Transport vessel or barge selection.......................................... 321 11.12 Tug selection............................................................................ 322 11.13 Towing equipment.................................................................... 330 11.14 Voyage planning....................................................................... 342 11.15 Bilge and ballast pumping systems...........................................351 11.16 Anchors (and alternatives) and mooring arrangements............ 354 11.17 Manned voyages....................................................................... 357 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 12 Contents 8.6 Transport of OWF components..................................................... 245 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8.5 Loadouts of OWF components..................................................... 245 11.20 Specific for towage in the Caspian Sea..................................... 373 11.21 Specific for voyages in inland waterways................................. 377 11.22 Specific for FSUs (FPSOs, FSOs, FLNG facilities, FRSUs etc.)..... 377 11.23 Specific for jacket voyages....................................................... 381 11.24 Specific for ship towage........................................................... 382 11.25 Specific for voyage to scrapping............................................... 384 11.26 Specific for towing of pipes and submerged objects................. 385 11.27 Specific for deep draught towages............................................393 11.28 Specific for jackup voyages..................................................... 393 11.29 Approaching a jackup location.................................................399 11.30 Rig move procedures (for all MOUs)......................................... 404 11.31 Specific for semisubmersible voyages..................................... 407 11.32 Information required................................................................ 410 Section 12 Tow out of drydock or building basin...............................................414 12.1 Introduction................................................................................ 414 12.2 Dry dock/construction basin.......................................................414 12.3 Design and strength................................................................... 415 12.4 Mooring and handling lines for towout...................................... 416 12.5 Intact and damage stability........................................................ 416 12.6 Underkeel clearance for leaving basin....................................... 416 12.7 Side clearances........................................................................... 417 12.8 Underkeel clearance outside basin............................................ 417 12.9 Towage and marine considerations.............................................418 12.10 Information required................................................................ 418 Section 13 Jacket installation operations............................................................419 13.1 Introduction................................................................................ 419 13.2 Environmental conditions............................................................419 13.3 Strength...................................................................................... 420 13.4 Jacket buoyancy, stability and seabed clearance........................ 421 13.5 Jacket lift.................................................................................... 425 13.6 Jacket launch.............................................................................. 426 13.7 Floating controlled upend and setdown ballasting..................... 432 13.8 Jacket position and setdown..................................................... 433 13.9 Buoyancy tank............................................................................ 435 13.10 Onbottom stability and piling.................................................. 436 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 13 Contents 11.19 Specific for towing in ice.......................................................... 362 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.18 Specific for multiple towages....................................................359 14.1 Introduction................................................................................ 443 14.2 Loads and structures.................................................................. 443 14.3 Stability and damage stability.................................................... 444 14.4 Mooring and fendering................................................................445 14.5 Construction spread.................................................................... 445 14.6 Operational requirements........................................................... 446 14.7 Information required.................................................................. 446 Section 15 Liftoff, mating and floatover operations......................................... 448 15.1 Introduction................................................................................ 448 15.2 General....................................................................................... 449 15.3 Loads.......................................................................................... 450 15.4 Systems and equipment..............................................................451 15.5 Vessels........................................................................................ 452 15.6 Operational aspects.................................................................... 453 15.7 Specific for liftoff operations..................................................... 455 15.8 Specific for mating operations.................................................... 458 15.9 Specific for floatover operations................................................465 15.10 Specific for docking operations.................................................475 15.11 Information required................................................................ 479 Section 16 Lifting operations.............................................................................. 484 16.1 Introduction................................................................................ 484 16.2 Load factors................................................................................ 485 16.3 Derivation of hook, lift point and rigging loads........................... 493 16.4 Sling and grommet design.......................................................... 496 16.5 Shackle design............................................................................ 502 16.6 Other lifting equipment design................................................... 503 16.7 Crane and installation vessel...................................................... 505 16.8 Structural analysis...................................................................... 508 16.9 Lift point design..........................................................................510 16.10 Fabrication yard lifts.................................................................514 16.11 Fabrication of rigging and lifting equipment............................. 517 16.12 Certification and inspection of rigging and lifting equipment.... 522 16.13 Clearances.................................................................................527 16.14 Bumpers and guides................................................................. 530 16.15 Heave compensation................................................................. 531 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 14 Contents Section 14 Construction afloat............................................................................ 443 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 13.11 Information required................................................................ 440 16.18 Information required................................................................ 557 Section 17 Mooring and dynamic positioning systems........................................ 560 17.1 Introduction................................................................................ 560 17.2 Codes and standards.................................................................. 561 17.3 Design environmental conditions................................................ 562 17.4 Environmental loads and motions............................................... 563 17.5 Mooring analysis......................................................................... 565 17.6 Design and strength................................................................... 568 17.7 Clearances...................................................................................571 17.8 Mooring equipment..................................................................... 575 17.9 Procedural considerations...........................................................579 17.10 Special considerations for inshore and quayside moorings....... 580 17.11 Weather restricted mooring considerations.............................. 585 17.12 Information required................................................................ 585 17.13 Dynamic positioning systems....................................................588 Section 18 Decommissioning and removal of offshore installations.................... 594 18.1 Introduction................................................................................ 594 18.2 General principles....................................................................... 594 Section 19 References.........................................................................................596 19.1 References.................................................................................. 596 Appendix A Changes historic...............................................................................601 A.1 Revision History Edition 201606............................................... 601 Appendix B Planning and execution.................................................................... 603 B.1 Documentation and certification for marine vessels..................... 603 B.2 Documentation required for lifting, towing and mooring gear.......606 B.3 Iceberg management operations.................................................. 608 B.4 Ensemble forecasting informative.............................................. 613 Appendix C Environmental conditions and criteria.............................................. 615 C.1 General......................................................................................... 615 C.2 Wind conditions............................................................................ 615 C.3 Wave conditions........................................................................... 616 Appendix D Ballasting and other systems........................................................... 623 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 15 Contents 16.17 Subsea lifting and installation.................................................. 543 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 16.16 Operations and practical considerations................................... 534 E.2 Bolted connections........................................................................628 Appendix F Gravity based structure (GBS)..........................................................635 Appendix G Cables, pipelines, risers and umbilicals............................................636 Appendix H Offshore wind farm installations Informative................................ 637 H.1 Introduction................................................................................. 637 H.2 General......................................................................................... 637 H.3 Cable challenges/cables............................................................... 640 H.4 Specific challenges/considerations for array cables..................... 643 H.5 Exclusions from marine warranty scope....................................... 643 Appendix I Land transport.................................................................................. 644 Appendix J Loadout............................................................................................645 Appendix K Sea voyages..................................................................................... 646 K.1 Example of main tow bridle with recovery system........................646 K.2 Example of emergency towing gear..............................................647 K.3 Example of Smittype clench plate............................................... 648 K.4 Emergency anchor mounting on a billboard..................................649 K.5 Alternatives to the provision and use of an emergency anchor..... 649 K.6 Alternative arrangements for towing connections for ship towages.............................................................................................. 651 K.7 Example of cribbing/seafastening force calculations Informative......................................................................................... 652 K.8 Good practice recommendations for the tiedown of lifting slings informative.......................................................................................655 K.9 Good practice recommendations for towing informative.............659 K.10 Ice classification informative................................................... 662 K.11 Options for MOU voyages in ice informative............................. 664 Appendix L Tow out of drydock or construction basin....................................... 665 Appendix M Jacket Installation........................................................................... 666 Appendix N Construction afloat...........................................................................667 Appendix O Floatover, mating and floatoff operations..................................... 668 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 16 Contents E.1 Fillet weld checking...................................................................... 624 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Appendix E Structural strength........................................................................... 624 P.2 Padeye calculations...................................................................... 673 P.3 Calculation of SKL.........................................................................677 Appendix Q Mooring and dynamic positioning systems.......................................680 Q.1 Good practice recommendations for quayside mooring Informative......................................................................................... 680 Q.2 Dynamic positioning systems informative.................................. 693 Appendix R Decommissioning and removal of offshore installations...................696 Changes – historic.............................................................................................. 697 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 17 Contents P.1 2Hook lift load factors and derivation of lift point loads............ 669 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Appendix P Lifting operations informative........................................................669 1.1 General 1.1.1 DNV GL Noble Denton marine services is a global provider of Marine Warranty Services and has set the industry standard for marine operations and marine assurance activities for the last 50 years. Our collective industry best practice and guidance documentation is referenced and used all over the world. This document includes the harmonized legacy DNV standards and legacy GL Noble Denton guidelines, with the exception of those for MODU/MOU site specific assessment. 1.1.2 Where DNV GL Noble Denton marine services is the Marine Warranty Survey provider, it should be read in conjunction with DNVGLSE0080 Noble Denton marine services – marine warranty survey, /38/, which provides a description of the process used by DNV GL Noble Denton marine services when providing marine warranty survey (MWS) services to evaluate whether a marine operation can be accepted for the purposes of insurancerelated MWS. It addresses both ‘project’ and MODU/MOU related MWS. 1.1.3 This document may be used in its complete form or using the relevant sections based on the asset type and/ or operation uses the Noble Denton marine services Marine Warranty Wizard available through My Services at https://www.veracity.com/. 1.1.4 The use of this standard presupposes and does not replace the application of industry knowledge, experience and knowhow throughout the marine operation activities. It should solely be used by competent and experienced organizations, and does not release the organizations involved from exercising sound professional judgment. DNV GL has however no obligations or responsibility for any services related to this standard delivered by others. DNV GL has a qualification scheme mandatory to approval engineers and surveyors providing services related to this standard. This ensures that all approvals and certificates delivered are carried out by well qualified personnel who understand the intention behind the standard, the limitations and the correct interpretations. The use of this document is at the user's sole risk. DNV GL does not accept any liability or responsibility for loss or damages resulting from any use of this document. 1.1.5 Further provisions and background information are contained in the appendices. Additional clarifications and interpretations are given in the Marine Warranty Wizard. 1.1.6 In some cases risk assessments can be used to justify projectspecific deviations from the standard criteria provided that the results are acceptable. When such risk assessments show that the risk levels are increased relative to those inherent in the standard criteria, the operation may be approved subject to disclosure by the client to, and agreement by, the insurance underwriters. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 18 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 1 INTRODUCTION Execution of operations not adequately covered by this standard shall be specially considered in each case. 1.1.8 Fulfilment of all requirements in this standard does not guarantee compliance with international and national (statutory) regulations, rules, etc. covering the same subjects/operations. 1.1.9 This standard should if required be used together with other recognized codes or standards applicable for marine operations. 1.1.10 In case of conflict between other codes or standards and this document, the latter shall be governing if this provides a higher level of safety or serviceability. 1.1.11 By recognized codes or standards are meant national or international codes or standards applied by the majority of professionals and institutions in the marine and offshore industry. 1.1.12 SWL and WLL 1.1.12.1 Safe Working Load (SWL) has generally been superseded by Working Load Limit (WLL) though both are in common use during the changeover period. However confusion can arise due to the very different safety factors being assumed by different equipment manufacturers and for different uses (e.g. mooring, lifting or towing). Whenever possible this standard uses minimum breaking load (MBL) or ultimate load capacity (ULC) to avoid these problems. 1.1.12.2 If the WLL or SWL of a shackle or other equipment is documented but the MBL or ULC is not, the owner or operator should obtain a document from the manufacturer stating the minimum Safety Factor defined as (MBL or ULC) / (WLL or SWL as appropriate). 1.1.12.3 There is often some confusion about the differences between WLL and SWL. SWL is a derated value of WLL, following an assessment by a competent person of the maximum static load the item can sustain under the conditions in which the item is being used. SWL may be the same or less than WLL but can never be more. 1.2 Objective 1.2.1 This standard is intended to ensure marine operations are designed and performed in accordance with recognized safety levels and to describe “current industry good practice”. Where applicable, this standard can be used in the approval of the marine operation(s) for Marine Warranty Survey purposes. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 19 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 1.1.7 1.3.1 This standard addresses the marine operations that can occur during the development of an offshore asset or when objects are moved by water from one place to another. It addresses the Marine Warranty Survey requirements relevant to loadout, construction afloat, voyages and installation and the load cases that should be addressed in the design. 1.3.2 The integrity of the final structure in the installed condition is the responsibility of the Assured and would normally be verified and accepted by the certifying authority. The Marine Warranty Survey company takes no responsibility for the installed condition unless the Marine Warranty Survey scope specifically addresses this case e.g. for jackup location approval. 1.3.3 With the exception of location approval of MOUs (Mobile Offshore Units) which are covered in DNVGL STN002, /39/, this standard covers most offshore assets and operations that are likely to require MWS approval. 1.4 References 1.4.1 Normative (i.e. mandatory) references 1.4.1.1 The standards and guidelines in Table 11 include provisions, through which reference in this text constitute provisions of this standard. Table 11 Normative (i.e. mandatory) standards Id Name Date ANSI/AISC 36016 Specification for Structural Steel Buildings 2016 DNVGLOSC101 Design of offshore steel structures, general – LRFD method 2015 DNVGLSTN002 Site specific assessment of mobile offshore units for marine warranty 2016 EN 1993 Eurocode 3, Design of steel structures IMO IMDG International Maritime Dangerous Goods Code 2014 and 2016 IMO Intact Stability Code Intact Stability Code 2008 and later amendments IMO International Convention on Load Lines IMO International Convention on Load Lines, Consolidated Edition 2002 IMO COLREGS IMO International Regulations for Preventing Collisions at Sea, 1972 (2003 consolidated edition with latest amendments) (COLREGS) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Revision 2002 2003 and latest amendments Page 20 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 1.3 Scope IMO International Safety Management Code ISM Code and Revised Guidelines on Implementation of the ISM Code by Administrations 2014 and any later amendments IMO ISPS Code International Ship and Port Facility Security Code (amendment to SOLAS convention) 2002 (effective 2004) IMO Resolution A.1024(26) Guidelines for ships operating in polar waters IMO Polar Code IMO International Code for Ships Operating In Polar Waters (Polar Code) 2016 ISO 199015 Petroleum and Natural Gas Industries “Specific requirements for offshore structures – Part 5: Weight control during engineering and construction”. 2016 Jan 2010 1.4.2 Informative references 1.4.2.1 All references appear in Sec.19. 1.5 Definitions 1.5.1 Verbal forms Table 12 Definitions of verbal forms Term Definition shall verbal form used to indicate requirements strictly to be followed in order to conform to the document should verbal form used to indicate that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others may verbal form used to indicate a course of action permissible within the limits of the document Where guidance notes have been included they are used for giving additional information, clarifications or advice to increase the understanding of preceding text. Therefore guidance notes shall not be considered as giving binding or defining requirements. Any values in guidance notes are not a requirement and shall be considered as an initial recommendation. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 21 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used IMO ISM Code 1.5.2.1 Terms defined elsewhere in Table 13 are within single quotation marks. Table 13 Definition of terms Term st 1 intercept (angle) 24hour Move nd 2 intercept (angle) Definition The first angle of static inclination at which the wind overturning moment is equal to the righting moment (see Figure 113 and Figure 114) A 'jackup' move taking less than 24 hours between entering the water and reaching a safe air gap with at least two very high confidence good weather forecasts for the 48 hours after entering the water, having due regard to area and season. The second angle of static inclination at which the wind overturning moment is equal to the righting moment (see Figure 113 and Figure 114) 9Part sling A sling made from a 'single laid sling' braided nine times with the sling rope and eyes forming each eye of the 9part sling. A&R Winch The Abandonment and Retrieval winch on a lay 'vessel' whose primary purpose is to lower the 'pipeline' to the seabed and to retrieve it back to the lay 'vessel' with sufficient working tension to control the pipe catenary within safe code limits at all stages. Accidental Limit State The limit state related to an accidental event. This can apply to either the intact structure resisting accidental loads (including operational failure) or the load carrying capacity of the structure in a damaged condition. Added Mass 'Added mass' or virtual mass is the inertia added to a system because an accelerating or decelerating body shall move some volume of surrounding water as it moves through it, since the object and fluid cannot occupy the same physical space simultaneously. This is normally calculated as Mass of the water displaced by the structure multiplied by the 'added mass coefficient'. Added Mass Coefficient Nondimensional coefficient dependant on the overall shape of the structure Alpha Factor The maximum ratio of 'operational criteria'/'design environmental condition' to allow for weather forecasting inaccuracies. See [2.6.9] Angle of Loll The static angle of inclination after flooding, without wind heeling (see Figure 114) Approval The act, by the designated the 'MWS company' representative, of issuing a 'Certificate of Approval'. Array Cable(s) Generic term collectively used for Inter Turbine Cables and Collector Cables. See also 'Infield Cables'. Asset A structure or object subject to an insurance warranty or at risk from an operation Assured The 'Assured' is the person who has been insured by some insurance company, or underwriter, against losses or perils mentioned in the policy of insurance. Barge A nonpropelled 'vessel' commonly used to carry 'cargo' or equipment. Barrel Cylindrical/conical structure that the 'product' is wrapped around. Base weight The calculated weight of a structure, excluding all allowances and contingencies. Sometimes known as net weight Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 22 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 1.5.2 Terms A mobile nonrotating horizontal circular storage facility with a vertical 'barrel' and side wall(s). 'Baskets' can be used to for storage, transportation and onshore or offshore installation. Product is loaded by 'coiling'. Bend Restrictor A device with several interlocking elements that lock when a design radius is achieved. Bend Strain Reliever (BSR) A tapered plastic sleeve fitted to a flexible pipe, umbilical or cable at the transition between a stiff section (typically an end fitting or connector) and the normal body of the pipe, umbilical or cable. Also known as Bend Stiffener Bending Factor γb A partial safety factor that accounts for the reduction in strength caused by bending round a shackle, 'trunnion', padear, diverter or crane hook. Benign (weather) area An area with benign weather as described in [3.6] Bifurcated tow The method of towing 2 (or more) 'tows', using one tow wire, where the second (or subsequent) 'tow(s)' is connected to a point on the tow wire ahead of the preceding 'tow', and with each subsequent towing pennant passing beneath the preceding tow. See [11.18.1.4] Birdcaging A phenomenon whereby armour wires locally rearrange with an increase and/or decrease in pitch circle diameter as a result of accumulated axial and radial stresses in the armour layer(s). Bollard Pull (BP) 'Certified' continuous static 'bollard pull' of a 'tug'. The mean bollard pull developed in a test by a 'tug' at 100% of the 'Maximum Continuous Rating' (MCR) of main engines over a period of 10 minutes. This is used for the selection of 'tugs' and sizing of towing equipment. Maximum bollard pull (at 110% of MCR) should not be used for tug selection. Buckle “Wet”/“Dry” A local collapse of pipe cross section in the span of pipe between the lay 'vessel' and the seabed. “Dry” means that the pipe wall is not breached and “Wet” means that the pipe wall is breached and seawater floods into the pipe. Bundle A configuration of two or more 'pipelines' joined together and either strapped or contained within a carrier or 'sleeve pipe'. Burial Assessment Survey A survey to assess the expected burial depths on a cable route using purpose built (BAS) sledges equipment with bottom penetrating sonar equipment or by towing a miniature plough. Burial Protection Index (BPI) A process to optimise 'cable burial' depth requirements based on a 'risk assessment' of threats to the cable and the soil strengths in the location of each risk. Cable Burial A submarine power cable is trenched into the seabed and covered with soil providing complete burial of a cable. Cable Grips 'Cable Grips' are used to pull or support cables and pipes. They work on the principle of the harder the pull, the tighter the grip. Cable Tank A circular storage area where cable is coiled. Cablelaid grommet A single length of 'unit rope' laid up 6 times over a core, as shown in IMCA M 179, /81/, to form an endless loop. Sometimes known as an endless sling Cablelaid sling A sling made up of 6 'unit ropes' laid up over a core 'unit rope', as shown in IMCA M 179, /81/, with a hand spliced eye at each end. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 23 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used (cable) Basket Where the item to be transported is carried on a vessel, it is referred to throughout this standard as the cargo. If the item is towed on its own buoyancy, it is referred to as the tow. Cargo overhang Distance from the side of the 'vessel' to the extreme outer edge of the 'cargo' Cargo ship safety certificates (Safety Construction) (Safety Radio) Certificates issued by a certifying authority to attest that the 'vessel' (Safety Equipment) (Basket or Reel) Carousel — complies with the cargo ship construction and 'survey' regulations, — has radiotelephone equipment compliant with requirements and — carries safety equipment that complies with the rules applicable to that 'vessel' type. A rotating horizontal circular platform with a vertical 'barrel' used in conjunction with a 'turntable'. Either: a) a 'basket carousel' with side wall(s) where the 'product' is loaded by 'winding' or b) a 'reel carousel' with an upper flange where the 'product' is loaded by 'reeling/ spooling'. The upper flange can be plated (fully or partially) or of spoke design. The upper flange can be adjustable or supplemented by an intermediate flange. 'Carousels' can be mobile or integrated with the 'turntable'. They can be used for storage, transportation and onshore or offshore installation. Carrier or Sleeve pipe The outer casing of a 'bundle' or 'pipeinpipe'. Catspaw An extreme type of loop thrown into cables where a combination of low tension and residual torsion forms a twisted loop. Commonly seen at repair 'Final Splice' locations where the 'Final Splice' is lowered too quickly. Certificate of Approval (CoA) A formal document issued by a 'MWS company surveyor' stating that, in his/her judgement and opinion, all reasonable checks, preparations and precautions have been taken to keep risks within acceptable limits, and an 'operation' may proceed. Certified Having (or proved by) a certificate from an acceptable source Characteristic load The reference value of a load to be used in the determination of load effects. The 'characteristic load' is normally based upon a defined fractile in the upper end of the distribution function for the load. Chinese Fingers Also known as pulling socks are used to pull or support cables and pipes. They work on the principle of the harder the pull, the tighter the grip. Classification A system of ensuring ships are built and maintained in accordance with the Rules of a particular Classification Society. Although not an absolute legal requirement, the advantages (especially as regards insurance) mean that almost all 'vessels' are maintained in Class. Client The company to which the 'MWS company' is contracted to perform marine warranty or consultancy activities. Coiling Operation where the 'product' (typically cable) is placed in layers of concentric rings into a 'tank'/'basket' that does not rotate, such that it is twisted 360 degrees per turn. Note: Not all cables can be coiled. Cold Stacking 'Cold stacking' is where the unit is expected to be moored or jackedup for a significant period of time and will have minimum or, in some cases, no services or personnel available. Column stabilised unit A MOU which floats on its columns during 'operation' or transit (e.g. 'semisubmersible'). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 24 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Cargo A 'competent person' carrying out a thorough examination/assessment /analysis/ certification shall have such appropriate practical and theoretical knowledge and experience of the equipment and/or activity. Although the 'competent person' may often be employed by another organisation, this is not necessary, provided they are sufficiently independent and impartial to ensure that inhouse examinations are made without fear or favour. However, this should not be the same person who undertakes routine maintenance of the equipment as they would then be assessing their own maintenance work. Note: Where local or national regulations define a 'competent person' with more onerous requirements, then the definition in these local or national regulations shall apply. Consequence Factor γc Factor applied in the design of critical components to ensure that these components have an increased factor of safety in relation to the consequence of their failure. Contingency operation An operation performed in response to an emergency situation. See [2.5.4]. Also the term for bringing an object into a 'safe condition' for operations that can be halted (see [2.6.5.2]). Controlled Depth Tow (CDT) A special towing 'operation' where the pipe string or 'bundle' is made almost buoyant and towed at a controlled depth within the water column, suspended between a lead and trail 'tug'. Crane vessel The 'vessel', ship or 'barge' on which 'lifting appliance' is mounted. For the purposes of this document it is considered to include: crane barge, crane ship, derrick barge, floating shearleg, heavy lift vessel, 'semisubmersible' crane vessel (SSCV) and 'jackup' crane vessel. Cribbing An arrangement of timber baulks, secured to the deck of a 'barge' or 'vessel', formally designed to support the cargo, generally picking up the strong points in 'vessel' and/or 'cargo'. Cross Linked Polyethylene A type of AC cable conductor insulation commonly used on submarine power cables. (XLPE) Cross Sectional Area (CSA) Normally the CSA of a single conductor in a submarine power cable x 3. For example a 2 submarine power cable with 3x600 mm in its designation would be a cable with three 2 conductors each of 600 mm . Dead Man Anchor (DMA) Anchor or multiple anchors (which may be clump weights, sometimes buried), typically used to initiate 'pipelay'. Deck mating The act of installing integrated topsides over a substructure, generally by 'floatover' and ballasting. Deck mating may take place inshore or offshore, onto a floating or a previously installed substructure. Deck Support Unit (DSU) Unit installed on the 'vessel' 'grillage' to support the structure before and during the 'floatover'. It can be designed to either provide a rigid vertical support and allow horizontal movement or utilise elastomers to absorb vertical and horizontal installation motions and forces. Deep water This is determined on a case by case basis but for installation of subsea equipment it is generally taken as greater than 500 m. Demolition towage 'Towage' of a “dead” 'vessel' for scrapping. Design environmental condition The design wave height, wave period, wind speed, current and other relevant environmental conditions specified for the design of a particular 'voyage' or 'operation'. Design load A load or load condition which forms basis for design and design verification. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 25 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Competent person A lift where the slinging arrangement is such that the sling loads are statically determinate, and are not significantly affected by minor differences in sling length or elasticity e.g. two and three point lifts Double tow The 'operation' of towing two 'tows' with two separate tow wires by a single 'tug'. See [11.18.1.2] Dry Towage The 'operation' of transporting a 'cargo' on a 'barge'. (cable) Drum A cylinder (the 'barrel'), normally with horizontal axis, with two flanges onto which a 'product' is wrapped by 'reeling'/'spooling'. Used for storage, transport and onshore or offshore installation. A 'drum' is normally unpowered and normally made of wood or steel. Also see 'reel'. Dunnage Typically 'dunnage' is inexpensive material used to protect 'cargo' during 'transport'. 'Dunnage' also refers to material used to support loads and prop tools and materials. See 'cribbing'. Dynamic Amplification Factor (DAF) The factor by which the weight is multiplied, to account for accelerations and impacts during the operation Dynamic Angle The smallest angle at which the area ratio in [11.10.3.1] is satisfied Dynamic hook load 'Static hook load' multiplied by the DAF. Engineered lift A lift which is planned, designed and executed in a detailed manner, with thorough supporting documentation. See [16.1.1.4]. Export Cable(s) Submarine power cables connecting the offshore wind farm transformer station to a landfall connection. Factored weight The calculated weight of a structure, including all allowances and contingencies. Sometimes known as gross weight. Fatigue Limit State The 'limit state' related to the capacity of the structure to resist accumulated effect of repeated loading. Field Joint Coating (FJC) Refers to single or multiple layers of coating applied to girth welds and associated cutback of the 'line pipe' coating. Coating can be applied in factory or field. Final Splice The location where a second joint is inserted into a cable system during a repair and includes the excess slack in the cable where the two ends of the 'final splice' come to the surface. Flag state The state under which a commercial 'vessel' is registered or licensed. It has the responsibility to enforce regulations over 'vessels' registered under its flag, including inspections, certification and issuance of safety or pollution prevention documents. Floating offload The reverse of 'floating onload' Floating onload The 'operation' of transferring a 'cargo', which itself is floating, onto a 'vessel' or 'barge', which is submerged for the purpose. Floating Production System (FPS) Including FPV, FPU, FPSO, FGSO, spar (buoy) or TLP FloatOver The 'operation' of installation/removal of a structure onto or from a fixed 'host structure' by manoeuvring and ballasting the transport 'vessel' to effect load transfer FlyingLead A type of 'umbilical jumper' that is normally lowered to the seabed using a supporting frame and then installed using ROV. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 26 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Determinate lift The metocean limits used when assessing weather forecasts to determine the acceptability of proceeding with (each phase of) an 'operation' beyond the next 'Point of No Return'. For a 'weather restricted operation/voyage' these equal the 'Operational Limiting Criteria' multiplied by an 'Alpha factor'. For 'weather unrestricted operation/voyage' see [2.6.6.2] Freeboard Freeboard is defined as the distance from the waterline to the 'watertight' deck level. In commercial 'vessels', it is measured relative to the ship's 'load line'. “Effective freeboard” is the minimum vertical distance from the still water surface to any opening (e.g. an open manhole) or downflooding point, after accounting for 'vessel' trim and heel. Global Positioning System A satellite based system providing geographic coordinate location. (GPS) Grillage A structure, secured to the deck of a 'barge' or 'vessel', formally designed to support the 'cargo' and distribute the loads between the 'cargo' and 'barge' or 'vessel'. Heave 'Vessel' motion in a vertical direction Heavy Transport Vessel (HTV) A 'vessel' which is designed to ballast down to submerge its main deck, to allow self floating 'cargo(es)' to be onloaded and offloaded. Host Structure The 'host structure' (e.g. 'jacket', GBS, TLP) onto which the structure or structure deck will be floated and supported, or from which it will be removed. Hydroacoustic Positioning Reference (HPR) A through water acoustic link between a 'vessel' and a seabed beacon. Used to locate and track vehicles in the water column and can be used as a DP reference. Indeterminate lift Any lift where the sling loads are not statically determinate, typically lifts using four or more 'lift points' Inshore Mooring A mooring 'operation' in relatively sheltered coastal waters, but not at a quayside. Inspection and Test Plan (ITP) A plan in which all test, witness and hold points for all aspects of a cable installation are listed. Insurance Warranty A clause in the insurance policy for a particular venture, requiring the 'Assured' to seek approval of a 'marine operation' by a specified independent survey house. International Association of Classification Societies (IACS) A listing of IACS members is given on the IACS web site http://www.iacs.org.uk/explained/members.aspx International Cable Protection Committee (ICPC) A trade body representing and lobbying on behalf of subsea cable owners. For historical reasons membership is predominately comprised of telecom companies. International Convention for the Safety Of Life At Sea SOLAS, /139/ An international treaty concerning the safety of merchant and other ships and MOUs. International Maritime Organization (IMO) The United Nations specialized agency with responsibility for the safety and security of shipping and the prevention of marine pollution by ships International Safety Management (ISM) The 'ISM Code' provides an International standard for the safe management and operation of ships and for pollution prevention. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 27 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Forecasted Operational Criteria The point at which two straight sections or tangents to a 'pipeline' curve, or two slings, meet when extended. ISM Code 'International Safety Management Code', /92/, the International Management Code for the Safe Operation of Ships and for Pollution Prevention Mandatory code referenced by SOLAS, /139/, Chapter IX (Management for the safe operation of ships). Itube A vertical tube fitted to offshore structures to install 'product' between the seabed and the structure topsides. Jacket A substructure, positioned on the seabed, generally of tubular steel construction and secured by piles, designed to support topsides facilities. Jackup A selfelevating MODU, MOU or similar, equipped with legs and jacking systems capable of lifting the hull clear of the water. JLay A laying method where the pipe joints are raised to a nearly vertical angle in a tower mounted on a 'pipelay' 'vessel' in a tower, assembled and lowered, curved through approximately 90° (J shape) to lie horizontally on the seabed. Jtube A J shaped tube fitted to offshore structures to install 'product' between the seabed and the structure topsides. Jumper Short length of pipe used to connect subsea assets. Kilometre Point The position of on 'pipeline' route at a given distance from an agreed reference point, typically at or near one end. LayBack The horizontal offset from the last pipe support on the lay 'vessel' to the 'touch down' point on the seabed. Lay Chute A 'lay chute' is generally a fixed plate shaped to protect the 'product' MBR. A 'lay chute' may also incorporate rollers. Lay Sheave A 'lay sheave' is a sheave with a radius greater than or equal to the 'product' MBR that may for example be at the top of a lay tower to guide the product from the reel into the lay tower or at the stern to guide the 'product' into the water. Leg Mating Unit (LMU) Unit that is designed and installed between the structure and the 'host structure' in order to absorb vertical and horizontal installation motions and forces. The units are normally either installed on the 'host structure' legs to receive the structure, or on the structure leg stubs, in order to interface with the 'host structure' legs. LMU’s can be also installed on the removal 'vessel'. Lift point The connection between the 'rigging' and the structure to be lifted. May include 'padear', 'padeye' or 'trunnion' Lifting Appliance Machine or appliance used for the purpose of lifting objects, or in special modes, personnel e.g. crane. Lifting beam/Lifting frame A 'lifting beam/frame' is a structure designed to be connected to a 'lifting appliance' at a single point; the object being lifted is connected to the bottom of the beam at two or more 'lift points'. The beam/frame shall resist the bending moments. It is not designed to carry compression loads. Lifting Equipment General expression including 'lifting appliances', lifting gear and 'loose gear' and other lifting attachments; used separately or in combination. Lifting Factor Equivalent to a 'load factor' but applied only in the design of slings and 'grommets' used for lifting operations. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 28 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Intersection Point Load carrying equipment designed, tested and used with a specific 'lifting appliance' but not necessarily permanently attached to the 'lifting appliance'. The examples under 'loose gear' may be considered as lifting gear when used in this way. 'Lifting gear' that is not for a specific 'lifting appliance' shall be considered as 'loose gear'. Lightship weight The weight of the hull plus permanently installed items. Limit state A state beyond which the product or component no longer satisfies the given acceptance criteria Limit State 1 (LS1) An ASD/WSD design condition where the loading is gravity dominated; also used when the exclusions of [5.9.7.3] apply. Limit State 2 (LS2) An ASD/WSD design condition where the loading is dominated by environmental/ storm loads, e.g. at the 10 year or 50 year return period level or, for 'weather restricted operations', (where the 'operational limiting criteria' are less than the 'design environmental criteria' due to the application of an 'Alpha Factor', see [2.6.9]). Line pipe Coated or uncoated steel pipe sections, intended to be assembled into a 'Pipeline' Linear Cable Engine (LCE) An industry term commonly used to refer collectively to cable lay 'tensioners'. Link beam/link span The connecting beam between the quay and the 'barge' or 'vessel'. It may provide a structural connection, or be intended solely to provide a smooth path for 'skidshoes' or 'trailers'/SPMTs. Load controlled condition A condition in which magnitude and direction of bending is governed by only the loads applied to the 'product', e.g. in the 'touchdown' region. Load Factor A factor applied to a 'characteristic load' in a 'limit state' analysis. In 'rigging' design it is termed 'lifting factor' to differentiate between the values that shall be applied in a limit state analysis to those that are applied in the design of slings and 'grommets' used for lifting operations. Load line The maximum depth to which a ship may be loaded in the prevailing circumstances in respect to zones, areas and seasonal periods. A Load line Certificate is subject to regular 'surveys', and remains valid for 5 years unless significant structural changes are made. Load transfer operation The operation to transfer the load (i.e. an object) from/to 'vessel(s)' without using cranes, i.e. by using (de)ballasting. Typical l'oad transfer operations' are 'loadout', lift off, mating and 'floatover'. Loadin The transfer of an assembly, module, pipes or component from a 'barge' or 'vessel', e.g. by horizontal movement or by lifting. Loadout The transfer of an assembly, module, pipes or component onto a 'barge' or 'vessel', e.g. by horizontal movement or by lifting. Loadout Support Frame (LSF) A structural frame that supports the structure during fabrication and 'loadout' and may support the structure on a 'barge'/'vessel' above 'grillage'. Loadout, floating A 'Loadout' onto a floating 'vessel'. Loadout, grounded A 'Loadout' onto a grounded 'vessel'. Loadout, lifted A 'Loadout' performed by crane. Loadout, skidded A 'Loadout' where the structure is skidded, using a combination of 'skidways', 'skidshoes' or runners, propelled by jacks or winches. Loadout, trailer A 'Loadout' where the structure is wheeled onto the 'vessel' using 'trailers' or SPMTs. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 29 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Lifting Gear A move of a MODU or similar, which, although not falling within the definition of a field '24hour move', may be expected to be completed with the unit essentially in 24hour field move configuration, without overstressing or otherwise endangering the unit, having due regard to the length of the move, and to the area (including availability of 'shelter points') and season. Loose Gear Load carrying equipment used to attach the lifted object to the 'lifting appliance' that are not part of the lifted object or used with a specific 'lifting appliance'. Includes devices and steel structures such as, but not limited to: a) grabs b) spreaders c) traverses d) lifting magnets e) attachment rings f) shackles g) swivels h) balls i) pins j) sheaves k) blocks (including hookblocks) l) hooks m) load cells n) chains o) claws p) clamps q) pliers r) load fastening ropes (slings/strops) s) lifting straps, etc. Magnetic Particle Inspection (MPI) A 'NonDestructive Testing' (NDT) process for detecting surface and slightly subsurface discontinuities in ferroelectric materials such as iron Marine operation See 'Operation' Marine Warranty Survey company MWS Company The Marine Warranty Survey (MWS) company is one that is specified on an 'insurance warranty' and has been contracted to approve specified 'operations' as a condition of the insurance. Marine Warranty Survey company surveyor (MWS company surveyor) An 'MWS company' surveyor is employed to review the proposed 'procedures' and equipment and, when satisfied that they and the weather forecasts are suitable, to issue a 'Certificate of Approval' for each relevant 'operation'. He /she may also attend during such 'operations' to monitor that the 'procedures' are followed or to agree any necessary changes. Matched pair of slings A 'matched pair of slings' is fabricated or designed so that the difference in length does not exceed 0.5d for cable laid slings or 'grommets' and 1.0d for 'single laid slings' or 'grommets', where d is the nominal diameter of the sling or 'grommet'. See Section 2.2 of IMCA M 179, /81/ for cable laid details Material Factor γm A factor used on a material’s yield stress in a 'limit state' analysis and is also a factor used in the design of slings and 'grommets' used for lifting operations. Note: For slings and grommets, the 'material factor' is a function of the age, certification and material type. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 30 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Location move Manufacturer’s recommended 'Maximum Continuous Rating' of the main engines. Mechanical Termination A sling eye termination formed by use of a ferrule that is mechanically swaged onto the rope. See ISO 2408 and 7531, /104/ and /105/. Minimum Bend Radius (MBR) Specified by the manufacturer of a flexible pipe, 'umbilical' or cable. This is the minimum radius to which a flexible, 'umbilical' or cable can be bent without compromising its integrity. Minimum Breaking Load (MBL) The minimum value of breaking load for a particular sling, 'grommet', wire or chain, shackle etc. Mobile Mooring 'Mooring system', generally retrievable, intended for deployment at a specific location for a shortterm duration, such as those for 'mobile offshore units'. Mobile Offshore Unit (MOU) For the purposes of this document, the term may include Mobile Offshore Drilling Units (MODUs), and nondrilling mobile units such as accommodation, construction, lifting or production units including those used in the offshore renewables sector. Monopile Tubular structure used as foundation for offshore wind turbine generator. Moored Vessel Within the scope of this document refers to any structure which is being moored. Mooring System Consists of all the components in the 'mooring system' including shackles windlasses and other jewellery and, in addition, 'rig'/'vessel' and shore attachments such as bollards. Most Probable Maximum Extreme (MPME) The value of the maximum of a variable with the highest probability of occurring over a period of 3 hours. NOTE The most probable maximum is the value for which the probability density function of the maxima of the variable has its peak. It is also called the mode or modus of the statistical distribution. It typically occurs with the same frequency as the maximum wave associated with the design sea state. Multiple towage The operation of towing more than one 'tow' by a single 'tug', or more than 1 'tug' towing one 'tow'. See [11.18] Nacelle The part of the wind turbine on top of the 'tower', where the hub, gearbox, generator and control systems are located. NonDestructive Testing (NDT) Ultrasonic scanning, 'magnetic particle inspection', eddy current inspection or radiographic imaging or similar. Can also include visual inspection. Not To Exceed (NTE) weight Sometimes used in projects to define the maximum weight of a structure for an operation. See [5.6.2.2] Object The item subject to an insurance warranty or at risk from an operation. Offhire survey A survey carried out at the time a 'vessel', 'barge', 'tug' or other equipment is taken offhire, to establish the condition, damages, equipment status and quantities of consumables, intended to be compared with the 'onhire survey' as a basis for establishing costs and liabilities. Offload The reverse of 'loadout' Offshore Converter Station The offshore converter station transforms the collected energy from the 'offshore transformer stations' (several wind parks) to Direct Current in order to send it to a land based converter station. Offshore pull The pulling of a 'pipeline' away from the shore using a lay 'vessel' Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 31 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Maximum Continuous Rating (MCR) The 'offshore transformer station' is transforming the collected energy from the wind turbines to a higher voltage. Onhire survey A survey carried out at the time a 'vessel', 'barge', 'tug' or other equipment is taken onhire, to establish the condition, any preexisting damages, equipment status and quantities of consumables. It is intended to be compared with the 'offhire survey' as a basis for establishing costs and liabilities. It is not intended to confirm the suitability of the equipment to perform a particular 'operation'. Operation reference period The 'Planned Operation Period', plus the contingency period. See [2.6.2] to [2.6.4] Operation, marine operation Generic term covering, but not limited to, the following activities which are subject to the hazards of the marine environment: a) 'Loadout'/'loadin' b) 'Voyage' c) Lift/Lowering (offshore/inshore) d) Towout/towin e) 'Floatover'/floatoff f) 'Jacket' launch/'jacket' upend g) 'Pipeline' installation h) Construction afloat Operational Limiting Criteria The metocean limits used when assessing weather forecasts to determine the acceptability of proceeding with (each phase of) an 'operation' beyond the next 'Point of No Return'. For a 'weather restricted operation'/'voyage' only these are the maximum environmental conditions in which it may be possible to perform the operation, however to account for uncertainty in the weather forecast they shall be reduced by the applicable alpha factor, see [2.6.8] and [2.6.9]. Padear A shaped 'lift point' around which a sling or grommet can be passed. The shaping of the bearing surface is normally elliptical to allow for flattening of the sling or grommet under load and incorporates a flange/keeper within the design. Padears are normally cast and can be either a single padear or a double padear. A retaining device is also included to secure the sling/grommet. For a typical arrangement of a padear, see Figure 163 in [16.9.4.2]. See also trunnion. Padeye A 'lift point' consisting essentially of a plate, reinforced by cheek plates if necessary, with a hole through which a shackle may be connected Permanent Mooring 'Mooring system' normally used to moor floating structures deployed for longterm 'operations', such as those for a 'floating production system'. Pigging The practice of passing a device known as a “pig” through a 'pipeline' for maintenance (e.g. for cleaning, gauging or inspection) without stopping the flow in the 'pipeline'. Pipe carrier A 'vessel' specifically designed or fitted out to transport 'line pipe' PipeinPipe A single rigid pipe held within a 'carrier pipe' by spacers and/or solid filler. Pipelay The operation of assembling and laying the 'pipeline' on the seabed, from startup point to laydown point. Pipeline Any marine pipeline system for the carriage of oil, gas, water or other process fluids. It may be of rigid material or flexible layered construction. For the purposes of this document the term pipeline includes flowlines as defined in API RP 1111, /3/ Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 32 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Offshore Transformer Station The planned duration of the operation from the forecast before either the operation start or 'Point of No Return', as appropriate, to a condition when the 'operations'/structures can safely withstand a seasonal design storm (also termed “safe to safe” duration) this excludes the contingency period Platform The completed steel or concrete structure complete with topsides Point of No Return (PNR) The last point in time, or a geographical point along a route, at which an 'operation' could be aborted and returned to a 'safe condition'. Port (or point) of shelter See 'Shelter point' Port of refuge A location where a 'towage' or a 'vessel' seeks refuge, as decided by the Master, due to events which prevent the 'towage' or 'vessel' proceeding towards the planned destination. A safe haven where a 'towage' or 'voyage' may seek shelter for 'survey' and/ or repairs, when damage is known or suspected. PreLoading The testing of soil foundations or anchors by loading to check that they can take subsequent loads. For 'jackup' foundations it is often done be adding water ballast to preload tanks or (with units with more than 3 legs) by predriving by removing load from other legs in turn. Procedure A documented method statement for carrying out an 'operation' Product A generic term used within this standard to reference 'pipelines' (rigid and flexible), risers, 'jumpers', 'umbilicals' and submarine cables. Product Storage Equipment Generic term for 'drum', 'reel', 'carousel' ('basket' and 'reel') and 'basket'. Pull Back Method A 'Jtube' pullin operation where the pullin winch is mounted on the installation 'vessel' and the end of the pullin wire connected to the cable runs from the 'vessel' to the 'J tube' bottom end up and over a sheave and back to the installation 'vessel' pullin winch. Quadrant A structure, usually with rollers, to limit the MBR as the cable travels over or though it and changes direction, typically during loading or laying during second end J tube pull in operations. Quadratic Transfer Function (QTF) Refers to the matrix that defines second order mean wave loads on a 'vessel' in bi chromatic waves. When combined with a wave spectrum, the mean wave drift loads and low frequency loads can be calculated. Quayside Mooring A mooring that locates a 'vessel' alongside a quay (usually at a sheltered location). Recognized Classification Society (RCS) Member of IACS with recognized and relevant competence and experience in specialised 'vessels' or structures, and with established rules and procedures for classification/ certification of such 'vessels'/structures under consideration. Reduction Factor, γr The Reduction Factor used in the design of slings or 'grommets' representing the largest Redundancy Check Check of the failure load case associated with the applicable extreme (survival) environment, e.g. the one line broken case. Reel Similar to a horizontal axis 'drum' but powered (by reel drive system, RDS) and usually larger. Used for storage, transport and onshore or offshore installation. Normally made of steel. See 'reel carousel' for when the 'barrel' axis is vertical. values of γb and γs. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 33 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Planned Operation Period A laying method where the pipeline is preassembled into long strings or stalks and wound onto a large reel with the pipe experiencing plastic deformation when wound on and off the reel and straightened when reeled off. Typical lay angles of 20 to 90 degrees are achieved. Reeling The operation of wrapping the product in layers around a rotating 'barrel' with back tension. The 'product' can be guided backandforth along the 'barrel' to complete each layer. The operation normally uses either a 'drum' or 'reel'. Registry Registry indicates who may be entitled to the privileges of the national flag, gives evidence of title of ownership of the ship as property and is required by the need of countries to be able to enforce their laws and exercise jurisdiction over their ships. The Certificate of Registry remains valid indefinitely unless name, flag or ownership changes. Remotely (Controlled) Operated Vehicle (ROV) A device deployed subsea on a 'tether' or umbilical, typically equipped with a subsurface acoustic navigation system and thrusters, to control its location and attitude, and a lighting and video system. Additional devices such as manipulators, acoustic scanning for 'touchdown' monitoring, etc., may also be provided. Responsible Person In accordance with ILO Convention 152, /136/, “a person appointed by the employer, the master of the ship or the owner of the gear, as the case may be, to be responsible for the performance of a specific duty or duties and who has sufficient knowledge and experience and the requisite authority for the proper performance of the duty or duties”. Response Amplitude Operator (RAO) Defines the vessel’s (first order) response in regular waves and allows calculation of 'vessel' wave frequency (first order) motion in a given sea state using spectral analysis techniques. Rig General reference term often used to describe a 'jackup' or 'semisubmersible' (Mobile Offshore Drilling Unit or MODU)see MOU) e.g. ‘Rig move procedures’ Rigging The slings, shackles and other devices including spreaders used to connect the structure to be lifted to the crane Rigging weight The total weight of 'rigging', including slings, shackles and spreaders, including contingency. Righting Arm (GZ) Righting Moment divided by the displacement Risk assessment A method of hazard identification where all factors relating to a particular 'operation' are considered. Rope An assembly of 'strands' wrapped around a core. When a 'rope' is used for 'cablelaid sling' or 'cablelaid grommet' it is referred to as a 'unit rope' (as per IMCA M 179, /81/). Rotor Configuration consisting of the complete set of blades, connected to the hub. Route Planning List (RPL) A tabularised list of the coordinates defining the route along which a submarine cable is to be installed and the planned installation slack. A post installation RPL will record the asbuilt cable route coordinates, installed slack and burial depths. Routine lift “Everyday” lift, without detailed design, planning or documentation, such as general cargo lifting operations or lifting portable units on/off a supply vessel. See [16.1.1.4]. Safe condition A condition where the object is considered to be exposed to a normal level of risk of damage or loss. See guidance note to [2.5.1.2] Safe Working Load (SWL) SWL is a derated value of WLL, following an assessment by a 'competent person' of the maximum static load the item can sustain under the conditions in which the item is being used. See [1.1.12] Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 34 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Reel Lay (for rigid pipe) A structured and documented system enabling Company personnel to implement the Company safety environmental protection policy. Sand Jacks A compartment filled with sand that is incorporated into the LMU to allow the final controlled lowering of the structure onto the 'host structure' Scour pit The result of scour around a pile, leg etc. See “Dynamics of scour pits and scour protection”, /119/. Sea room The distance that a disabled 'vessel' or 'tow' in bad weather can drift before grounding. See [11.14.1.5]. Seafastenings The means of restraining movement of the loaded structure on or within the 'barge' or 'vessel'. SelfPropelled Modular Transporter (SPMT) A 'trailer' system having its own integral propulsion, steering, jacking, control and power systems. Semisubmersible A floating structure normally consisting of a deck structure with a number of widely spaced, large crosssection, supporting columns connected to submerged pontoons. Serviceability Limit State (SLS) A design condition where the structure is required to fulfil its primary operational function. Setback The space on the derrick floor where stands of drill pipe or tubing are “setback” and racked in the derrick. It can also mean the amount of drill pipe etc. in this area. Shelter point (or port of shelter, or point of shelter) An area or safe haven where a 'towage' or 'vessel' may seek shelter, in the event of actual or forecast weather outside the design limits for the 'voyage' concerned. A planned holding point for a 'staged voyage' Shore pull The pulling of a cable or 'pipeline' to the shore from a lay 'barge'/'vessel' Simultaneous Operations (SIMOPS) 'Operations' usually involving various parties and 'vessels' requiring coordination and definitions of responsibilities. Single Laid Sling A sling normally made up of 6 'strands' laid up over a core, as shown in ISO 2408 and 7531, (/104/ and /105/), with terminations each end. Single tow The operation of towing a single 'tow' with a single 'tug'. Site Move An operation to move a structure or partially assembled structure in the yard from one location to another. The site move may precede a 'loadout' if carried out as a separate 'operation' or may form part of a 'loadout'. The site move may be subject to approval if so desired. Skew Load Factor (SKL) A factor to account for additional loading caused by 'rigging' fabrication tolerances, fabrication tolerances of the lifted structure and other uncertainties with respect to asymmetry and associated force distribution in the 'rigging' arrangement. Skidshoe A bearing pad attached to the structure which engages in the 'skidway' and carries a share of the vertical load Skidway The lower continuous rails, either on the quay or on the 'vessel', on which the Structure is loaded out, via the 'Skidshoes'. Slack Management A generalized term used by the submarine cable installation industry to refer to the control of cable payout out against a predefined installation plan. Slamming loads Transient loads on the structure due to wave impact when lifting through the splash zone. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 35 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Safety Management System (SMS) A laying method where the pipe is assembled horizontally, fed out of the stern or bow of the 'barge' or 'vessel', typically over a stinger Can also be without stinger at certain depths or at the end of the 'shore pull' before the water depth increases to a depth where stinger becomes necessary, and then makes a double curve (shallow S shape) to lie horizontally on the seabed. Sling design Load The maximum calculated dynamic axial load in a lifting sling, including all relevant 'load factors'. Sling eye A loop at each end of a sling, either formed by a 'splice' or 'mechanical termination' Specified Minimum Yield Stress (SMYS) The minimum yield stress specified in standard or specification used for purchasing the material. Splice That length of sling where the 'rope' (or 'unit rope' for 'cablelaid sling') is connected back into itself by tucking the tails of the strands (or 'unit ropes') back through the main body of the 'rope' (or 'unit ropes'), after forming the 'sling eye' Spool (piece) A short length of rigid pipe used to connect pipe (e.g. 'pipeline', riser) and/or subsea asset. Spooling Similar to 'reeling'. See 'winding' and 'coiling' for where the 'product' is wrapped without back tension Spreader bar (also known A spreader bar or frame is a structure designed to resist the compression forces induced as Spreader beam)/ by angled slings, by altering the line of action of the force on a lift point into a vertical Spreader frame plane. The bar (beam)/frame shall also resist bending moments due to geometry and tolerances. Spud A large metal post which penetrates the seabed under its own weight and is used to prevent lateral movement of a 'barge'. A dredge 'barge' will typically have two spuds in guides near its stern. Squeeze load The radial force applied to the 'product' by a 'tensioner', clamp or similar. Staged voyage A weather restricted 'voyage' in which there is a commitment to seek shelter (or 'jack up' at a standby location) on receipt of a weather forecast in excess of the operational criteria. See [11.14.4.1]. Static Hook Load (SHL) The weight plus the 'rigging weight' (see [16.3.2]). This load is suspended by a crane hook during lifting operations. Strand An assembly of wires wound together to create a 'strand'. Wire rope consists of multiple 'strands' wound together. For example: 6x36 wire rope construction indicates that the wire rope consists of 6 strands, each having 36 wires. Structure The object to be transported, lifted or installed, or a subassembly, component or module. Submerged Weight Weight of the 'structure' minus the weight of displaced water. Suitability survey A 'survey' intended to assess the suitability of a 'tug', 'barge', 'vessel' or other equipment to perform its intended purpose. Different and distinct from an 'onhire survey'. Surge 'Barge' or 'vessel' motion in the longitudinal direction OR A change in water level caused by meteorological conditions Survey Attendance and inspection by a 'MWS company surveyor'. Other surveys which may be required for a 'marine operation', including suitability, dimensional, structural, navigational and Class surveys. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 36 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used S–Lay The 'MWS company' representative carrying out a ‘Survey’ or an employee of a contractor or Classification Society performing, for instance, a suitability, dimensional, structural, navigational or Class 'survey'. Sway 'Vessel' motion in the transverse direction System Pressure Test A pressure test at a pressure normally at a 1.25 to 1.5 times the 'pipeline' design pressure (for rigid 'pipelines'), which is made after installation operations are substantially or wholly completed, to provide proof of pressure and strength integrity of the 'pipeline' and 'spools'. Tandem tow The operation of towing two or more 'tows' in series with one tow wire from a single 'tug', the second and subsequent 'tows' being connected to the stern of the 'tow' ahead. Tangent Point The point where the bend of a 'pipeline' begins or ends. (cable) Tank A static nonrotating circular storage area (on vessel, on land), which is loaded by 'coiling'. Tensioner Equipment to keep and control tension in the 'product' during installation operation. Termination factor γs A partial safety factor that accounts for the reduction in strength caused by a 'splice' or 'mechanical termination'. Tether A tether is a mooring line used for pulling and mooring the installation /removal 'vessel' into the required position. It may also be the 'umbilical' to an ROV or part of a TLP’s 'mooring system'. Tidal range Where practicable, the tidal range referred to in this document is the predicted tidal range corrected by locationspecific tide readings obtained for a period of not less than one lunar cycle before the 'operation'. Tonnage A measurement of a 'vessel' in terms of the displacement of the volume of water in which it floats, or alternatively, a measurement of the volume of the 'cargo' carrying spaces on the 'vessel'. Tonnage measurements are principally used for freight and other revenue based calculations. Tonnage Certificates remain valid indefinitely unless significant structural changes are made. Tonnes Metric tonnes of 1,000 kg (approximately 2,204.6 lbs) are used throughout this document. The necessary conversions shall be made for equipment rated in long tons (2,240 lbs, approximately 1,016 kg) or short tons (2,000 lbs, approximately 907 kg). Touchdown Seabed location at which a submarine 'pipeline', 'umbilical' or cable touches down on the seabed during installation, or a mooring line during 'operation'. Tow The item being towed. This can be a 'barge' or 'vessel' (laden or unladen) or an item floating on its own buoyancy. Towage The operation of towing a nonpropelled 'barge' or 'vesse'l (whether laden or not,) or other floating object (wet 'tow') by 'tug(s)'. Towed bundle A 'pipeline' system comprising one or more 'pipelines', tubes or cables contained within a 'carrier pipe', and fitted with towing and trailing heads. The 'bundle' is usually assembled on land and launched. The 'bundle' may be towed off bottom, on surface, or at an intermediate controlled depth. Tower (OWF) The tubular element from the top of the flange on the foundation to the bottom of the flange below the 'nacelle', generally built up of several sections. Towing arrangements The hardware from the towing winch to the towing connections plus the bridle recovery and emergency towing equipment. (They do not normally include the towing 'procedures'.) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 37 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Surveyor 'Ultimate load capacity' of towline connections, including connections to 'vessel', bridle and bridle apex. Towline Pull Required (TPR) The towline pull computed to hold the 'tow', or make a certain speed against a defined weather condition. Trailer A system of steerable wheels, connected to a central spine beam by hydraulic suspension which can be raised or lowered. Trailer modules can be connected together and controlled as a single unit. Trailers generally have no integral propulsion system, and are propelled by tractors or winches. See also SPMT. Transition Piece A tubular structure on top of a 'monopile' to provide support for the 'tower'. Transport The 'operation' of transporting a 'cargo' on a powered 'vessel'. Trunnion A 'lift point' consisting of a horizontal tubular stub with a flange/keeper plate at the end, around which a 'sling' or 'grommet' is passed. A retaining device is also included to secure the sling/grommet. The stub is normally welded to the supporting member. An upending trunnion can be used to rotate a structure from horizontal to vertical, or vice versa, and the trunnion forms a bearing round which the 'sling', 'grommet' or another structure will rotate. See also Padear. Tug The 'vessel' performing a 'towage' (including tug supply and anchor handling towing 'vessels'). 'Approval' by the 'MWS company' of the tug will normally include consideration of the general design, classification, condition, towing equipment, bunkers and other consumable supplies, emergency communication and salvage equipment, and manning. Tug efficiency (Te or Teff) Effective bollard pull produced in the weather considered divided by the 'certified' continuous static 'bollard pull'. Tug Management Positioning System (TMPS) A system installed on the AHV and the anchoring 'vessel' to allow the accurate placing of the 'tug' and anchors. Turntable An active drive system used in conjunction with a mobile or integrated 'carousel' (both basket and reel). Ultimate Limit State (ULS) The 'limit state' related to the maximum load carrying capacity. Also see 'Limit State 1' and 'Limit State 2'. (ULS) Ultimate Load Capacity (ULC) Ultimate load capacity of a wire 'rope', chain or shackle or similar is the 'certified' 'minimum breaking load'. The 'load factors' allow for good quality 'splices' in wire rope. Ultimate load capacity of a 'padeye', clench plate, delta plate or similar structure, is defined as the load, which will cause general failure of the structure or its connection into the 'barge' or other structure. Ultrasonic Testing (UT) Detection of flaws or measurement of thickness by the use of ultrasonic pulsewaves through steel or some other materials. Umbilical Typically a combination of cables and flexible pipes used to provide energy and/or chemicals and remote control for equipment (e.g. subsea), or to provide communications and life support for a diver UnderKeel Clearance (UKC) The clearance below the keel or base of a vessel or structure, after allowances for motions, and the seabed (or the 'host structure' during mating operations) Unit Rope The 'rope' from which a 'cablelaid sling' or 'cablelaid grommet' may be constructed, made from either 6 or 8 'strands' around a steel core, as indicated in ISO 2408 and 7531, (/104/ and /105/) and IMCA M 179, /81/. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 38 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Towline connection strength Weight added to the 'Lightship weight' to obtain the total weight for a particular 'towage' or operation, including 'cargo', liquids and temporary equipment. Vessel A marine craft designed for the purpose of 'transporting' by sea or construction activities offshore. This can include ships and 'barges' Voyage For the purposes of this standard, voyage covers both 'towages' and 'transport' from one place to another. Watertight A watertight opening is an opening fitted with a closure designated by Class as watertight, and maintained as such, or is fully blanked off so that no leakage can occur when fully submerged. Wear Factor, γw A factor used in the design of slings and 'grommets' used for lifting operations to account for physical condition of the sling or 'grommet'. Weather restricted operation An operation for which (any of) the applied characteristic environmental conditions are less than the characteristic 'environmental conditions' calculated based on the statistical extremes for the area and season. See also [2.6.7] Weather restricted voyage A 'voyage' for which the strength or stability will not meet the weather unrestricted environmental criteria (typically 10 year return). It can either be or staged (see [11.14.4.1]) or weatherrouted (see [11.14.4.4]) depending on the 'sea room' and 'shelter point' availability. Weather routed voyage A 'weather restricted voyage' in which a weather forecasting organisation advises the relevant captain on the best route to avoid weather exceeding the 'Operational Limiting Criteria'. (See [11.14.4.4]). Weather routeing may also be used for nonweather restricted 'voyages' to reduce fuel costs or 'voyage' time. Weather unrestricted operation An operation for which (all of) the applied characteristic environmental conditions are calculated based on the statistical extremes for the area and season. See also [2.6.6]. Weather unrestricted towage Any 'towage' which does not fall within the definition of a weather restricted 'towage', or any 'towage' of a MODU or similar which does not fall within the definition of a '24hour move' or 'location move'. Weather unrestricted voyage Any 'voyage' which does not fall within the definition of a 'weather restricted voyage'. Weather Window A period that the forecasted environmental conditions are less than or equal to OPWF (the 'Forecast Operation Criteria'). Weathertight A weathertight opening is an opening closed so that it is able to resist any significant leakage from one direction only, when temporarily immersed in green water or fully submerged. Weighing Contingency Factor A factor applied to the weighed weight of an object to account for uncertainties in the weighing equipment. Weight Contingency Factor A factor applied to the weight of an object, when an object is not to be weighed, to account for uncertainties related to the design and fabrication of the object. Wet towage The operation of transporting a floating object by towing it with a 'tug'. Wind Heeling Arm (WHA) Wind Heeling Moment divided by the displacement Winding Operation where the 'product' is placed into a rotating 'carousel' in layers of concentric rings without back tension. See 'reeling' and 'spooling' for where the product is wrapped with back tension. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 39 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Variable Load This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Working Load Limit (WLL) The maximum static load which a piece of equipment is authorized to sustain in general service when the 'rigging' and connection arrangements are in accordance with the design. See [1.1.12]. 1.6 Acronyms, abbreviations and symbols 1.6.1 Acronyms and abbreviations within single quotation marks in Table 14 are defined in Table 13. Table 14 Acronyms, abbreviations and symbols Short form In full ABS American Bureau of Shipping AC Alternating Current ADL Absolute minimum Deployable Length (of towline) AHC Active Heave Compensation AHV Anchor Handling Vessel AISC American Institute of Steel Construction ALARP As Low As Reasonably Practicable ALS 'Accidental Limit State' AMS Anchor Management System ANSI American National Standards Institute API American Petroleum Institute ARPA Automatic Radar Plotting Aid ASD Allowable Stress Design (effectively the same as WSD) ASOG Activity Specific Operations Guidelines ASPPR Arctic Shipping Pollution Prevention Regulations ATA Automatic Thruster Assist AUT Automatic Ultrasonic Testing AWS American Welding Society AWTI Above Water TieIn BAS 'Burial Assessment Survey ' BF Beaufort Force BBL Bridle Breaking Load BHP Brake Horse Power BP 'Bollard Pull' Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 40 'Burial Protection Index' BS British Standard BSR 'Bend Strain Reliever' BV Bureau Veritas BWM Ballast Water Management CAM Critical Activity Mode of Operation CAMO Now being replaced by CAM CASPRR Canadian Arctic Shipping Pollution Prevention Regulations CCTV Closed Circuit Television CDT 'Controlled Depth Tow' CFD Computational Fluid Dynamics CFM Controlled Failure Mode CMID Common Marine Inspection Document CoB Centre of Buoyancy CoG Centre of Gravity COMOPS Combined Operations COSHH Control of Substances Hazardous to Health CRBL Calculated Rope Breaking Load CSA 'Cross Sectional Area' CSBL Calculated Sling Breaking Load DAF 'Dynamic Amplification Factor' DFF Design fatigue factor DGPS Differential Global Positioning System DHL Dynamic Hook Load DMA 'Dead Man Anchor' DNV Det Norkse Veritas DNV GL Det Norske Veritas Germanischer Lloyd DOC Depth of Cover DOL Depth of Lowering DP Dynamic Positioning or Dynamically Positioned DR Design Review DSC Digital Selective Calling DSU 'Deck Support Unit' DTL Deployable Towline Length Standard — DNVGLSTN001. 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Requires a valid subscription to be used BPI Page 41 Factor for ratio of mean to specified bolt pretension E Modulus of Elasticity ECA Engineering Criticality Assessment EER Escape, Evacuation and Rescue EIPS Extra Improved Plow Steel EP HAZOP Early Procedure Hazard and Operability study EPIRB Emergency Position Indicating Radio Beacon ESD Emergency Shut Down η Permissible Usage Factor FAT Factory Acceptance Tests FBE Fusion Bonded Epoxy FEA Finite Element Analysis FEED Front End Engineering Design FGSO Floating Gas Storage and Offloading Vessel FJC 'Field Joint Coating ' FLNG Floating Liquefied Natural Gas FLS 'Fatigue Limit State ' FMEA Failure Modes and Effects FMECA Failure Modes, Effects and Criticality Analysis FoS Factor of Safety FPS 'Floating Production System' FPSO Floating Production, Storage and Offloading Vessel FPU or FPV Floating Production Unit or Floating Production Vessel FRSU Floating Storage Regasification Unit FSD Sling or grommet design load FSO Floating Storage and Offloading Vessel FSU Floating Storage Unit (including FPSO, FSO, FLNG facility, FRSU etc.) γb 'Bending Factor ' γc 'Consequence Factor' γf 'Load Factor' γh 'Lifting Factor' γm 'Material Factor' γr 'Reduction Factor' Standard — DNVGLSTN001. 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Requires a valid subscription to be used Du Page 42 'Termination Factor' γsf Combined factors (Lifting, Consequence, Reduction, Wear, and Material and Twist) γw 'Wear Factor' γweight 'Weight Contingency Factor (unweighed objects only) GA General Arrangement GBS Gravity Base Structure (foundation) GL Germanischer Lloyd GM Initial metacentric height GMDSS Global Maritime Distress and Safety System GN Guidance Note GOMO Guidelines for Offshore Marine Operations GPS 'Global Positioning System' GZ 'Righting Arm' HAT Highest Astronomical Tide HAZMAT Hazardous Materials HAZID Hazard Identification HAZOP HAZards and Operability study HDD Horizontal Directional Drilling HDPE Highdensity polyethylene hf Factor for fillers in bolted connections HIRA Hazard Identification and Risk Assessment HISC Hydrogen Induced Stress Cracking HMPE Highmodulus polyethylene HPR 'Hydroacoustic Positioning Reference' HPU Hydraulic Power Unit HSE Health, Safety and Environment or Health and Safety Executive (in context of UK HSE) HTV 'Heavy Transport Vessel'. (not to be confused with HLV (Heavy Lift Vessel) which has heavy lifting appliance(s)) HVDC High Voltage Direct Current IACS 'International Association of Classification Societies' IAPP International Air Pollution Prevention ICPC 'International Cable Protection Committee' IEC International Electrotechnical Commission ILO International Labor Organization Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used γs Page 43 Internal Lifting Tool IMCA International Marine Contractors Association IMDG Code International Maritime Dangerous Goods Code IMO 'International Maritime Organization' IOPP Certificate International Oil Pollution Prevention Certificate (see also MARPOL) ISM 'International Safety Management' ISO International Standards Organisation ISPS International Ship and Port Facility Security ITP Inspection Test Plan JIP Joint Industry Project JONSWAP Joint North Sea Wave Project JSA Job Safety Analysis ks Hole clearance factor LARS Launch And Recovery System LAT Lowest Astronomical Tide LBL Long Baseline Array LCE 'Linear Cable Engine' LCG Longitudinal Centre of Gravity LMU 'Leg Mating Unit' LOA Length Over All LR Lloyd’s Register LRFD Load and Resistance Factor Design LS1 'Limit State 1' LS2 'Limit State 2' LSF 'Loadout Support Frame' MARPOL International Convention for the Prevention of Pollution from Ships 1973/78, as amended MBL 'Minimum Breaking Load' MBR 'Minimum Bend Radius' MCR 'Maximum Continuous Rating' MDR Master Document Register MOC (procedure) Management of Change (procedure) MODU Mobile Offshore Drilling Unit MOU 'Mobile Offshore Unit' MPI 'Magnetic Particle Inspection' Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used ILT Page 44 'Most Probable Maximum Extreme' MRU Motion Reference Unit MSL Mean Sea Level MTS Marine Technology Society MWS 'Marine Warranty Survey' n/a Not Applicable ND Noble Denton NDT 'NonDestructive Testing' NMD Norwegian Maritime Directorate Ns Number of slip planes for bolted connections NTE (weight) 'Not To Exceed (weight)' OCIMF Oil Companies International Marine Forum OCIMF MEG OCIMF Mooring Equipment Guidelines OIM Offshore Installation Manager OPLIM Operational limiting criteria OPWF Forecasted operational criteria OSS Out of Straightness Survey OVID Offshore Vessel Inspection Database OWF Offshore Wind Farm PHC Passive Heave Compensation Ф Hole factor for slip resistant bolts PIC Person In Charge PLEM Pipeline End Manifold PLET Pipeline End Termination PMS Positioning Monitoring System PNR 'Point of No Return' PRT Pipeline Recovery Tooling/Tool QC Quality Control QTF Quadratic Transfer Function RAO 'Response Amplitude Operator' RCS 'Recognized Classification Society' RCSC Research Council on Structural Connections RIB Rigid Inflatable Boat Rd Design resistance Standard — DNVGLSTN001. 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Requires a valid subscription to be used MPME Page 45 'Remotely (Controlled) Operated Vehicle' Rn Nominal slip resistance RPL Route Planning List RTBL Required Towline Breaking Load SAR Synthetic Aperture Radar SART Search and Rescue Radar Transponder SCF Stress Concentration Factor SCR Steel Catenary Riser SE Shore End SF Safety Factor SHL 'Static Hook Load' SIMOPS 'Simultaneous Operations' SJA Safe Job Analysis SKL 'Skew Load Factor' SLS 'Serviceability Limit State' SMC Safety Management Certificate SMO Safest Mode of Operation SMS 'Safety Management System' SMYS 'Specified Minimum Yield Stress' SOLAS International Convention for the Safety Of Life At Sea, /139/ SOPEP Shipboard Oil Pollution Emergency Plan SPMT 'SelfPropelled Modular Transporter' SPS Special Purpose Ship SQRA SemiQuantitative Risk Analysis SSCV Semisubmersible crane vessel STF Storm Factor SWL 'Safe Working Load' TA Thruster Assist TAM Task Appropriate Mode Tb Minimum fastener pretension for bolted connections TBL Towline Breaking Load TC Contingency period TCG Transverse Centre of Gravity Standard — DNVGLSTN001. 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Requires a valid subscription to be used ROV Page 46 Touchdown point Te or Teff 'Tug efficiency' TLP Tension Leg Platform TMPS 'Tug Management Positioning System' TMS Tether Management System Tp Peak period TPOP Planned operational Period (without contingencies, TPR 'Towline Pull Required' TR Operation Reference Period (including contingencies, Tsafe Time to safely cease the operation TWF Time between weather forecasts Tz Zeroup crossing period for waves UHF Ultra High Frequency UK United Kingdom UKC 'UnderKeel Clearance' ULC 'Ultimate Load Capacity' ULS 'Ultimate Limit State' USBL Ultra Short Baseline Array UT 'Ultrasonic Testing' UTM Universal Transverse Mercator UV Ultra Violet UXO Unexploded Ordnance VCG Vertical Centre of Gravity VHF Very High Frequency VIV Vortex Induced Vibration VLA Vertical Load Anchors VMO VERITAS Marine Operations WD Water Depth WF Weather Forecast WHA 'Wind Heeling Arm' Wld Lower bound design weight WLL 'Working Load Limit' WMO World Meteorological Organisation Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used TDP TC) TC) Page 47 Welding Procedure Specification Wrt with respect to WSD Working Stress Design (effectively the same as ASD) Wud Upper bound design weight Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used WPS Page 48 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 2 PLANNING AND EXECUTION 2.1 Introduction 2.1.1 Scope 2.1.1.1 This Section includes the general requirements for planning, organization, execution and documentation of marine operations. 2.1.2 Revision history 2.1.2.1 The following changes have been made: — — — — — — — — — — — — — General: Editorial changes to improve clarity. [2.2.5.3]: New clause with planning and design sequence diagram included. [2.2.5.4]: New clause added. [2.2.5.5]: New clause added. [2.6.5.2]: New guidance note added. [2.6.6.2]: Clause modified. [2.6.9.5]: New guidance note about wave period uncertainty added. [2.6.10.4]: Clause modified to clarify use of provided alpha factors. [2.6.12.1]: Clause modified to allow option to use LRFD alpha factors where not limited by strength considerations. [2.9.2.2]: Guidance note modified to reference [3.4.15.3]. [2.11.1.4]: Clause modified to shall from should. [2.11.6]: Title modified. [2.11.6.1] Clause modified. 2.1.2.2 The changes made to this section for the June 2016 edition are shown in App.A. 2.2 General project requirements 2.2.1 Project organisation 2.2.1.1 An appropriate Project organisation chart shall be set up, illustrating how the marine operations integrate with the rest of the project. 2.2.1.2 All project interfaces between (key) contractors shall be clearly defined. 2.2.1.3 For organisation during the marine operation see [2.8]. 2.2.2 Health, safety and environment 2.2.2.1 Personnel safety shall be duly considered throughout the marine operation(s). This subject shall be managed by the client or his nominated contractor in accordance with local jurisdiction, as well as appropriate guidelines and specifications regarding health, safety and the environment (HSE). Guidance note: By following the recommendations in this standard it is assumed that the safety of personnel and an acceptable working environment are ensured in general during the operations. However, specific personnel safety issues are not covered. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 49 2.2.3 Jurisdiction 2.2.3.1 Marine operations are subject to national and international regulations and standards on personnel safety and protection of the environment. It should also be noted that a marine operation can involve more than one nation’s area of jurisdiction, and that for barges and vessels the jurisdiction of the flag state will apply. Documented relevant regulatory approval is a prerequisite to MWS approval. 2.2.3.2 If a part of the marine operations is to be carried out near other facilities or their surroundings any safety zone(s) defined by the owner shall be duly considered. 2.2.4 Quality assurance and administrative procedures 2.2.4.1 A quality management system in accordance with the current version of ISO 9001, /106/, or equivalent should be adopted by the designer(s) and installation contractor(s) and be in place. 2.2.5 Technical procedures 2.2.5.1 Technical procedures shall be in place to control engineering related to the marine activities. 2.2.5.2 The technical procedures shall consider the planning and design process. For this process it is recommended that the following sequence is adopted: a) b) c) d) e) f) Identify relevant and applicable regulations, rules, company specifications, codes and standards, both statutory and selfelected. Identify physical limitations. This may involve presurveys of structures, local conditions and soil parameters. Plan the overall operation i.e. evaluate operational concepts, available equipment, limitations, economic consequences, etc. Describe/define unambiguously with adequate detailing the design basis and main assumptions, see [2.2.7]. Carry out engineering and design analyses. Develop operation procedures. 2.2.5.3 The indicated sequence is illustrated in Figure 21 where the engineering and design verification and the operational procedures should be considered as an iterative process. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 50 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used endofguidancenote 2.2.5.4 A review of all operations, from start to finish of the marine operation, shall be performed in order to identify the analysis scope. Guidance note: In the initial phase of design, simplified checks of critical operations are typically performed, while in the final design, detailed analyses are typically required. endofguidancenote 2.2.5.5 Analyses shall be performed to ensure that relevant limit state criteria are satisfied for environmental conditions up to and including the operational limiting criteria, OPLIM. The analyses shall form the basis for establishing applicable operational parameters (e.g. lay angle, layback etc.) to ensure that relevant limit state criteria are not exceeded for product, vessel, equipment and installation aids. Guidance note: Where applicable, the hydrodynamic modelling of product and components could be done in accordance with DNVGLRPC205 /46/. endofguidancenote 2.2.5.6 The procedures shall include sufficient information to ensure agreement and uniformity on all relevant matters such as: a) b) c) d) e) f) g) International and national standards and legislation Certifying authority/regulatory body standards Marine warranty survey company standards or guidelines Project criteria Design basis Metocean criteria Calculation procedures Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 51 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 21 Planning and design sequence Change management. Guidance note: It will also normally be applicable to include requirements to assure compliance, where relevant, with any peerreviewed best industry practice, e.g. IMCA, MTS, GOMO, NORSOK, etc. endofguidancenote 2.2.6 New technology 2.2.6.1 Design and planning of marine operations shall as far as feasible be based on well proven principles, techniques, systems and equipment. 2.2.6.2 If new technology or existing technology in a new environment is used, this technology shall be documented through an acceptable qualification process, e.g. in DNVGLRPA203, /45/. 2.2.7 Design basis and design brief 2.2.7.1 A design basis and/or a design brief shall be developed and provided for early acceptance in order to obtain a common basis and understanding for all parties involved during design, engineering and verification. 2.2.7.2 The Design Basis should describe the basic input parameters, main assumptions, characteristic environmental conditions, characteristic loads/load effects, load combinations and load cases, including those for the proposed marine operations. 2.2.7.3 The Design Brief(s) should describe the planned verification activities, analysis methods, software tools, input specifications, acceptance criteria, etc. 2.3 Technical documentation 2.3.1 General 2.3.1.1 Fulfilment of all the requirements in this standard applicable for the considered marine operation(s) shall be properly documented. Guidance on required documentation is given throughout this standard. However, it shall always be thoroughly evaluated if additional documentation is required. 2.3.1.2 A document plan describing document hierarchy, issuance schedule and scope for each document should be provided for major marine operations/projects. Guidance note: Normally this will be in the form of MDR(s) that are distributed for review/markup by involved parties including the MWS Company. endofguidancenote 2.3.1.3 A system/procedure ensuring that all required documentation is produced in due time and distributed according to plan, should be implemented. 2.3.1.4 It shall be ensured that all the documentation pertaining to a specific marine operation has been accepted by Authorities, Company, other Contractors and MWS, as relevant, before any operation starts. 2.3.2 Documentation required 2.3.2.1 The design basis shall be clearly documented, see [2.2.7]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 52 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used h) 2.3.2.3 The acceptability of the following shall be documented: the object, all equipment, temporary or permanent structures, vessels, etc. involved in the operation. Recognized certificates (e.g. classification documents) are normally acceptable as documentation if the basis for certification is clearly stated and complies with the philosophy and intentions of this standard. Guidance note 1: By basis for certification it is meant acceptance standard, basic assumptions, design loads, including dynamics, limitations, etc. For items without certificates see [2.3.2.4]. endofguidancenote Guidance note 2: Note that all elements of the marine operation should be properly documented. This also includes onshore facilities such as quays, bollards and foundations. endofguidancenote 2.3.2.4 Design calculations/analysis shall be documented by design reports and drawings. 2.3.2.5 The condition of all involved equipment, structures and vessels shall be documented as acceptable by means of certificates and test, survey and NDT reports. Guidance note: For vessels, such documentation may be recent inspections to acceptable industry standards, e.g. OVID or CMID, provided all relevant nonconformances are closed out. See also [2.11.2]. endofguidancenote 2.3.2.6 Operational aspects shall be documented in form of operation manuals and records. 2.3.2.7 Relevant qualifications of key personnel shall be documented. rd 2.3.2.8 Required 3 also [2.4.4]. Party verification, e.g. to fulfil the warranty clause, shall be properly documented. See 2.3.3 Documentation quality and schedule 2.3.3.1 An integrated document numbering system for the entire project is recommended, including documents produced by client, contractors, subcontractors and vendors. 2.3.3.2 Documents relating to marine operations should be grouped into levels according to their status, for example: a) b) c) Criteria and design basis documents Procedures and operations manuals Supporting documents, including engineering calculations, systems operating manuals and equipment specifications and certificates. 2.3.3.3 The documentation shall demonstrate that philosophies, principles and requirements of this standard are complied with. This documentation shall be provided to the MWS Company. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 53 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.3.2.2 Environmental conditions for the actual area shall be documented by reliable statistical data, see Sec.3. The operation and document type dictates the level of review by the MWS company. The following terms have been used as an indication of the level of detail: — Documented – An indepth document that is subjected to a detailed review by the MWS company e.g. analysis reports, procedures and operation manuals — Submitted – A document that is provided to the MWS company in advance where the checking is limited e.g. a certificate to confirm that piece of equipment has the required capacity. In some cases this could be immediately prior to the operation but this may lead to delays if the documents are incorrect and/or insufficient. endofguidancenote 2.3.3.4 Documentation for marine operations shall be selfcontained, or clearly refer to other relevant documents. 2.3.3.5 The quality and details of the documentation shall be such that it allows for independent reviews of plans, procedures and calculations, for all parts of the operation. 2.3.3.6 All significant updates shall be clearly identified in revised documents. 2.3.3.7 The document schedule shall allow for the required (agreed) time for independent reviews. Guidance note: The time available for review should be at least 10 working days, and more for complex documents. endofguidancenote 2.3.4 Input documentation 2.3.4.1 Applicable input documentation, such as; — — — — — documents covering the aspects described in [2.2.5], relevant parts of contractual documents, concept descriptions, basic/FEED engineering results, environmental studies including weather window analysis for weather restricted operation. should be identified before any detailed design work is performed. 2.3.5 Output documentation 2.3.5.1 Documentation shall be prepared to prove that all relevant design and operational requirements are fulfilled. Typical output documentation is: a) b) c) d) Planning documents including design briefs and basis, schedules, concept evaluations, general arrangement drawings and specifications. Design documentation including motion analysis, load analysis, global strength analysis, local design strength calculations, stability and ballast calculations and structural drawings. Operational manuals/procedures, see [2.3.7] and [2.9.5]. Operational records, see [2.3.8]. 2.3.6 Availability of technical documentation 2.3.6.1 All relevant documentation shall be available and accessible on site or on board during execution of the operation. In addition to the marine operations manual this should include the documents referenced therein. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 54 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 2.3.6.3 Vessel and equipment certificates and NDT reports shall be submitted. See [B.1] and [B.2] for the information that is typically required. Guidance note: In order to avoid possible delays due to unacceptable or incomplete documentation, it is recommended that such documentation is submitted for review as soon as possible. endofguidancenote 2.3.6.4 Procedure documents, intended to be used as an active tool during marine operations should include a section which clearly shows their references to higher and lower level documents, and should list all inter related documents. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 55 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.3.6.2 The top level procedure document should define the OnScene Commander in the event of an emergency situation and the interfaces between the various parties involved. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: A document organogram is often helpful as shown in Figure 22. Figure 22 Example of document organogram endofguidancenote 2.3.7 Marine operation manuals 2.3.7.1 An operational procedure shall be developed for the planned operation, and shall reflect characteristic environmental conditions, physical limitations, design assumptions and tolerances. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 56 For complex operations it is recommended that a high level presentation of the marine operation is made available as an animation or picture series. See also [2.8.3]. endofguidancenote 2.3.7.2 The operational procedures shall be described in a marine operation manual covering all aspects of the operation and should include the following, as applicable: a) b) c) d) e) f) g) h) i) j) k) l) m) n) o) p) q) r) s) t) u) v) w) x) y) z) aa) ab) ac) ad) reference documents general arrangement permissible load conditions outline execution plan organogram and lines of command jobdescriptions for key personnel safety plan, see [2.3.7.5] authorities and permits including notification and approval requirements contractual approvals and hand over, see also [2.3.7.4] environmental criteria, including design and operational criteria weather (forecast) and current/wave reporting operational bar chart, showing the anticipated duration of each activity, interrelated activities, key decision points, hold points specific stepbystep instructions (procedures/task plans) for each phase of the operation including sequence, timing, resources and check lists reference to related drawings and calculations, e.g. environmental loads, moorings, ballast, stability, bollard pull permissible draughts, trim, and heel and corresponding ballasting plan how to handle any changes in the procedure during the operation, see also [2.2.5.6] h). contingency and emergency plans emergency preparedness bridging document monitoring during the operation, see [2.9.5] clearances and tolerances systems and equipment including layout systems and equipment operational instructions vessels involved tow routes and ports of refuge navigation safety equipment recording and reporting routines sample forms equipment operation history check lists for preparation and performance of the operation. 2.3.7.3 Operational limiting criteria for marine operations or parts thereof shall be clearly stated in the Manual. 2.3.7.4 The Manual shall describe the decision point for issuing the CoA from the MWS company. It may also be found relevant to include (other) “gates” at which agreement from representatives of the principal parties involved should be obtained before continuing to next stage of operation. 2.3.7.5 A safety plan shall be included in the operation manual. This plan consists of the safety rules that apply to minimise the following risks encountered during each operation: a) Risks inherent from the metocean conditions Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 57 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Risks Risks Risks Risks incurred by construction, transport, installation and commissioning activities to the environment due to simultaneous operations (SIMOPS) – see IMCA M 203, /83/ due to working on live assets, etc. 2.3.7.6 Essential documentation in the form of certificates, release notes and classification documents for all equipment and vessels involved in the marine operation shall be enclosed and/or listed in the Manual. See also [2.3.6.3]. 2.3.8 Operation records and reporting 2.3.8.1 The execution of marine operations shall be logged. Recording form templates shall be included in the marine operations manual. 2.3.8.2 The following should as a minimum be recorded during the operation: a) b) c) d) e) log of (main) tasks carried out any modifications in the agreed procedure unexpected events and any deviations from or alterations of procedure imposed by such environmental conditions and critical monitoring results. 2.3.8.3 Any significant modifications in the agreed procedure shall be reported promptly to the MWS Company. Guidance note: It is recommended that all changes to previously agreed/approved procedures are signed off by the principal representatives of the parties involved. See also [2.3.7.2] p), and that this is described in the MOC procedure. endofguidancenote 2.3.8.4 For larger projects, communications to the client (and MWS company) on site should be confirmed in writing, e.g. by daily reports. 2.3.8.5 Regular, at least daily, reports shall be issued to MWS company from operations (e.g. towage) where the MWS company is not attending. 2.3.8.6 Any incidents, accidents or nearmisses relevant to the safety of the structure or future marine operations shall be reported to MWS company. 2.4 Risk management 2.4.1 General 2.4.1.1 Risk management shall be applied to the project to reduce the overall risk. The preferred approach is to address the following: a) b) c) d) Identification of potential hazards Preventative measures to avoid hazards wherever possible Controls to reduce the potential consequences of unavoidable hazards Mitigation of the consequences, should hazards occur. 2.4.1.2 The overall responsibility for risk management shall be clearly defined when planning marine operations. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 58 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used b) c) d) e) It is recommended that risk management is performed according to DNVGLRPN101, /54/, in order to ensure a systematic evaluation and handling of risk. It is also a premise for a successful risk management that a project team with sufficient competence to understand the marine operation and the potential risk/hazard is mobilized, see [2.8]. endofguidancenote 2.4.1.3 Risk evaluations shall be carried out at an early stage for all marine operations in order to define the extent of risk management required, and to identify and mitigate risk as early in the design process as possible. Guidance note 1: The type and amount of risk evaluations should be based on the complexity of each marine operation. DNVGLRPN101 [D.5], /54/, gives advice on how to carry out initial risk evaluations. The effect of (planned) redundancy, backup, safety barriers, and emergency procedures should be taken into account in the (initial) risk estimates. Contingency situations with a documented (joint) probability of occurrence less than 104 per operation may be disregarded. endofguidancenote Guidance note 2: Ideally, each of the various studies outlined should be managed by a competent independent person familiar with the overall concept, but outside the team carrying out the relevant system or structure design or operational management. endofguidancenote 2.4.1.4 Risk assessments shall be documented and the mitigated risks accepted by the MWS company. 2.4.1.5 Detailed hazard studies should include the personnel and organisations involved in the design of structures and systems, as well as those involved in the marine operation and the MWS company. The studies shall be performed for: a) b) Each major marine operation. Each major system essential to the performance and safety of marine operations. For example, the power generation and the ballast and compressed air systems. Guidance note: Hazard identification activities (see [2.4.2]) may be used to systematically evaluate risk applicable to any operation, to compare levels of risk between alternative proposals or between known and novel methods, and to enable rational choices to be made between alternatives. endofguidancenote 2.4.2 Hazard identification activities 2.4.2.1 Risk identification techniques and methods shall be used as applicable for the intended operation. Examples of applicable techniques and methods are: a) b) c) d) e) f) g) h) i) Preliminary risk assessment in order to assess concepts and methods Hazard Identification Analysis (HAZID) Early Procedure Hazard and Operability study (EP HAZOP) Hazard Identification and Risk Assessment (HIRA) Design Review (DR) System HAZOP Failure Mode Effect (and Criticality) Analysis (FMEA/FMECA) Procedure HAZOP SemiQuantitative Risk Analysis (SQRA) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 59 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Safe Job Analysis (SJA) / Job Safety Analysis (JSA). Guidance note: DNVGLRPN101 App.B, /54/, defines and describes most of the risk identifying activities listed above in detail. The HAZOP is not only focused on possible hazards, but also on issues related to the operability of an activity or operation, the plant or system, including possible improvements. endofguidancenote 2.4.2.2 All identified possible hazards shall be reported and properly managed. 2.4.3 Risk reducing activities 2.4.3.1 Relevant corrective actions from the risk identifying activities shall be implemented in the planning and execution of the operations. 2.4.3.2 The following risk reducing activities for marine operations shall be used as applicable for the intended operation: a) b) c) d) e) f) g) h) i) j) k) Operational feasibility assessments Document verification Familiarisation Personnel safety plans Emergency preparedness Marine readiness verification Inspection and testing Survey of vessels Toolbox talk Safe Job Analysis / Job Safety Analysis Survey of operations. Guidance note: DNVGLRPN101 App.C, /54/, describes the above listed risk reducing activities in detail. Note that Safe Job Analysis is in DNVGLRPN101, /54/, mentioned only in DNVGLRPN101 App.B Hazard Identification Activities. endofguidancenote rd 2.4.4 3 party verification and MWS rd 2.4.4.1 As a part of the risk management the requirements for 3 Party verification of calculations, procedures, vessels, equipment, etc. and survey of the operations shall be defined. 2.4.4.2 If applicable a Marine Warranty Survey company shall be contracted to ensure that the marine warranty clause is fulfilled. 2.4.4.3 It shall be ensured that the MWS (marine warranty survey) Company’s (minimum) scope of work has been adequately defined to fulfil the intention of the marine warranty clause. Specific requirements of warranty clause to be given to MWS as early as possible. 2.4.4.4 Thorough knowledge of this standard shall be documented in order to carry out marine warranty survey with the intention of confirming compliance with this standard. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 60 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used j) 2.5.1 Philosophy 2.5.1.1 Marine operations shall be planned according to safe and sound practice, and according to defined codes and standards. 2.5.1.2 A marine operation shall be designed to bring an object from one defined safe condition to another. Guidance note: “Safe Condition” is defined as a condition where the object is considered to be exposed to a normal level of risk of damage or loss (i.e. the risk is similar to that expected for the inplace condition). Normally this will imply a (support) condition for which it is documented that the object fulfils the design requirements applying the relevant weather unrestricted, see [2.6.6], environmental loads. endofguidancenote 2.5.1.3 Risk management, see [2.4], should normally be included in the planning. 2.5.2 Type of operation 2.5.2.1 To define the (sub) operations as either weather unrestricted or weather restricted can have a great impact on the safety and cost of the operation. Hence, the type of operation should, if possible, be defined early in the planning process. See also [2.6.5]. 2.5.2.2 The planning and design of marine operations should normally be based on the assumption that it can be necessary to halt the operation and bring the object to a safe condition e.g. by reversing the operation. 2.5.2.3 For operations passing a point where the operation cannot be reversed, a point of no return (PNR) shall be defined. The first safe condition after passing a PNR shall be defined and considered in the planning. 2.5.3 Operations in ice areas 2.5.3.1 The risk of significant ice shall be considered in the operation planning. I.e. operations in ice areas should be subject to suitable ice management operations, details of which appear in [B.3]. 2.5.3.2 Towages in ice are considered in [11.19] and voyages in [K.11]. 2.5.3.3 The evacuation from rigs/offshore structures in ice shall be properly planned. Guidance note: ISO 19906, /103/ Clause 18 and Annex A.18 provide appropriate normative requirements and informative guidance for escape, evacuation and rescue (EER) operations from Arctic offshore structures. Additional guidance on the design of an appropriate EER system may be found in Barents 2020 (2012), /21/, Chapter 4. This includes performance standards for emergency response vessels and guidance for Arctic evacuation methods. endofguidancenote 2.5.4 Contingency and emergency planning and procedures 2.5.4.1 All possible emergency situations shall be identified, and contingency procedures or actions shall be prepared for these situations. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 61 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.5 Planning of marine operations Foreseeable emergencies and contingencies can include: a) Severe weather b) Planned precautionary action in the event of forecast severe weather c) Structural parameters approaching preset limits d) Stability parameters approaching preset limits e) Failure of mechanical, electrical or control systems f) DP or power failure "black ship" g) Fire h) Collision, grounding i) Leakage, flooding j) Pollution k) Structural failure l) Equipment failure m) Mooring failure n) Icebergs, excessive ice (see also [2.5.3.3]) o) Human error p) Man overboard q) Personnel accidents or medical emergencies r) Terrorism and sabotage. endofguidancenote 2.5.4.2 Possible emergency situations to be considered may be defined or excluded based on conclusions from risk identifying activities, see [2.4.2]. 2.5.4.3 Contingency and emergency planning shall consider redundancy, backup equipment, supporting personnel, emergency procedures and other relevant preventive measures and actions. 2.5.4.4 The contingency procedures should form part of the operational procedures. 2.6 Operation and design criteria 2.6.1 Introduction 2.6.1.1 Marine operations shall be executed ensuring that the assumptions made in the planning and design process are fulfilled. 2.6.1.2 Marine operations shall be classified as weather restricted or as weather unrestricted (see [2.6.5]). Guidance note: The main difference between these operations is how the environmental loads are selected. See Table 51. endofguidancenote 2.6.2 Operation reference period TR 2.6.2.1 The duration of marine operations shall be defined by an operation reference period, TR: TR = TPOP+TC Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 62 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: TR TPOP TC = Operation reference period = Planned operation period = Estimated maximum contingency time. 2.6.2.2 The start and completion points for the intended operation or parts of the operation shall be clearly defined. See also [2.6.7.3] and [2.6.7.4]. 2.6.3 Planned operation period – TPOP 2.6.3.1 The planned operation period, TPOP, shall if possible be based on a detailed schedule for the operation. Guidance note: In cases (e.g. in the early planning phase) were a detailed schedule is not available TPOP can be based on experience with similar operations. endofguidancenote 2.6.3.2 The time estimated for each task in the schedule should be based on a reasonably conservative assessment of experience with same or similar tasks. Guidance note: Normally a probability of (maximum) 1020% of exceeding TPOP during the actual operations should be aimed at. endofguidancenote 2.6.3.3 Time delaying incidents that are experienced frequently should be included in TPOP. 2.6.4 Estimated contingency time – TC 2.6.4.1 Contingency time, TC, shall be added to cover: a) b) c) General uncertainty in the planned operation time, TPOP Unproductive time during the operation, e.g. to solve unforeseen procedural problems Possible contingency situation(s), see [2.5.4], that will require additional time to complete the operation. Guidance note: It is normally not necessary to add the estimated additional time from several (two) rare independent contingency situations. However, it can be relevant to consider that more than one of the frequently experienced incidents mentioned in [2.6.3.3] (e.g. equipment malfunction) may occur. endofguidancenote 2.6.4.2 If TPOP uncertainties and the required time for contingency situations is not assessed in detail the operation reference period should normally be taken to be at least twice the planned operation period, i.e.TR ≥ 2 × TPOP. Guidance note: A contingency time TC of 50% of TPOP can normally be accepted for: — Operations with an extensive experience basis from similar operations, e.g. positioning (anchoring) of MOUs. — Towing operations with redundant tug(s) and properly assessed towing speed, see Sec.11 for more information. — Repetitive operations where TPOP has been accurately defined based on experience with the actual operation and vessel. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 63 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used where: Guidance note: TC < 6 hours is unlikely to be acceptable except for short simple marine operations involving only robust equipment. endofguidancenote 2.6.5 Weather unrestricted and restricted operations 2.6.5.1 An operation shall be defined as weather unrestricted, see [2.6.6], or weather restricted, see [2.6.7]. See [2.5.2] and Figure 23 for further guidance. 2.6.5.2 Operations with a duration that is too long to be planned as weather restricted, see [2.6.7.1], may still be defined as weather restricted if a continuous surveillance of actual and forecasted weather conditions is implemented, and the operation can be halted and the object brought into a safe condition within the maximum allowable period for a weather restricted operation. See flowchart in Figure 23. Guidance note 1: If found beneficial also operations with TPOP < 72h and TR < 96h may also be planned with possible stops, see also [2.6.7.7]. endofguidancenote Guidance note 2: The indicated maximum allowable period for a weather restricted operation, as per [2.6.7.1], is a theoretical value. For most continuous operations a considerably shorter period should be documented in order to make the operation feasible without risking too much delay. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 64 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.6.4.3 A contingency time TC less than 6 hours is normally not acceptable unless thoroughly documented. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 23 Flow chart to determine whether an operation is weather restricted or weather unrestricted 2.6.6 Weather unrestricted operations 2.6.6.1 Marine operations that cannot be defined as weather restricted (see [2.6.5] and [2.6.7]) shall be defined as weather unrestricted operations. Environmental criteria for these operations should be based on extreme value statistics, see Sec.3. If found beneficial, operations of shorter duration may also be defined as weather unrestricted. Guidance note: A reduction in the weather criteria based on extreme value statistics could in some situations be acceptable based on active use of the (long term) weather forecast. Such typical situations are: — Operations in areas and seasons where it has been shown and documented that the long term weather forecasts can predict any extreme weather conditions within the defined TR for the operation. — Open (Ocean) voyages where the vessel speed is sufficient to avoid extreme weather conditions. Such a reduction in the design criteria may be accepted by the MWS company, but normally an accidental load case (ALS) considering extreme value statistics should be included. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 65 Guidance note: Note that certain operations require a start criterion although designed for weather unrestricted conditions. Further information is given for the respective operations in this standard. endofguidancenote 2.6.7 Weather restricted operations 2.6.7.1 Marine operations with a reference period (TR) less than 96 hours and a planned operation time (TPOP) less than 72 hours may normally be defined as weather restricted. However, in areas and/or seasons where the duration of the reliable weather forecast is less than 96 hours, the maximum allowable TR is the duration of the reliable forecast. Guidance note: The above indicated limits for TR and TPOP define the maximum allowable period for a weather restricted operation. endofguidancenote 2.6.7.2 A weather restricted operation shall be planned to be executed within a reliable weather window, see Figure 24. 2.6.7.3 The planned operation period start point for a weather restricted operation shall normally be defined as being at the issuance of the last weather forecast. See Figure 24. Figure 24 Operation Periods 2.6.7.4 The operation shall only be considered completed when the object is in a safe condition, see [2.5.1.2]. 2.6.7.5 Restricted operations may be planned with design environmental conditions selected independent of statistical data, i.e. set by owner, operator or contractor. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 66 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.6.6.2 For operations where the design environmental condition is based on extreme value statistics, the operation could theoretically be performed with acceptable risk without considering the weather forecast. However, it is normally not recommended that an operation is started if extreme weather conditions are expected, and a start criterion may apply. If the weather restricted design environmental condition is too low, severe waiting on weather delays can occur. The design environmental condition should be selected based on an overall evaluation of operability i.e. there should be an acceptable probability of obtaining the required weather window. See also [3.3]. endofguidancenote 2.6.7.6 The start of a weather restricted operation is conditional on an acceptable weather forecast, see [2.7.3]. 2.6.7.7 Operations that could be carried out within the maximum allowed period may be planned with (possible) stops in (case of) periods with weather conditions above the OPLIM. The following shall be taken into account: a) b) c) Increased risk for halting (and restarting) due to additional operations. Increased risk due to the nature of the “temporary” safe position of the object. Increased weather risk due to an increased total operation period. 2.6.7.8 If the planning indicated in [2.6.7.7] is implemented the Alpha (α) factors shall be adjusted accordingly, e.g.: — Depending on the risk evaluations in [2.6.7.7] b) and [2.6.7.7] c) it may be applicable to reduce the Alpha factor for the final stage of the operation due to an increased total operation period. — If no significant increased risk is identified due to [2.6.7.7] a) and [2.6.7.7] b) alpha factor(s) according to [2.6.9.3] applies. 2.6.8 Operational limiting criteria 2.6.8.1 Operational limiting environmental criteria (OPLIM) shall be established and clearly described in the marine operation manual. 2.6.8.2 The OPLIM shall not be taken greater than the minimum of: — The environmental design criteria. See [3.3]. — Maximum wind and waves for safe working and object handling (e.g. on vessel deck) or transfer conditions for personnel. — Weather restrictions for equipment (e.g. ROV and cranes). Guidance note: Weather restrictions for equipment should be based on specified limitations if available. They may also be assessed and/or refined based on items as criticality, backup equipment and contingency procedures. endofguidancenote — Limiting weather conditions of diving system (if any). — Limiting conditions for position keeping systems. — Any limitations identified, e.g. in HAZID/HAZOP, based on operational experience with involved vessel(s), equipment, tools, etc. — Limiting weather conditions for carrying out identified contingency plans. 2.6.9 Forecasted and monitored operational limits, alpha factor (α) 2.6.9.1 Uncertainty in both the monitoring and the forecasting of the environmental conditions shall be considered. This should be done by defining a forecasted (and, if applicable, monitored at the operation start) operational criteria OPWF, defined as OPWF = α × OPLIM. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 67 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: To ensemble weather forecasts which identify the expected ‘spread’ of weather conditions and assess the probability of particular weather events could be an alternative for applying the tabulated alpha factors. Such weather forecasts will anyhow give useful additional information to evaluate uncertain weather situations. Further description of ensemble forecasting is in [B.4]. endofguidancenote 2.6.9.2 The planned operation period (TPOP, see [2.6.3]) from issuance of the weather forecast to the operation is completed shall be used as the minimum time for selection of the Alpha Factor. See Figure 24. 2.6.9.3 For operations that can be halted, see [2.6.5.2], the Alpha Factor can normally be selected based on a TPOP defined as the time between weather forecasts plus the required time to safely cease the operation and bring the handled object into a safe condition. If a proper procedure based on continuously reliable (see [2.9.3]) monitoring readings, is established the time between weather forecasts can normally be disregarded in the estimation of TPOP. However, the maximum expected reaction time from monitoring readings above OPWF to initiation of ceasing of the operation, shall be included in TPOP. A reaction time below 2 hours should normally not be considered. 2.6.9.4 The following should be used as guidelines for selecting the appropriate Alpha Factor for waves: a) b) The expected uncertainty in the weather forecast should be calculated based on statistical data for the actual site and the operation schedule, i.e. TPOP. The Alpha Factor should be calibrated to ensure that the probability of exceeding the operational environmental limiting criteria (OPLIM) by more than 50% in 4 LRFD (see [2.6.11]) is less than 10 . Reliable wave and/or vessel response monitoring system(s) and applied weather forecast level, see [2.7.2], could be taken into account. 2.6.9.5 Special considerations should be made regarding uncertainty in the wave periods i.e. if the operation is particularly sensitive to some wave periods (e.g. swell), the uncertainty in the forecasted wave periods shall also be considered. Guidance note: The alpha factors given herein relate only to uncertainty in the wave height. Traditionally, calculations for marine operations have been carried out for the complete range of possible wave periods for a wave height (see [3.4.11]). Hence, there was no need to include uncertainty in the wave period. This approach can be too conservative and therefore different limiting wave heights each with corresponding period ranges have been specified in more recent projects. In such cases, and where the period is critical, it is important that there is ample margin between the forecasted and allowable period. endofguidancenote 2.6.10 Selection of alpha factors 2.6.10.1 The (tabulated) Alpha Factor(s) shall be selected based on: — The applicable table, see [2.6.10.4] and Table 21 — Operational limiting criteria, OPLIM, see [2.6.8] — The planned operational period, TPOP, see [2.6.9.2] 2.6.10.2 The Alpha Factor can be assumed to vary in time for one operation, e.g. for an operation with TPOP= 36 hours, Hs= 4.0 m, the Alpha Factor is 0.79 for the first 12 hours, 0.76 for the next 12 hours and 0.73 for the last 12 hours of the operation. 2.6.10.3 Design wave heights less than one (1) meter are normally not applicable for offshore operations. If a smaller design wave height nevertheless has been applied the Alpha Factor may be duly considered in each case. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 68 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 2.6.10.5 The uncertainty in forecasted and actual weather conditions shall be considered also in other offshore areas than mentioned in [2.6.10.4]. If reliable data is not available to establish alpha factors, see [2.6.9.4], the approach in [2.6.10.4] should also be used for other areas. Guidance note: The tabulated Alpha Factors are based on the work performed in a Joint Industry Project during the years 20052007 with the aim to establish a revised set of αfactors for European waters. For details of the JIP see DNV Report 2006_1756 Rev. 03, “DNV Marine Operation Rules, Revised Alpha Factor JIP Project”. endofguidancenote Table 21 Selection of Alpha Factor table(s) WF level A1 A2 & B C Environmental monitoring? Yes No Yes No Yes No Wave Alpha Factor – LRFD Table 27 Table 26 Table 25 Table 24 Table 23 Table 22 Wave Alpha Factor – ASD/ WSD Table 214 Table 213 Table 212 Table 211 Table 210 Table 29 Wind Alpha Factor – LRFD Table 28 Wind Alpha Factor – ASD/WSD Table 215 2.6.11 Tabulated alpha factor – LRFD method 2.6.11.1 The Alpha Factor for waves applying LRFD, see [5.9.8], shall be selected according to Table 21 and are given in Table 22 through Table 27. Values for wind are in Table 28. Table 22 LRFD Alpha Factor for waves, Level C – No Environmental Monitoring Planned Operation Period [h] Operational limiting (OPLIM) significant wave height [m] Hs = 1 TPOP ≤ 12 0.65 TPOP ≤ 24 0.63 1 < Hs < 2 Hs = 2 2 < Hs < 4 0.76 0.71 4 < Hs < 6 0.79 0.73 Linear Interpolation Hs = 4 0.80 0.76 Linear Interpolation 0.78 Linear Interpolation TPOP ≤ 36 0.62 TPOP ≤ 48 0.60 0.68 0.71 0.74 TPOP ≤ 72 0.55 0.63 0.68 0.72 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS 0.73 Hs≥6 0.76 Page 69 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.6.10.4 In the North Sea and the Norwegian Sea the Alpha Factor table to be used should normally be selected using the tables referenced in Table 21 considering the applied weather forecast (WF) level, see [2.7.2], applicable environmental monitoring, see [2.9.3], and design method (LRFD or ASD/WSD). This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 23 LRFD Alpha Factor for waves, Level C – With Environmental Monitoring Planned Operation Period [h] Operational limiting (OPLIM) significant wave height [m] Hs = 1 1 < Hs < 2 Hs = 2 2 < Hs < 4 Hs = 4 4 < Hs < 6 Hs≥6 TPOP ≤ 4 0.90 0.95 1.00 1.00 TPOP ≤ 12 0.72 0.84 0.87 0.88 TPOP ≤ 24 0.66 TPOP ≤ 36 0.62 TPOP ≤ 48 0.60 0.68 0.71 0.74 TPOP ≤ 72 0.55 0.63 0.68 0.72 Linear Interpolation 0.77 Linear Interpolation 0.71 0.80 0.73 Linear Interpolation 0.82 0.76 Table 24 LRFD Alpha Factor for waves, Level A2 or B – No Environmental Monitoring Planned Operation Period [h] Operational limiting (OPLIM) significant wave height [m] Hs = 1 TPOP ≤ 12 0.68 TPOP ≤ 24 0.66 1 < Hs < 2 Hs = 2 2 < Hs < 4 0.80 4 < Hs < 6 0.83 0.77 Linear Interpolation Hs = 4 0.84 0.80 Linear Interpolation 0.75 0.77 Hs≥6 0.82 Linear Interpolation TPOP ≤ 36 0.65 0.80 TPOP ≤ 48 0.63 0.71 0.75 0.78 TPOP ≤ 72 0.58 0.66 0.71 0.76 Table 25 LRFD Alpha Factor for waves, Level A2 or B – With Environmental Monitoring Planned Operation Period [h] Operational limiting (OPLIM) significant wave height [m] Hs = 1 1 < Hs < 2 Hs = 2 2 < Hs < 4 Hs = 4 4 < Hs < 6 Hs≥6 TPOP ≤ 4 0.90 0.95 1.00 1.00 TPOP ≤ 12 0.72 0.84 0.87 0.88 TPOP ≤ 24 0.66 TPOP ≤ 36 0.65 TPOP ≤ 48 0.63 0.71 0.75 0.78 TPOP ≤ 72 0.58 0.66 0.71 0.76 Linear Interpolation 0.77 0.75 Linear Interpolation Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS 0.80 0.77 Linear Interpolation 0.82 0.80 Page 70 Planned Operation Period [h] Operational limiting (OPLIM) significant wave height [m] Hs = 1 TPOP ≤ 12 0.72 TPOP ≤ 24 0.69 1 < Hs < 2 Hs = 2 2 < Hs < 4 0.84 0.78 4 < Hs < 6 0.87 0.80 Linear Interpolation Hs = 4 0.88 0.84 Linear Interpolation 0.80 Hs≥6 0.86 Linear Interpolation TPOP ≤ 36 0.68 0.84 TPOP ≤ 48 0.66 0.75 0.78 0.81 TPOP ≤ 72 0.61 0.69 0.75 0.79 Table 27 LRFD Alpha Factor for waves, Level A1 – With Environmental Monitoring Planned Operation Period [h] Operational limiting (OPLIM) significant wave height [m] Hs = 1 1 < Hs < 2 Hs = 2 2 < Hs < 4 Hs = 4 4 < Hs < 6 Hs≥6 TPOP ≤ 4 0.90 0.95 1.00 1.00 TPOP ≤ 12 0.78 0.91 0.95 0.96 TPOP ≤ 24 0.72 TPOP ≤ 36 0.68 TPOP ≤ 48 0.66 0.75 0.78 0.81 TPOP ≤ 72 0.61 0.69 0.75 0.79 Linear Interpolation 0.84 0.78 Linear Interpolation 0.87 0.80 Linear Interpolation 0.90 0.84 2.6.11.2 The appropriate Alpha Factor for wind should be selected (estimated) considering the following: — — — — Statistical data and local experience for the actual site. Planned operation period from issuance of weather forecast, TPOP. Applied wind speed compared with the maximum possible wind speed, i.e. 10 year return wind speed. Criticality of exceeding the design wind speed, e.g. by considering the contribution from wind on the total design load. 2.6.11.3 If no reliable data is available the Alpha Factors indicated in Table 28 shall be considered as the maximum allowable. Table 28 LRFD Recommended Alpha Factor for wind Planned Operation Period Operational limiting (OPLIM) wind speed – Vd Vd < 0.5 x V10 year return Vd > 0.5 x V10 year return TPOP ≤ 24 0.80 0.85 TPOP ≤ 48 0.75 0.80 TPOP ≤ 72 0.70 0.75 2.6.11.4 The possibility for unpredictable strong wind, e.g. squalls and polar lows, should be duly considered in the selected Alpha Factor for wind (and if relevant also for waves). Alternatively, if possible, operational contingency actions that sufficiently reduce the criticality of such wind, could be planned. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 71 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 26 LRFD Alpha Factor for waves, Level A1 – No Environmental Monitoring 2.6.12.1 The Alpha factors for waves and wind applicable to the ASD/WSD, see [5.9.7] design approach shall be selected based on Table 21 and are shown in Table 29 through Table 215. These factors are calibrated for the ASD/WSD format, with the objective of ensuring that a given structure will be treated equally under ASD/WSD and LRFD. The Alpha factors for ASD/WSD are therefore lower than the values given in [2.6.11] because the inherent safety margin in ASD/WSD checks is less than that in LRFD checks, so higher design values are needed to achieve this equivalence. Where the operational limiting criteria are not the result of strength considerations the alpha factors given in [2.6.11] may be used. Table 29 ASD/WSD Alpha Factor for waves, Level C – No Environmental Monitoring Planned Operation Period [h] Operational Limiting (OPLIM) significant wave height [m] Hs = 1 TPOP ≤ 12 0.58 0.68 0.70 0.71 TPOP ≤ 24 0.56 0.65 0.68 0.69 TPOP ≤ 36 0.55 TPOP ≤ 48 0.53 0.61 0.63 0.66 TPOP ≤ 72 0.49 0.56 0.61 0.64 1 < Hs < 2 Linear Interpolation Hs = 2 2 < Hs < 4 Linear Interpolation 0.63 Hs = 4 0.65 4 < Hs < 6 Linear Interpolation Hs≥6 0.68 Table 210 ASD/WSD Alpha Factor for waves, Level C – With Environmental Monitoring Planned Operation Period [h] Operational Limiting (OPLIM) significant wave height [m] Hs = 1 1 < Hs < 2 Hs = 2 2 < Hs < 4 Hs = 4 4 < Hs < 6 Hs≥6 TPOP ≤ 4 0.80 0.85 0.89 0.89 TPOP ≤ 12 0.64 0.75 0.77 0.78 TPOP ≤ 24 0.59 TPOP ≤ 36 0.55 TPOP ≤ 48 0.53 0.61 0.63 0.66 TPOP ≤ 72 0.49 0.56 0.61 0.64 Linear Interpolation 0.69 0.63 Linear Interpolation Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS 0.71 0.65 Linear Interpolation 0.73 0.68 Page 72 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.6.12 Tabulated alpha factor ASD/WSD method Planned Operation Period [h] Operational Limiting (OPLIM) significant wave height [m] Hs = 1 TPOP ≤ 12 0.61 TPOP ≤ 24 0.59 1 < Hs < 2 Hs = 2 2 < Hs < 4 0.71 4 < Hs < 6 0.74 0.69 Linear Interpolation Hs = 4 0.75 0.71 Linear Interpolation 0.67 0.69 Hs≥6 0.73 Linear Interpolation TPOP ≤ 36 0.58 0.71 TPOP ≤ 48 0.56 0.63 0.67 0.69 TPOP ≤ 72 0.52 0.59 0.63 0.68 Table 212 ASD/WSD Alpha Factor for waves, Level A2 or B – With Environmental Monitoring Planned Operation Period [h] Operational Limiting (OPLIM) significant wave height [m] Hs = 1 1 < Hs < 2 Hs = 2 2 < Hs < 4 Hs = 4 4 < Hs < 6 Hs≥6 TPOP ≤ 4 0.80 0.85 0.89 0.89 TPOP ≤ 12 0.64 0.75 0.77 0.78 TPOP ≤ 24 0.59 TPOP ≤ 36 0.58 TPOP ≤ 48 0.56 0.63 0.67 0.69 TPOP ≤ 72 0.52 0.59 0.63 0.68 Linear Interpolation 0.69 Linear Interpolation 0.67 0.71 0.69 Linear Interpolation 0.73 0.71 Table 213 ASD/WSD Alpha factors (waves) Level A1 – No Environmental Monitoring Planned Operation Period [h] Operational Limiting (OPLIM) significant wave height [m] Hs = 1 TPOP ≤ 12 0.64 TPOP ≤ 24 0.61 1 < Hs < 2 Hs = 2 2 < Hs < 4 0.75 0.69 4 < Hs < 6 0.77 0.71 Linear Interpolation Hs = 4 0.78 0.75 Linear Interpolation 0.77 Linear Interpolation TPOP ≤ 36 0.61 TPOP ≤ 48 0.59 0.67 0.69 0.72 TPOP ≤ 72 0.54 0.61 0.67 0.70 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS 0.71 Hs≥6 0.75 Page 73 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 211 ASD/WSD Alpha factors (waves) Level A2 or B – No Environmental Monitoring Planned Operation Period [h] Operational Limiting (OPLIM) significant wave height [m] Hs = 1 1 < Hs < 2 Hs = 2 2 < Hs < 4 Hs = 4 4 < Hs < 6 Hs≥6 TPOP ≤ 4 0.80 0.85 0.89 0.89 TPOP ≤ 12 0.69 0.81 0.85 0.85 TPOP ≤ 24 0.64 TPOP ≤ 36 0.61 TPOP ≤ 48 0.59 0.67 0.69 0.72 TPOP ≤ 72 0.54 0.61 0.67 0.70 Linear Interpolation 0.75 0.69 Linear Interpolation 0.77 Linear Interpolation 0.71 0.80 0.75 2.6.12.2 If no reliable data is available the Alpha Factors indicated in Table 215 shall be considered as the maximum allowable in ASD/WSD. See also [2.6.11.2] and [2.6.11.4]. Table 215 ASD/WSD Alpha factors (wind all forecast requirements) Planned Operation Period Operational Limiting Wind Speed (Vd) Vd < 0.5 x V10 year return Vd > 0.5 x V10 year return TPOP ≤ 24 0.71 0.76 TPOP ≤ 48 0.67 0.71 TPOP ≤ 72 0.62 0.67 2.7 Weather forecast 2.7.1 General 2.7.1.1 Arrangements shall be made for receiving weather forecasts at regular intervals before, and during, the marine operations. Such weather forecasts shall be from recognized sources and be project specific. Guidance note: Public domain weather forecast(s) may be found acceptable as Level C forecasting, but the inherent increased uncertainty should be considered. Applicable Alpha Factors are found by multiplying the factors in Table 22 (Table 29) and Table 215 (Table 216) with 0.75. endofguidancenote 2.7.1.2 Independent weather forecasts shall be taken from different weather providers. The providers shall be different organizational bodies. Each body shall document which different atmospheric and oceanographic models have been evaluated and taken into account in the generation of the forecasts. 2.7.1.3 The weather forecasts (WF) shall be area/route specific. For nonstationary marine operations (e.g. sea voyages or subsea laying operations) it shall be ensured that weather forecasts comprise the position (at the time of the WF) of the transport vessel/barge and all alternative routes that could be chosen in the period covered by the weather forecast. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 74 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 214 ASD/WSD Alpha factors (waves) Level A1 – With Environmental Monitoring 2.7.1.5 The weather forecasts shall be in writing and the confidence level(s) should be stated. 2.7.1.6 In addition to a general description of the weather situation and its predicted development, the weather forecast shall, as relevant, include: — — — — — — — — wind speed and direction waves and swell, significant and maximum height, mean or peak period and direction rain, snow, lightning, ice etc. tide variations and/or storm surge visibility temperature barometric pressure possibility for unpredictable strong wind, see [2.6.11.4]. for each 12 hours for a minimum of the TR plus 24 hours. In addition an outlook for at least the next 24 hours should normally be included. 2.7.1.7 The forecast shall clearly define forecasted parameters, e.g. average time and height for wind, characteristic wave periods (Tz or Tp). The content and format of the weather forecast should be agreed with the meteorologist in due time before the operation starts. 2.7.2 Weather forecast levels 2.7.2.1 The required weather forecast level shall be selected based on the operational sensitivity to weather conditions and the operation reference period (TR). The following weather forecast levels are defined in this standard: — Level A that applies to major marine operations sensitive to environmental conditions. — Level B that applies to environmental sensitive operations of significant importance with regard to value and consequences — Level C that applies to conventional marine operations less sensitive to weather conditions, and carried out on a regular basis. 2.7.2.2 For operations that require a Level A weather forecast it shall be thoroughly considered to have the dedicated meteorologist present on site. See Table 216 for further advice regarding selection of the forecast level and for requirements to the weather forecast procedure. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 75 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.7.1.4 Weather forecast procedures should consider the nature and duration of the planned operation, see [2.7.2.1]. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 216 Weather forecast levels Weather Forecast Level A1 A2 Operation Sensitivity High C Moderate — multi barge towing — major (e.g. GBS) tow out operations — offshore installation operations — jackup rig moves. — sensitive laying operations Meteorologist on site Yes No Dedicated Meteorologist Yes Yes Minimum independent 2) WF sources 2 Maximum WF interval 12 hours — onshore/inshore lifting — weather routed sea transports — offshore float over — loadout operations — short tows in sheltered waters/ harbour tows — offshore lifting — subsea installation — semisubmersible rig moves — standard sea transports without any specified wave restrictions. — standard laying operations. 4) No No 2 6) 1) Low — towout operations — mating operations Examples B 2) 5) 12 hours No 1 12 hours Notes: 1) See [2.7.1.1] GN. 2) Meteorologist shall be consulted if the weather situation is unstable and/or close to the defined limit. 3) See [2.7.1.2] for definition of independent WF sources. 4) It is assumed that the dedicated meteorologist (and other involved key personnel) will consider weather information/forecasts from several (all available) sources. 5) The most severe weather forecast shall be used. 6) Based on sensitivity with regards to weather conditions smaller intervals may be required. However, see [2.7.3.5]. 2.7.3 Acceptance criteria 2.7.3.1 The acceptance criteria for the weather forecast(s) shall clearly define the applicable limitations, see [2.6.9] and the minimum required weather window, see [2.6.2] and Figure 24. The acceptance criteria shall be included in the marine operation manual. 2.7.3.2 If the weather forecasts received from the two sources do not agree the most severe weather forecast should be considered governing, unless otherwise justified. If the discrepancy between the forecasts is significant the weather situation should be carefully evaluated to determine whether it is too uncertain to safely start an operation. 2.7.3.3 Based on the available weather forecasts the weather situation shall be assessed according to a worst case scenario development. This is particularly important for unstable weather situations and for forecasts which are stated (considered) to be of low confidence. 2.7.3.4 Uncertainties in forecasted weather window duration shall be duly considered i.e. the forecasted weather window duration should be conservatively assessed. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 76 2.8 Organization of marine operations 2.8.1 General 2.8.1.1 The organisation and responsibility of key personnel involved in marine operations shall be established and described before execution of marine operations. The responsibilities and duties of each function shall be clearly defined to minimise uncertainties and overlapping responsibilities. 2.8.1.2 Organisation charts, including names and functional titles of key personnel, shall be included in the marine operations manual. Authority during the operation shall be clearly defined. 2.8.1.3 Operations shall be carried out in accordance with the conditions for design, the approved documentation, and sound practice, such that unnecessary risks are avoided. This is the responsibility of the operation superintendent or manager. 2.8.1.4 Responsibilities in possible emergency situations shall be described. 2.8.1.5 Access to the area for the operation should be restricted. Only authorised personnel should be allowed into the operation area. Guidance note: Where necessary, a suitable security and tracking system should be in use to record personnel on the structure or vessels, to track their whereabouts. endofguidancenote 2.8.2 Qualification and training 2.8.2.1 Operation supervisors shall possess thorough knowledge and have experience from similar operations. Other key personnel shall have knowledge and experience within their area of responsibility. 2.8.2.2 CVs for supervisors and key personnel involved in major marine operations shall be submitted. 2.8.2.3 Vessel manning and personnel qualifications shall as a minimum fulfil statutory requirements. Additional manning shall be considered for complex operations or to satisfy specific project requirements. 2.8.2.4 Adequate training appropriate to each individual’s function and situation should be given, including job training, site safety training and briefings, marine safety and survival training. 2.8.2.5 A qualification matrix is recommended for correct tracking and control of personal qualifications. 2.8.2.6 Computer simulation and training, and/or model tests can give valuable information for the personnel carrying out the operation. Where relevant, a fullmission simulation should be undertaken. 2.8.3 Familiarisation and briefing 2.8.3.1 Operation supervisors shall familiarise themselves with all aspects of the planned operations and possess a thorough knowledge with respect to limitations and assumptions for the design. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 77 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.7.3.5 Weather forecasts are based on extensive computer analyses. In cases where forecast updates are made at intervals of less than 12 hours it shall be documented that the updates are based on sufficient data to be as accurate as ordinary forecasts. 2.8.3.3 Other personnel participating in the operations shall be briefed about the operation with emphasis on their assigned tasks/responsibilities and safety. Guidance note: The use of visual aids for presenting complex marine operations is highly recommended, either through picture series and/or animations. endofguidancenote 2.8.3.4 For complex marine operations a separate and detailed familiarisation program shall be prepared and thoroughly implemented involving all personnel. Guidance note: Familiarisation should for offshore operations normally be initiated prior to vessel mobilisation. The familiarisation should cover all involved personnel, including marine crew, project personnel and third party, and should address all aspects of the operation. endofguidancenote 2.8.4 Communication and reporting 2.8.4.1 Communication lines and primary and secondary means of communication shall be defined, preferably in a communication chart, including as appropriate: — — — — — — — — — — — — — rd Client’s representative and 3 Party/MWS representative (if relevant) Overall project management Operation management Involved vessels Mooring systems and marine spread Ballast system operation Monitoring Weather forecasting Support services Field engineers providing expertise as required Safety Statutory, regulatory and approving bodies Emergency response. 2.8.4.2 Communication systems, including radio channels, telephone numbers, email addresses and outof hours numbers shall be identified and checked for accuracy. 2.8.4.3 The primary operational communication system should be used only for information needed for managing and controlling the operation. Important information should be given dedicated lines/channels. 2.8.4.4 The planned flow of information during the operation shall be described. 2.8.4.5 A common language understood by all personnel involved should be used for VHF/UHF communication. Radio channels should be allocated early to avoid possible interference. Guidance note: If a common language could lead to misunderstandings, it can be acceptable to use two or more languages. Such communication needs to be duly planned and rehearsed. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 78 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.8.3.2 Key personnel shall familiarise themselves with the operations. A thorough briefing by the supervisors regarding responsibilities, communication, work procedures, safety and other items of importance shall be performed. 2.8.4.7 All communication and reporting should be made available for continuous monitoring by the MWS during the operation. (See also [2.3.8]). 2.8.5 Shifts 2.8.5.1 For operations with a planned duration exceeding 12 hours, a shift plan shall be established. 2.8.5.2 Where personnel changes occur during the course of an operation because of shift changes, these shall be identified. Every effort should be made to avoid changes of key personnel during critical stages of the operation. 2.8.5.3 Where transfer of responsibility is involved, times of and procedures for handover from one organisation to another (e.g. from fabrication to marine operations, from onshore to offshore) shall be identified. 2.8.5.4 When continuous operations using more than 1 shift are not standard practice then special provision to prevent fatigue shall be made for operations that could continue beyond normal working hours. This includes provision of suitably experienced and briefed alternate personnel with good handovers at each shift change. 2.9 Monitoring 2.9.1 General 2.9.1.1 Actual parameters should be monitored and compared against those used in design to as great an extent as practicable during and also if applicable before marine operations. 2.9.1.2 The monitoring methods should duly reflect the required accuracy (i.e. acceptable monitoring tolerances). 2.9.1.3 Target values and maximum deviations from target values, i.e. tolerances, for monitoring should be clearly defined. Guidance note: Maximum allowable measured deviations should normally be within 75% of ‘deviations considered in the design’ less the ‘monitoring tolerance’. endofguidancenote 2.9.1.4 General and backup requirements to monitoring instrumentation systems are given in [4.2]. 2.9.2 Environmental conditions 2.9.2.1 Environmental conditions can be monitored by both direct monitoring of environmental conditions and by monitoring responses caused by environmental effects, see [2.9.3]. 2.9.2.2 For marine operations particularly sensitive to environmental conditions such as waves, swell, current, tide etc., systematic monitoring of these conditions before and during the operation shall be arranged. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 79 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.8.4.6 Communication of important information that may be misunderstood, e.g. monitoring results, should be confirmed in writing. In some areas, tide behaviour can vary considerably locally. In such cases a local tide variation curve should be established based on extensive tide monitoring including at least one period with the same lunar phase as for the planned operation. Tidal variations should be plotted against established astronomical tide curves. Any discrepancies should be evaluated, considering barometric pressure and other weather effects. See also [3.4.15.3]. endofguidancenote 2.9.2.3 Expected values, for the remaining time of the operation, of significant environmental conditions should be continuously predicted during execution of a marine operation. Such predictions should, as relevant, be based on the monitored variations, tabulated values and weather forecasts. 2.9.3 Loads and/or responses 2.9.3.1 Full scale monitoring can be used for the determination of responses (e.g. accelerations on a vessel) or loading effects (e.g. straingauge measurements). All full scale load and/or response monitoring shall be carried out according to agreed procedures, see e.g. [2.9.5]. Guidance note: Full scale monitoring is normally carried out to meet one or both of the following objectives: — To obtain valuable design information for future projects. — To control that design criteria (ULS or FLS) are not exceeded during an operation. endofguidancenote 2.9.3.2 During full scale monitoring it can be difficult to accurately measure the load which causes the measured response. The information obtained may therefore be of a statistical nature, and the use of statistical methods can be necessary in order to draw conclusions. Guidance note: Full scale monitoring has limitations, e.g. as indicated above, that need to be duly considered if such monitoring is used as an (assisting) operational means of control. endofguidancenote 2.9.4 Alpha factor related monitoring 2.9.4.1 It shall be documented that monitoring systems and procedures used as a means to increase the Alpha Factor for waves have adequate accuracy and reliability. Normally this implies fulfilment of all the following: — Continuous monitoring. — The monitoring device should be adequately located (e.g. no shielding effects) to give correct readings and not in any case more than 3 (three) nautical miles from the location of the operation. — Documented monitoring accuracy better than ±5% of the measured maximum values. — Statistical treatment of the results which continuously indicate the expected maximum value within a defined time period (normally 3 hours). — It should be possible to relate the response monitoring results to the wave conditions. See also [2.9.3]. — A secondary system and/or procedure that will detect any significant erroneous results produced by the primary system. 2.9.4.2 A procedure shall be made that describes how the interface between monitoring results and weather forecasts is to be handled. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 80 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: The procedure should, as a minimum, cover the following: — Discrepancies between weather forecast for the present time and monitoring results. — How to calibrate the weather forecast for the coming hours based on the monitoring results. — Feedback to meteorologist(s) endofguidancenote 2.9.5 Monitoring procedure 2.9.5.1 A monitoring procedure describing at least monitoring methods and intervals, responsibilities, reporting and recording shall be prepared. 2.9.5.2 Any unforeseen monitoring results shall be reported without delay. 2.9.6 Backup and contingency 2.9.6.1 The requirements of [4.2.1.10] apply. 2.9.6.2 If the monitoring backup system does not have the same accuracy as the original system this should be considered in the contingency planning. 2.10 Inspections and testing 2.10.1 General 2.10.1.1 Testing and inspection of equipment, structures, systems and vessels shall be carried out according to relevant and recognized codes/standards and/or relevant specifications, functional requirements and assumptions for the design. 2.10.1.2 Inspection during the operation shall include a systematic review and evaluation of monitoring results, see [2.9]. 2.10.1.3 The MWS company shall identify any inspections and tests to be witnessed by its own representatives. 2.10.2 Test program 2.10.2.1 The required inspections and tests both in the preparation phase and during the operation shall be described in a test and inspection program. 2.10.2.2 The test and inspection results shall be documented. Guidance note: The inspections and testing can be documented by reports and completed checklists. endofguidancenote 2.10.2.3 For larger operations it is recommended that a test/commissioning program is developed specifying the planned inspections and tests. The test program should indicate expected characteristics, and state acceptance criteria based on the design assumptions. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 81 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Acceptance criteria for tests may also be functional requirements. endofguidancenote 2.10.3 Systems 2.10.3.1 All systems and their backup shall be tested before the start of an operation. Such tests shall demonstrate that they function as intended. If critical, the capacity of the system shall be adequately checked. 2.10.3.2 Change over from a primary to a secondary system shall be tested. 2.10.3.3 Instrumentation systems shall be calibrated and tested before the operation. The calibration procedure may be subject to review. 2.10.3.4 Essential systems shall be function and capacity tested in their final configuration and connected to the same power supply/HPU as intended to be used during operation. If several consumers are connected to the same power supply/HPU, the test should be performed realistically with all consumers running in order to test capacity. 2.10.3.5 Emergency systems/functions and failsafe configurations shall, as far as practically possible, be tested in a realistic scenario with adequate loading. 2.10.4 Communication 2.10.4.1 Primary and secondary means of communication shall be tested before operation. 2.10.4.2 For operations with complex communication and reporting procedures, or where proper information flow is vital, a runthrough of communication routines shall be carried out. Guidance note: This rehearsal should be performed with the nominated personnel and under conditions similar to those expected during the actual operation. See also [2.8.4.5]. endofguidancenote 2.10.5 Inclining tests 2.10.5.1 The requirement to perform inclining and/or displacement tests shall be agreed with the MWS Company. Guidance note: Vessels with a valid Trim and Stability booklet, including all modifications since the last inclining test, do NOT normally require an inclining test when conservative estimates of cargo weight and centre of gravity show adequate reserves of intact and damage stability. Where ideally an inclining test would be performed but may not give sufficiently accurate results the calculations may be based on outputs from the weight control programme checked against a displacement test. This would only apply if there is a sufficient reserve of stability to cover possible inaccuracies. Where a number of very similar units are constructed at the same place, the requirement for inclining tests on the later units may be reduced after a study of weight variations (from displacement tests) and Centre of Gravity variations (from inclining tests) of the previous units, and agreement with the MWS company. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 82 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: a) b) c) d) e) f) g) They should be performed before any marine operation where the displacement, centre of gravity or stability may be critical. They should be performed according to the guidance in IMO Intact Stability Code 2008, /89/, Part B Annex 1. if applicable, an allowance shall be made for the presence and compressibility of any air cushion if the vessel is not axisymmetric then inclining tests may be required about two axes, as agreed with the MWS company. (This normally applies to bodies with an irregular shaped plan view, not vessels with a list). Upon completion of the inclining test, a report containing measurements/readings and corresponding calculations of displacement (and light displacement if relevant), metacentric height (GM), and the position of the centre of gravity of the structure, should be prepared. The output from the inclining test should be used to check and calibrate the output from the weight control programme. A rigorous weight control system should be enforced from the inclining test until the relevant marine operation is completed. A sensitivity analysis of the parameters affecting the test results should be performed. 2.11 Vessels 2.11.1 General 2.11.1.1 This section includes general requirements for vessels involved in marine operations. Where applicable, further requirements are given for each type of operation vessel in Sec.6 through Sec.18. 2.11.1.2 Vessels shall satisfy the relevant hydrostatic stability requirements given in [11.10]. 2.11.1.3 A general description of the vessel systems to be used shall be documented. Ballast and towing equipment/systems shall be described in detail if used. 2.11.1.4 Vessels shall be suitable for their planned tasks during the operation. Guidance note: If there is any doubt about the vessel suitability for a specific operation it is recommended to carry out an independent suitability survey of the vessel. endofguidancenote 2.11.1.5 See [17.13] for further requirements to Dynamic Positioned vessels. 2.11.2 Condition and inspections 2.11.2.1 All vessels shall be in acceptable condition and with valid certificates, see [B.1]. 2.11.2.2 All vessels involved in the operations should be inspected before the operation to confirm compliance with the design assumptions, validity of certificates, suitability (see [2.11.1.4]) and acceptable condition. 2.11.2.3 The global and local condition of the vessels with respect to corrosion shall be confirmed and considered in strength verifications. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 83 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.10.5.2 Where inclining and/or displacement tests are required: 2.11.3.1 Adequate global and local structural strength shall be documented for all vessels. Guidance note: The strength may be documented by either ensuring that the vessel is operated within the Class requirements, see [2.11.4], or by calculating the strength according to the relevant requirements in Sec.5. endofguidancenote 2.11.3.2 If the allowable deck load is based on load charts, the limitations and conditions for these with respect to number of loads and simultaneousness of loads shall be clearly stated. The applied design factors shall be specified. 2.11.4 Class requirements 2.11.4.1 Where a vessel is classed by a Classification Society it shall be operated in accordance with requirements from the Society. The limitations for Class as given in “Appendix to Class Certificate” or similar shall be submitted. 2.11.4.2 For Mobile Offshore Units the following annexes (or similar) to the maritime certificates shall be submitted; — Annex I Operational limitations, — Annex II Resolutions according to which the unit has been surveyed, and possible deviations from these. 2.11.4.3 Valid recommendations (conditions) given by the Classification Society shall be submitted. Guidance note: Modifications to vessel structure or equipment can require approval from the Classification Society. endofguidancenote 2.11.4.4 If it is planned to use a vessel or its equipment (e.g. crane) outside the limitations stated by Class, a statement of acceptance from Class shall be submitted. 2.11.5 Certificates 2.11.5.1 All required certificates shall be valid, or relevant exemptions shall be submitted. Guidance note: The documents (certificates) to be carried on board different types of vessels can be found in IMO FAL.2/Circ.87MEPC/Circ.426 MSC/Circ.1151. endofguidancenote 2.11.6 Collision avoidance 2.11.6.1 All vessels and towed objects (unless submerged) shall meet the requirements of the International Regulations for Preventing Collisions at Sea, 1972 (COLREGS, /91/) and any local regulations. These requirements include the carrying of lights and shapes and, for manned vessels and towed objects, sound signalling devices. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 84 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.11.3 Structural strength Guidance note: Solar powered navigation lights should be compliant with UL 1104 (USCG) and/or EN14744 (EU Marine Equipment Directive). Additional power provided by solar panels may be considered if an adequate track record is documented. endofguidancenote 2.11.6.3 Where possible, a duplicate system of lights should be provided. 2.11.6.4 Towed objects which may offer a small response to radar, such as barges or concrete caissons with low freeboard, should be fitted with a radar reflector. The reflector should be mounted as high as practical. Octahedral reflectors should be mounted in the “catchrain” orientation. 2.11.7 Contingency situations 2.11.7.1 All vessels shall be selected with due consideration to possible contingency situations. Guidance note: This could e.g. result in the selection of redundant (twin screw) tugs for towing operations in narrow waters. See also the operationspecific requirements in Sec.10 to Sec.18 of this standard for further guidance. endofguidancenote 2.11.7.2 Where several tugs (vessels) are involved, a standby tug to assist or remove vessels in case of blackout, engine failure, etc. should be considered. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 85 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2.11.6.2 Navigation lights shall be independently powered (e.g. from an independent electric power sources or from gas containers). Fuel or power sources shall be adequate for the maximum duration of the towage, plus a reserve. Spare mantles or bulbs should be carried, even if the tow is unmanned. 3.1 Introduction 3.1.1 General 3.1.1.1 This Section refers to the environmental design criteria applicable for marine operations. The focus is on the criteria applicable to weather unrestricted marine operations however, design environmental criteria for weather restricted marine operations are addressed in [3.3]. 3.1.1.2 Metocean criteria are generally used for analysis to a recognised standard (including relevant safety factors). In this standard, the environmental criteria to be used for the ASD/WSD approach are different to those to be used for the LRFD approach. 3.1.1.3 Each marine operation shall be designed to withstand the loads caused by the most adverse environmental conditions expected. In the case of a voyage this shall account for the areas and seasons through which it will pass. Any agreed mitigating measures may be taken into account. 3.1.1.4 For each phase of a voyage or marine operation, the design criteria should be defined, consisting of the design wave or sea state, design wind and, if relevant, design current. It should be noted that the maximum wave and maximum wind may not occur in the same geographical area, in which case it may be necessary to check the extremes in each area, to establish governing load cases. 3.1.2 Scope 3.1.2.1 The environmental design criteria should be established dependent on the duration of each discreet phase of a marine operation, which may be a weather restricted or a weather unrestricted operation as defined in [2.6.5]. 3.1.2.2 This section defines the default return periods that can be used to determine applicable environmental criteria. App.C gives more detailed approaches for the determination of design winds and waves as a function of the exposure duration and locationspecific metocean parameters. 3.1.3 Revision history 3.1.3.1 The following changes have been made to this section: — General: Editorial changes to improve clarity. — Table 31: Table modified to remove unrequired note. — Table 32: Table modified to revise return periods for quayside mooring. 3.1.3.2 The changes made to this section for the June 2016 edition are shown in App.A. 3.2 Design environmental condition 3.2.1 The design environmental condition consists of the wave height, wind speed, current and other relevant environmental conditions specified for the design of a particular marine operation. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 86 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 3 ENVIRONMENTAL CONDITIONS AND CRITERIA A weather unrestricted operation is not limited by practical aspects, and therefore the operational criteria are the design environmental condition. In this case the design environmental condition is based on extreme statistical data and is addressed in [3.4]. 3.2.3 The environmental design data should be representative of the geographical area or site and operation in question. 3.2.4 Where it is impractical and/or uneconomical to design marine operations based on extreme statistical data, the design environmental condition can be set independent of extreme statistical data for weather restricted operations see [2.6.7] and [3.3]. 3.3 Design environmental criteria for weather restricted operations 3.3.1 For weather restricted operations the design wind could be selected independent of statistical data. Guidance note: Characteristic wind velocities less than 10 m/s are generally not recommended. See also [3.3.4] for general considerations. endofguidancenote 3.3.2 The ratio between forecasted wind and design wind should be determined in accordance with Table 28 or Table 215 as applicable. 3.3.3 Wave conditions for weather restricted operations, i.e. operations with wave heights (and/or periods) selected independent of statistical data, should be as described by [C.3.4]. 3.3.4 The significant wave height(s) and associated period(s) should be selected considering: — — — — Feasibility and safety of the planned operation. Typical weather conditions at the site. Operation period. Uncertainties in weather forecasts. Guidance note: Other factors such as the length of delay that can be accepted due to waiting on weather, and possible contractual obligations should be considered as found relevant. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 87 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3.2.2 Maximum wave height for weather restricted operations should be calculated according to the following equation: Hmax = STF × Hs where: STF = 2.0 for all reference periods. Guidance note: For short reference periods STF < 2.0 may be acceptable. See DNVGLRPN102 Table 22, /55/, for guidelines. endofguidancenote An appropriate range of wave periods associated with Hmax should be considered. In the absence of other data, the range of Tass can be taken as: 3.3.6 Where relevant, applicable information from [3.4] may be used e.g. [3.4.12]. 3.4 Design criteria for weather unrestricted operations 3.4.1 General 3.4.1.1 Whilst an operation may be defined as weather unrestricted, specific portions can be dependent on suitable weather forecasts, e.g. the departure of a tow from safe haven as described in [11.14.1.4]. Such restrictions shall be agreed before the start of an operation and are normally included on the Certificate of Approval. 3.4.2 Environmental statistics 3.4.2.1 Environmental phenomena are usually described by physical variables of statistical nature. Statistical data should as far as possible be used to establish characteristic environmental conditions. The statistical description should reveal the extreme conditions as well as the long and shortterm variations. 3.4.2.2 Statistical data used as basis for establishing characteristic environmental criteria shall cover a sufficiently long time period. Guidance note: For meteorological and oceanographic data a minimum of three to four years of data collection is recommended. When using seasonal data longer periods are required. See DNVGLRPC205 /46/ for more info. endofguidancenote 3.4.2.3 The validity of older (typically more than 20 years) statistical data should be carefully considered with respect to both monitoring methods/accuracy and possible long term climate changes. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 88 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3.3.5 Guidance note: Regression analysis of twoparameter Weibull distributions are recommended based on the 30% highest data points, i.e. P(x > X) = 0.3. endofguidancenote 3.4.3 Return periods for determining environmental criteria (apart from moorings) 3.4.3.1 The return periods that shall be used for determining environmental criteria for weather unrestricted marine operations (apart from moorings and the elevated operation of jackups), should be related to its operation reference period, as defined in [2.6.2]. For design criteria for moorings see [3.4.4], and for the elevated operation of jackups see DNVGLSTN002, /39/. 3.4.3.2 As general guidance, the criteria in Table 31 may be applied provided that the independent extremes are considered concurrently. 3.4.3.3 The intention of the return periods and load, safety and material factors used in the LRFD approach is to ensure a probability for structural failure less than 1/10000 per operation (104 probability). Note that this probability level defines a structural capacity reference. When the probability of operational errors is included, the total probability of failure is increased. Guidance note: When including operational errors, the level of probability of total loss per operation cannot be accurately defined. However, the recommendations and guidance given in this standard are introduced in order to obtain a probability of total loss As Low As Reasonable Practicable (ALARP principle). endofguidancenote 3.4.3.4 The return periods for the ASD/WSD approach have been calibrated with the objective of ensuring that a given structure will be treated equally under ASD/WSD and LRFD. The inherent safety margin in ASD/WSD checks is less than that in LRFD checks, so that higher design values are needed to achieve this equivalence. 3.4.3.5 Seasonal and/or directional variations may be used. Data for the month(s) of the operation and the following month shall be used. If the operation is to be carried out in the first 10 days of the month, the data used shall include the preceding month. 3.4.3.6 When seasonal variations are taken into account, this shall not imply a shorter return period, as would occur if the monthly return period values are derived from only the data in that month without adjustment of the target probability level. There are differing approaches to obtaining the monthly or seasonal data at required return period (e.g. the “one year return”). One approach is to perform an extreme value analysis by month/season, and consider a conditional probability corresponding to that month/season. For example, to determine the Nyear return period extremes for say March, perform extreme value analysis on the subset of data for March, consisting of 3 hr seastates, 240 per month in the data, and fit a Weibull curve to the cumulative distribution function. Select the required probability level for the Nyr extreme calculated as: 1/(365.25*8*N*C) where C = conditional probability for month = 1/12. Another approach is to obtain relative weightings of the severity of each month in a year, and scale the monthly or seasonal values such that the worst month in the year has the same extremes as the allyear value at the required return period. 3.4.3.7 Similarly, when directional variations are taken into account, this shall not imply a shorter return period. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 89 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3.4.2.4 If statistical environmental data are assumed to follow a twoparameter Weibull distribution, the regression analysis should be performed with emphasis on a correct representation of the extreme values. Operation reference period ASD / WSD Wind Up to 3 4) days 1) 3) LRFD Wave 2) and Current Wind 1) 3) Wave 2) and Current Td≥5 year Td≥3 month Td≥10 year Td≥1 month 3 to 7 days Td≥10 year Td≥1 year Td≥10 year Td≥3 month 7 days to 1 month Td≥25 year, (or obtain from 10 yr and 50 yr environmental criteria values using: 10yr + 0.7*(50 yr10 yr) ) Td≥10 year Td≥10 year Td≥1 year 1 month to 1 year Td≥75 year (or obtain from 50 yr and 100 yr environmental criteria values using: 50yr +0.7*(100 yr50 yr) ) Td≥50 year Td≥100 year Td≥10 year More than 1 year 100 year return Td≥100 year Td≥100 year Td≥100 year Notes: 1) More accurate design wind speeds may be determined as a function of the operation reference period and site specific metocean parameters using the method shown in [C.1]. 2) More accurate design waves may be determined as a function of the operation reference period and sitespecific metocean parameters using the method shown in [C.3]. 3) See [3.4.3.4]. 4) Operations up to 3 days may also be defined as weather restricted operations. See Section [2.6.7]. 3.4.3.8 If conditions are determined using the joint probability of different parameters, then the return period should be increased by a factor of 4 i.e. 10 years to say 50 years and 50 years to 200 years, unless the loadings are dependent on a single parameter in which case the value of that parameter shall be taken from a joint probability combination in which it is maximised. 3.4.3.9 For voyages that are governed for ULS and ALS by a single sea area, the operation reference period may be taken as 7 days to 1 month. For FLS the whole voyage shall be considered, see [11.9.12]. 3.4.3.10 For voyages, the design extremes may be reduced below the 10 year seasonal return, to give the same probability of encounter as a 30 day exposure to a 10 year seasonal storm. In this case the “adjusted” design extremes are defined in terms of the 10% risk level, see [3.4.17.3]. The design extremes for weather unrestricted voyages shall not be reduced below the 1 year seasonal return. 3.4.4 Return periods for determining environmental criteria for moorings 3.4.4.1 Table 32 identifies minimum return periods applicable to a various of mooring types for weather unrestricted operations. The return periods specified in this document are based on ISO 199017 /100/, however the selection of return period will depend on the choice of the design code (See [17.2] for acceptable mooring codes) and the associated factor of safety. For weather restricted operations, see [3.3]. More onerous, local requirements can override the requirements stated in Table 32, for example ISO 199017, Annex B. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 90 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 31 Metocean minimum design return periods, Td – unrestricted operations Mooring Type Quayside/Inshore Offshore Mobile near another asset Offshore Mobile in Open Location Return Period Table 31 (LRFD) 1) 10 year 5 year Notes: 1) Where the unit is capable of leaving the quay on receipt of poor weather forecast a lower return period can be acceptable. 3.4.4.2 For mobile moorings deployed for a duration extending beyond the inspection cycle of the components of the mooring system, the system and its components should be assessed against the requirements for designing a permanent mooring system. 3.4.4.3 Joint probability data should only be used when permitted by the referenced standard. 3.4.4.4 Mobile moorings should generally be designed with reference to a 10 year return period when in the vicinity of any other infrastructure. Where a mobile mooring is in an open location, with reduced consequence from mooring failure, a five year return period may be acceptable. Where applicable seasonal/monthly and/or directional metocean data as in [3.4.5] can be used with the specified return period. 3.4.4.5 When evaluating the consequence of failure, consideration should be given to whether risers will be connected, proximity to other installations and the type of operation being undertaken. For pipe laying operations, the expected duration of the operation, plus a suitable contingency value, should be addressed. 3.4.5 Use of seasonal/directional metocean data for moorings 3.4.5.1 Metocean data specific to the month(s) or season(s) during which the mooring will be utilised may be used where appropriate. 3.4.5.2 Directional metocean data may also be used with suitable spreading functions to reflect directional divergence in the design environment. 3.4.6 Wind 3.4.6.1 The averaged wind velocity over a defined time is referred to as the mean wind. Guidance note: Forecasted wind velocity is normally given as the 10 minute mean wind (tmean = 10 min) at a reference height of 10 m (z = 10 m). endofguidancenote 3.4.6.2 The design wind speed shall generally be the 1 minute mean velocity at a reference height of 10 m above sea level. A longer or shorter averaging time should be used for design depending upon the nature of the operation, the size of the structure involved and the response characteristics of the structure to wind. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 91 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 32 Return periods for determining environmental criteria for moorings The following averaging times are given as examples; Fixed structures L < 50 m 3 [s] Fixed structures L > 50 m 15 [s] For any structure if wave load dominating 1 [minute] 15 [s] Quay mooring, large (Wind area > 2000 m ) vessels/objects 1 [minute] Stability calculations, normally 1 [minute] Catenary mooring of vessels/objects 10 [minutes] Catenary mooring of GBS 60 [minutes] Quay mooring, small vessels/objects 2 endofguidancenote Guidance note 2: OCIMF (2007) gives further guidance with respect to mean wind periods to be used for quay mooring of vessels. For static wind calculations on lifted objects the recommendations for fixed structures above normally apply. See also DNVGLST0378 App.A, /129/. endofguidancenote 3.4.6.3 For dynamic wind analysis the mean wind period recommended for the applied wind spectrum should be used. See [3.4.6.7]. 3.4.6.4 The mean wind velocity varies with the averaging time and height above the sea surface or height above ground (yard lift). For these reasons, the averaging time for wind speeds and the reference height shall always be specified. 3.4.6.5 The wind velocity profile in open sea can be related to a reference height (zr) and mean time period (tr, mean) according to the equation below, see also Table 33 and ISO 199011 “Metocean design and operational considerations”, /98/. Where: z zr tmean tr, mean U(z, tmean) U(zr, tr, mean) = Height above sea surface. = Reference height 10 [m]. = Averaging time for design. = Reference averaging time 10 [minutes]. = Average wind velocity. = Reference wind speed. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 92 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 1: z (m) Averaging time 3s 15 s 1 min. 10 min. 1 hour 1 0.93 0.86 0.79 0.69 0.60 5 1.15 1.08 1.01 0.91 0.82 10 1.25 1.17 1.11 1.00 0.92 20 1.34 1.27 1.20 1.10 1.01 50 1.47 1.39 1.33 1.22 1.14 100 1.56 1.49 1.42 1.32 1.23 Guidance note: The wind profile given in Table 33 is for open sea and should not be considered applicable to (partly) sheltered inshore locations. Wind profiles for such locations should be selected based on local data. endofguidancenote 3.4.6.6 Gust wind: For elements or systems sensitive to wind oscillations (e.g. where dynamics or fatigue governs the design) the short and long term wind variations should be considered. 3.4.6.7 The wind variations may be described by a wind spectrum. See e.g. DNVGLRPC205, /46/; NORSOK N003, /111/ or ISO 199011, /98/. 3.4.6.8 Squalls: If squalls are possible during a marine operation maximum realistic (in the actual area) characteristic wind speeds during squalls shall be considered in the planning and execution of the operation. Guidance note: Squalls are strong winds (22 knots or more) characterised by a sudden onset, duration of minimum 1 minute, and then a rather sudden decrease in speed. Squalls are caused by advancing cold air and are associated with active weather such as thunderstorms. Their formation is related to atmospheric instability and is subject to seasonality. endofguidancenote 3.4.7 Wind for moorings 3.4.7.1 In addition to the requirements in [3.4.6], for permanent moorings the more onerous of the following should be considered: — Steady one minute mean velocity; or — One hour mean plus a suitable gust spectrum. Generally the ISO 199011 gust spectrum, /98/, would be applicable unless an alternative can be clearly justified. 3.4.7.2 For mobile moorings either a steady state wind speed or a suitable gust spectrum may be used depending upon the stiffness of the mooring system. 3.4.7.3 For inshore or quayside moorings care shall be taken to ensure that all natural periods of response of the system have been considered. Some of the mooring system response periods may be shorter than one minute but on the other hand the use of shorter gust periods may not represent a sustained design wind that will act at the same time across the whole of the structure. The representative design wind sampling period, therefore, has to be carefully established on a case by case basis for inshore and quayside moorings, but the averaging time shall not be longer than 1 minute if applying static wind load. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 93 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 33 Wind profile, U(z, tmean)/ U(zr, tr, mean) 3.4.8 Waves design methods 3.4.8.1 Wave conditions are defined by characteristic wave height, Hc, or the significant wave height, Hs, and corresponding periods. 3.4.8.2 Wave conditions for design may be described either by a deterministic design wave method, or by a stochastic method. 3.4.8.3 In the deterministic method the design sea states are represented by regular periodic waves characterised by wave length (or period), wave height and possible shape parameters. 3.4.8.4 In the stochastic method the design sea states are represented by wave energy spectra characterised by main parameters Hs and Tz or Tp. 3.4.9 Waves weather unrestricted operations, general 3.4.9.1 Characteristic wave conditions for weather unrestricted operations shall be based on long term statistical data. 3.4.9.2 Long term variations of waves may be described by a set of sea states characterised by the wave spectrum parameters. 3.4.10 Wind seas and swell 3.4.10.1 All possible combinations of wind seas and swell should be considered. Guidance note: The wave conditions in a sea state can be divided into two classes, i.e. wind seas and swell. Wind seas are generated by local wind, while swell have no relationship to the local wind. Swells are waves that have travelled out of the areas where they were generated. Note that several swell components may be present at a given location. endofguidancenote 3.4.11 Characteristic waves for weather unrestricted operations 3.4.11.1 Characteristic values shall be based on the defined operation reference period. Periods less than 3 days shall not be used. These can be based on the return periods given in Table 31 or Table 32 as applicable. Alternatively, the Characteristic significant wave height, Hs, c may be taken according to [C.3.2.1] and the corresponding maximum wave height, Hmax, c, may be taken according to [C.3.2.2]. Guidance note 1: The significant wave height frequencies, Hs is approximately equal to where m0 is the sea surface variance. In sea states with only a narrow band of wave (the mean height of the largest third of the zero upcrossing waves). endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 94 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3.4.7.4 For locations prone to squall events, system design should include assessment for squall events. Guidance on squall assessment is provided in DNVGLOSE301, /27/. The Hmax, c corresponds to an approximate 10% probability of exceeding this individual wave height during the anticipated operation reference period. If an alternative method is applied it should be documented that this corresponds to an equal or less probability. endofguidancenote 3.4.11.2 When a regular wave analysis is applicable, the design maximum wave shall be the most probable highest individual wave in the design sea state, assuming an exposure of 3 hours. The determination of the height, crest elevation and kinematics of the maximum wave should be determined from an appropriate higherorder wave theory and account for shallow water effects. For most practical purposes the kinematics of regular deterministic waves can be described by the following theories: h/λ ≤ 0.1 0.1 < h/λ ≤ 0.3 h/λ > 0.3 Solitary wave theory for particularly shallow water th Stokes 5 order wave theory or Stream Function wave theory. th Linear wave theory (or Stokes 5 order) where: h λ = water depth. = wave length. A range of wave heightperiod combinations shall be investigated, including those that can cause resonance, see [C.3.3]. For more information on the kinematics of regular waves, see DNVGLRPC205, /46/. 3.4.11.3 Sea states shall include all relevant spectra up to and including the design storm sea state for the construction site or voyage route. Longcrested seas shall be considered unless there is a justifiable basis for using shortcrested seas or these are more critical, see [3.4.12]. Consideration should be given to the choice of spectrum. 3.4.11.4 Wave spectra defined by the Jonswap or the PiersonMoskowitz spectra are most frequently used. Wave conditions with combined wind sea and swell may be described by a double peak wave spectrum. See DNVGLRPC205, /46/, for further guidance. 3.4.11.5 In the simplest method the peak period (Tp) for all sea states considered, should be varied. In areas where swell is insignificant, the range of Tp can be taken as: in areas where swell is significant, the range of Tp can be taken as: for Hs ≤ 5.7 m for Hs > 5.7 m where: Hs Tp = significant wave height in metres = wave peak period in seconds Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 95 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 2: The equations for areas where swell could be significant are based on the equations for Tz given in [C.3.4.3], assuming that Tp = 1.24Tz for steep waves (gamma = 5) and Tp = 1.4Tz for long waves (gamma = 1.0). The relation between zerocrossing period Tz and the spectral peak period Tp can be found in Table 34. See also DNVGLRPN103 [2.2.6], /56/ or DNVGLRPC205 [3.5.5], /46/. endofguidancenote Alternatively, see [C.3.4.3]. 3.4.11.6 The effects of swell, see [3.4.14], should also be considered if not already covered in this peak period range. A reduced range of Tp may be used if the route or sitespecific data and natural periods allow. 3.4.11.7 However, [3.4.11.5] incorrectly assumes that all periods are equally probable. As a result this method should generally produce higher design responses than would be the case when using the more robust HsTp method described in [3.4.11.8], which may be used when desired. 3.4.11.8 In the alternative method, a contour (IFORM) is constructed within the HsTp plane that identifies equally probable combinations of Hs and Tp for the design return period. This contour should also cover swell. The contour should be checked for accuracy e.g. against the theoretical constraints on wave breaking. HsTp combinations from around the contour should be tested in motion response calculations to identify the worst case response (there is no need to consider a range of Tp with each Hs). 3.4.11.9 The relationship between the peak period Tp and the zeroup crossing period Tz is dependent on the spectrum. For a mean JONSWAP spectrum (γ=3.3) Tp/Tz = 1.286; for a PiersonMoskowitz spectrum (γ=1) Tp/Tz = 1.41. 3.4.11.10 Table 34 indicates how the characteristics of the JONSWAP wave energy spectrum vary over the range of recommended sea states. The constant, K, varies from 13 to 30 as shown in the equation in [3.4.11.5]. T1 is the mean period (also known as Tm). Table 34 Value of JONSWAP γ, ratio of Tp :Tz and Tp : T1 for each integer value of K Constant K γ Tp / T z Tp / T1 Constant K γ Tp / T z Tp / T 1 13 5.0 1.24 1.17 22 1.4 1.37 1.27 14 4.3 1.26 1.18 23 1.3 1.39 1.28 15 3.7 1.27 1.19 24 1.1 1.40 1.29 16 3.2 1.29 1.20 25 1.0 1.40 1.29 17 2.7 1.31 1.21 26 1.0 1.40 1.29 18 2.4 1.32 1.23 27 1.0 1.40 1.29 19 2.1 1.34 1.24 28 1.0 1.40 1.29 20 1.8 1.35 1.25 29 1.0 1.40 1.29 21 1.6 1.36 1.26 30 1.0 1.40 1.29 3.4.11.11 For operations involving phases sensitive to extreme sea states, such as temporary onbottom stability or green water assessment, the maximum wave height and associated period should be used. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 96 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 3.4.11.13 Attention should also be paid to areas prone to strong currents acting against the waves which would amplify the steepness of the sea state (i.e. reduce the wave encounter period that drives dynamic response). 3.4.12 Short crested seas 3.4.12.1 A directional short crested wave spectrum, see the equation below, may be applied based on non directional spectra. where: = Wave spectrum, see [3.4.11.4]. θ = Angle between direction of elementary wave trains and the main direction of the short crested wave system. = Directional short crested wave power density spectrum. = Directional function. 3.4.12.2 Energy conservation requires that the directional function fulfils; In absence of more reliable data the following directional function may be applied for wind sea, where: Γ( ) = gamma function. Due consideration should be taken to reflect an accurate correlation between the actual seastate and the constant n. Typical values for wind seas are n = 2 to n = 10. Swell should normally be taken as long crested, n > 10. Guidance note: For cases where long crested seas are conservative, it is recommended that long crested seas are used for the original design work. If short crested seas are introduced in connection with estimating extremes, the exponent, n, should not be taken lower than 10 without more detailed documentation. Swell seas should be taken as long crested. For fatigue assessment, where low and moderate sea states are governing the fatigue accumulation, n could be taken as the most unfavourable value between 2 and 6. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 97 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3.4.11.12 For precise operations sensitive to small fluctuations of the sea level even under calm sea state conditions, the occurrence of long period, small amplitude swell on the site should be checked and its effects on the operations evaluated. 3.4.13 Waves for moorings 3.4.13.1 In addition to the requirements in [3.4.8], for mobile moorings it is generally acceptable to consider a single extreme significant wave height and a range of associated peak periods corresponding to the relevant return period for a location. 3.4.13.2 For permanent moorings a number of HsTp combinations along the 100 year return period contour line shall be considered in the analysis. If a contour plot is not available, a sensitivity study by varying peak period for the 100 year return period sea state is required. This is to ensure that extreme line tensions due to low frequency motion at lower periods are captured in the analysis, especially for ship shaped floaters. 3.4.13.3 Long crested waves shall be assumed for analysis unless otherwise documented. 3.4.14 Swell 3.4.14.1 Swell type waves should be considered for operations sensitive to long period motion or loads. 3.4.14.2 Swell type waves may be assumed regular in period and height, and may normally also be assumed independent of wind generated waves. 3.4.14.3 Critical swell periods should be identified and considered in the design verification. 3.4.14.4 Characteristic height(s) and period(s) for swell type waves for weather restricted operations may be selected independently of statistical data. 3.4.14.5 Characteristic height(s) and period(s) for swell type waves for weather unrestricted operations should be based on statistical data and the applicable return periods. 3.4.15 Current 3.4.15.1 The design current shall be the rate at mean spring tides, taking account of variations with depth and increases caused by the design environmental condition, storm surge, fluvial (river) and winddriven components. 3.4.15.2 Currents can be divided into two different categories: — Tidal currents — Residual currents that remain when the tidal component is removed, including river outflows, surge, wind drift, loop and eddy currents. 3.4.15.3 Tidal currents can be predicted reliably, subject to long term measurement (at least one complete lunar cycle at the same season of the year as the actual planned operation). Residual currents can only be reliably predicted or forecast using sophisticated mathematical models. 3.4.16 Other parameters 3.4.16.1 Other factors including the following may be critical to the design, operations or voyages and should be addressed: — Water level including tide and surge Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 98 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3.4.12.3 Short crested seas should not be considered for significant wave heights exceeding 10 m, unless they cause more onerous response(s). Sea icing, icing on superstructure Exceptionally low temperature Large temperature differences Water density and salinity Bad visibility. 3.4.17 Calculation of adjusted design extremes, weather unrestricted voyages 3.4.17.1 The risk of encounter of extreme conditions on a particular voyage is dependent on the length of time that it spends in those route sectors where extreme conditions are possible. If the length of time is reduced, then the probability of encountering extreme conditions is similarly reduced. 3.4.17.2 It is generally accepted that for a prolonged weather unrestricted voyage the wind and wave design criteria should be those with a probability of exceedance per voyage of 0.1 or less. For a voyage of 30 days (or more), through meteorologically and oceanographically consistent areas, this corresponds to the 10 year monthly extreme. 3.4.17.3 Many voyages last less than 30 days, or are potentially exposed to the most severe conditions for less than 30 days. Consequently, for shorter exposures, the 10 year monthly extreme may be adjusted for reduced exposure. This value is equivalent to the 10 voyage extreme and is also referred to as the 10% risk level extreme. This shall not be confused with the 10% exceedance value for the voyage, as discussed in [3.4.19.6]. 3.4.17.4 When the 10% risk level extremes are less than the 1 year return monthly extremes, the 1 year monthly extremes are the minimum that shall be used for design. 3.4.17.5 If the 10 year extremes are due to a tropical cyclone it may not be appropriate to design to adjusted extremes. This is likely to be the case for barge or MODU towages that are not able to respond effectively to weather routeing. 3.4.18 Calculation of exposure 3.4.18.1 For the purpose of the calculation of “adjusted” extremes the exposure time to potentially extreme or near extreme conditions is calculated taking consideration of the following points: — The initial 48 hours of the voyage is assumed to be covered by a reliable departure weather forecast and is excluded — The speed of the voyage is reduced by taking the monthly mean wave heights along the route into consideration as described in [3.4.18.3]. — The speed of the voyage is adjusted to take into consideration the mean currents as described in [3.4.18.4]. — A contingency time of 25 per cent of the time is added. This allowance is to account for severe adverse weather, for tug breakdowns or other operational difficulties — A minimum exposure time of 3 days is considered. 3.4.18.2 The voyage duration in each route sector shall be calculated using the speed in the monthly mean sea state for each route sector and shall allow for adverse currents and adverse prevailing winds as described in [3.4.18.3]. 3.4.18.3 The effect of the mean sea state on the voyage speed in each route sector shall be calculated as a function of the wave height in which the voyage is assumed to come to a dead stop, b (metres). This can Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 99 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — — — — — where Hm is the monthly mean wave height in that route sector. 3.4.18.4 The effect of the mean current on the voyage speed in each route sector shall be calculated by adding the current vector (resolved with respect to the voyage heading). 3.4.18.5 For the calculation of exposure to the extreme conditions only prevailing winds or currents which act to delay the voyage shall be taken into account. 3.4.19 Calculation of adjusted extremes 3.4.19.1 The probability of nonexceedance of a value of wind speed or significant wave height in a particular route sector is expressed as a cumulative frequency distribution (e.g. a Weibull distribution). 3.4.19.2 The probability that during some 3 hour period for waves (or 1 hour for wind) the voyage will experience a significant wave height (or wind speed) less than some value x is given by Fx(X). 3.4.19.3 If it takes M hours to pass through the route sector and making the assumption that consecutive wave height and wind speed events are independent then the probability of not exceeding the value x is given by where N = M/T where T = 1 hour is applied for winds and T = 3 hours for waves, which are a more persistent form of energy. 3.4.19.4 If it is reasonable to expect that extremes of wind speed or wave height could occur in more than one route sector then the probability of not exceeding the value x is given by the product 3.4.19.5 The probability of encountering an extreme value of wind speed or significant wave height, during a particular voyage, that is reached or exceeded once on average for every 10 voyages, is 0.1. The value of x is varied until to give the 10 voyage extreme for the voyage or towage. 3.4.19.6 This value is also referred to as the “adjusted” extreme for the voyage, or as having a risk level of 10%. The method can be adjusted to give other risk levels (e.g. 1% or 5%). This should not be confused with the percentage exceedance (see guidance note to [3.4.19.7]). 3.4.19.7 The extremes used for design shall not be less than the 1 year return monthly extremes. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 100 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used typically be taken 5 m for barge towages, and 8 m for ships. The speed in the each route sector can be taken as the calm weather speed is multiplied by the factor, F, for that route sector defined by: The percentage exceedance is obtained as follows: — Given a series of values of wind speed or significant wave height, as may be observed during a complete voyage, some value y will be exceeded at some times but not others and the percentage exceedance of value y is equal to: — If each observed value of wind speed or significant wave height is assumed to last for some duration (typically 1 hour for winds and 3 hours for waves) then for example, during a voyage lasting 10 days there will be 240 wind events and 80 wave events. On the voyage, if a wind speed greater than 30 knots is observed during 24 separate, hourly occasions then the percentage exceedance of 30 knots is 10%. — The 10% risk level (as defined in [3.4.17.3]) for a voyage along a specific route, departing on a specific date is expected to occur only once, on average, in every 10 voyages. However a value with a 10% exceedance level for the same route and departure date is likely to occur on average for 10% of the time on every voyage. — Thus a 10% exceedance value is far more likely to occur than a 10% risk level value, or an adjusted, 10 year extreme value. endofguidancenote 3.4.20 Criteria from voyage simulations 3.4.20.1 If continuous time series of winds and waves are available along the entire voyage route (e.g. from hindcast data or satellite observations), an alternative way to develop criteria with a specified risk of exceedance in a single voyage is to perform tow simulations. A large number of simulations can be performed, with uniformly spaced (in time) departure times during the specified month of departure over the number of years in the database. For each simulated voyage, the maximum wind speed and the maximum wave height experienced somewhere along the tow route are retained. Then the probability distribution of these voyagemaxima can be used to determine the design value with a specified risk of exceedance. For example, the value exceeded once in every 20 voyages, on average, can be determined by reading off the th value of wave height from the distribution of voyagemaximum wave heights at the 95 percentile level. 3.4.20.2 If fatigue during tow is an issue, the complete distributions of winds and waves experienced during the simulated voyages (not just the voyagemaximum values) can be retained. These can be used to give scatter diagrams of wave height against period and/or direction, and wind speed against direction. 3.4.20.3 The voyage simulation method can be made to be very realistic and account for variation of speed due to inclement weather or ocean currents, weather avoidance enroute through forecasting/routeing services, or the use of safe havens, etc. If the voyage simulator cannot accommodate all these features, a reasonably conservative estimate of criteria can be derived by using a conservative (slow) estimate of the average speed. Care should be taken when choosing the average speed estimate a slow speed may not be conservative if it results in the vessel apparently arriving in a route sector late enough to miss severe weather, which might have been encountered if arrival had been earlier. 3.4.21 Metocean database bias 3.4.21.1 Regardless of whether the method described in [3.4.19] or the method described in [3.4.20] is used, it is important to know the accuracy of the metocean database being used. Specifically, if there is a known bias in the wind or wave statistics for any segment of a tow, it is essential to adjust the criteria accordingly. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 101 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 3.4.22.1 The design extremes are not normally used for calculation of bollard pull requirements (except when there is limited sea room), which is covered in [11.12.2] 3.5 Weather/metocean forecast requirements 3.5.1 The requirements for weather forecasting are given in [2.7] and the requirements for environmental monitoring in [2.9]. 3.6 Benign weather areas 3.6.1 Areas considered benign are shown in Table 35 and Figure 31 for different months. In general they have the following characteristics: — virtually free of monsoons, Tropical Revolving Storms or Tropical Cyclones — exceeding Beaufort Force 5 for <20% of any month (in a “typical” year) — However these areas may experience sudden vicious squalls and very rare tropical storms or cyclones. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 102 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3.4.22 Metocean data for bollard pull requirements This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 35 Northern and Southern boundaries of benign weather areas by month Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 103 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 31 Map showing benign weather areas Marine operations and marine warranty DNV GL AS Page 104 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 4.1 Introduction 4.1.1 Scope 4.1.1.1 This section includes general requirements to system and equipment design. It covers all (temporary) systems, see [4.2.1.7], used during marine operations, with emphasis on ballast systems. 4.1.2 Revision history 4.1.2.1 No main changes have been made to this section. Editorial corrections may have been made in this section. 4.1.2.2 The changes made to this section for the June 2016 edition are shown in App.A. 4.2 System and equipment design 4.2.1 General 4.2.1.1 Systems and equipment shall be designed, fabricated, installed, and tested in accordance with relevant codes and standards. 4.2.1.2 Systems and equipment shall, as far as possible, be designed to be failsafe and arranged such that a single failure in one system or unit cannot spread to another unit. The most probable failures, e.g. loss of power or electrical failures, shall result in the least critical of any possible new conditions. 4.2.1.3 Alarm system(s) should be incorporated for essential functions and be audible/visible at operators’ station. 4.2.1.4 Work stations shall be arranged to provide the user with good visibility and easy access to controls required for the operations. 4.2.1.5 Systems and equipment shall be selected based on a thorough consideration of functional and operational requirements for the complete operation. Emphasis shall be placed on reliability and the expected behaviour in possible contingency situations. 4.2.1.6 Depending on the complexity and duration of the operation, and the structure itself, risk evaluations may be required to determine the systems and equipment required for a safe operation, see [2.4.2]. Such studies shall include normal operations as well as emergency situations. 4.2.1.7 The following systems shall be considered where applicable: 1) 2) 3) 4) 5) 6) 7) 8) power supply fuel supply electrical distribution systems machinery control systems alarm systems valve control systems bilge and ballast systems compressed air systems Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 105 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 4 BALLAST AND OTHER SYSTEMS firefighting systems Cooling systems ROV systems lifting systems positioning systems, see guidance note communications systems and instrumentation systems for monitoring of; — — — — — — — — loads and/or deformations environmental conditions, such as tide ballast and stability conditions heel, trim, and draught position (navigation) tide underkeel clearance and penetration/settlements. Guidance note: Object guiding and positioning systems, including structural and functional requirements are covered in [4.4]. If applicable, the requirements in this section should be considered regarding mechanical parts and operation of such systems. Vessel position systems are described in Sec.17. endofguidancenote 4.2.1.8 Computerised control or data acquisition systems should be equipped with uninterruptible power supply system (UPS). 4.2.1.9 All systems shall be inspected and tested according to [2.10]. 4.2.1.10 Where a permanent system is complimented by a temporary system, the integration of the two systems shall be inspected and tested according to [2.10]. 4.2.2 Backup 4.2.2.1 All essential systems, parts of systems or equipment shall have backup or backup alternatives. Necessary time for a change over to the backup system or equipment shall be assessed. Guidance note: It is recommended that the marine operation manual includes an inventory of main spare parts available on site. It is also recommended to assess the necessity of having repair or service personnel available on site during operations. endofguidancenote 4.2.2.2 All backup systems should be designed and fabricated to the same standard as the primary systems. 4.2.2.3 Backup systems should be adequately separated from the main system such that failure of any component does not adversely affect the safe conduct of the operation. 4.2.2.4 For systems consisting of multiple independent units, backup may be provided by having a sufficient number of available spare units available on site. 4.2.2.5 If umbilicals are necessary to provide power and/or hydraulic services during any marine operation, adequate backup capability shall be provided, and failsafe systems shall be incorporated into critical controls. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 106 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 9) 10) 11) 12) 13) 14) 15) 4.3 Ballasting systems 4.3.1 General 4.3.1.1 This subsection is mainly applicable for ballasting and deballasting of vessel(s) involved in load transfer operations. Guidance note: See [11.15] regarding pumping capacity requirements during voyages. For jacket installations additional requirements apply, see [13.7.2]. For ballasting of (crane) vessels during lifting see Sec.16. endofguidancenote 4.3.1.2 Regardless of any requirement to change draught during construction, towage or installation operations, floating structures should normally be fitted with a means of pumping out water from all compartments. 4.3.1.3 The (de)ballasting system design shall properly consider the operation class (see [4.3.3]) as well as functional requirements related to: — — — — — — layout and reliability of the system tank capacities including contingency situations ballasting capacity including contingency situations strength limitations easily controllable ballasting tide 4.3.1.4 General requirements to (de)ballasting systems are given in [4.2.1]. 4.3.1.5 Adequate testing of the ballast system considering the actual operation shall be carried out, see [2.10]. 4.3.2 Ballast system power supply 4.3.2.1 Adequate power supply considering the actual operation shall be provided for the ballast system. 4.3.2.2 The need for emergency power supply due to the following situations shall be considered: a) b) c) Breakdown of any one power unit Breakdown of the common energy supply Unexpected increase in the consumption of energy above the expected value. Guidance note: The backup capacity for accidental conditions represented by a) and b) may be spare units in standby position. The backup capacity for conditions represented by c) may be spare capacity in the main unit or a backup unit installed to assist the main unit. endofguidancenote 4.3.2.3 Sufficient main and backup power supply capacity should be documented by calculations. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 107 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 4.2.2.6 Automatic control systems shall be provided with a possibility for manual overriding. Necessary power supply for ballasting should be based in the required ballasting capacity given in Table 42 for the relevant load out class. For evaluations of backup requirements, an independent power supply source should be regarded as a “pump system”, see Note 3) in Table 42. endofguidancenote 4.3.3 Operation classes 4.3.3.1 An operation class should be defined for load transfer operations see Table 101 for loadouts and Table 151 for liftoff, mating and floatover operations. 4.3.4 Ballast system layout and reliability 4.3.4.1 The ballast pumps may be the vessel’s internal pumps, pumps purposely installed for the operation/ project, or a combination of these. Internal vessel pumps that are not frequently in use, as the primary pumping means, should be carefully considered and demonstrated fit for purpose. Guidance note: Internal vessel pumps can have unreliable service records. Also, permanent piping systems are inherently inflexible. endofguidancenote 4.3.4.2 Where accurate control of the ballast amount is crucial, ballasting by flooding (i.e. opening of bottom valves) and/or deballasting by air pressurisation (or ballasting by vacuum – low pressure) of ballast tanks shall be avoided during load transfer phases. Guidance note: Ballasting by flooding during load transfer phases where accurate control of ballast amount is crucial may be allowed if the system has sufficient redundancy (e.g. double valves to compensate a failure to close a valve) and/or backup ballast plans are available where mechanical failures can be compensated by an alternative ballast procedure. endofguidancenote 4.3.4.3 Umbilicals used for air pressurisation of submerged vessel compartments should be connected to valves at the vessel tanks. 4.3.4.4 Where a compressed air system is used, the time lag needed to pressurise or depressurise a tank should be taken into account, as should any limitations on differential pressure across a bulkhead. It should be remembered that compressed air systems cannot always fill a tank beyond the external waterline. Air pressurised vessel tanks shall be fitted with safety (pressure relief) valves. 4.3.4.5 Hoses, umbilicals and power cables shall be placed with due consideration to other ongoing activities during the load transfer. 4.3.4.6 Required access throughout the load transfer for (possibly) needed equipment, e.g. fork lifts for replacing pumps, should be demonstrated. 4.3.4.7 All internal compartments shall be cleaned of debris before ballasting starts. 4.3.4.8 When inlets are near the seabed, care shall be taken to avoid sucking in mud or sand that can block the pumping systems or filters. 4.3.4.9 Where inlets or outlets are near the seabed, care shall be taken to avoid scour that could have adverse effects on foundations of any structure or grounded vessel, or reduce underkeel clearances. 4.3.4.10 Except when in use for inlet or discharge, all openings to sea shall be protected by a double barrier. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 108 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 4.3.4.12 All essential pipework in temporary systems should be of permanenttype construction and shall be hydrostatically tested to a minimum of 1.3 times the design pressure. Temporary flexible hoses shall only be used when a risk assessment, in accordance with [2.4], demonstrates the acceptability of the system. Guidance note: For offshore operations temporary flexible hoses are not generally permitted unless their use cannot be avoided, for instance for supply of backup compressed air from a compressor barge alongside. endofguidancenote 4.3.4.13 Permanenttype ballast systems used in marine operations should fulfil the Class requirements for construction and testing. Guidance note: For permanent ballast systems not subject to Class approval the requirement in [4.3.4.12] apply. endofguidancenote 4.3.5 Ballast tank capacity 4.3.5.1 The ballast tanks shall meet the capacity requirements in Table 41 for the required floating position(s) throughout the operation for both planned and contingency situations. 4.3.5.2 A reasonable amount of residual water in the tanks should be taken into account. Guidance note: The amount to be considered will depend on details and location of the pumping intake(s), heel/trim of the vessel and structural elements at the tank bottom. For tanks in use during the load transfer without any special arrangements allowing easy tank stripping, the minimum water head should be taken equal to the height of the tank bottom stiffeners plus 0.05 metres. endofguidancenote 4.3.5.3 The required tank capacities should include relevant spare capacity to compensate for the following: a) b) c) d) Tide levels below or above the predicted values. Total vessel weight, including vessel lightship, consumables and temporaries (e.g. project equipment, grillages, etc.), being higher or lower than expected Possible object weight and CoG variations Operational delays. Table 41 Tank capacity requirements Operation Class The tank capacity shall be adequate for the following scenarios (see Table 101 for loadout classes and Table 151 for floatons and floatoffs). — Normal (planned) operations All 1 — Spare tank capacity to cover items [4.3.5.2] and [4.3.5.3] shall be ensured in all situations. — Any necessary pumping capacity contingency involving modifications in ballasting procedures. See Table 42. — See All — Reversing of the operation. Tide compensation if stop of load transfer, considering maximum possible (defined) duration of the load transfer. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 109 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 4.3.4.11 Any external valves and pipework shall be protected against collision and fouling by towlines, mooring lines or handling wires. 2 3 4 5 — Ballasting through a complete tide cycle at any stage of the load transfer. Maximum tide variations within the operation period (TR) shall be considered. Reversing of the operation, if applicable. — See All — Ballasting through a complete tide cycle at any stage of the load transfer. Maximum tide variations for at least the coming 35 days shall be considered. — See All — Reversing of the operation, if applicable. — See All 4.3.6 Ballast pumping capacity 4.3.6.1 The ballast pumping capacity shall meet the capacity requirements in Table 41 for the required floating position(s) throughout the operation for both planned and contingency situations. Pump capacity shall be based on the published pump performance curves, taking account of the maximum head for the operation and pipeline losses. 4.3.6.2 Adequate capacity shall be documented considering the requirements to nominal, spare and backup capacity given in this subsection. 4.3.6.3 The nominal ballasting capacity shall be determined by the worst combination of expected tide rise/ fall and planned load transfer velocity. 4.3.6.4 For operation classes 2 and 3, it shall be documented that the ballast systems have capacity to compensate for the tide rise/fall through one complete tide cycle with the object in any position. Guidance note: If the tidal range increases in the days following the planned operation start, this should be considered when evaluating the consequences of a delayed start or delays during the operation. endofguidancenote 4.3.6.5 Pumps which require to be moved around the barge in order to be considered as part of the backup capacity, shall be easily transportable, and may only be so considered if free access is provided at all stages of loadout between the stations at which they may be required. Adequate resources shall be available to perform this operation. 4.3.6.6 Spare pumps should normally be installed and tested in the position they are planned to be used as backup. However, for pumps that may be replaced during the operation, spare pumps in standby position that require minimum replacement time may be used. Required number of spare pumps should be conservatively assessed. The replacement time shall be documented. See [4.3.4.6]. 4.3.6.7 Requirements for minimum total ballasting capacity, including backup, are given in Table 42, including the notes. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 110 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — See All Operation Class Normal Operation Load transfer as planned Tide Compensation Load transfer unexpectedly stopped 1 Minimum 200% capacity with intact system and minimum 120% capacity in all tanks with any one pump system failed. Minimum 150% capacity with intact system and minimum 100% capacity in all tanks with any one pump system failed. 2 Minimum 130% capacity with intact system and minimum 100% capacity in all tanks with any one pump system failed. As for Class 1 3 Minimum 130% capacity with intact system and a contingency plan covering pump system failure. As for Class 1 4 As for Class 2 No requirements 5 As for Class 3 No requirements Notes: 1) 100% pump capacity during normal operation is the capacity required to carry out the operation at the planned speed. The required pump capacity for a reduced speed could be acceptable as “100%”, if ballast calculations are documented for this case, and the impact of the increased activity duration is properly taken into account. 2) 100% pump capacity during tide compensation is the capacity required to compensate for the maximum expected tidal rate of change. 3) A pump system includes the pump(s) which will cease to operate due to a single failure in any component. 4) The backup requirement X% capacity in all tanks could be covered by a modified ballast procedure giving X% capacity in all tanks involved in this modified procedure. 4.3.7 Vessel strength considerations 4.3.7.1 All ballast conditions shall be checked against longitudinal strength requirements. Any hull beam strength limitations shall be considered in the ballast procedure. 4.3.7.2 The effect of hull beam deflections on the object support load distribution shall be considered, see [5.6.11]. 4.3.7.3 Differential pressures across bulkheads shall be demonstrated to be within allowable values. 4.3.7.4 Any restrictions, e.g. any requirement to mimic the vessel voyage condition, on ballast condition(s) during welding of seafastening shall be considered. 4.3.7.5 Possible significant strength reduction due to cut outs (e.g. for ballast hoses, pumps or other equipment) in structural elements shall be considered. 4.3.8 Ballasting control 4.3.8.1 A straightforward ballasting control system and procedure shall be used. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 111 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 42 Ballast pumping capacity requirements It is recommended that it is possible to operate the ballast pumps from one control centre during operation. For multi barge operations, a control centre on each barge may be applicable. However, the control centre at one of the barges should be defined as the master ballast control centre. The arrangement should be such that simultaneous deballasting can be effected for all the relevant tanks at each stage. endofguidancenote 4.3.8.2 It shall be thoroughly documented how the ballasting will be done (controlled) for all possible combinations of tide level and load transferred. 4.3.8.3 Each tank should preferably be used to compensate one effect (see guidance note) only. To use a system/tank for compensation of more than two effects shall be avoided. Guidance note: In order to maintain maximum control with the ballasting it could be advisable to use separate systems/tanks for compensation of the effects of tide variation, weight transferred, and CoG position in both directions (trim and heel). endofguidancenote 4.3.8.4 A ballasting control monitoring system including backup shall be established. A communication system shall be established when pumps are operated manually away from the control centre. 4.3.9 Ballast calculations 4.3.9.1 Ballast calculations shall be carried out in order to establish required nominal capacity (i.e. the 100% capacity, see Note 1 in Table 42) pumping capacities. 4.3.9.2 For ballast calculations the expected CoG and weight without any contingencies should normally be used as the base case. However, the effect of possible weight and CoG variations shall be considered, see [5.6.2]. 4.3.9.3 The ballast calculations shall include sufficient steps to accurately define the required ballasting throughout the (load transfer) operation. 4.3.9.4 All considered contingency situations shall also be covered with an adequate number of ballast calculation steps. 4.3.9.5 The results of the ballast calculations, i.e. required pumping in all steps, shall be clearly outlined in ballast procedure(s). 4.3.10 Contingency and backup 4.3.10.1 Means for adequate handling of all ballast system contingencies identified in the risk management process shall be provided. 4.3.10.2 The contingencies indicated in Table 43 shall be considered. Minimum requirements to backup have also been indicated. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 112 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Contingency situation No Minimum requirement 1 Tidal velocities above (or below) the predicted values. Spare pump(s) or spare capacity in the main pump(s). See Table 42 for specific requirements. 2 Unplanned stops in load transfer (e.g. object movement stopped due to repair work, etc.) Adequate tank and pump capacities to handle the situation. See Table 41 and Table 42 for specific requirements. 3 Reversal of operation, if required. Ballast procedures/calculations with corresponding pump layout and tank capacities for this case shall be documented. 4 Reduced pump capacity. Spare pump capacity. See Table 42 for specific requirements in %. 5 Breakdown of ballast pump(s). Spare pump(s) or spare capacity in the main pump(s). See Table 42 for specific requirements. 6 Breakdown of power supply, including cables. Backup required, see [4.3.2.2], or adequate pump capacity, see Table 42, considering any power supply unit failed shall be documented. 7 Failure of any control panel/switchboard. 8 Failure of any ballast valve or hose/pipe. Sufficient backup to fulfil the requirements in Table 42 for one pump system failure. Alternative pump/ valve control methods (locations and procedures) could also be accepted as backup. See Notes. Notes: 1) All remotely controlled valves shall be capable of operation by a secondary, preferably manual system. Any automatic or radio controlled system shall have a manual override system. 2) The secondary valve operation system may be by ROV, provided that ROV access and a suitable ROV are available at all stages of the operation. The time for the ROV to get to and operate the valve shall ensure that the valve can be operated before the flow through it is critical. 4.4 Guiding and positioning systems 4.4.1 General 4.4.1.1 This sub section applies for design and verification of (object) guiding and positioning systems to be used for marine operations. Guidance note 1: Guiding systems are often designed with a primary and secondary system. The primary system is normally designed to absorb possible impact energy, and provide guiding onto the secondary system. The secondary system is normally designed to ensure accurate and controlled positioning of the object. endofguidancenote Guidance note 2: Additional operational specific guidance and requirements to guiding and positioning systems for lifting may be found in [16.14]. Requirements to positioning systems for vessels are given in Sec.17. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 113 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 43 Contingency requirements 4.4.1.3 After the design impact(s), guides and bumpers shall be able to resist loads due to the environmental conditions during operation, and operational loads from tugger lines, mooring lines etc. 4.4.1.4 After the design impact(s), guides and bumpers shall also provide a positive clearance towards neighbouring and supporting structure, and maintain their functionality. 4.4.1.5 DNVGLRPN102 [3.3.5], /55/, contains more recommendations and guidelines especially related to guiding systems used during removal of offshore platforms. 4.4.1.6 The stiffness of bumper and guide members should be as low as possible, in order that they may deflect appreciably without yielding. 4.4.1.7 Design of bumpers and guides should cater for easy sliding motion of the guide in contact with a bumper. Sloping members should be at an acute angle to the vertical. Ledges and sharp corners should be avoided in areas of possible contact, and weld beads should be ground flush. 4.4.1.8 Asbuilt bumper and guide dimensions shall be documented. 4.4.2 Characteristic loads 4.4.2.1 Characteristic impact loads for bumpers should be based on impact and deformation energy considerations. Alternatively for lifts in air only, the characteristic guide loads may be calculated according to the simplified method in [16.14.4]. 4.4.2.2 Realistic impact velocities, impact positions and deformation patterns shall be assumed. 4.4.2.3 Characteristic loads for the guiding and positioning phase shall be based on environmental conditions during operation, in addition to operational loads from tugger lines, mooring lines etc. 4.4.2.4 Combination of horizontal and vertical loads during guiding shall be considered in the design load cases. Realistic friction coefficients shall be used. 4.4.2.5 Characteristic loads for positioning lines (tugger lines, mooring lines, etc.) and attachments (padeyes, brackets etc.) shall be the expected maximum line tension. Possible dynamic effects shall be considered. 4.4.2.6 The characteristic loads shall be used as the basis for determining the maximum entry speed of the lifted object into the guiding system. 4.4.3 Design verification 4.4.3.1 Structural strength of guiding and positioning systems should be verified according to Sec.5. 4.4.3.2 The connection into the object and the members framing the bumper or guide location should be at least as strong as the bumper or guide. 4.4.3.3 The bumpers and guides shall be designed as either — To the ASD/WSD approach LS2 or, Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 114 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 4.4.1.2 Guides and bumpers shall have sufficient strength and ductility to resist impact and guiding loads during positioning without causing operational problems (e.g. excessive positioning tolerances), and without overloading members of the supporting structure. Plastic deformation of guides and bumpers due to impact loads may be allowed. The possibility and consequences of multiple impacts shall be considered. 4.4.3.4 To avoid overloading the supporting structure it shall be designed either — To the ASD/WSD approach LS1 or, — To the LRFD approach ULS with a consequence factor of 1.3. 4.4.3.5 Positioning padeyes should be designed to behave in a ductile manner in case of overloading. 4.4.3.6 Submerged brackets or padeyes shall be arranged such that failure will not breach any tank or compartment. 4.4.4 ALS conditions 4.4.4.1 If greater impact loads (velocities) than used in the ULS verification are considered possible, the guide system should be verified for ALS. 4.4.4.2 If the ALS (impact) load considered can cause failure (extensive damage) in the guiding system, it should be documented that installation of the object still will be feasible. Alternatively it should be possible to reverse the operation and return the object to a safe condition. 4.4.5 Position monitoring systems 4.4.5.1 The positioning equipment system accuracy and redundancy shall be specified. System accuracy shall be suitable for congested areas or where dimensional tolerances become tighter, e.g. for tieins, capture of docking piles. 4.4.5.2 System redundancy shall be in accordance with [4.2.1.10] appropriate to safety criticality and operational criticality requirements. 4.4.5.3 Subsurface positioning of ROV’s or other targets shall interface with the surface positioning system and should display on the same equipment. Subsea acoustic transceivers/beacons shall be separately identifiable and on coordinated channels. Survey systems using lineofsight shall recognise and cater for crossing surface vessels possibly occluding the system. Survey systems should be commissioned and calibrated before start of installation operations. 4.4.5.4 Normally, two independent on board positioning monitoring systems (PMSs) shall be utilized for operational monitoring and control purposes. Both systems shall be in operation at any time, each serving as the backup for the other. Each should be fed by an independent power source. 4.4.5.5 Where underwater accuracy is important, at least one PMS shall be an underwater, hydroacoustic reference system. 4.5 ROV systems 4.5.1 Planning 4.5.1.1 ROV systems and tooling shall be selected based on the environmental conditions that are to be expected at the worksite during the planned and contingency intervention/observation tasks. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 115 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — To the LRFD approach ULS. a) b) c) d) e) Minimum practical operational depth in the expected wave conditions, also considering possible wake from vessel thrusters. ROV working range, i.e. maximum horizontal offset vs. available tether length, considering the worst expected current conditions. Planning and design of the ROV operation shall as far as possible minimise the operational influence of the ROV operator's skill and experience. Poor visibility due to e.g. disturbed soil conditions, stirred up by contact or thruster or tool use close to seabed. Access to working site. 4.5.1.3 Planned ROV downtime and statistical uptime of ROV shall be taken into consideration when establishing TPOP, see [2.6.3]. If statistical data for ROV uptime is not available a conservative estimate shall be made. 4.5.1.4 For subsea operations where the operation reference period (TR, see [2.6.2]) is based on using ROVs (i.e. ROV activities are on critical path), ROV contingencies shall be documented and available. This can include a backup ROV spread on an independent system, i.e. there shall be no possible single failure identified that may cause an unacceptable long downtime for both ROV spreads. 4.5.1.5 The need for backup of essential ROV tools shall be assessed, and if applicable, the time needed to switch ROV tools/skids between ROVs shall be considered in the planning. 4.5.1.6 ROV tooling shall be provided with sufficient spares and backup tooling to allow the work to proceed with minimum delay. 4.5.1.7 For operations requiring assistance of both ROV(s) and diver(s), any restrictions on simultaneous working shall be considered and be clarified in advance. 4.5.2 Stationkeeping and positioning 4.5.2.1 The stationkeeping capability and manoeuvrability of the ROV during operation shall be considered. If the ROV is carrying equipment or is equipped with tooling packages/skids, this needs to be accounted for. Guidance note: Any ROV manipulator or tooling operation that requires the pilot to actively control the position of the ROV, e.g. if the target is moving, during performance of the task should be avoided. See also [4.5.2.3]. endofguidancenote 4.5.2.2 The required ROV thrust capacity shall be documented by verified capability plots (if available) and/ or detailed calculations considering: — — — — maximum current speeds at applicable depth(s), see [3.4.3]. appropriate drag areas and factors for ROV, cable and any tools all relevant relative ROV and current directions need for spare capacity, to be at least 30% for crucial ROV operations. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 116 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 4.5.1.2 When planning for a subsea operation, the following ROV limitations and recommendations should be noted: If detailed calculations are not made the horizontal current force on the ROV and the submerged cable may be taken as: [kN] where: dcab= diameter of submerged cable [m] lcab= projected length of submerged cable [m] = AROV projected cross sectional area of ROV including any tools [m ] vcur= maximum current velocity [m/s] 2 endofguidancenote 4.5.2.3 Grab bars to aid ROV positioning for manipulative or observation tasks should be provided where critical path ROV operations are planned. 4.5.3 Testing 4.5.3.1 For complex and critical stages of the installation that are dependent on ROV operations, Client/ Contractor shall demonstrate ROV capability of executing the planned intervention. This can be demonstrated by used of 3D models, mockup tests, previous experience, etc. Guidance note: This may involve the manufacture of mockups. If mockups are used, great care shall be taken to ensure that the mockups replicate the actual item. endofguidancenote 4.5.3.2 System Integration Testing should be carried out onshore to prove that the integration of all components and tooling can be achieved. 4.5.3.3 Dry tests and FAT should be carried out for critical and complex systems, the failure of which would result in significant and unacceptable schedule delay. 4.5.3.4 Before acceptance of ROV operations, maintenance records and dive logs for each ROV should be submitted. Sufficient spares should be available. 4.5.4 Launch and recovery system 4.5.4.1 Once installed, the launch and recovery system (LARS) shall be load tested according to the applied design/certification standard. 4.5.4.2 ROV launching and recovery restrictions shall be defined based on the capacity of the launch and recovery system, including capacity of the umbilical. In addition any restrictions related to operational aspects need to be considered. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 117 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: The following should be considered as rough guidance when establishing the ROV restrictions: — The launch and recovery system should incorporate a (guide/cursor) system that ensures adequate clearance with vessel side during lowering through the splash zone in the limiting wave conditions. — Overboard launching and retrieval of large ROV's is not generally recommended to take place in sea states exceeding 2.53.0 m (Hs) if the ability to operate in a safe manner under more severe conditions has not been documented. Higher waves may be applicable if the launch and recovery always may take place on leeward, for Moonpool ROV operations and if heavy weather side rail systems are used. — High wind speeds, and operational aspects (e.g. risk of entanglement) may also be critical. endofguidancenote 4.5.4.3 The overboarding system shall be safely operated within its intended design limit and due consideration of ROV recovery needs to accounted for in the definition of the weather criteria. 4.5.4.4 Launch and recovery shall as much as practically possible take place at safe distance from sensitive subsea infrastructure. See [5.6.6.6]. 4.5.4.5 A tether management system (TMS) should be used in deep water sites to ease the deployment of the ROV to the worksite. The tether shall be of sufficient length to allow the ROV to get from the TMS to the worksite. 4.5.5 Monitoring 4.5.5.1 Video monitoring of all subsea operations should in general be provided, e.g. ROV, diveroperated, etc. Any critical part of the operation should be performed with such monitoring. 4.5.5.2 All diving and complex WorkROV operations should be monitored by independent ROV with monitoring as its only task in the period it is carrying out such critical monitoring. 4.5.5.3 The ROV used for monitoring subsea operations should, as far as practically possible, be operated from the installation vessel. 4.5.5.4 If the ROV operation has to be performed by a vessel other than the installation vessel, the stability and reliability of the videolink system between the vessels shall be proven under the given conditions. Guidance note: Some operations can require a large horizontal distance between the installation vessel and the observation ROV, thus necessitating a separate ROV vessel. The videolink should be tested before start of operation. endofguidancenote 4.5.5.5 Means for locating and tracking of the ROV from the surface are required for navigational purposes and emergency recovery. 4.5.6 Human factors 4.5.6.1 The feasibility of subsea operations often relies on the correct completion of tasks by ROV it should therefore be ensured that ROV operators have the necessary experience and skills. 4.5.6.2 If complex operations reliant on the skill of the ROV operator alone cannot be avoided, ROV operator experience shall be evaluated. Training sessions specially adapted for the proposed operation can be appropriate. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 118 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 4.5.7.1 ROV equipment capacities shall be chosen to suit the relevant depth and consider the following: — Both the ROV and any ROV tooling should be “depth rated”, and their stated depth limitation should not be exceeded. — General wear on the complete ROV spread during deep water operations is more extensive than during moderate depth operations, it is important therefore that all required maintenance is done before operation. — During deep water operations special attention shall be given to lubrication systems which can be affected by the external water pressure. 4.5.7.2 Current forces acting on the umbilical and ROV shall be defined, see guidance note in [4.5.2.2]. 4.5.7.3 Potential effects due to resonance in wires, cables, umbilicals, etc. shall be investigated and accounted for in the design. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 119 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 4.5.7 Deepwater ROV operations 5.1 Introduction 5.1.1 General 5.1.1.1 This section addresses loading categorisation, load effects, load cases and load combinations. 5.1.1.2 The requirements for structural strength are given, mainly related to steel structures. For structures of other materials, adequate safety levels shall be achieved by use of recognized standards. 5.1.2 Scope 5.1.2.1 This section presents the requirements for strength checking of steel structures using both Allowable Stress Design (ASD) / Working Stress Design (WSD) and Load and Resistance Factor Design (LRFD). Alternatively, probabilistic methods can be used. 5.1.2.2 The ASD/WSD and LRFD checks have differing inherent levels of safety. To compensate, this Standard has differing requirements for the design loading. It is therefore important that the applied environmental loading is determined using the return period applicable to the checking method selected. 5.1.3 Revision history 5.1.3.1 The following changes have been made to this section: — — — — — — — — — — — — — — — — — — — — General: Editorial changes to improve clarity. [5.4.4.3] g): Guidance note modified. [5.4.4.4]: New clause for when fullscale tests are not viable. [5.6.2.3] e): Clause modified to account for equipment accuracy being considered when determining CoG envelope. [5.6.5.4] c): New clause related to the effects of vibration included. [5.6.5.5] a): New guidance note about when green water may normally be ignored. [5.6.9.5]: Clause modified to make calculation of upper bound friction consistent with other sections. [5.6.15]: Section modified to cover ballasting for counteracting of wind heel. [5.6.15.4]: Clause modified for motions derived from DNV GL and DNV rules for classification of ships. [5.6.16.3]: Clause and guidance note modified to clarify requirements for quartering sea cases. [5.9.2.1]: Clause modified for load cases for motions derived from DNV GL and DNV rules for classification of ships. [5.9.7]: Title modified. [5.9.7]: Section modified to include load factors for motions derived from DNV GL and DNV ship rules, permissible utilisations for welds and slip critical bolted connections and updated Table 58 and Table 59. [5.9.8]: Title modified. [5.9.8.4] 3): New guidance note added to cover use of plastic design provisions in Eurocode 3, /61/. [5.9.8.4] 5): Clause modified to include weld in good shop conditions. Guidance note updated to clarify requirements related to welds on board. [5.9.8.5] 2): Clause modified to include webbing straps. [5.9.8.5] 3): New clause covering material factor for shackles, turnbuckles and complete web lashing assemblies. [5.9.9]: New guidance note added regarding less conservative material factors for friction. [5.10.2.3] 8): Clause modified to clarify waiting time requirements. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 120 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 5 LOADING AND STRUCTURAL STRENGTH 5.2 Design principles 5.2.1 Introduction 5.2.1.1 The object subject to marine warranty survey, together with the associated equipment shall be shown to possess adequate strength to resist the loads imposed during the marine operation. 5.2.1.2 The overall design shall be performed with due consideration to the execution of marine operations. 5.2.1.3 Structures shall be robustly designed such that an incident does not lead to consequences disproportional to the original cause. 5.2.1.4 Simple load and stress patterns shall be aimed for in the design. 5.2.1.5 Structural elements should be fabricated according to the requirements given in DNVGLOS C401, /26/, or another recognized standard. 5.2.1.6 Structural components and details should be designed so that the structure behaves, as far as possible, in a ductile manner. Guidance note: A structure or a structural element, can exhibit brittle behaviour even if it is made of ductile materials e.g. when there are sudden changes in section properties, when exposed to low temperatures. endofguidancenote 5.3 Specific design considerations 5.3.1 Connections 5.3.1.1 Connections should be designed with smooth transitions and proper alignment of elements. Stress concentrations should be avoided as far as possible. 5.3.1.2 The transmission of tensile stresses through the thickness of rolled steel elements (plates, beams etc.) should be avoided unless materials with proven (tested) zquality are applied. Alternatively, the material can be subject to nondestructive testing (NDT) using UT to demonstrate that it is free of laminations, see [5.10.2.3] 5). 5.3.1.3 Structural details above the still water level shall be so arranged that water will not be trapped in the structure if this can cause damage such as e.g. rupture due to freezing of the water, when the operation is in an area and season when this can occur. 5.3.2 Penetrations 5.3.2.1 The object shall be reinforced as necessary in the area adjacent to any penetrations (e.g. for risers or Jtubes) below the water line against hydrostatic pressures and against accidental impact from dropped objects and vessel impact if likely at any draught. 5.3.2.2 Penetrations shall be positively sealed to prevent the ingress of water whilst the structure is afloat. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 121 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.1.3.2 The changes made to this section for the June 2016 edition are shown in App.A. 5.3.3.1 Doubler plates are generally recommended for use: — When attaching seafastenings or sacrificial anodes to permanent steel work subject to fatigue or if the permanent structure could be damaged when the attachments are burnt off after use. — To avoid welding onto other welds. 5.3.3.2 Doubler plates are generally NOT recommended for use when tension can cause overstress in the doubler plate or the structure to which it is attached. 5.3.4 Tension connections 5.3.4.1 Where tension connections to a vessel deck are required, attention shall be given to the connection between the deck plate and underdeck members. In cases of any doubt about the condition, an initial visual inspection should be undertaken, to establish that fully welded connections exist, and that the general condition is fit for purpose. Further inspection may be required, depending on the stress levels imposed and the condition found. See also [5.10.2.3] 5) regarding throughthickness properties of the deck plate. Guidance note: The welds between vessel deck plates and under deck stiffeners/bulkheads (including cut out infills) are normally small and can limit the capacity. endofguidancenote 5.3.5 Bolted connections for seafastening 5.3.5.1 Appendix [E.2] gives the requirements for bolted connections for seafastenings which involving cyclic loading due to the dangers of progressive collapse. 5.3.6 Lightweight metallic and composite structures 5.3.6.1 The designers or manufacturers shall specify any handling/connection requirements which shall appear in the relevant procedures and towing/transport manuals. Guidance note: Tugger line systems are especially important when handling lightweight alloy, composite and other items in order to avoid any impact with seafastening, grillage or offshore structures which could cause plastic deformations. endofguidancenote 5.3.6.2 The structural strength of objects of innovative design and/or material shall be documented. Guidance note: Particular attention should be given to local strength in way of supports, seafastening etc. endofguidancenote 5.3.7 Compressed air 5.3.7.1 Compressed air may be used to resist hydrostatic head on internal or external walls during ballasting, for reducing draught, or for reducing overall bending moments by air cushions in skirt cells under well controlled conditions. However its absence should not, in general, result in structural collapse i.e. it should be used only to increase structural safety factors. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 122 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.3.3 Doubler plates 5.3.7.3 Some practical considerations on the use of compressed air are given in [12.6.2]. 5.3.8 Inspection 5.3.8.1 Sufficient access for inspection, maintenance, and repair shall be provided during planning of the operation. 5.3.8.2 Instrumentation (monitoring) can be used as a supplement to other inspection, see [2.9]. 5.3.9 Existing structures 5.3.9.1 Strength calculations for marine operations often include the verification of existing steel structures of e.g. barges, other vessels and objects for dismantling. The calculations shall account for any reductions in the design capacity. Examples of possible causes include: — corrosion — damage — modifications not shown on drawings. 5.3.9.2 Existing structures should normally be inspected in order to assess possible reductions in the design capacity, see [5.3.9.4], [5.9.8.4], [5.10.2.2], and [5.10.2.3] 5). See DNVGLRPN102, /55/, for further guidance on existing structures and their inspection. 5.3.9.3 Project related strength verifications of vessels should normally be carried out conservatively with either the asbuilt thickness reduced to account for possible corrosion or based on detailed inspections including thickness measurements. Where the thickness is reduced to account for corrosion the thickness used in calculations should be the thickness indicated on the asbuilt drawings less the vessel’s class corrosion allowance, or reduced by 0.2 mm per year from each side. For new vessels with a proper corrosion protection system, e.g. painting or coating, no thickness reduction need to be considered for the first five years of the vessel’s life. Guidance note: Typical corrosion allowance requirements can be found in DNVGLRUSHIP Pt.3 Ch.3 Sec.3, /35/. endofguidancenote 5.3.9.4 Weld capacity should be calculated according to [5.9.7.5] for ASD/WSD or [5.9.8.4] for LRFD, as applicable. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 123 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.3.7.2 Where the requirements of [5.3.7.1] cannot be met, then a risk assessment shall be carried out to determine possible causes and probabilities of loss of compressed air. Mitigating measures to reduce the risks to an acceptable level shall be agreed with the MWS company. When checking vessel welds the following should be noted: a) Class acceptance for these welds can be required, especially for new/reinforced welds. b) All loads (force components) normal to the deck plate should generally be considered transferred to the under deck welds. However, when the force is only compressive, i.e. there is no tension force in any load combination, this force component may be assumed to be transferred through direct contact between the deck plate and the web frames/bulkheads, and the weld may be checked for shear stress only, see item f). If the force varies between compression and tension, the weld should be able to transfer also the compression force in order to ensure intact welds, unless the capacity of the seafastening system is documented in ALS assuming that the connection under consideration is broken. c) All loads (force components) parallel to the deck plate can be disregarded, see however item f). d) The dispersion angle through the deck plate should be taken as maximum 45° unless a greater dispersion can be justified. e) Size reduction due to possible corrosion should be considered. If not otherwise documented the size should be as shown on the drawing less the Class corrosion allowance. f) Note that shear stress in stiffener/girder welds due to local bending/shear in these should be included in the equivalent stress (the effects due to global vessel behaviour can be ignored). endofguidancenote 5.3.10 Protection against accidental damage 5.3.10.1 The structure shall be protected against accidental damage by application of the following two principles: — reduction of damage probability — reduction of damage consequences. 5.3.10.2 If damage to piping, equipment, structures, etc. could lead to severe consequences (e.g. accidental flooding, explosion, fire or pollution) such items shall be protected to minimise the risk of accidental damage. Guidance note: Protection may be established by methods such as providing a sheltered location, by local strengthening of the structure, or by appropriate fender systems. endofguidancenote 5.4 Testing 5.4.1 General 5.4.1.1 Testing can be used in order to establish or verify design parameters. Material and weld testing should be carried out according to a relevant recognized standard, e.g. DNVGLOSC401, /26/, see also [5.10] which summarises key requirements. 5.4.1.2 Adequate and reliable test data should be used to verify/correlate values that are considered unreliable based on theoretically calculations only. This is particularly relevant for geometrically complex structures and for new design or operational concepts. 5.4.1.3 For marine operations, such (project) specific testing is normally most relevant to determine or verify: — response, e.g. motions by model testing, — loads, e.g. by direct measuring of loads in model tests and — resistance, e.g. by load testing or testing of friction. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 124 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 5.4.2.1 Model testing is most frequently used for the determination of response and loading effects but can also be used for determination of structural resistance. 5.4.2.2 Model tests should be carried out according to a verified test program/procedure using: — — — — models representing the object(s), vessel(s) and real conditions as accurately as required, qualified test personnel, adequate testing facilities, and calibrated monitoring equipment with sufficient accuracy. 5.4.2.3 Normally the testing should be combined with theoretical calculations. 5.4.2.4 The laws of similarity shall be considered in order to ensure that the quantities measured in the model test can be correctly transformed. 5.4.2.5 Effects that can influence the measured quantities and that are not represented in the model test shall be identified and the consequences of these effects should be evaluated. Guidance note: For example, the correct relative stiffness (of vessels/structures) will normally not be obtainable in model tests and effects of this on the results should be evaluated. endofguidancenote 5.4.3 Full scale load testing 5.4.3.1 Full scale load testing should be carried out according to agreed procedures. 5.4.3.2 Requirements for standardised load testing, e.g. of lifting appliances, are not described in this standard. Such testing should be carried out as described in the relevant standard, e.g. DNVGL ST0378, /129/, and DNVGLSTE273, /17/. 5.4.3.3 Full scale load testing may be carried out by loading test pieces to destruction. The characteristic th th strength should normally be defined based on the 5 or the 95 percentile of the test results, whichever is the most conservative. 5.4.3.4 If sufficient design documentation is not available to verify the strength (capacity) of an item, it can be acceptable to document the strength of the item by means of a load test. Guidance note: Typical items for which this type of testing could be applicable include: — Anchors for which no holding power calculations have been carried out. — Shore bollards without relevant certificates or where the underground design and workmanship is not documentation. — Holding power of clamps or other types of connections. — Local soil capacity (deflection), e.g. of loadout tracks. — Existing (steel) structures with no/limited inspection access. endofguidancenote 5.4.3.5 For such tests the load should normally be at least 0.9 times the maximum design load (i.e. including load factor) for the item. All relevant load directions should be tested. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 125 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.4.2 Model testing 5.4.4 Testing of friction 5.4.4.1 Testing may be carried out in order to establish applicable friction coefficients. The testing conditions should represent the expected friction surface and load intensity as close as possible. 5.4.4.2 In marine operations the dynamic friction coefficient will normally be the most relevant and testing of this should hence be included unless it is not needed for the particular application. 5.4.4.3 Where testing is carried out, a detailed test procedure shall be documented. Guidance note: The test procedure should consider the following: a) Possible variations in applicable conditions (e.g. wet and dry surfaces). See [5.4.4.1] and [5.4.4.2]. b) Dynamic friction, if applicable, should be tested and measured by a recognised method. c) The characteristic friction coefficient should be defined based on the 5 th or the 95 th percentile confidence level of the test results, whichever is the most conservative. d) At least 5 test pieces should be made, and each tested at least twice for each actual condition. e) The design friction coefficient is calculated using the characteristic friction coefficient and an appropriate material factor. See [5.9.9], [5.9.5.3] and [5.9.6.2]. f) Where fewer tests are performed e.g. because of the scale, more conservative material factors should be used. g) Where a greater number of tests are performed, less conservative material factors may be justified and used. endofguidancenote 5.4.4.4 In cases where fullscale tests are not viable, the characteristic friction shall be documented by an engineering assessment based on an adequate number of applicable smallscale tests using a validated calculation methodology. 5.5 Load categorisation 5.5.1 Introduction 5.5.1.1 This section defines load categories and describes loads of general interest for marine operations. 5.5.1.2 The appropriate characteristic value should be defined (calculated) for all relevant loads. 5.5.1.3 More detailed descriptions of the loads to be considered are given for each type of marine operation/ object type in Sec.6 to Sec.18. 5.5.1.4 See [5.6] for load combinations, [5.7] for the failure modes to be considered, [5.8] for guidance on analytical models and [5.9] for strength assessment. 5.5.2 Load categories 5.5.2.1 Loads and load effects shall be categorised as follows: — Permanent Loads G — Variable Functional Loads Q — Deformation Loads D Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 126 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.4.3.6 A thorough inspection shall be carried out of items that have been subject to testing. Defects that could reduce the strength (capacity) shall not be allowed. 5.5.2.2 The characteristic values of loads shall be selected as indicated in Table 51 for all applicable loads. Table 51 Characteristic load selection Limit states Load category 2) – Temporary design conditions ALS 1) ULS FLS Permanent (G) Variable (Q) Intact structure SLS Expected maximum and minimum values (weight/buoyancy) Specified value 3) 3) Specified load history Environmental (E) – Weather restricted Specified value Specified load history Environmental (E) – Weather unrestricted 4) Operations Based on statistical 5) data Expected load history n/a n/a Expected extreme value Expected load history Accidental (A) Deformation (D) Damaged structure Specified 3) value(s) Specified value(s) n/a 5) Based on statistical data Specified value n/a and 6) n/a Specified value(s) Notes: 1) See [5.5.3] to [5.5.7] for definitions of load categories 2) See [5.9.1.3] for definitions of limit states. 3) The specified value (load history) shall, if relevant be justified by calculations. See also [5.6.6]. 4) See [2.6.6] 5) See Sec.3. 6) Joint probability of accident and environmental condition could be considered. 5.5.3 Permanent loads (G) 5.5.3.1 Permanent loads are loads which will not be moved or removed during the phase of the marine operation being considered. Such loads can be due to: — — — — weight of stationary structures weight of permanent ballast and equipment that cannot be removed external/internal hydrostatic pressure of permanent nature pretension. 5.5.3.2 Characteristic permanent loads shall be based on reliable data. For weight see [5.6.2]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 127 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — Environmental Loads E — Accidental Loads A. 5.5.4.1 Variable functional loads are loads that can be moved, removed or added. Such loads can be due to: — — — — — — — operation of winches pull/push forces weight of moving structures loads from adjacent vessels ballasting operational impact loads stored materials, equipment or liquids. 5.5.4.2 Characteristic variable functional loads shall be specified with maximum and minimum values, which shall be considered as necessary to determine the worst case(s). 5.5.5 Deformation loads (D) 5.5.5.1 Deformation loads are associated with inflicted deformations. Such loads can be caused by: — — — — — installation or set down tolerances barge hull beam global deformations caused by moving ballast water (or temperature) structural restraints between structures differential settlements temperature deformations. 5.5.5.2 Characteristic deformation loads shall be maximum or minimum specified values, which shall be considered as necessary to determine the worst case(s). The specified values shall, if applicable, be based on results from analysis considering extreme conditions. 5.5.6 Environmental loads (E) 5.5.6.1 All loads caused by environmental phenomena shall be categorised as environmental loads. Such loads can be due to phenomena including: — — — — — — wind waves current storm surge tide ice. 5.5.6.2 Where applicable, see [5.6.11], seafastening (and grillage/cribbing) reactions due to barge hull beam global deformations caused by waves should be considered as environmental loads. See also [5.6.17]. 5.5.6.3 Gravity load components caused by the roll and pitch angles of a floating object due to wind and waves, shall be categorised as environmental loads. 5.5.6.4 The environmental design loads shall be calculated based on a process involving, as applicable: — definition of characteristic conditions see [2.2.7] — calculation of characteristic loads – see [5.5] and [5.6] — load analysis see [5.6.2] to [5.6.11] Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 128 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.5.4 Variable functional loads (Q) 5.5.7 Accidental loads (A) 5.5.7.1 Accidental loads are loads associated with exceptional or unexpected events or conditions. Such loads can be due to: — — — — — collisions from vessels dropped objects loss of hydrostatic stability flooding loss of internal pressure. 5.5.7.2 Characteristic accidental loads shall be based on realistic accidental scenarios. See also [5.6.6]. 5.6 Loads and load effects (responses) 5.6.1 General 5.6.1.1 This section describes the loads and load effects that should be considered. 5.6.2 Weight and centre of gravity (CoG) 5.6.2.1 Introduction 1) 2) 3) For calculation purposes, conservative values of weight and CoG should be used. Weight control shall be performed by means of a welldefined and documented system, complying with ISO 199015 – Weight control during engineering and construction, /99/. ISO 199015 states (inter alia) that: — “Class A (weight control) will apply if the project is weight or CoGsensitive for lifting and marine operations or during operation (with the addition of temporaries), or has many contractors with which to interface. Projects may also require this high definition if risk gives cause for concern”. — “Class B (weight control) shall apply to projects where the focus on weight and CoG is less critical for lifting and marine operations than for projects where Class A is applicable”. — “Class C (weight control) shall apply to projects where the requirements for weight and CoG data are not critical”. 4) Class A weight control shall apply unless it can be shown and agreed with the MWS company that a particular structure and all its marine operations are not weight or CoG sensitive. 5) Weight reports should be issued in accordance with section 8 of /99/. Contents and format of weight reports that are not in accordance shall be agreed with MWS company at an early stage of the project. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 129 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — motion analysis see [5.6.12] — selection of load cases see [5.6.13] — load factors see [5.9]. 1) An upper bound design weight (Wud) shall be defined for all operations. Where the minimum weight could be critical in an operation e.g. voyage motions, a lower bound design weight (Wld) shall be defined. Guidance note 1: The upper/lower bound design weights are normally defined to cover the expected range of weights in the weight report with additional margins to account for uncertainties during the design process and the factors in 2) or 3) for unweighed and weighed objects respectively. endofguidancenote Guidance note 2: Where a Not To Exceed (NTE) weight has been defined and used as the upper bound design weight the actual maximum permissible value is less than the NTE weight. In addition to any inplace considerations, the following can control the NTE weight: — Draught and stability for towout, towages, mating operations and installation; — Allowable stresses in the structure for marine operations; — Limitations due to crane, loadout trailers, other equipment or groundbearing capacity. endofguidancenote 2) Where an object (excluding piles) is not to be weighed, the following shall be true for the asbuilt weight report: WReport, Factored ≤ Wud/γWeight WReport, Base ≥ Wld γWeight(where applicable) Where: WReport, Factored WReport, Base Wud Wld γWeight 3) = Factored weight in weight report = Base weight in weight report = Upper bound design weight = Lower bound design weight = Unweighed object weight margin factor as per Table 52 Where an object (excluding piles) is to be weighed, the following shall be true for the final weighed condition corrected for any post weighing modifications: WWeighed≤Wud/γWeighing WWeighed ≥ WldγWeighing (where applicable) Where: WWeighed = Net weight in weight report = Upper bound design weight Wud = Lower bound design weight Wld γWeighing = 4) Factor to account for weighing equipment inaccuracy i.e. ( ) The weight contingency factors for piles shall be agreed with the MWS company and shall consider the following as a minimum: — plate thickness tolerance — fabrication tolerances. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 130 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.6.2.2 Weight considerations Weight Class (as defined by ISO 199015, /99/) γWeight A 1.05 B and C 1.10 5.6.2.3 Centre of gravity factors a) b) For weight Class A and B structures, see [5.6.2.1] 3), a CoG envelope shall be applied to allow for CoG inaccuracies. For Class C structures a CoG envelope is recommended. The size of the CoG envelope should reflect the operational and structural sensitivity to CoG variations and the most conservative centre of gravity position within the envelope should be taken. Guidance note 1: For early design stages, too small an envelope should be avoided and envelope sizes should generally be no less than 0.05L x 0.05B x 0.05H, where L, B and H are the Length, Breadth and Height of the structure. endofguidancenote Guidance note 2: For operations with a linear relation between shift in CoG and resulting load effects, or operations less sensitive to CoG shifts, the inaccuracy in estimated CoG may alternatively be accounted for by an inaccuracy factor applied to the weight. This factor should normally not be taken less than 1.05. endofguidancenote c) d) e) f) For Class C, if a CoG envelope is not used then a CoG inaccuracy factor of 1.10 shall be applied to the weight. Where it can be documented that a lower CoG inaccuracy factor is applicable, this should be agreed with the MWS company. The CoG contingency factors for piles shall be determined considering the pile length and the plate manufacturer’s plate thickness tolerance specification. Normal weighing operations can be used only to identify the CoG position in a horizontal plane; the effects of weighing equipment inaccuracy shall be considered when determining the associated CoG envelope. Inaccuracies in the vertical CoG position should be specially considered for operations that are sensitive to the vertical CoG position. If applicable the vertical CoG can be verified by means of an inclining test (see [2.10.5]). 5.6.2.4 Weight control a) The actual weight and CoG position shall be determined by weighing unless agreed otherwise with MWS company. Guidance note: Gravity based structures and launched jackets are generally excluded from being weighed. endofguidancenote b) c) d) A weighing procedure for the structure shall be produced and include the specification, including accuracy, for all equipment. The accuracy of the weighing equipment shall be certified by a Competent Body. The weighing should preferably be carried out a minimum of 3 times with the load cells interchanged between each of the weighing operations. Before any structure is weighed, a predicted weight and CoG report shall be issued, so that the weighed weight and CoG can immediately be compared with the predicted results. The cause(s) of significant deviations between the weighed and predicted results (both weight and CoG) shall be investigated and reported. Where weight is added to/removed from the structure after weighing, a weight control system shall be adopted to ensure that the weight and CoG details based on the weighing are updated with any changes. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 131 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 52 Unweighed object weight margin factors f) g) 5.6.2.5 Buoyancy a) b) c) d) e) Buoyancy (hydrostatic external load) normally counteracts another load and shall be categorised accordingly. Where the buoyancy or distribution of buoyancy is critical to the marine operation, the dimensional and buoyancy control and monitoring shall be maintained to an appropriate degree of accuracy. The buoyancy of the object and the position of the centre of buoyancy should be determined on the basis of an accurate geometric model. Characteristic buoyancy loads should be based on maximum and/or minimum expected values. Buoyant cargoes, particularly where the buoyancy contributes to stability requirements, shall be adequately secured against liftoff unless it can be shown that liftoff will not occur. 5.6.3 Wind loads 5.6.3.1 Wind loads shall be calculated based on the characteristic wind speed, see Sec.3, and recognised calculation methods. 5.6.3.2 Wind induced loads shall be based on projected area. The total wind load shall consider both lateral and parallel load components. 5.6.3.3 The possibility of lift effects and their magnitude shall be considered. 5.6.3.4 The gravity components due to wind induced heeling shall be considered. Guidance note: DNVGLRPC205, /46/, gives further information with respect to shape coefficients as well as to effects of wind direction relative to member, solidification and shielding. endofguidancenote 5.6.4 Current loads 5.6.4.1 Current loads shall be calculated based on the characteristic current velocity, see Sec.3, and recognised methods. 5.6.4.2 The increase in current velocities/loads due to shallow waters or narrow channels shall be considered. Guidance note: DNVGLRPC205, /46/, gives further information with respect to shape coefficients as well as to effects of flow direction relative to member, solidification and shielding. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 132 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used e) The weight changes due to items that are added and removed shall include their weighing contingency factors. The final calculated or weighed weight and CoG values shall be documented. Where the calculated or weighed weight, including weighing and contingency factors, or the CoG is outside the design values considered, the effects of the deviations shall be quantified and the operational procedures and documents modified as required. When the installation of a large number of nominally identical items is to be approved, the weight control programme should be documented to show the effects of all potential variations on the final weights and the results documented by competent personnel. See [18.2.1.2] for weight control for decommissioning/removal. 5.6.5.1 Combined wavecurrent induced drag loads shall be calculated considering the vector sum of the current and wave particle velocities. 5.6.5.2 First order wave loads a) Wave loads should be estimated according to a deterministic or stochastic design method. A wave period range according to [3.4.11.5] and [3.4.11.2] should be investigated. Guidance note: If any responses are found governing for the response should be checked in these areas with endofguidancenote b) c) d) Wave loads shall be determined using methods applicable for the location and operation, taking into account the type of structure, its size and shape and its response characteristics. The effects of wave elevation shall be evaluated, and if necessary included in the design. Wave slamming, see [5.6.5.4], hydrodynamic and hydrostatic loads on members protruding over the vessel side shall be considered. The effect of such loads on the motion characteristics and on the seafastenings and grillage/cribbing shall be taken into account. 5.6.5.3 Second order wave loads a) b) Second order wave drift forces can be important in the design of some marine operations. The effects of second order drift forces shall be considered in these cases, which include large volume structures, mooring and positioning systems, towing resistance estimates, etc. Second order wave loads consist of mean wave drift forces and slow varying wave drift forces. Long period responses excited by slow drift forces shall be investigated. 5.6.5.4 Slamming loads and breaking waves a) b) c) Cargo overhangs and elements in the splash zone or overhanging the periphery of the floating body shall be investigated with regards to possible slamming loads and/or immersion. The effect of shock pressures on surfaces in the splash zone, caused by breaking waves, shall be investigated for conditions up to the design sea state for all headings. The effect of vibrations due to wave slamming loads on the vessel hull and/or on overhanging cargo shall be assessed. Typical consequences include: — Reduction in the effectiveness of friction restraint. — That seafastening is needed to prevent swinging/vibration of slender members/equipment/pipes. — Unintended unscrewing of nuts/bolts. d) Loads due to slamming and breaking waves should normally be calculated according to DNVGLRP C205, /46/. Guidance note: Further information regarding slamming loads and breaking waves can be found in DNVGLRUSHIP Pt.3 Ch.10, /35/, and NORSOK N003, /111/. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 133 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.6.5 Wavecurrent loads a) The possible effects of green water (extensive amounts of water on deck due to waves), shall be considered. The effects on both the structure and stability (weight and free surface) shall be investigated. Guidance note 1: See e.g. NORSOK N003, /111/, for further information regarding green water effects. Design forces for sea pressure from green water can be based on requirements for deck houses, see DNVGLRUSHIP Pt.3 Ch.4 Sec.5 [3], /35/. endofguidancenote Guidance note 2: The effects of green water are not normally expected for voyages that are stagedtows with shelter available (see [11.14.6] for requirements related to the availability of shelter) and where the vessel is at a draught less than the load line draught. endofguidancenote b) Deck cargoes vulnerable to damage from green water on deck should be protected by breakwaters or increasing freeboard. 5.6.5.6 Swell a) The effects of loads and motions due to swell shall be considered. See [3.4.14] and [5.6.18]. Swell can be governing for operations designed for small irregular waves (e.g. weather restricted tows). In such cases swell operational limits and forecasting shall be established. 5.6.6 Accidental loads 5.6.6.1 Accidental loads should be defined based on relevant accidental scenarios. In many cases the probability of accidental scenarios can be reduced to a level such that there is no need to consider them further. 5.6.6.2 The accidental load design principles indicated in DNVGLOSA101, /40/, should be considered as applicable for the planned marine operation. DNVGLRPC204, /31/, gives further guidance related to design philosophy and calculation of relevant accidental loads due to e.g. collisions and dropped objects. 5.6.6.3 Load effects due to all possible accidental scenarios/conditions shall be considered. Accidental cases and contingency situations may be defined or excluded based on results from HAZOP’s or risk evaluations/ assessments. 5.6.6.4 DNVGLOSA101, /40/, is, in general, based on annual probabilities, whilst this Standard is based on probability per operation. This can be considered when the (magnitude of) applicable accidental loads are defined. However, unless a justification for lower loads is documented the loads indicated in DNVGLOS A101, /40/, should be considered. 5.6.6.5 Vessel collision a) b) Characteristic collision loads shall be estimated from energy considerations. Estimates of the collision energy should be based on reasonable assumptions of possible collision scenarios, velocities, directions, ship or object type, size, mass and added mass. Estimates of deformation energy should be based on the most likely impact points and probable deformation patterns. The behaviour of the vessels or structures during the impact, and thus the distribution of impact energy between kinetic rotation and translation and deformation energy, should be considered by dynamic equilibrium or energy considerations. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 134 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.6.5.5 Green water Local effects (deformation, damage, etc.) and global load effects (acceleration, global stress, etc.) shall be considered. Guidance note: In some cases collisions will have been covered under the design and classification of the vessel. endofguidancenote 5.6.6.6 Dropped objects a) b) c) Loads caused by dropped objects can be relevant for some ALS load cases. The characteristic load due to a dropped object should be based on the weight of objects that could fall and their potential fall height. For objects falling through water maximum possible impact velocity should be considered. The maximum velocity is normally the terminal (free fall in water) velocity. See DNVGLRPN103 [4.7.3.5], /56/, and DNVGLRPF107 [5.3], /52/, for guidance. Loads on subsea items due to dropped objects may be ignored if operations that could cause dropped objects are carried out at a safe distance. The safe distance should be calculated considering the maximum possible dispersion angle for each type of object falling through the water. The effect of current should be considered. Risk analysis may be used in order to eliminate physical possible high dispersion angles by showing that the risk of hitting specified critical locations is acceptably low for such high angles. See DNVGLRPF107, /52/, for further risk assessment guidance. If detailed assessments are not made, the safe distance can normally be taken as the larger of 50 meters or that determined from a dispersion angle of 20° to the vertical. 5.6.6.7 Other causes a) b) Other relevant accidental loadings shall be considered. These can include, but are not limited to, cases such as: “one line broken”; “one compartment damaged”; malfunction of critical systems e.g. heave compensation, leaking valves; erroneous operation e.g. the use of the wrong valve; unexpected values of parameters e.g. deformations, friction, vessel GM, tidal variation, weights and CoG’s, etc. The static loads resulting from any one compartment damage, as described in [11.10.4] to [11.10.7], shall be considered and, if significant, designed for as a LS2 or ULS case. 5.6.7 Dynamics 5.6.7.1 The potential for dynamic response shall be investigated, and the effects shall be included in the design analysis when they are of significance. Dynamic response is typically caused by wave forces, wind loads (gusts), vortex shedding in air or water, slamming loads, etc. 5.6.7.2 Dynamics shall be investigated by recognised methods using realistic assumptions for the natural period, damping, material properties etc. 5.6.7.3 The response to dynamic effects e.g. structural stress and deflections can be relevant for all Limit States. 5.6.7.4 Means of determining whether vortex shedding could be critical for any particular member are contained in DNVGLRPC205, /46/, DNVGLRPC205 Sec.9 and “Dynamics of Fixed Marine Structures”, /122/, Section 7.2. 5.6.8 Nonlinearities 5.6.8.1 Nonlinear effects shall be considered in cases where these significantly influence the estimated responses. Nonlinear effects are typically caused by: — nonlinear materials — nonlinear geometry (largedisplacement effects) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 135 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used c) 5.6.8.2 Nonlinear load effects due to combinations of environmental loads should be taken into account e.g. wavecurrent drag forces are a function of the square of the sum of the wave and current particle velocities. 5.6.9 Friction 5.6.9.1 Possible unfavourable effects of friction shall be considered. Well documented favourable effects of friction may be included in the design. 5.6.9.2 A friction coefficient range, i.e. both a maximum and a minimum friction coefficient, should be considered in the design calculations or it should be proven that a conservative minimum (or maximum) coefficient suffices. 5.6.9.3 The characteristic friction coefficient range shall be defined according to recognised industry standards or tests, see [5.4]. Indicative operationspecific values are given Table 102, [11.9.2], Table 118, Table 1120, Table 135 and in DNVGLRPN102 Table 24, /55/. For soilmaterial interfaces, guidance is provided in DNVGLRPF109, /53/, [3.4.6] and DNVGLRPF114, /51/. 5.6.9.4 The lower bound design friction coefficient (μld) shall be the lower bound characteristic value (μlc) divided by a material factor. 5.6.9.5 The upper bound design friction coefficient (μud) shall be the upper bound characteristic value (μuc) divided by a material factor less than 1.0. 5.6.9.6 The appropriate material (safety) factor for friction shall be selected dependent upon the limit state considered and the risk involved in exceeding (or going below) the design friction. See [5.9.5], [5.9.6] and [5.9.9]. These factors are applicable to both LRFD and ASD/WSD. For bolts see [5.9.7] or [5.9.8.5]. 5.6.9.7 The minimum design friction force shall be taken as the minimum design load (i.e. including relevant load factors) perpendicular to the friction surface multiplied by μld. 5.6.9.8 The maximum design friction force shall be taken as the maximum design load (i.e. including relevant load factors) perpendicular to the friction surface multiplied by μud. 5.6.9.9 If the friction coefficient range is based on uncertain data the consequences of the maximum possible variation in friction coefficients shall be evaluated. See [5.6.14]. 5.6.9.10 Vibrations, varying or uncertain surface conditions etc. affecting the friction shall be considered. 5.6.9.11 Restraint effects caused by combination of friction and global deflections shall be considered. 5.6.10 Tolerances 5.6.10.1 Loads caused by operational or fabrication tolerances exceeding the tolerances stated in the design standards/codes shall be considered. Typical examples include: — — — — setdown tolerances (loadout, positioning) shimming tolerances uncertain deformation (in load distributing material) fabrication tolerances, see [5.10.1.4]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 136 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — nonlinear damping — nonlinear combination of load components or response components — wave elevation e.g. due to waveindeck, nonlinear effects of dragloading (especially with current), etc.. 5.6.11 Relative deflections 5.6.11.1 The effects of relative deflections between structures shall be considered and included in the design whenever applicable. These can be of particular significance when they induce loads in connections and supports such as grillages and seafastenings. The causes of relative deflections include: — — — — vessel deflection (longitudinal bending) in waves, ballasting, deballasting or redistribution of ballast, temperature differences, relative deflections that need to be considered during the operation. 5.6.11.2 For sea voyages the potential effects of longitudinal wave bending effects should always be considered when: a) b) c) d) e) The The The The The towed hull is not a classed, seagoing vessel or barge, or rd cargo is longer than about 1/3 of the transport barge or vessel length, or cargo is supported longitudinally on more than 2 groups of supports, or relative stiffness of the hull and cargo could cause unacceptable stresses to be induced in either, or seafastening design allows little or no flexibility between cargo and vessel. 5.6.11.3 Some cargoes, such as large steel jackets, can be inherently much stiffer than the barge, and will reduce vessel deflections, at the expense of increased cargo stresses. 5.6.11.4 See also [11.9.3.2] for friction, [11.9.5] for seafastening design and [11.28.4.3] for jackups. 5.6.11.5 The restraint loads should be defined in the same category as the load that causes the relative deflections, i.e. restraint loads caused by environmental conditions should be defined as Eloads, see [5.5.6]. 5.6.12 Motion analysis 5.6.12.1 General 1) Motions of floating objects shall be determined for the relevant environmental conditions and loads. These may be from simplified conservative estimates, however it is normally recommended that the analysis (and tests) described in this subsection are carried out. Guidance note: Detailed analyses and model tests are not normally needed for the transportation of smaller cargoes on standard vessels. endofguidancenote 2) Inertia loads due to motion should be calculated for all six degrees of freedom. Guidance note: This includes also an evaluation of mass (rotational) inertia effects from roll and pitch. These effects should as a minimum be quantified, and the effect evaluated. This is particularly relevant for barge voyages with large roll motions. endofguidancenote 3) Testing of models, see [5.4.2], or full scale structures, see [5.4.3], may be carried out where the accuracy of theoretical approaches is uncertain, or where the design is particularly sensitive for motions. Guidance note: Estimation of motions from model testing or by theoretical calculation has associated advantages and disadvantages. The two approaches are generally to be considered as complimentary rather than as alternatives. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 137 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.6.10.2 Loads caused by effects described in [5.5.5]. It is recommended that theoretical calculations are correlated against relevant model test data (if available) in cases where strongly nonlinear behaviour is expected. Such cases can occur when, for example: — overhanging cargo is occasionally submerged, or — there are large changes in the waterplane area with draught. 5) The analytical models should be checked with respect to sensitivity to input parameters, see [5.6.14]. 6) Recognised and well proven sixdegree of freedom linear or linearized computer programs, utilising the strip theory or 3D sink source techniques are generally recommended. Special consideration shall be given to nonlinear damping effects. The effect of forward speed shall be evaluated, where this is more onerous. 7) Computer programs shall be validated against a suitable range of model test or full scale results in irregular seas. When using new software or for new or unconventional applications or new problems, this validation shall be documented. Similarly justification of drag coefficients, added mass and damping shall be documented. Guidance note: Guidance on drag and added mass coefficients for a range of standard shapes can be found in DNVGLRPC205, /46/. endofguidancenote 8) Firstorder motion response analysis program generally report heave in a global fixed axis system. In these cases heave shall be assumed to be parallel to the global vertical axis and therefore the component of heave parallel to the deck at the computed roll or pitch angle (theta) is additive to the forces caused by the static gravity component and by the roll or pitch acceleration. 9) In general, motion response calculations should be based upon a 3D panel model of the vessel. If a 2D strip theory model is used, the computer program needs to include the proper treatment of head/ stern sea wave excitation loads. Simplified calculations should only be applied for noncritical routine operations or screening purposes. 5.6.12.2 Wave headings a) The full range of wave headings shall be analysed. Spacing between the analysed wave headings should not exceed 45°. Guidance note: For the cases where reduced design wave heights are acceptable from some headings, see [11.8], this applies to all headings. However, symmetry can be considered when relevant provided appropriate means of accounting for cargo CoG offset are included. endofguidancenote b) Short crested sea shall be considered for wave analysis where all headings are not carried out with equal wave heights i.e. typically motion analysis in order to find limiting installation wave heights for different vessel headings. Guidance note: If short crested waves are considered the spacing between analysed wave headings should normally not exceed 22.5°. See also [3.4.12]. endofguidancenote c) Short crested sea may be considered for wave analysis where all headings are included with equal wave height i.e. typically motion analysis for sea voyages without any heading restrictions. 5.6.12.3 Wave periods a) A wave period range with corresponding wave heights, see [3.4], shall be considered when evaluating characteristic motions and accelerations. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 138 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 4) a) b) c) RAO’s for the basic six degrees of freedom can be utilised to calculate displacements, velocities, accelerations, and reaction forces for points in a body fixed coordinate system, or to establish RAO’s for these points. These RAO’s may be used for calculation of significant and maximum responses. When combining different responses, the phase angle between the different components may be considered. The gravity component shall be considered when determining the RAO’s for inertia loads (e.g. transverse accelerations). 5.6.13 Load cases and load combinations 5.6.13.1 Loads and load effects shall be combined to form load cases that are applicable to and physically feasible for the actual object(s) and type of operation under consideration. 5.6.13.2 All possible load cases which can influence the feasibility of the marine operation shall be considered in the design. 5.6.13.3 Characteristic loads may be combined taking into account their probability of simultaneous occurrence. 5.6.13.4 Characteristic static (mean) load components and characteristic dynamic (varying) load components which are statistically independent may be combined according to the formulae below. where: Fi,mean Fi,amp = Characteristic static load components = Amplitude of dynamic load components Guidance note: Dynamic load components in the above formulae are normally restricted to loads with periods less than 10 minutes. The maximum values of dynamic loads with periods greater than 10 minutes are normally added as static loads (i.e. Fi,mean equal to the maximum load, and Fi,amp =0). endofguidancenote 5.6.13.5 Correlated dynamic load components shall be added as vectors, unless statistical data of simultaneous occurrence are available. Load components due to first order motions should be considered to be correlated. The combination of these components is described in [5.6.15.2] and [5.6.15.4]. 5.6.14 Sensitivity analysis 5.6.14.1 The load cases shall include a parametric sensitivity analyses whenever a single load or parameter significantly affects the design or selection of the method or equipment to determine whether small changes significantly affect the design. 5.6.14.2 Where the operational safety is critically dependent on a sensitive input, conservative characteristic values shall be used. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 139 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.6.12.4 Response amplitude operators (RAO’s) 5.6.15.1 Load cases for each heading shall be derived by the addition of fluctuating loads resulting from wind and wave action to static loads resulting from gravity and still water initial conditions. 5.6.15.2 In lieu of a refined analysis the worst possible combination of the individual responses for the same heading, including components from the selfweight and wind, shall be combined, i.e.: where: Sd S( ) Fx, Fy, Fz = Design load or load effect. Fwx, Fwy = Wind forces (vectors), in x and y directions including relevant load factors. The horizontal load components due to wind induced heel or trim shall be included. = Response/load effect function. = Inertia forces (vectors), in x, y and z directions including relevant load factors and gravity components. Where ballasting during transport is possible to counteract wind heel, and this is documented in the procedures, wind induced heel on the vessel can be computed based on difference between 1minute mean and the 1hour average windforce. W = Load due to selfweight (vectors). 5.6.15.3 Alternatively, the fluctuating components shall be the worst possible combination of the loads resulting from calculations or model tests carried out in accordance with [11.3.7.1] through [11.3.7.3], with due account to be taken of the effects of phase. All influential loadings shall be considered: however the following static and environmental loadings are the most likely to be of importance: S1 = Loadings caused by gravity including the effects of the most onerous ballast condition on the voyage. F1 = Loadings caused by the wind heel and trim angle. Where ballasting during transport is possible to counteract wind heel, and this is documented in the procedures, wind induced heel on the vessel can be computed based on difference between 1minute mean and the 1hour average windforce. F2 F3 F4 F5 F6 F7 F8 = Loadings caused by surge and sway acceleration = Loadings caused by pitch and roll acceleration = Loadings caused by the gravity component of pitch and roll motion = Loadings caused by direct wind = Loadings caused by heave acceleration, including heave.sin(theta) terms = Loadings caused by wave induced bending = Loadings caused by slam and the effects of immersion. 5.6.15.4 One of the following four methods in this paragraph shall be used to determine the design loadings: a) b) Except as noted in [11.7.2.1], the effects of phase differences between the various motions can be considered, if resulting from model test measurements, or if the method of calculation has been suitably validated. In cases where it is not convenient or possible to determine the relative phasing of extreme wind loadings and heave accelerations with roll/sway or pitch/surge maxima, a reduction of 10 percent may be applied to fluctuating load cases F1 through F8 which combine maximum wind and wave effects. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 140 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.6.15 Loads due to motions and wind where: Fmot F#(1 hour) F#(1 min) F# = Maximum load due to wind and wave motions = Loads based on 1 hour mean wind speed = Loads based on 1 minute mean wind speed = F1 through F8 as applicable Where ballasting during transport is possible to counteract wind heel, and this is documented in the procedures, the wind induced heel due to the 1hour average wind speed can be ignored: d) e) For deck cargo units carried on ships assessed using DNVGLRUSHIP Pt.3 Ch.4 Sec.3, /35/, see [11.6]. For ships classed to DNV Rules for Classification of Ships, /15/, objects may be assessed to Pt.3 Ch.1 Sec.4 B600, B700 and B800, see [11.6]. 5.6.15.5 Where transfer functions for motions are available these may be combined to a transfer function for the actual response or load effect. The phasing between the different components may be considered. Guidance note: This method requires careful evaluation of the responses to be analysed. All responses which will be governing for the design should be considered. endofguidancenote 5.6.16 Default motion criteria 5.6.16.1 For loads computed in accordance with [11.7], the loads applied to the cargo shall be: S1+F1+F3+F4+F6 where: S1, F1, F3, F4 and F6 are as defined in [5.6.15.3]. 5.6.16.2 The effects of buoyancy and wave slam loading shall also be considered if appropriate. 5.6.16.3 As stated in [11.7.2.2] roll and pitch cases are to be considered separately. Combined roll and pitch are generally not required. Guidance note: Quartering seas should also be included if deemed critical for any structural element. (See also IMO Res. A.714(17), Annex 13 regarding allowable angles of securing devices.) Quartering seas can be included by combining 60% of the horizontal transverse and 60% of the longitudinal acceleration with both the minimum and maximum vertical acceleration i.e. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 141 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used c) However, if the wind induced load or the wave induced load exceeds the reduced load, then the greatest shall be considered. The total loads may be calculated by combination of loads as follows: 5.6.17.1 Restraint loads due to vessel deflections in waves, see [5.6.11], loads due to vessel motions and wind may be combined as shown below. where: Ftot = Total design load Fdef = Maximum loads due to deflections Fmot = Maximum load due to wave motions and wind. 5.6.18 Loads due to irregular waves and swell 5.6.18.1 Loads and load effects from irregular waves and swell shall be combined. These loads and load effects may normally be combined assuming that they are statistically independent. See [5.6.13.4]. 5.7 Failure modes 5.7.1 All relevant failure modes shall be investigated. A failure mode is relevant if it is considered possible and the anticipated consequence(s) of the failure cannot be disregarded. 5.7.2 The relevant failure modes can be grouped as either as global (total system) or local (individual members) as indicated in the following sections. 5.7.3 Global modes of failure include: — — — — — — — — structural collapse overturning sliding liftoff loss of hydrostatic or hydrodynamic stability sinking settlement free drift. 5.7.4 Local modes of failure include: — plastic deformation (yield) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 142 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.6.17 Loads due to restraint deflections, vessel motions and wind buckling fracture large deflections excessive vibration. 5.8 Analytical models 5.8.1 The analytical models used for evaluation of loads, responses, structural behaviour and resistance shall be relevant considering: the design philosophy, the type of operation and the possible failure modes. The models should satisfactorily simulate the behaviour of the object’s structures, its supports and the environment. 5.8.2 Design analyses shall be carried out considering all relevant loads and failure modes, see [5.7]. 5.8.3 The design analysis shall be thoroughly documented that the results shown to satisfy the relevant requirements and criteria. 5.9 Strength assessment 5.9.1 General 5.9.1.1 Structural strength can be assessed using either ASD/WSD methodology or LRFD methodology. These are discussed below. 5.9.1.2 Whichever methodology is applied, the loading conditions/limit states shown in Table 51 shall be considered when verifying structural strength. 5.9.1.3 A limit state is commonly defined as a state in which the structure ceases to fulfil the function, or to satisfy the conditions, for which it was designed. See also DNVGLOSC101 Ch.2 Sec.1 [3], /24/. 5.9.1.4 Limit states shall be defined for all possible failure modes, see [5.7]. 5.9.1.5 The FLS and SLS load cases requirements are the same for ASD/WSD and for LRFD. It is however important that the load cases assessed for the ALS and LS / ULS are developed using the applicable environmental inputs for ASD/WSD or LRFD. Table 53 Description of loading conditions/limit states Loading condition / limit state ASD / WSD name LRFD name Maximum capacity, usually for maximum environmental and functional loads (permanent, variable, deformation) LS1 LS2 ULSa ULSb Loading history – important for structures exposed to significant cyclic/repetitive loading FLS FLS ALSI ALSI Intact structure subjected to loads from an accidental event Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 143 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — — — — Serviceability checks (alignment, clearances, deflection, vibration, etc.) ALSD ALSD SLS SLS 5.9.2 Design approach 5.9.2.1 The format of the ASD/WSD method implies that strength/capacity verification of structures or systems involves the following steps: — Identify all relevant limit states, see [5.9.1]. — Identify all relevant loading conditions, see [5.6.13]. — For each loading condition define the relevant characteristic loads, see [5.5.2], and design conditions, see Table 51. — For each loading condition and failure mode, see [5.6] and [5.7], find the design loads — For each loading condition determine the design load effect, see [5.6] — Ensure adequate safety by proving that the design load effect does not exceed the allowable, as described in [5.9.4], [5.9.5], [5.9.6] and [5.9.7]. LS2 is applicable only when the loading is dominated by environmental/storm loads, e.g. for weather unrestricted operations the extreme loads due to the applicable design return period environmental criteria, see Table 31; for weather restricted operations, where an Alpha Factor according to [2.6.9] is to be applied. Any LS2 load case may be treated as a gravityload dominated limit state (LS1). LS2A is applicable only when the loading is determined from classification society rules, see [11.6]. Any LS2 load case may be treated as a gravityload dominated limit state (LS1A). 5.9.2.2 The format of the LRFD method implies that strength/capacity verification of structures or systems involves the following steps: — Identify all relevant limit states, see [5.9.1]. — For each limit state define the relevant characteristic loads, see [5.5.2], and design conditions, see Table 51. — For each limit state find the design loads by applying the relevant load/design factors, see [5.9.4.2], [5.9.5.2], [5.9.6.2] and [5.9.8.3]. — For each limit state determine the design load effect, see [5.6] and [5.9.3.2] b). — For each limit state determine the characteristic resistance, see [5.9.3.3]. — For each limit state determine the design resistance, see [5.9.3.2] d). — Ensure adequate safety by proving that the design load effect does not exceed the design resistance, See [5.9.3.2] a). 5.9.3 LRFD checks 5.9.3.1 General a) Where the LRFD (load and resistance factor design) method is used for design verification the load and material factors specified in this section shall be used according to the principles of the method. Guidance note: The safety factor format applied for lifting slings in Sec.16 could be regarded as an ASD/WSD (permissible stress) method, but the safety level is correlated according to the applicable LRFD factors. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 144 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Damaged structure subjected to postdamage loading a) The level of safety is considered to be satisfactory if the design load effect, Sd, does not exceed the design resistance, Rd, i.e.: Sd ≤ Rd for all limit states b) The equation Sd = Rd defines the respective limit state. A design load effect is an effect (e.g. stress, mooring line load, sling load, deformation, overturning moment, cumulative damage) due to the most unfavourable combination of design load(s) i.e.: where: Sd = design load effect Fd = design load(s) S = load effect function. c) d) A design load (Fd) is obtained by multiplying the characteristic load (Fc) by the appropriate load factor, see [5.9.8.3], [5.9.4.2], [5.9.5.2] and [5.9.6.2]. A design resistance (Rd) is obtained by dividing the characteristic resistance (Rc), see [5.9.3.3], by a material or design factor, see [5.9.8.3], [5.9.4.1] g), [5.9.5.2] and [5.9.6.2]. 5.9.3.3 Characteristic resistance a) Rc shall be calculated based on the characteristic values of the relevant parameters or determined th th by testing. Characteristic values should be based on the 5 or the 95 percentile of the test results, whichever is the most conservative. See also [5.4]. Guidance note 1: The resistance for a particular load effect is, in general, a function of parameters such as structural geometry, material properties, environment and load effects (interaction effects). endofguidancenote Guidance note 2: The characteristic static resistance of steel, fc, is to be taken as the smaller of: — the guaranteed minimum yield stress, fy, or — 0.85 times minimum tensile strength of the material. endofguidancenote Guidance note 3: Rc for materials not mentioned e.g. concrete, concrete reinforcement, wood, synthetic materials, soil, etc. could normally be based on recommendations/requirements in the applied design code or standard. For soil see DNVGLOSC101 Ch.2 Sec.10 [1.3], /24/. endofguidancenote b) Rc for (wire and fibre) ropes and chains should be taken as the certified MBL. 5.9.4 Fatigue limit states – FLS 5.9.4.1 General a) b) For all structures exposed to significant cyclic loads during a marine operation the possibilities and effects of fatigue should be considered. The FLS design conditions should be based on the defined operation period and the anticipated or expected load history during the marine operation. See Table 53. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 145 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.9.3.2 Acceptance criteria d) e) Possible dynamic load effects due to e.g. slamming and vortex shedding should be investigated. See [5.6.7]. Restraint loads, see [5.6.17.1], could be important and shall hence be thoroughly evaluated and included in the FLS calculations. The FLS shall be evaluated according to procedures given in a recognised code or standard. See e.g. DNVGLOSC101 Ch.2 Sec.5, /24/, for general requirements for checking of fatigue limit states. Guidance note 1: Reference can be made to DNVGLRPC203, /29/, and DNVGLCG0129, /20/, for practical details with respect to fatigue design. endofguidancenote Guidance note 2: For new structures that are susceptible to fatigue, it is advisable to check for adequate fatigue life by analysis for voyages over about 50 days, including possible waiting time at sea, where the nominal peakstress range is less than 350 N/mm 2 2 and the SCF does not exceed 2.5. If the peakstress range is increased to 550 N/mm then a fatigue analysis is advisable for voyages over about 10 days. endofguidancenote Guidance note 3: Newbuild MOU's are normally verified for fatigue for the initial delivery voyage in the classification process and a separate analysis is not normally required for this voyage. For subsequent voyages, it is desirable to undertake a fatigue analysis, however in many cases there is insufficient time and/or data regarding prior use. In such cases it is good practice to undertake a thorough NDT inspection of fatiguecritical areas before the voyage and to repair any cracks, see [11.28.5.3]. endofguidancenote f) g) For mooring systems, the FLS is mainly of concern for steel components where fatigue endurance limits the design. For fibrerope segments, the timedependent strength can limit the design; consequently stress rupture or creep failure should be incorporated in the checks for ULS and ALS as appropriate. See also DNVGLOSE301, /27/. Where structural items e.g. grillages and seafastenings, are to be reused they should be demonstrated to have sufficient fatigue life for the sequence of planned operations, including all previous operations. An appropriate inspection regime shall be proposed including NDT at appropriate intervals e.g. close visual examination after every use and NDT after every 10 uses; if there are highly utilised areas, more frequent NDT could be appropriate. For bolts, see [E.2]. 5.9.4.2 Design factors FLS a) b) c) d) All load factors shall be: γf=1.0 Design fatigue factors (DFF) shall be applied to increase the probability of avoiding fatigue failures The calculated cumulative damage ratios for the defined design conditions times the applicable DFF according to Table 54 shall be less than or equal to 1.0. Lower values for the Miner’s sums than 1.0 can be relevant if the structure has been or will be subjected to fatigue loading before or after the considered marine operation. In such cases the maximum allowable Miner’s sum for the actual marine operations shall be determined by considering the total load history the structure will be exposed to. Table 54 Design fatigue factors (DFF) Inspection during operation (and repair) planned Elements in inspection category I Elements in inspection categories II & III Yes 2.0 1.0 No 3.0 2.0 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 146 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used c) 1) The elements shall be categorised according to the definitions in Table 511. 2) Higher DFF than indicated may be applicable based on other (project) governing codes. 3) The indicated DFF are applicable only for the fatigue utilization during the considered marine operation. Hence, if the fatigue utilization is combined with the utilization from other phases, see [d)], a different DFF may be applicable. 5.9.5 Accidental limit states – ALS 5.9.5.1 General 1) Accidental limit states for marine operations include verification of: — ALSI: The intact structure or system for the defined accidental load effect(s) combined with other relevant load effects, see Table 51 (i.e. loads of type E may be ignored). — ALSD: The damaged structure or system, see [5.9.5.1] 2), for relevant design load effects, see Table 51. Guidance note: See also Table 53 for definition of ALSI and ALSD. endofguidancenote 2) The damage to the structure or system in ALSD is normally defined by either: — the damage caused by the defined accidental load effect(s) or, — a defined damaged or an accidental condition/scenario, see [5.6.6]. 5.9.5.2 Design approach and load and resistance factors a) b) c) d) e) Accidental loads are defined in [5.6.6]. Design against accidental loads shall primarily consider global failure modes, see [5.7.3]. E.g. increasing of local strength which may reduce the safety against overall failure of the structure should be avoided. Load factors should in ALS normally, see d), be taken according to Table 55 or Table 56. Load factors greater than 1.0 shall be considered if an LRFD method ALS load or condition is not considered to have a sufficient low, i.e. ≤ 104 per operation, probability. If working to the ASD/WSD approach, the factors should be similarly increased. The characteristic environmental load (E) in the ALSD load condition should/may be defined considering the probability of the analysed accident/damage and the anticipated maximum period (i.e.TR, see [2.6.2]) the damaged situation will remain. Table 55 ASD/WSD Load factors for ALS member strength checks using ANSI/AISC 36016 Type ANSI/AISC 36016 ASD/WSD option strength checking ALSI 0.6 ALSD 0.6 Notes: 1) The load factor of 0.6 for the ASD/WSD case arises because the basic allowable stress in ANSI/AISC 36016 is 0.6*yield. In order to effectively work to yield, the load is multiplied by 0.6 and used with the standard allowable of 0.6*yield. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 147 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Notes: Load Categories Load Condition G Q D E A ALSI 1.0 1.0 1.0 n/a 1.0 ALSD 1.0 1.0 1.0 1.0 n/a Notes: 1) Load categories G, Q, D, E and A are described in [5.5.2] 5.9.5.3 Material factor ALS The material factor may in ALS generally be taken equal to: γm, ALS=γm/1.15 where γm = the applicable material factor in ULS, see [5.9.8.3]. Guidance note: E.g. the ALS material factor for steel wire ropes may be taken as γm, ALS = 1.5/1.15 = 1.3. endofguidancenote 5.9.6 Serviceability limit states – SLS 5.9.6.1 General a) b) For some marine operations it is relevant to check SLS related to the feasibility of the operation. Such serviceability limit states could be associated with required clearances, push/pull capacities and vessel (barge) level (compared e.g. with quay height). See DNVGLOSC101 Ch.2 Sec.7, /24/, for typical SLS requirements for offshore steel structures. 5.9.6.2 Safety factors a) b) For SLS related to feasibility the load factors are normally equal to 1.0. Relevant safety factors/margins should be defined considering the actual operation. See Sec.6 to Sec.18 for guidance. SLS for structural elements shall normally be checked applying load and material factors equal to 1.0. Guidance note: In SLS the object (or equipment/vessel) owner is free to define higher load and material factors if this is found applicable. endofguidancenote 5.9.7 ASD/WSD strength checks to LS1/LS1A or LS2/LS2A loading 5.9.7.1 The ASD/WSD design approach is described in [5.9.2.1]. 5.9.7.2 The primary structure and any critical temporary works like lifting attachments, spreader bars and seafastenings shall be of high quality structural steelwork with full material certification and NDT inspection certificates showing appropriate levels of inspection. 5.9.7.3 The infrequent load cases, generally limited to survival and damaged cases, including design cases for weather restricted operations where an Alpha factor according to [2.6.12] is to be applied, shall be treated as an LS2 or LS2A case (environmental load dominated) as applicable. This does not apply to: a) Steelwork subject to deterioration and/or limited initial NDT unless the condition of the entire load path has been verified, for example the underdeck members of a barge or vessel. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 148 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 56 LRFD Load factors for ALS c) d) e) Steelwork subject to NDT before elapse of the recommended cooling and waiting time as defined by the Welding Procedure Specification (WPS) and NDT procedures. In cases where this cannot be avoided by means of a suitable WPS, it may be necessary to increase the strength or impose a reduction on the design/permissible sea state. Steelwork supporting sacrificial bumpers and guides. Spreader bars, lift points and primary steelwork of lifted items. Structures during a loadout. 5.9.7.4 Traditionally AISC has also been considered a reference code, e.g. by API RP2A. If the ANSI/ AISC 36016 American National Standard “Specification for Structural Steel Buildings” of July 2016 (in the th AISC “Steel Construction Manual”, 15 edition) is used, the allowables shall be not less than the member stresses determined using a load factor on all loads (dead, live, environmental, etc.) of no less than the applicable of those detailed in Table 57. Table 57 Load factors for ASD/WSD method strength checks using ANSI/AISC 36016 Type ANSI/AISC 36016 ASD/WSD option strength checking Limit State 1 (LS1) 1.00 1) Limit State 1A (LS1A) 1.12 1) Limit State 2 (LS2) 0.75 Limit State 2A (LS2A) 1) 2) 3) 0.84 , , 1) 4) , Notes: 1) Where the Sec.11 loads are due to accelerations determined according to DNV or DNV GL class rules, see [11.6], LS1A or LS2A shall be used. 2) The load factor of 0.75 for ASD/WSD in the LS2 case arises because the basic allowable stress in ANSI/AISC 360 16 is 0.6*yield and the traditional 1/3 increase to 0.8*yield (i.e. to 0.6*yield*4/3) for environmental load cases is not included. As an alternative, the load is multiplied by 3/4 and used with the standard allowable of 0.6*yield in order to achieve the safety levels that have been used and accepted over many years. 3) Any load LS2 case may be treated as a gravityload dominated limit state LS1. 4) Any load LS2A case may be treated as a gravityload dominated limit state LS1A. 5) Where the loads are determined using IMO, then the strength shall be checked using IMO requirements. Guidance note: nd The API RP2A 22 th edition references the 9 Edition of AISC “Steel Construction Manual”, which includes the traditional “1/3 increase” for infrequent environmentally dominated load cases. The AISC “Steel Construction Manual” 15 th Edition does not reference the 1/3 increase, instead it allows the referencing code to specify load factors. The LS2 load factors herein effectively allow the 1/3 increase. endofguidancenote 5.9.7.5 Stresses in welds determined from an analysis using the applicable load factor from Table 57 shall have utilisations no greater than the applicable value from Table 58 and be assessed according to either: a) b) The method given in DNVGLOSC102 Ch.2 Sec.9 [2.5], /25/, or equivalent, or The method illustrated by the example given for the assessment of fillet welds for brackets given in [E.1]. Below deck welds in vessels classed to DNV ship rules may be checked against 90fw in shear on the weld throat and 160fw for normal stress perpendicular to the weld throat, where fw is the material factor for the applicable strength group as given in /15/. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 149 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used b) For welds made on board the vessel the permitted utilisation for welds made at a fabrication site is acceptable provided that the welding conditions are good, see [5.10.2.2], and there is good weld fitup (e.g. control of correct/no gaps to deck plate). endofguidancenote Guidance note: For welds made on board the vessel the permitted utilisation for welds made at a fabrication site is acceptable provided that the welding conditions are good, see [5.10.2.2], and there is good weld fitup (e.g. control of correct/no gaps to deck plate). endofguidancenote Table 58 Weld permissible usage factors for ASD/WSD method Permissible usage factors, η Welding location DNV GL or DNV class rules, see [11.6] LS1A LS2A 2) Other approaches given in this standard 1) (excluding IMO) LS1 LS2 Good “shop” conditions 0.60 0.60 Fabrication site 0.53 0.53 On board the vessel 0.46 0.46 Notes: 1) Where the loads are determined using IMO, then the strength shall be checked using IMO requirements. 2) Where the Sec.11 loads are due to accelerations determined according to DNV or DNV GL class rules, see [11.6.2] and [11.6.6], LS1A or LS2A shall be used. 5.9.7.6 The allowable strength of slip critical bolted connections shall be assessed according to the method given in [E.2] and have utilisations no greater than the permissible usage factors in Table 59. The loads shall be determined from an analysis using the applicable load factor from Table 57. Table 59 Slip critical bolted connections permissible usage factors for ASD/WSD method Permissible usage factors, Bolt hole type DNV GL or DNV class rules, see [11.6] 2) η Other approaches given in this standard 1) (excluding IMO) LS1A LS2A LS1 LS2 Standard hole clearances 0.55 0.41 0.55 0.41 Oversize or slotted holes 0.49 0.37 0.49 0.37 Notes: 1) Where the loads are determined using IMO, then the strength shall be checked using IMO requirements. 2) Where the Sec.11 loads are due to accelerations determined according to DNV or DNV GL class rules, see [11.6.2] and [11.6.6], LS2A may be used. 3) The permissible usage factors for LS2 and LS2A are less than those for LS1 because it is required that bolts are effectively checked to LS1. 5.9.7.7 The design of nontubular connections shall be in accordance with an appropriate standard such as AISC/AISC 36016, /2/, using a consistent safety format and factors. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 150 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 5.9.8.1 General DNVGLOSC101 Ch.2 Sec.4, /24/, gives provisions for checking of ultimate limit states for typical structural elements used in offshore steel structures. 5.9.8.2 Load factors ULS a) For the ultimate limit states (ULS) the two load conditions “ULSa” and “ULSb” as given in the Table 510 shall be considered. Table 510 Load factors for ULS Load Categories Load Condition G Q D E A ULSa 1.3 1.3 1.0 0.7 n/a ULSb 1.0 1.0 1.0 1.3 n/a Notes: 1) b) Load categories G, Q, D, E and A are described in [5.5]. For loads and load effects that are well controlled a reduced load factor and Q loads instead of 1.3 in load condition ULSa. γf = 1.2 may be used for the G Guidance note: Examples where γf = 1.2 may be applicable are: — External hydrostatic pressure caused by an accurately defined water level. — Loads due to an accurately distributed (i.e. static determinate) well defined selfweight. — Functional loads accurately defined (limited) by the maximum (possible) capacity of equipment. endofguidancenote c) d) e) Where a permanent load G (e.g. selfweight or hydrostatic pressure) causes favourable load effects, a load factor γf = 1.0 shall be used for this load in load condition ULSa. See also [5.6.2.2] and [5.6.2.3]. In cases where the load is the result of counteracting and independent large hydrostatic pressures the appropriate load factor shall be applied to the pressure difference. However, the pressure difference should not be taken less than 0.1 times the hydrostatic pressure. In dynamic problems the application of load factors should be given special consideration. In lieu of a probabilistic analysis, the load effects may be found by application of load factors after having found the responses, e.g. after having solved the equations of motion for vessel motion response analysis. 5.9.8.3 ULS material factors a) Applicable material factors in ULS are given in [5.9.8.4] to [5.9.9]. Material factors for materials not mentioned in [5.9.8.4] to [5.9.9] e.g. concrete, concrete reinforcement, wood, synthetic materials, soil, etc. shall be in accordance with a recognised code or standard. See also [5.9.3.3]. b) If a material factor used. γm = 1.0 is found more unfavourable than the indicated values, γm = 1.0 shall be 5.9.8.4 Material factors for structural steel 1) 2) In ULS the material factors for steel structures should be taken as minimum: γm = 1.15. For members in compression a higher material factor may be applicable. The material factor should normally be chosen according to the applied design code, but never smaller than 1.15. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 151 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.9.8 LRFD strength checks to ULS loading If EN 1993 (Eurocode 3) /61/ is used for calculation of structural resistance, the material factors listed in DNVGLOSC101 Ch.2 Sec.4, /24/, for steel structures and DNVGLOSC101 Ch.2 Sec.8, /24/, for welded connections shall be applied. Guidance note 1: See also Table 61 in NORSOK N004, /112/, for applicable material factors. endofguidancenote Guidance note 2: The plastic design provisions in Eurocode 3, /61/, should be used only when the loading is applied in a constant direction and, if there will be repeated loading then only for lower strength materials (i.e. yield no greater than 355 MPa). endofguidancenote 4) 5) In ULS the material factor for static strength of tubular joints should be chosen according to the applied design code, but never smaller than 1.15. An increased (i.e. larger than 1.15) material factor shall be considered if the production is carried out in an environment where reduced control of dimensions, materials and fabrication could be expected, e.g. welding on board vessels. The following minimum material factors, γmW, apply when the weld capacity is calculated according to DNVGLOSC101 Ch.2 Sec.8, /24/, EN 199318 or [E.1]: — For welds made in good shop conditions: γmW = 1.15 — For welds made at a fabrication site: γmW = 1.3 — For welds made on board the vessel: γmW = 1.5 Guidance note: For welds made on board the vessel γmW for welds made at a fabrication site is acceptable provided that the welding conditions are good, see [5.10.2.2], and there is good weld fitup (e.g. control of correct/no gaps to deck plate). endofguidancenote 5.9.8.5 Material factors for ropes, chain and bolts 1) In ULS the material factor for certified steel wire ropes and chains should normally be taken as: γm = 1.5 Guidance note: γm = 1.15/0.85/0.9 = 1.5 where: 1.15 is the general steel material factor, 0.85 is a factor to account for that the characteristic strength, see [5.9.3.3] guidance note 2, of ropes and chains is based on the tensile strength (MBL), and 0.9 is a general factor because wire ropes are considered more vulnerable to “undetectable” wear and material irregularities than regular steel structures. For new ropes with a 3.2 certificate it may be acceptable to use 1.0, see [16.4.9.2]. (Note also that an additional wear factor could be applicable). endofguidancenote 2) For fibre ropes and webbing straps the material factor depends on the material and relevant failure mode. The following minimum factors apply: — Polyester: 1.65 — HMPE and Aramid: 2.0 — Other fibre materials: 2.5. Guidance note: For fibre slings subject to a robust certification process, other material factors may be considered acceptable; however, γm should not be less than 1.65. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 152 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3) When used in lashings, the minimum material factor for shackles, turnbuckles and complete web lashing assemblies should normally be taken as: γm = 1.95 4) When using DNVGLOSC101 Ch.2 Sec.11 [2], /24/, Eurocode 3 /61/ or [E.2], the material factor for slip resistant bolt connections shall be taken as minimum: — — γm = 1.25 for standard clearances in the direction of the force. γm = 1.4 for oversize holes or long slotted holes in the direction of the force. Guidance note: [E.2] provides for further information regarding slip resistant bolt connections and an alternative methodology. endofguidancenote 5.9.9 Material factors for friction a) A material factor of minimum γm = 1.4 should normally be used to calculate the lower bound design friction coefficient for load bearing friction effects. b) A material factor of maximum friction coefficient. See [5.4]. γm = 0.8 should normally be used to calculate the upper bound design Guidance note 1: In each case, the design friction coefficient should obtained by dividing the characteristic friction coefficient by the material factor. endofguidancenote Guidance note 2: Where less conservative material factors have been justified, the factor used to calculate the lower bound design friction coefficient should not be reduced below 1.25 and the factor used to calculate the upper bound friction coefficient should not be increased above 0.85. endofguidancenote 5.10 Materials and fabrication 5.10.1 Design considerations 5.10.1.1 Applicable codes a) In general material selection, fabrication method, and nondestructive testing should be carried out according to a recognised offshore code, e.g. DNVGLOSC101, /24/, or DNVGLOSC401, /26/. Guidance note: Recognised codes or standards are meant to be national or international codes or standards applied by the majority of professional people and institutions in the marine and offshore industry. endofguidancenote b) Independent of the applied code, it shall be documented that the requirements in this section [5.10] are fulfilled. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 153 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3) 1) Structural elements and connections shall be grouped in categories determined according to: — — — — — — — 2) type of stress presence of cyclic loading presence of stress concentrations presence of restraint loading rate consequences of failure redundancy. Guidelines for selection of applicable materials for offshore steel structures can be found in DNVGLOS C101 Ch.2 Sec.3, /24/. Guidance note: For steel with yield stress below 500 MPa, the test temperature need not be taken lower than 40° C endofguidancenote 3) For materials in temporary structures used for marine operations, the following apply: — The design temperature, see DNVGLOSC101 Ch.2 Sec.3 [2], /24/, should be defined based on the season and location(s) of the marine operation. Note that a design temperature above 0ºC may be applicable. — See Table 511 for guidelines regarding selection of structural category. See also DNVGLOSC101 Ch.2 Sec.3 [3], /24/. — For materials that could be welded under adverse conditions the yield strength (SMYS) should not exceed 355 MPa. 5.10.1.3 Material quality a) b) c) d) Selection of steel types shall be determined based on the structural application and the required category Table 511. All steel materials shall be suitable for the intended service conditions and shall have adequate properties of strength, ductility, toughness, weldability and corrosion resistance. Material types and qualities should comply with requirements in DNVGLOSB101, /23/. Nonstructural steels shall have mechanical properties and weldability suitable for the intended application. Table 511 Structural categories Selection criteria for structural category Failure consequence Substantial, the structure possesses 2) limited residual strength Examples for typical structures involved in marine operations Structural part Complex joints 1) Simple joints and members Recommended structural category NORSOK N004 Equivalent /112/ Insp. Cat., DNV GL Special DC1 – SQL1 I Primary 3) (Special) DC2 – SQL2 3) (SQL1) 4) DNVGLOSC101 — Padeyes and other lifting points — Seafastening elements without redundancy — Spreader bars Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS 5) I or II Page 154 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 5.10.1.2 Structural categories Unsubstantial, as local failure will be without substantial consequences Complex joints 1) Simple joints and members Structures for connection of: — Mooring and towing lines — Grillages 2) — Redundant elements seafastening Primary 3) (Special) DC3 – SQL2 3) (SQL1) II Primary 3) (Special) DC4 – SQL3 3) (SQL1) II Secondary DC5 – SQL4 III — Bumpers and guides Any structural part — Fender structures 2) — Redundant grillages (parts of) Notes: 1) Complex joints are joints where the geometry of connected elements and weld type leads to high restraint and to triaxial stress pattern. 2) Residual strength (redundant) means that the structure meets requirements corresponding to the damaged condition in the check for ALS, with failure in the actual joint or component as the defined damage. 3) Selection where the joint strength is based on transference of tensile stresses in the through thickness direction of the plate. 4) The design classes and material selection according to NORSOK M120, /110/, should be considered as guidance only. 5) Extent of NDT to be according to DNV GL category I in Table 512, but category II may be used as “input” in Table 512 regarding waiting time for these welds. Regarding extent of inspection according to NORSOK M101, /109/ inspection category B is normally acceptable. 5.10.1.4 Tolerances a) b) c) d) Asbuilt deviations shall not exceed fabrication tolerances assumed in the applied structural codes and standards, or in the design analysis, unless specially considered on a casebycase basis. Acceptance of any asbuilt deviations exceeding specified tolerances shall be confirmed in writing by, as applicable, the owner, designer, installation contractor, etc. DNVGLOSC401 Ch.2 Sec.6 [11], /26/, indicates fabrication tolerances that are normally acceptable. Some marine operations procedures can be difficult (or impossible) to execute when standard tolerances are applied. In these cases consideration can be given to defining and documenting the consequences of using tolerances that are less onerous than those indicated in DNVGLOSC401, /26/. 5.10.2 Fabrication 5.10.2.1 Workmanship a) b) Workmanship during fabrication shall be of good standard and according to accepted practice. See also DNVGLOSC401 Ch.2 Sec.2 [3], /26/. Guidelines regarding assembly and welding can be found in DNVGLOSC401 Ch.2 Sec.6 [8], /26/, and DNVGLOSC401 Ch.2 Sec.6 [9], /26/. 5.10.2.2 Marine work Environmental conditions during marine construction work can be unfavourable and the time available is often limited. Also accurate fitup can be difficult to obtain e.g. due to a dented barge deck. Such issues regarding marine work shall be duly considered in the planning of the work. See also [5.9.7.5] or [5.9.8.4]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 155 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Not substantial, the structure possesses 2) residual strength Due to the special conditions during marine construction work, the following precautions are recommended: a) Welding procedure specifications should be qualified by welding procedure tests carried out under conditions representative of the actual working environment; see DNVGLOSC401 Ch.2 Sec.5 [2.2], /26/. b) Thorough inspections of fitup and welding should be planned for. c) Weather conditions and forecast to indicate acceptable conditions for welding considering the welding method and available shelter at the welding locations. d) Use of increased weld size in order to compensate for inaccurate fitup (i.e. oversized gaps) to be considered. e) Robust and well proven welding methods and procedures to be applied. f) Use of material with improved weldability; see DNVGLOSC101 Ch.2 Sec.3 [4.2], /24/, to be considered. endofguidancenote 5.10.2.3 Weld inspection 1) 2) 3) 4) All NDT (nondestructive testing) of structures and structural components shall be carried out by qualified personnel and covered by written specifications and procedures. Personnel evaluating results from NDT shall possess thorough knowledge and experience with NDT. The NDT method selected shall be suitable for detection of the type of defects considered detrimental to the safety and integrity of the structures. The extent of NDT shall be based upon the importance of the connection in question. Aspects which shall be considered in specifying the extent of NDT are: — — — — — — 5) stress level and stress direction cyclic loading material toughness redundancy of the member overall integrity of the structure accessibility for examination. Where through thickness properties of the steel are used, the material should be certified accordingly (Zquality). Where this is not feasible, the material under throughthickness tension should be checked for laminations after the recommended cooling and waiting time as defined by the Welding Procedure Specification (WPS) and NDT procedures. The reason for waiting is that laminations can also be subject to hydrogen embrittlement, the same as welds, see SSC290, /118/, for more details of lamellar tearing. If access is not possible after welding, prewelding checks could be acceptable. Guidance note 1: For noncritical seafastenings and their supports, throughthickness testing should be carried out when the tensile stress normal to any plate exceeds 100 MPa. endofguidancenote Guidance note 2: The tensile stress should be calculated in a section between the deck plate and the weld (i.e. not in the critical weld section). If the under deck weld is smaller, this weld should be used as a reference, see also Guidance note to [11.9.5.29]. Stresses greater than 100 MPa, caused by e.g. a local moment on seafastening brackets can generally be accepted in limited areas without lamination testing. endofguidancenote 6) Requirements to nondestructive testing (NDT) of welds can be found in DNVGLOSC401 Ch.2 Sec.7, /26/. Equivalent standards may be used e.g. EEMUA 158 “Construction specification for fixed offshore structures in the North Sea” /59/ and AWS D1.1/D1.1M2015 “Structural welding code – steel” /8/. 7) Minimum extent of inspection should be as shown in DNVGLOSC401 Ch.2 Sec.7 Table 1, /26/, with “Inspection Category” as defined in Table 511. See also Table 512 for a summary and especially note 4) to the table. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 156 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Normally final inspection and NDT of welds shall not be carried out before 48 hours after completion. A shorter minimum waiting time may be acceptable depending on material thickness and yield strength. See NORSOK M101, /109/, Sec.9.1 and DNVGLOSC401 Ch.2 Sec.7 [1.2], /26/, for further details. 9) For marine operations with weld inspection on the critical path, the minimum waiting time should be selected according to Table 512 however, the decreased waiting may only be used if the precautions listed in [5.10.2.2] are fulfilled. Guidance note: Weld inspection can be completed after a voyage has commenced provided that procedures are in place to remediate or mitigate any defects that are found. endofguidancenote Table 512 Minimum extent of NDT and waiting time Minimum extent of NDT Minimum waiting time before NDT Inspection Category Visual I 100% 100% 24 hours II 100% 20% 5) Cold weld III 100% 5% Other 1) 5) SMYS 2) ≤355 MPa 3) 2 3) SMYS ) > 355 MPa 4) 48 hours 4) 6) 24 hours 4) 6) 24 hours ) Cold weld 4 Notes: 1) Test method to be selected according to the type of connection, see DNVGLOSC401 Ch.2 Sec.7 Table 1, /26/. 2) SMYS to be defined according to the specification for the actual material used and not according to the minimum required design value. 3) For thickness less than 40 mm the limiting SMYS is 420 MPa. 4) The use of PWHT (post weld heat treatment) can reduce the required waiting time. 5) An increased % extent shall be evaluated if defects are found and/or the weld conditions and precautions, see [5.10.2.2], are not fully satisfactory. 6) The NDT can start when the weld is cold, but it is recommended to wait as long as practicable. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 157 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8) 6.1 Introduction 6.1.1 General and scope 6.1.1.1 This section is mainly applicable to “Condeep”type gravity based structures (with one or more columns above a submerged base). However the principles will apply to most types of steel and concrete gravity based platforms. 6.1.1.2 The areas shown in Table 61 are covered. Depending on the type of structure and method of construction, some or all of the following sections will give the relevant requirements. Table 61 Requirements for different GBS phases General requirements See Sec.2 to Sec.4 Stability and freeboard (all phases) See [6.2] Structural strength See [6.3] and Sec.5 Temporary ballasting and compressed air systems See [4.3] Construction basin and towout See Sec.12 Construction and/or solid ballasting afloat See Sec.14 Deckmating (inshore or offshore) See Sec.15 Towage(s) See Sec.11 Instrumentation See [6.4] Installation at location See [6.5] Ensuring onbottom stability See [13.10] 6.1.2 Revision history 6.1.2.1 The following changes have been made to this section: — General: Editorial changes to improve clarity. — [6.2.1]: Former clause [6.2.1.7] moved to [11.10.4.3]. 6.1.2.2 The changes made to this section for the June 2016 edition are shown in App.A. 6.2 Floating GBS stability and freeboard 6.2.1 General 6.2.1.1 Sufficient positive stability and reserve buoyancy shall be ensured during all stages of the marine operations. Both intact and damage stability shall be evaluated, on the basis of an accurate geometric model. This shall include inclining tests of the GBS in accordance with [2.10.5] at stages agreed with the MWS company. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 158 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 6 GRAVITY BASED STRUCTURE (GBS) 6.2.1.3 The output of the weight control programme as described in [5.6.2] shall be taken into account. 6.2.1.4 Stability calculations should include corrections and allowances for: a) b) c) d) e) Free surface Air cushion Icing Influence of moorings, including a check on the consequences of failure. Temporary Loads and Structures (including any cantilevered structures) 6.2.1.5 The number of openings in buoyant elements adjacent to the sea shall be kept to a minimum. Where penetrations are necessary for access, piping, ventilation, electrical connections, etc. arrangements shall be made to maintain watertight integrity. During construction phases, particular attention should be paid to openings near the waterline, which will vary as construction proceeds. 6.2.1.6 Damage stability requirements shall be evaluated considering the operation procedure, environmental loads and responses, the duration of the operation and the consequences of possible damage. Compartments that may be subject to flooding or partial flooding include: a) b) c) Compartments adjacent to the sea Compartments inside the structure, crossed by seawater filled pipes Skirt compartments containing compressed air. 6.2.1.7 Special attention should be paid to flooding which may be caused by: a) b) c) d) Impact loads from vessels Damage to structure or pipework from dropped objects Mechanical system failure Human error. 6.2.1.8 Flooding as a result of vessel impact is assumed to occur in a zone bounded by two horizontal planes normally positioned 5 m above and 8 m below the waterline. These levels should be reviewed if deep draught vessels are likely to be operating nearby. 6.2.1.9 For operations where the structure cannot meet damage stability criteria, measures shall be taken to minimise the risk, by: a) b) c) d) e) Limiting the exposure period Providing additional local structural strength Providing additional protection, such as fendering Minimising vessel movements near the structure Dedicated procedures and experienced personnel. 6.2.1.10 For operations where at any stage stability or reserve buoyancy is critical or where damage stability cannot be obtained, a risk assessment in accordance with [2.4] shall be carried out. The duration of the critical condition should be minimised. Requirements for backup or protection systems, or special procedures should be assessed. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 159 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 6.2.1.2 In calculations of stability and reserve buoyancy/freeboard, due allowance shall be included for uncertainty in mass, buoyancy, volume, location of centre of gravity, density of liquid and solid ballast, and density of seawater. 6.2.2.1 The initial GM shall not be less than 0.5 m (after allowing for all possible inaccuracies in measuring it) unless agreed with MWS Company. 6.2.2.2 The maximum inclination of the floating GBS or platform should not exceed 5° in the design environmental condition as defined in [3.1] apart from possible exceptions during installation as described in the guidance note to [6.5.4.4]. Calculation of maximum inclination should take into account: a) b) c) Maximum amplitude of pitch or roll motion in the design sea state, plus Inclination due to design wind, plus Inclination due to mooring line tensions or required towline pull. Guidance note: The maximum inclination of 5° is due to the large height of GBS structures and the corresponding motion experienced at this height. endofguidancenote 6.2.2.3 During towing, the static inclination in still water when subjected to 50% of required towline pull should not normally exceed 2°. Differential ballasting may be used to reduce the static inclination resulting from towline pull only by not more than 1°. 6.2.2.4 The area under the righting moment curve shall be not less than 140% of the area under the overturning moment curve as shown in Figure 112. Both curves shall be bounded by the least of: a) b) c) d) The second intercept of the righting and overturning moment curves The angle of downflooding The angle which would cause any part of the GBS to touch bottom in the minimum water depth at the construction site or along the towage route. This requirement may be deleted for installation at the offshore site. The angle at which allowable stresses are reached in any part of the structure, construction equipment, topsides or topsides attachments, if applicable. 6.2.2.5 The wind used for overturning moment calculations should be the design wind for the operation, as defined in [3.3]. Short duration operations during construction or towage may be considered as weather restricted operations, provided the structure can achieve or be returned to a safe condition, within the operation reference period 6.2.3 Effective freeboard 6.2.3.1 For inshore towages and construction afloat, the effective freeboard, as defined in Table 13, shall not be less than the greater of: a) b) 1 m above the design wave crest height, with allowance for runup, all around the structure, under the design storm loading from the most critical direction, 6 m in the intact condition, if the unit does not have onecompartment damage stability. 6.2.3.2 For offshore towages, after damage, an effective freeboard of not less than 5 m shall remain above the design wave crest height, with allowance for runup, all around the structure, from the most critical direction. Calculation of the freeboard shall account for motions experienced as a result of the design environmental conditions and mooring line tensions or required towline pull. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 160 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 6.2.2 Intact stability 6.2.4.1 For towout from drydock, onecompartment damage stability is not required as it is a controlled operation and the underkeel clearance is limited. 6.2.4.2 For other inshore tows the structure should have onecompartment damage stability, as defined in [6.2.1.6] through [6.2.1.8]. 6.2.4.3 If onecompartment damage stability requirements cannot be fulfilled, the requirements for construction afloat in [6.2.5.2] shall apply. 6.2.5 Damage stability during construction afloat 6.2.5.1 During the period of construction afloat, the platform shall possess onecompartment damage stability, for as much of the construction period as is practical. 6.2.5.2 When the platform does not possess onecompartment damage stability, then in addition to [6.2.1.9]: a) b) c) d) e) f) g) h) A means should be available to compensate for inclination due to flooding of any compartment, and There shall be sufficient structural strength in the outer walls to withstand impact loads from the construction spread and vessels, which may be in close proximity to the platform, and Fendering may be used to reduce impact loads in critical areas, and Lifting of heavy objects shall be carefully controlled. Protection shall be provided against dropped objects. Any lifts which, if dropped, could endanger the platform shall be identified and additional precautions taken, and Any objects or equipment on barges alongside, which if dropped, could endanger the platform shall be similarly identified and additional precautions taken, and Rigorous procedures shall be developed to minimise the risk of flooding. These shall include consideration of collision, leakage through the ballast or other systems, reliability and redundancy of pumping arrangements and power supplies, and At all times there shall be adequately trained personnel on board the platform, and As per [6.2.1.10], a risk assessment of flooding shall be carried out in accordance with [2.4]. 6.2.6 Damage stability for offshore tows and installation 6.2.6.1 When towing on the caisson or columns the platform should possess onecompartment damage stability. 6.2.6.2 It is acknowledged that for an offshore tow, the requirement in [6.2.6.1] might be impractical, in which case: a) b) c) The structure shall be locally reinforced within the zone defined in [6.2.1.8], to withstand impact from the largest towing or attending vessel, and/or Rigorous procedures shall be developed to minimise the risk of flooding, and A risk assessment of flooding shall be carried out in accordance with [2.4]. 6.2.6.3 It is acknowledged that during installation, it might be impractical to provide reinforcement against collision over the full range of waterlines. Planning and risk assessment shall include a procedure to return the structure to the reinforced waterline should the installation operation be aborted. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 161 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 6.2.4 Damage stability for towout and inshore tows 6.3.1 Concrete gravity structures load cases 6.3.1.1 The requirements of Sec.5 apply. 6.3.1.2 Load cases shall be derived by the addition of fluctuating loads resulting from wind, wind heel, wave action and the effect of towline pull or mooring loads to the static forces resulting from gravity and hydrostatic loads for the following temporary phases before it is safely installed: 1) 2) 3) 4) 5) towout from construction basin or drydock (with and without any air cushion) the most critical construction afloat stages any towages, with or without a deck deep submergence for deck mating installation on the seabed, including: — — — — any impact with the seabed including any rocks or debris during installation penetration and grouting phases any impact with scour protection during its placement. Any other critical phase as agreed with the MWS company 6.3.1.3 Accidental loadings shall also be considered for all of the phases in [6.3.1.2]. 6.3.1.4 The specific load cases considered shall be documented. For all load cases it shall be documented that the design (global and local) is acceptable. 6.3.1.5 The unit shall be able to safely withstand a static heel angle of 10°, or any greater angle required during construction, towage or installation. If it has damage stability, the unit shall also be able to withstand the static and dynamic loads caused by the flooding of any one compartment in the lesser of the 10year return period environmental conditions or a 25 m/s wind and associated waves. These should be assessed as LS1 or ULS conditions, unless it is demonstrated that alternative criteria apply. 6.3.1.6 Hydrostatic loads on the substructure at the deepest draught during deckmating can be the governing load case. It shall be demonstrated that a thorough independent check of the calculations covering this load case has been carried out, and that the design and reinforcement details assumed in the calculations concur with the asbuilt condition. 6.3.1.7 Any limitations on the maximum allowable duration of deep immersion due to concrete creep, in relation to the structural stability of the unit, should be established and the procedures planned accordingly. 6.3.2 Structural concrete 6.3.2.1 The strength of concrete and its reinforcement including any pre or posttensioning shall comply with a recognised and appropriate concrete design code, such as those listed in ISO 19903, /101/. Any time dependent properties of the materials shall be taken into account. Adequate global and local strength shall be documented. 6.3.2.2 The strength of the structure in the installed condition should be covered by the relevant certifying authority or classification society who will normally refer to a suitable offshore structural code or rules such as DNVGLSTC502 – Offshore Concrete Structures, /41/. 6.3.2.3 Testing of concrete for permanent works should be covered by the certifying authority and testing for temporary works should follow the same requirements. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 162 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 6.3 Structural strength 6.4.1 Instrumentation shall be in accordance with [4.2] and adequate instrumentation shall be installed to monitor the following, as applicable, during the operation to ensure loads, etc., remain within analysis and/or operational limits and assumptions: a) b) c) d) e) f) g) h) i) j) The water level in all compartments, quantity and percentage Status of all valves Pump status and flow rates Main and emergency power supply status Platform draught, heel and trim Compartment air pressure Compressor status Air cushion pressure Water seal level in skirt compartments Status of access doors and manholes. 6.5 GBS installation 6.5.1 General 6.5.1.1 This section describes the general requirements for the installation of a concrete gravity platform at its final offshore location. The installation procedures will vary, depending on parameters including: a) b) c) d) e) f) g) h) i) j) k) l) The size and design of the platform Water depth The positioning tolerances required in all 6 degrees of freedom The positioning/stationkeeping system proposed Whether cranes, winches or external buoyancy is required for lowering and/or positioning Whether the operation involves docking over a template, docking piles or other structures Stability at all stages of immersion Whether a vertical or inclined installation is required Tolerances on differential ballast levels The skirt design, and penetration method Whether underbase grouting is required Whether solid ballast or scour protection is required. 6.5.2 Survey 6.5.2.1 The position of the site location shall be given in both geographical and grid coordinates. 6.5.2.2 The water depth and bathymetric tolerances shall be determined. 6.5.2.3 When determining the extent of the survey area, the following shall be accounted for: a) b) c) Tolerances on site survey position Inaccuracy of position monitoring systems during installation Operational tolerances Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 163 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 6.4 Instrumentation The approach corridor Whether a holding location is required close to the site Whether an inclined installation, with previous offsite touchdown is required The proximity of any other platforms or subsea assets at or near the location. 6.5.2.4 The bottom topography shall be established by swathe bathymetry, high resolution echo sounder techniques, side scan sonar, and checked by magnetometer and ROV video for obstructions and possible unexploded ordnance. The extent of any required levelling or other seabed preparation should be decided at the design stage. Guidance note: Swathe bathymetry is now available in portable units and is installed on most survey vessels so should be used as standard on all survey projects. Due to constraints imposed by calibration and processing requirements (single point obstructions may be removed in processing), conventional highresolution bathymetry and side scan sonar should be run in conjunction. endofguidancenote 6.5.2.5 The seabed and subseabed conditions shall be established by coring, magnetometer, insitu testing, lab testing and subbottom profiling. 6.5.2.6 Sufficient current surveys shall be completed to determine the current profile with depth. 6.5.2.7 The area should be checked to ensure that there are no travelling sandwaves or other seabed erosion/accretion that could affect the structure during installation. 6.5.2.8 A site survey of the installation area covering the full area of any anchor pattern, carried out not more than 4 weeks before the start of installation, shall be provided to verify the location of all subsea infrastructure, debris and obstructions. 6.5.3 Seabed preparation 6.5.3.1 The required tolerances for level and compaction shall be documented at an early stage. 6.5.3.2 Where surveys shows the seabed is out of tolerance it shall be prepared to correct for uneven levels or consistency. Description of the preparation works, including details of how tolerances shall be achieved, shall be documented. Guidance note: Typical seabed preparation methods include: a) Controlled dumping and compacting of gravel before final levelling b) Placing sandbags c) Excavating of unsuitable soils before replacing as in a) or b). endofguidancenote 6.5.4 Installation method principles 6.5.4.1 In general it is desirable for all installation phases to be reversible though this may not always be possible, especially if there are temporary unstable phases. 6.5.4.2 The approval criteria shall be agreed with the MWS Company. The agreed criteria shall depend on the installation methods and consider the following: a) b) The required external assistance (e.g. temporary buoyancy, winches, cranes, etc.) Range of positive stability at all stages of installation. Also see [6.5.4.4]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 164 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used d) e) f) g) Length of weather windows required and sensitivity to bad weather or strong currents Possible requirement of scour protection immediately after emplacement (see [6.5.7]). 6.5.4.3 For structures towed on their side, an agreed Up–End procedure shall be documented. 6.5.4.4 Ideally platforms should be shown to be stable at all phases of the installation. Guidance note: Shallow draught platforms frequently undergo a phase of instability during submergence of the base, and an inclined installation procedure may then be used in which case the requirements of [6.5.4.5] will apply. Sometimes it may be necessary to touch down on one edge to achieve stability or to use temporary buoyancy or crane /winch assistance. endofguidancenote 6.5.4.5 In the event of an inclined installation the following shall be considered: a) b) c) d) e) f) All machinery, systems and personnel, if aboard, shall be able to work efficiently in the inclined condition Monitoring of ballast levels, and allowable differential levels Structural capacity of the skirt at touch down, and possible impact loads imposed Skirt touch down, if on the final site, may disturb the seabed, and prejudice the final skirt penetration or base slab bearing If the skirt touch down is on the final site, accurate position control may be difficult in the inclined condition If skirt touch down is remote from the final site, the deballast capability required by [4.3.5] will be used. 6.5.5 Positioning and position monitoring systems 6.5.5.1 The positioning system shall be designed to meet the required installation tolerances. This will normally be by means of tugs, often the tow fleet is rearranged into a star configuration. 6.5.5.2 Where more precise positioning is required, the tugs may be connected at the bow to prelaid anchors though other mooring systems are possible. Mooring systems shall comply with Sec.17. 6.5.5.3 Where the position and orientation tolerances are not critical, the tugs may be in free floating configuration. 6.5.5.4 Where docking piles are to be used the requirements in [13.8.4] apply 6.5.5.5 A position monitoring system in accordance with [4.4.5] shall be provided. The system shall allowing monitoring of capturing docking piles if being used. 6.5.6 Ensuring onbottom stability/skirt penetration 6.5.6.1 The requirements in [13.10.1] apply including specifying the depth(s) of any required penetration(s). 6.5.6.2 Calculations shall be documented to demonstrate that the base or skirts will penetrate to the required depths. The calculations shall specify if negative pressure is required in addition to gravity/buoyancy loads. Additionally the calculations should consider the following: a) b) c) d) expected (and maximum and minimum) soil friction expected (and maximum) suction versus penetration depth soil sealing differential pressure versus penetration depth capacity of suction pumps Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 165 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used c) d) Guidance note: Design of the pipework should take into account the requirements for removal on decommissioning. endofguidancenote 6.5.6.4 Skirts shall be shown to meet the requirements of [4.4.5.1] for all expected loads during the installation process. 6.5.6.5 If differential pressure or suction is applied, then it shall be demonstrated that an adequate seal can be obtained at the skirt tip, with minimal risk of “piping” between outside and inside each skirt compartment. 6.5.6.6 Requirements to minimum pumping pressure and flow rate should be established 6.5.6.7 All relevant parameters shall be controlled, monitored and recorded during the installation. This shall include: a) b) c) differential pressure (suction) penetration flow rate 6.5.7 Antiscour precautions 6.5.7.1 All locations, especially with high current speeds, should be investigated to see if scour could cause problems during the installation and subsequent temporary stages. 6.5.7.2 Details of antiscour precautions where required shall be documented. Possible solutions to scour include: — Controlled rock dumping or placing sandbags immediately after the unit is installed. Care shall be taken to avoid any damage to the unit especially near penetrations, pipelines, cables or other subsea assets. Scour may start immediately after installation, especially in bad weather. — Artificial seaweed or other seabed stabilisation methods. This solution needs to be demonstrated to be successful under these conditions. — Increased skirt lengths, though this should have been determined at an early design stage. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 166 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 6.5.6.3 A venting system sufficient to ensure foundation integrity shall be provided to allow water in the skirt compartments to escape and where required to allow negative pressure to be applied. 7.1 Introduction 7.1.1 Scope 7.1.1.1 This section addresses the requirements for marine operations involving pipelines, risers, jumpers, umbilicals and submarine cables (refered to a product, see [1.5.2]), including: a) b) c) d) e) f) Loadouts of rigid and flexible product via lifting of drums/reels/baskets/carousels or reeling/spooling/ coiling/winding (including transpooling operations). Transporting rigid and flexible products. SLay or JLay of rigid single or piggyback pipelines or pipeinpipe using laying vessels assembling the line from joints of pipe and held on station by moorings or dynamic positioning. Reel lay of rigid single pipes or piggyback pipelines or pipeinpipe where a straightener is used. Laying cables, umbilicals, flexible pipelines and risers using vessels which carry the completed product on reel(s) or carousel(s), or in turntable(s) or basket(s)/tank(s). These can be laid using chutes or purpose built lay towers. Shore and offshore pulls. Guidance note: See Table 13 for definitions used in this standard in particular reeling, spooling, winding, coiling, carousel, turntable, basket, tank, drum and reel. endofguidancenote 7.1.1.2 Requirements for the following specific activities are covered as well: 1) Marine lay operations including: — — — — — — — vessel mooring or stationkeeping on DP pipe handling lay initiation laydown and recovery pipeline and cable crossings above water tieins (AWTI) and landfalls. 2) Burial of cables, pipelines, risers and umbilicals by trenching and backfill, jetting or rock placement or dumping. 3) Seabed survey and route. 4) The installation of flexible or rigid risers into external clamps or Jtubes, and steel catenary risers and flexible risers between subsea infrastructure and floating units, including riser arches or other buoyancy units. 5) Installation of deep water steel catenary risers (SCR), including pullin and hangoff. 6) Installation of PLETs (pipeline end terminations) and inline structures as an integral part of pipeline catenary. 7) Shore pull and offshore pull, which are often used for connection to onshore section or facilities. 8) Installation of spools and jumpers. 9) Subsea tieins. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 167 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 7 CABLES, PIPELINES, RISERS AND UMBILICALS Transportion and installation of subsea assets separately to any product are covered elsewhere in this standard, notably Sec.11 and Sec.16. endofguidancenote 7.1.1.3 This standard does not address the following: a) b) c) d) e) f) Fitness for purpose. Manufacture of cables, pipelines, risers and umbilicals and their permanent appurtenances (although protection of product integrity during installation is covered by this standard). Welding, nondestructive testing (NDT), field joint coating or anodes for cathodic protection. Diving procedures. Tunnelled and drilled shore crossings. Cables, pipelines, risers and umbilicals in the Arctic and other similar cold regions that are subject to sea ice, iceberg and/or icing conditions (additional requirements could apply in these cases). 7.1.1.4 Specific requirements for transport/installation of pipelines and pipeline bundles by wet/submerged towing are covered in [11.26]. Requirements for towage and transport in Sec.11 also apply. 7.1.1.5 For any lay operation supported by lifting operations, the relevant requirements of Sec.16 apply. Specific requirements for subsea lifting are covered in [16.17]. 7.1.2 Revision history 7.1.2.1 This section replaces the applicable sections of the following documents: — GL Noble Denton, Guidelines for Submarine Pipeline Installation, 0029/ND, — GL Noble Denton, Guidelines for Offshore Wind Farm Infrastructure Installation, 0035/ND, and — DNV offshore standard, Loadout, transport and installation of subsea objects (VMO Standard Part 26), DNVOSH206. 7.1.3 Codes and standards 7.1.3.1 A number of recognised standards and design codes covering products are already in existence. These recognised design codes shall be used to establish the limit state criteria for the product. This document presents requirements related only to ensuring the limit state criteria for the product are not exceeded during any marine operations (e.g. loadout, transportation and installation). Any preservice conditions requirements also specified in the recognised design code shall be satisfied. 7.1.3.2 Table 71 gives codes that may be considered as recognised design codes. Table 71 Typically acceptable product recognised design codes Product Design code Rigid pipelines (submarine) DNVGLSTF101, /42/ Dynamic risers DNVGLSTF201, /43/ Rigid pipelines (not specifically offshore) API RP 1111, /3/ EN 14161, /10/ Risers in general API STD 2RD, /4/ Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 168 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: ISO 1362811, /97/ API RP 17B, /133/ Umbilicals ISO 136285, /96/ Subsea power cables Relevant IEC standards Cigré Technical Brochure Nos. 490 /11/, 496 /137/ and 623 /12/ DNVGLST0359, /132/ Guidance note 1: The default standard for rigid pipeline system design and approval is DNVGLSTF101, /42/, Submarine pipeline systems. DNVGL STF101 Sec.10, /42/, gives requirements for installation/offshore construction of submarine pipeline systems. Parts of DNVGL STF101 Sec.10, /42/, are also generally applicable for flexible pipes and risers. Hence, requirements in DNVGLSTF101, /42/, are referred to and/or repeated in this section where applicable. It is intended for this standard to be consistent with DNVGLSTF101 Sec.10, /42/, and therefore the requirements presented there are normally acceptable in their entirety. endofguidancenote Guidance note 2: Flexible pipes may be used for both static and dynamic applications. A flexible dynamic pipe will normally be categorized as a dynamic riser. endofguidancenote Guidance note 3: Guidance regarding installation of subsea power cables in shallow water can be found in DNVGLRP0360, /58/. Subsea power cables for wind power plants are also covered in DNVGLST0359, /132/. Additional guidance for wind farm installations can be found in Sec.8 of this standard. It is intended for this standard to be consistent with DNVGLST0359, /132/ and therefore the requirements presented there are normally acceptable. endofguidancenote Guidance note 4: A design code that specifies design loads and criteria for typical failure modes applicable to installation and operation of subsea power cables is currently not available. The IEC standards and Cigré recommendations typically applied in design of subsea power cables focus primarily on requirements to electrical performance after exposure to relevant electrical, thermal and mechanical loads. Limit state criteria applicable to installation and operation, such as minimum allowable bending radius etc., are typically established by the cable supplier based on previous experience, and the cable design qualified and/or verified by testing. endofguidancenote 7.1.3.3 For some products, it may be necessary to refer to a recognised design code for a similar product type. Care shall be taken to use coherent input data, analysis methods and safety factors; in general this means that these should be taken together from a single source. Combining the least conservative options from different sources is not acceptable. 7.2 Design philosophy 7.2.1 Main principles 7.2.1.1 This section applies to all marine operations for product and is supplementary to the general requirements for the planning and execution of marine operations given in Sec.2. 7.2.1.2 DNV GL’s basic concept for design of marine operations is to ensure that the level of safety specified in relevant design codes is not jeopardised. This is achieved through careful planning of operations to ensure Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 169 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Flexible pipes ISO 136282, /95/ API Specification 17J, /134/ 7.2.2 Planning of operations 7.2.2.1 In order to achieve the required level of safety, an operation shall be planned in such a manner that the product can be brought into a safe condition if the limiting weather conditions for the operation or sub operation are exceeded. A safe condition is defined as a condition in which weather conditions in excess of the limiting weather conditions for an operation will not jeopardise the required level of safety for the product. A safe condition may be established by: — completing the operation — reversing the operation — abandoning the operation according to a safe and preplanned contingency procedure, which should allow for a recovery of the object (e.g. cutting and laydown of pipeline), or — establishing a standby configuration that ensures that product integrity is maintained until normal operations can be resumed. 7.2.2.2 The planning shall include risk management including relevent requirements of [2.4] and the recognised design code. Guidance note: A HAZID is often the preferred tool to identify critical operations and required contingency operations. Normally the items in DNVGLSTF101 [10.1.3.4], /42/, would be considered as part of the risk management process. See also DNVGLRPN101, /54/. endofguidancenote 7.2.2.3 Contingency operations shall be identified through HAZID/HAZOP studies (see also [2.4.2]) and/or defined by the client. Contingency and emergency planning requirements in [2.5.4] should be considered. 7.2.2.4 Any limitations related to the product’s properties (structural strength, size etc.), product components and/or installation equipment shall be considered in the planning of operations, both in relation to limiting weather conditions and contingency procedures, e.g. waiting on weather. Any such limitations shall be identified in the procedures. If relevant, the limitations in [2.6.8.2] should be considered. Guidance note: For example, the horizontal and vertical angle coverage of a chute may restrict vessel heading during laying of flexible products. endofguidancenote 7.2.2.5 Relevant operation parameters and limiting weather conditions to ensure safe operations for personnel, product and installation equipment shall be specified in the installation procedures. The installation criteria shall account for uncertainties in the weather forecast. 7.2.2.6 Environmental criteria for the installation operations shall be in accordance with Sec.3 and shall be appropriate to the location, the season and the expected duration of the installation operations. See [2.6] for requirements and associated operational limiting criteria for weather restricted and weather unrestricted operations. 7.2.2.7 Operation duration 7.2.2.8 Lay operations with a planned duration exceeding the limitation for weather restricted operations, see [2.6.5], may still be defined as such subject to the following: — Continuous surveillance of actual and forecast weather conditions is implemented. — The handled object can be brought into a safe condition within the maximum allowable period for a weather restricted operation. A safe condition (see [2.5.1.2]) may be established by; reversing the Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 170 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used that the loads experienced are in line with the exceedence probability specified in the design codes. The overall objective is to ensure safety of personnel, equipment and product. Guidance note: See also [2.6.7.7] and [2.6.7.8], for lay operations with a planned duration less than the limitation for weather restricted operations. endofguidancenote 7.2.2.9 As per [2.6.5.2], if the duration is too long to be considered as a weather restricted operation then procedures shall be developed to establish a safe condition in the event that the weather forecast should indicate that the forecasted operational criteria may be exceeded prior to completion. Time needed to establish the safe condition shall be considered, as well as the safety of personnel working on deck under the specified limiting weather conditions. Guidance note: In this case weather in excess of the limiting conditions specified for an operation is not considered an emergency, as procedures for establishing a safe condition shall be in place. endofguidancenote 7.2.2.10 Standby 7.2.2.11 Where a weather standby condition is planned, the temporary configuration shall be such that relevant limit state criteria are satisfied for weather conditions exceeding the limiting installation conditions. Guidance note: Lowering and suspending a rigid pipeline from the vessel is an example of a typical standby configuration, as is use of temporary buoyancy attached to umbilicals and subsea power cables to establish a lazy wave configuration. endofguidancenote 7.2.2.12 Maximum allowable standby duration due to weather, equipment failure, repair or similar, shall be specified, if applicable, considering the product’s total fatigue budget. Unless free vessel heading can be demonstrated, a conservative wave heading shall be assumed. Guidance note: DNVGLSTF101 [5.4.8], /42/, provides guidance on allowable fatigue utilization during the construction phase for various safety categories of rigid pipeline safety criticality. endofguidancenote 7.2.2.13 In the event that a standby configuration is to be established for weather conditions in excess of the limiting conditions for an operation, it shall be demonstrated by analysis that relevant limit state criteria are satisfied for the maximum allowable standby conditions specified for the operation. 7.2.2.14 Relevant installation parameters shall be established as input to the operational procedures. 7.2.2.15 It shall be ensured that the parameters of the standby configuration determined for a given depth interval are applicable for the full range of water depths within the interval (typically maximum and minimum water depth of the interval). 7.2.2.16 Recovery 7.2.2.17 An operation shall, as far as possible, be planned to enable reversal and recovery of the product. If reversal/recovery of the product is not possible, this shall be catered for through contingency planning. 7.2.2.18 In order to ensure sufficient capacity of both product and installation equipment, loads related to recovery shall account for effects of the following, as applicable: — friction over a chute or similar Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 171 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used operation, abandoning the operation or establishing a standby configuration that ensures that product integrity is maintained until normal operations can be resumed. 7.2.2.19 Fatigue damage due to recovery and reinstallation shall be considered with respect to the fatigue budget. 7.2.3 Operational procedures 7.2.3.1 The marine operation manual shall provide a full suite of documentation for the project and comprise manuals, specifications, method statements, procedures, drawings, calculations, records, certificates, etc. necessary to fully define the safe execution of the operations. See [2.3.7]. 7.2.3.2 Limiting weather conditions and maximum allowable duration of the planned operation, including any planned standby or contingency configuration, shall be specified along with applicable operational parameters to ensure that relevant limit state criteria are not exceeded. Guidance note: See [3.4.3.5] for requirement about use of monthly environmental data. endofguidancenote 7.2.3.3 Operational procedures shall be supported by analyses to ensure that relevant limit state criteria are satisfied for weather conditions up to and including the limiting conditions for the operation and/or suboperation. The uncertainty of predicted weather increases with the duration of the forecast, and this uncertainty shall be considered in the planning of operations. Guidance note: The uncertainity of predicted weather is normally accounted for by applying an alpha factor. Further guidance on the use of alpha factors in operations is in [2.6] and in particular [2.6.7], [2.6.8] and [2.6.9]. See also [7.3.1.1]. endofguidancenote 7.2.3.4 Procedure changes required by events in the field shall be controlled by a suitable management of change procedure. Any major change to procedure or document subject to the specifications of the management of change procedure which can critically affect the intergrity of the product or operability and relevant for MWS company shall be informed to the MWS company before implementation. If MWS company is not present then the MWS company office should be contacted. Guidance note: It is common that the management of change procedure is part of the marine operation manual, as per [2.3.7.2]. endofguidancenote 7.3 Installation engineering 7.3.1 Design process 7.3.1.1 Relevant limit state criteria defined in the recognised design code shall be checked applying the loads and/or load effects determined in the analyses and using the format applied in the recognised design code. Where the alpha factors in [2.6] are to be used and unless steel work has been designed in accordance with the ASD/WSD requirements then the LRFD alpha factor may be used (see also [2.6.12.1]). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 172 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — breakout force, e.g. in relation to a halt in a shore pull or pullin operation. The different design codes apply different design formats: — The standards for steel risers and pipelines, respectively DNVGLSTF201, /43/, and DNVGLSTF101, /42/, apply a partial safety factor format called load and resistance factor design (LRFD) format. — The ISO standards for design of unbonded flexible pipes (ISO 136282) and umbilicals (ISO 136285) use a single (permissible) utilization factor approach. The most obvious difference in the two formats is that LRFD applies separate safety factors for different load components and the resistance (capacity), reflecting the uncertainty in each of them, while the a single (permissible) utilization factor applies one safety factor and is akin to the ASD/WSD methods. The main types of load components relevant in a capacity check of product are: — pressure (internal and/or external) — tension (some apply the effective tension directly) — moment or curvature. Some design codes distinguish between functional loads and environmental loads. For rigid pipes designed to DNVGLST F101, /42/ see guidance note to [7.3.4.2]. A functional load is typically well defined and associated with less uncertainty than environmental loads. The LRFD format accounts for this lower uncertainty using a lower safety factor for functional loads than for environmental loads. Environmental loads are defined as loads resulting directly or indirectly from wind, waves and current. The effect of an environmental load is the difference between the total dynamic response and the static response. In some cases other special load components may be relevant. Guidance is provided in the relevant design code. For rigid pipelines, the capacity checks combine the effect of the main load components. See applicable design codes, e.g. DNVGL STF101, /42/, for more details. For flexible pipes, the capacity check is performed for single load effects, e.g. characteristic tension to be less than specified tensile strength and characteristic curvature to be less than maximum allowed curvature. For umbilicals and subsea power cables the load effects tension, curvature and internal/external pressure (as applicable) are considered simultaneously in the capacity checks. endofguidancenote 7.3.2 Laying/installation analysis 7.3.2.1 The laying/installation analyses shall demonstrate the suitability of the proposed installation spread and proposed installation method. 7.3.2.2 The analyses shall establish operational parameters for a range of configurations and/or weather conditions, e.g. minimum allowable layback for sea states up to and including the limiting sea state for an operation. The sophistication of the analyses, and hence software, shall be appropriate to the criticality of the operations, recognising technical complexity or novelty, reserves of strength and stability in the product and in the equipment involved and prior industry experience. Guidance note: Lay analyses may vary from static linear elastic to dynamic, stochastic nonlinear elastoplastic modelling. endofguidancenote 7.3.2.3 The vessel RAOs used in the laying/installation analyses shall be conservative and representative for the relevant conditions of the vessel during the installation. This could be done through sensitivity analysis. The need for applying more than one set of RAOs in the analysis should be considered as vessel response may vary depending on loading condition, water depth etc. Appropriate RAO’s shall be used for shallow water cases. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 173 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: The vessel loading condition may have changed significantly from the beginning of the operation to the final phases due to effects such as reduction in product on board, reduction in consumables and fuel etc. Such aspects may require analysis based on more than one set of RAOs. endofguidancenote 7.3.2.4 The effect of any variation in parameters (section, weight, coating, etc.) along the length of the product shall be considered. Any significant change of mechanical properties or stiffness shall be accounted for in analyses. Guidance note: Normally, field joint coating or variation between insulation and centraliser in a pipeinpipe may be excluded from the analysis. endofguidancenote 7.3.2.5 As stiffness properties of flexible products in tension and axial compression can differ, nonlinear stiffness properties shall be considered in the analyses if there is a nonnegligible impact on the operational criteria derived from this analysis. This should also be considered for bending stiffness. 7.3.2.6 For rigid pipe, any discontinuity in the pipe properties, except those permitted by the recognised design code (e.g. dimensional tolerances) shall be considered. Any such discontinuity shall not result in the exceedance of any limit state during reeling/unreeling operations and should be justified by appropriate tests and/or FEA. Guidance note: For example a discontinuity may occur due to changes in tangential stiffness, different wall thickness, varying material properties or insulation coating thickness. Where a discontinuity occurs there is an increased potential for buckles to occur. endofguidancenote Guidance note: For nonsacrificial transition spools detailed nonlinear elastoplastic analyses may be required of any transitions between pipe joints of differing dimensions (greater than mill tolerance on the specified wall thickness either side of the joint) or through a tapering transition piece or at differing specified minimum yield strengths (differing by more than 5% of the lesser) and at any pipe joints containing internal or external design geometry changes. For complex cases e.g. outer diameter changes, one wrap on the reel and through the straightener may need to be included in the analyses. endofguidancenote 7.3.2.7 The effect of any inline bulkheads, connectors, joints, bend restrictors or other structures on the product shall be considered. Special care shall be taken for lifting of ends or inline structures with a large relative mass compared to the product. The consequences of relative movements of such objects relative to the product (e.g. pendulum motions, rotation of lifted object) should be closely considered. Focus should also be given to situations where tension and/or handling loads are provided by more than one source to ensure that this does not become a risk to the product integrity (e.g. minimum bending radius). 7.3.2.8 Where installation aids are required, they should be considered and included in the analysis when they can impact the product response and/or the lay configuration. 7.3.2.9 Sensitivity analyses shall be performed to assess effects of tolerances and variations in product tension, lay angle and/or layback, and thereby demonstrate robustness of the proposed procedure. 7.3.2.10 Product can be damaged due to overbending at the chute exit or against the side flanges of the chute. Therefore the angle of coverage of a chute, both in the vertical and the horizontal planes should be considered. The calculated lead angles shall include the effect of cross currents and the product checked for bending over edges. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 174 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 7.3.2.12 Lay tables shall be established with relevant installation parameters for the governing weather conditions and wave headings for the full range of water depths along the lay route. A sufficient number of water depths shall be included to reflect the variations in the product configuration and response. It shall be ensured that the installation parameters determined for a given depth interval are applicable for the full range of water depths within the interval (typically maximum and minimum water depth of the interval). 7.3.2.13 Dynamic movement in installation equipment, such as stingers and lay chutes, shall be considered. For SLay methods, if the vessel includes a hinged buoyant stinger, specific analysis by a time domain analysis shall be completed to verify that the stinger will provide the support required and to determine the weather threshold for abandonment of laying operations. The limiting sea state shall be set below the conditions which causes the product to lift off and bump onto the support rollers in the stinger. Guidance note: Movement in this equipment, such as loss of pipe contact with the supports, can determine the limits rather than overloading, noting that such dynamics can cause pipe overbending, fatigue or cracking or damage to the pipe coatings or anodes. For SLay methods, it is preferable to make the liftoff point of the pipeline at the next to last roller, so that in case of small loss of tension, the contact of the pipe will be with the next to last roller and the last roller could also provide support to the pipe, thereby avoiding excessive bending at the last roller. With a camera at the last roller, if the separation between the pipe and the last roller is seen to be too small, the tension can be increased to maintain an acceptable lay curvature of the line. endofguidancenote 7.3.2.14 For spooled/reeled lay, the optimum balance between lay tension applied at the tensioner and on the drum shall be assessed, included in the lay analyses and installation procedures and controlled during laying. 7.3.2.15 Flexible product 7.3.2.16 For flexible products passing over rollers whilst under tension, then the loads from the rollers on the product shall be verified by the manufacturer to ensure that product internals are not damaged unless negligible compared to manufacturer’s allowable value. 7.3.2.17 Rigid pipe 7.3.2.18 For rigid pipelines, checks shall be documented for potential local buckling during pipelay and for subsequent propagation buckling initiation and running in accordance with a recognised design code. The external pressure should be checked against the propagation pressure. Where propagation is expected, appropriate buckle arrestors shall be installed. Guidance note: See DNVGLSTF101, /42/, for guidance. endofguidancenote 7.3.2.19 For rigid pipelines, where the recognised design code (e.g. DNVGLSTF101, /42/) allows the controlled yielding of the pipe in the section supported by the stinger, consideration should be given to residual flattening, torsion or twisting that can be formed in the pipe during installation. Plastic strain history shall be considered for design of parts of the line which will or can experience fatigue loading during operation. Buckling consequences and mitigations shall be clearly documented including control and recovery measures for collapse and buckle propagation. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 175 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.3.2.11 Installation analyses shall cover the expected range of water depths, considering relevant or conservative environmental conditions, lay vessel draughts and trims. Laying in shallow water should be considered especially, with particular focus on effects of vessel motion (both vertical and horizontal). The elasticplastic bending behaviour between the reel and straightener is highly nonlinear and sometimes highly susceptible to changes in stiffness of the pipe. endofguidancenote 7.3.2.20 For rigid pipeline that is to be reeled/spooled, where the pipe will be required to deform plastically, the bend radius shall be sufficient to avoid local pipe buckling or coating failure. An operation specific reeling/ spooling analysis should be perfomed, and be: — backedup by demonstation bend tests or small scale reeling simulation testing and/or — demonstration of successful track record of similar product and arrangement. Guidance note: For low criticality pipelines the requirement for analysis may be waived subject to adequate documentation demonstrating successful track record of similar product and arrangement. endofguidancenote 7.3.2.21 Residual ovalisation shall be accounted for in the pipelay strength and buckling analyses, and in the analyses for operating conditions. 7.3.2.22 Ovalisation due to bend strain should be calculated in accordance with DNVGLSTF101, /42/. Guidance note: The installation contractor may offer other bases supported by documented testing or by prior successful application for determination of ovalisation due to reeling/spooling, and for the extent or recovery from ovalisation due to straightening. endofguidancenote 7.3.2.23 The total strain shall be assessed as per DNVGLSTF101, /42/. 7.3.2.24 Installation strain history shall be recognised in analyses of any fatigue loadings during operation. Total strain induced at reeling/spooling and laying shall be accounted for in the fatigue design as reeling/ spooling can lead to reduction in the fatigue life due to increased size of existing flaws in a weld. 7.3.2.25 A fatigue check is required to account for periods when laying is halted (e.g. for extended welding, weather downtime, equipment failure, etc.) and the product is subject to vessel motions. Consideration of cumulative fatigue damage from operations shall be considered. 7.3.2.26 For rigid pipelines, minimum allowable lay rate (slow lay) shall be determined considering the available fatigue budget, if applicable. 7.3.2.27 Abandonment and recovery 7.3.2.28 Abandonment and recovery (A&R) analysis shall be performed at suitable water depth intervals representative of the lay route. 7.3.2.29 The configuration at the beginning of the abandonment analysis should be the same as the configuration just prior to abandonment, considering the most conservative layback and weather conditions, as a minimum. The number of steps analysed should be sufficient to ensure a smooth laydown or recovery and avoid exceeding relevant limit state criteria. Guidance note 1: For recovery of rigid pipe using the SLay method, the tension may be slightly increased (by approximately 10%) when the head approaches the stinger to increase the clearance of the head with the stinger in order to avoid the risk of clash between the A&R head and the stinger. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 176 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Good practice is to change the tension in 5 to 10 tonne steps. endofguidancenote 7.3.2.30 End termination assemblies/inline components 7.3.2.31 Assesments (supported by analyses as required) shall be performed to establish or validate a procedure for safe handling of the component/assembly attached to the product from the vessel storage location to the installed condition including through the splash zone. It shall be ensured that the most critical load condition has been considered for the most critical configuration and demonstrated that relevant limit state criteria are satisfied for the limiting weather conditions specified for the operation. Guidance note: As per [7.1.1.5], the lifting requirements in Sec.16 and in particular those for subsea lifting in [16.17] apply. endofguidancenote 7.3.2.32 If critical, the effects of wave slamming on end termination assemblies and inline components shall be considered, as well as snap loads in the lifting wire. Guidance note: Guidance with respect to lifting and lowering of structures may be found in DNVGLRPN103, /56/. endofguidancenote 7.3.2.33 Contact with stinger rollers, radius controllers, chutes or similar shall be considered, with special attention to the transition in bending stiffness at the interface between the product and end fitting/ termination, joint or component. Correct modelling of stiffness properties (also bend restrictors and bend stiffeners) shall be ensured. 7.3.2.34 Clump weights 7.3.2.35 If one or more clump weights are attached to the product to pull down a buoyant riser section, product response, particularly at the vessel interface and in the touchdown area, shall be analysed to establish the effect of: — attaching each clump weight to riser — landing each clump weight on the seabed. 7.3.2.36 The part of the operation involving attachment and landing of a clump weight is of relatively short duration, and may therefore be considered as transient. 7.3.2.37 The effect of sudden impact between clump weight and seabed due to vessel heave motion can cause axial compression in the product at the vessel interface. Attachment point and length of clump weight wire should therefore be determined considering the product response as the clump weight is landed. 7.3.2.38 Size of clump weight shall be determined considering interference with the product. 7.3.3 Limit state criteria 7.3.3.1 As per [5.9.1.3], a limit state is commonly defined as a state in which the structure ceases to fulfil the function, or to satisfy the conditions, for which it was designed. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 177 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 2: As per [5.9.1.2], the limit states are typically grouped into the following four categories: — Ultimate limit states (ULS) corresponding to the ultimate resistance for carrying loads. — Fatigue limit states (FLS) related to the possibility of failure due to the effect of cyclic loading. — Accidental limit states (ALS) corresponding to damage to components due to an accidental event or operational failure. — Serviceability limit states (SLS) corresponding to the criteria applicable to normal use or durability. endofguidancenote 7.3.3.2 As per [5.7], all relevant failure modes shall be investigated. A failure mode is relevant if it is considered possible and the anticipated consequence(s) of the failure cannot be disregarded. Guidance note: Possible causes of failure include (specific applicability depends on product type): — excessive bending — excessive tensile or axial compressive loads — excessive torsion/twist — excessive crushing/bearing loads (e.g. tensioner squeeze load) — excessive point loads — local and global buckling — fatigue — excessive ovalisation — excessive pressure — excessive displacement (in relation to onbottom stability) — excessive free span, and — excessive residual curvature (e.g. for pullin operations, fitting of components etc.). endofguidancenote 7.3.3.3 Installation loads and limit state criteria shall comply with the requirements of a recognised design code, see [7.1.3]. A coherent set of criteria shall be adopted throughout. The selected criteria shall be specified in an installation design basis. Where the recognised design code includes a safety class this should be considered. 7.3.3.4 Flexible product 7.3.3.5 For flexible products, the limit state criteria relevant for installation design are presented in Table 72. Product specific limit state criteria shall be provided by the supplier in accordance with the recognised design code, see [7.1.3]. Guidance note: The limit state criteria are required input to installation design, and are typically outlined in data sheets and/or a handling specification provided by the manufacturer of the product. For umbilicals, a capacity curve specifying allowable curvature/bending radius for different tensions is common. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 178 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Limit state Limit state criterion Maximum allowable tension Minimum allowable bending radius Minimum allowable storage radius ULS Maximum allowable axial compression Maximum allowable tensioner squeeze load Maximum allowable point load Maximum allowable twist FLS Maximum allowable standby duration ALS Minimum breaking load 7.3.3.6 For allowable tension and allowable bending radius, the following shall be specified as a minimum: a) b) Minimum allowable bending radius at maximum installation tension for both load controlled (bending in free space) and displacement controlled (bending over support) conditions. Unless otherwise specified, a conservative estimate of maximum installation tension may be assumed. Minimum allowable bending radius at a tension representative of the touchdown region and conditions during storage and handling. 7.3.3.7 If axial compression is allowed, the product supplier shall specify axial and bending stiffness of the product in compression (as well as tension). 7.3.3.8 The need for providing the maximum allowable point load limit state criterion should be agreed with the client. If required, details of the contact surface shall be specified. 7.3.3.9 The bending radius shall not be less than the displacement controlled or load controlled, as applicable, minimum bend radius (MBR) at any time. Details of the specification of the MBR, including any margins, shall be documented. MBR to be adhered to shall be those provided by the product manufacturer. 7.3.3.10 Unless it is justified that fatigue is negligible, the product supplier shall specify maximum allowable duration of a standby condition. Alternatively maximum fatigue damage over the crosssection, for specified load combinations (i.e. tension and curvature) shall be provided by the installation contractor to the supplier for input to their fatigue calculations in an agreed format. 7.3.3.11 Rigid pipe 7.3.3.12 For rigid pipelines, the limit states shall be as per the recognised code e.g. DNVGLSTF101, /42/. The following typical design conditions shall be checked, as applicable, against the relevent limit state in the recognised code depending on installation method: — — — — onreeling (reeling installation only) over bend (as applicable) stinger tip (as applicable) sag bend (all installation methods). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 179 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 72 Limit state criteria applicable to flexible products Reellay presents additional design and material requirements for the pipe compared to SLay and JLay. The main considerations are: a) the pipe and coatings’ suitability for the strain cycling for reeling/spooling onto and off the vessel’s reel b) limiting the D/t ratio to prevent buckling when reeling/spooling and c) resistance to collapse and propagation buckling due to residual flattening of the pipe section following reeling/spooling, un reeling and straightening. endofguidancenote 7.3.3.13 Anticorrosion coatings and concrete weight coatings shall be specified and proven to be resistant to the range of shear and crushing loads applied at the pipelay tensioners and support rollers. Pipe tensioners impart very high loads into the pipeline which shall be analysed and/or prequalified before implementing them in the field. Guidance note: Individual tensioner loads are likely to be higher for JLay than for SLay, so it is important that intercoating shear bond and crush strengths are specified, and demonstrated by project specific or prior representative qualification testing. endofguidancenote Guidance note: For pipeinpipe, the flooded cases to be analysed and tensions to be used for squeeze settings normally are: — when laid empty considering either flooding of annulus or bore, whichever is greater — when laid with flowline flooded with both flowline and annulus considered flooded. endofguidancenote 7.3.3.14 Where the JLay system requires collars to suspend the pipe, the collar system shall be suitable for the maximum design load, including any waterfilled condition, and in accordance with a recognised design code. Guidance note: Collars are normally located close to every butt weld in order to suspend the pipe. endofguidancenote 7.3.3.15 Other failure modes that shall be checked, as applicable, are: — — — — — — — squeeze and slippage in tensioner/clamp concrete crushing rotation anode integrity residual ovality residual curvature bottom tension and curve stability. 7.3.4 Loads and load effects 7.3.4.1 The specification and design of product is only of direct concern to the MWS approval process in that the design shall be capable of being safely installed, in accordance with verified design documentation and the approved procedures and good industry practice. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 180 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: The specification and design of the product are generally determined by required performance in the service condition in the design environment. However, installation method often influences certain parameters, such as wall thickness, material properties and protection coating type and thickness. For pipeinpipe and carrier pipe bundles, the installation method largely determines the carrier pipeline system design. endofguidancenote 7.3.4.2 The general requirements for loading and structural strength in Sec.5 should be considered. Requirements for load categories are given in [5.5] and for loads and load effects in [5.6]. All loads relevant for the objects covered in this section shall be taken into account. Guidance note: It should be noted that DNVGLSTF101, /42/, and DNVGLSTF201, /43/, categorize loads somewhat differently than this standard, as indicated below: — both G and Q loads are called functional loads in DNVGLSTF101 [4.2], /42/ — E loads have the same definition, i.e. environmental loads see DNVGLSTF101 [4.3], /42/ — DNVGLSTF101 [4.5], /42/, defines interference loads. These can be considered as accidental loads with probability greater than 1/10 000 per operation. endofguidancenote 7.3.4.3 All applicable load combinations specified in the recognised design code shall be considered. Guidance note: For example for rigid pipe the ULS condition b) in DNVGLSTF101 Table 44, /42/, or the ULS condition in DNVGLSTF201 Table 52, /43/, would normally be considered whenever relevant in addition to the load combinations defined in [5.9.8]. Where considered relevant this is normally fulfilled by applying the load combinations in [5.9.8], with a load factor of 1.1 on G and Q loads in ULS combination b). endofguidancenote 7.3.4.4 The most unfavourable load scenarios for all relevant installation phases and conditions shall be considered. 7.3.4.5 All loads and forced displacements which can influence the product shall be taken into account. For each crosssection or part of the system to be considered and for each possible mode of failure to be analysed, all relevant combinations of loads which can act simultaneously shall be considered. 7.3.4.6 Heavy items, structures and end terminations stored with the product can influence the CoG of the reel/basket/carousel significantly and shall be taken into account when undertaking the design for lifting and transport. 7.3.4.7 When considering the environmental load, the most unfavourable relevant combination, position and direction of simultaneously acting environmental loads shall be used when documenting the integrity of the system, see also [5.6.13]. Guidance note: This includes the effect of temperature gradients. endofguidancenote 7.3.4.8 Any possible accidental loads shall be considered, see also [5.5.7]. Guidance note: Accidental loads are described in DNVGLSTF101 [4.6], /42/, and interference loads in DNVGLSTF101 [4.5], /42/. endofguidancenote 7.3.4.9 Requirements for vessel motion analysis are given in [5.6.12.1] 7). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 181 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 7.4.1 General 7.4.1.1 The general requirements for system design in [4.2] apply. 7.4.2 Vessels 7.4.2.1 These requirements apply to all vessels performing product installation operations, and supporting operations, such as trenching and burial. 7.4.2.2 The vessel requirements given in [2.11] apply. The installation spread for vessels performing installation of products as described in [7.1] shall comply with the requirements of the recognised design code. Guidance note: For example DNVGLSTF101 [10.4], /42/, gives requirements for vessels, position reference systems/ navigation reference systems, anchor systems, anchor patterns, anchor handling, dynamic positioning, cranes and lifting equipment, lay vessel arrangement, laying equipment, instrumentation, mobilization activities, qualification of vessel and equipment, calibration and testing. For further guidance regarding installation spread for cables see DNVGLRP0360 [6.2], /58/. endofguidancenote 7.4.2.3 Vessel(s) shall have adequate documented stationkeeping and manoeuvering characteristics for all planned and contingency situations. 7.4.2.4 Vessel information, including but not limited to, the information listed in [7.13.2] shall be submitted. Additionally, equipment safety, operating and maintenance manuals and critical equipment maintenance records with any current backlog listing should be submitted. 7.4.2.5 Where a vessel has additions or modifications for a project specific mobilisation, these may require a separate suitability survey (in addition to that required by [2.11.2.2]). Guidance note: This is separate to any class survey and is to ensure the suitability of the equipment for the planned operation. Items covered by any class survey e.g. vessel strength would normally be excluded from the suitability survey. endofguidancenote 7.4.3 Mooring equipment 7.4.3.1 All mooring equipment, including, but not limited to, mooring winches, control system, mooring wires, anchors, pennant wires, buoys, and ancillary fittings, shall be in serviceable condition with valid certification in place as appropriate. See [17.8]. 7.4.3.2 A mooring control system and equipment FMEA shall be produced. The MWS company shall be notified of any critical findings or results. 7.4.3.3 The lay vessel should have a centralised mooring control and monitoring system, monitoring and displaying winch operational status with tested alarms of line out and line tension reporting into a central control room or bridge. The mooring control station shall be equipped with an open communications system to all relevant control points and shall have monitors with feeds from the survey suite and the AMS (anchor management system). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 182 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.4 Vessel and installation equipment Guidance note: This is normally only acceptable where mooring equipment has been installed on the vessel for a specific project only. endofguidancenote 7.4.3.5 Mooring winches shall have local line out recorders and tension monitors with read outs at the winch control station. 7.4.3.6 Mooring winches shall be monitored by CCTV with screens installed at the mooring control station. 7.4.3.7 Where mooring equipment has been installed on vessel only for a specific project, the requirements of [7.4.3.5] and [7.4.3.6] may be exempted when there are acceptable localized watch arrangements. In such cases, readouts shall be regularly communicated to the mooring control station, where a log book will be kept. 7.4.3.8 Mooring and anchor handling operations shall be monitored and controlled with an anchor monitoring system (AMS) continuously logging anchor positions. The mooring control station and the anchor handling vessel navigation bridge shall be equipped with screens showing anchor positions. 7.4.3.9 The AMS shall be capable of showing when an anchor has slipped from its deployed position. 7.4.3.10 The lay vessel survey display and the AMS shall be integrated to provide real time position displays of the vessel, anchor locations, installed cables, and other subsea assets/hazards, including third party assets. 7.4.4 Dynamic positioning system 7.4.4.1 The following requirements apply for operations using DP: a) b) c) The general requirements for DP operations in [17.13]. The vessel should have minimum DP equipment class 2. See Table 179. DP capability analyses shall consider the effect of lay tension, and any ploughing or trenching forces. 7.4.5 Monitoring equipment 7.4.5.1 A sufficient amount of instrumentation and measuring devices shall be installed to ensure that relevant lay parameters are monitored and maintained within specified limits at all times, and stored for documentation purposes. Guidance note: Monitoring requirements for specific installation equipment are specified in [7.4.7] to [7.4.13]. Requirements for monitoring during laying are in [7.9.8]. endofguidancenote Guidance note: It is preferable that the output from monitoring equipment goes to a central control room or the bridge. For monitoring of mooring equipment see [7.4.3]. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 183 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.4.3.4 Where a lay vessel does not have a centralised mooring control and monitoring system, a controlled procedure for reporting parameters from the local control and monitoring systems shall be implemented. 7.4.6.1 The requirements in this section, [7.4.6], apply to all installation equipment for product related marine operations. Requirements for specific installation equipment aboard vessels relevant to the particular method of installation are given in [7.4.7] to [7.4.13]. 7.4.6.2 Calibration and testing requirements are in [7.4.13.1]. 7.4.6.3 Equipment used for operations involving product shall be designed to prevent any relevant limit state(s) being exceeded. Guidance note: Measurement of the MBR is not typically practicable and is ensured by the following of lay tables and layback ranges from analysis. Sometimes specific handling tools/aids (such as a quadrant, shoein tool, bend restrictors, chutes or rollers) are used to limit the bending radius. endofguidancenote 7.4.6.4 Installation equipment shall be arranged such that the insertion of tees or inline valves does not interfere with the operation of the equipment. 7.4.6.5 All equipment shall be set to the parameters determined by the installation analyses and/or as specified in the operation manual. Guidance note: For example for rigid pipelines, equipment includes pipe tensioners, clamps, welding stations, NDT stations, field joint coating stations, pipe handling systems (see [7.4.10.3]) and any multiple jointing stations. endofguidancenote 7.4.6.6 Temporary installation equipment shall also comply with Sec.11, for both transport and operational loads. 7.4.7 Lifting equipment 7.4.7.1 Lifting equipment shall be in accordance with Sec.16. Guidance note: For cranes see [16.7.2] and [16.7.3]. For slings, shackles and other rigging certification requirements see [16.12]. See [16.4] for sling design, and [16.5] for shackle (and other connecting equipment) design. endofguidancenote 7.4.7.2 Lifting equipment used to handle inline and end structures/end terminations including pullin frames and winches shall be designed in accordance with Sec.16. The design of lifting equipment and lift points on such structures should be given special consideration to ensure that all possible load directions and distributions between different parts of the rigging are considered. 7.4.7.3 Lifting magnets shall only be used when certified and approved for the work and proven not to permanently magnetize the pipe, unless a controlled degaussing is planned to remove residual magnetisation before offshore welding. 7.4.7.4 Lifting and pulling points of A&R heads, laydown heads and similar, shall be designed in accordance with Sec.16, including the consequence factors (see [16.8.3]). These shall be designed for the maximum dynamic tension expected and consider the worst possible load directions. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 184 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.4.6 Installation equipment – general 7.4.7.6 For well planned one time pullin operations and if permitted by the recognised design code the consequence factor may be discarded provided that the following conditions are satisfied: a) b) c) a risk assessment of the operation has been carried out to evaluate potential consequences of winch and winch wire failure, and it can be documented that a failure of the end termination/fitting, pullin head or installation aid will not cause personnel injury, environmental pollution or damage to vessel, installation equipment or other installations, and necessary contingency procedures are in place, supported by analyses as appropriate. Guidance note: Consequence factor during pullin operation is addressed in [7.9.13.1]. endofguidancenote 7.4.7.7 The A&R system including the wire shall be in serviceable condition with valid certification with line out and tension readouts calibrated. The A&R system should be able to abandon the product safely including any waterfilled condition. In case the A&R system is incapable of recovering the product, alternative methods should be available. Guidance note: For PipeinPipe systems, it is normally acceptable to assume only that the inner pipe or the annulus is flooded, not both. endofguidancenote 7.4.8 Tensioners 7.4.8.1 The tensioner shall be failsafe and shall be rated to hold the heaviest flooded product contingency case. The tensioners should also be able to lower the heaviest flooded product to the seabed. If not, mitigation measures shall be implemented to ensure safety in case of a flooding scenario and include contingency plans for retrieving the water filled pipe. Guidance note: In deep waters it may not be possible/practical to design the installation equipment for the loads associated with a flooded pipe. endofguidancenote 7.4.8.2 The tensioner’s capacity to support product tension shall account for the following as applicable: — — — — — — — — — — the product’s squeeze load capacity number of tensioner tracks squeeze load applied by tensioner tracks contact length between tensioner tracks and product geometry and material properties of track pads friction between tensioner tracks and product externals friction between the product outer layer(s) and tensile components creep of polymer materials in the product crosssection effects of temperature, e.g. on creep rate etc., and wet conditions including product internal annular flooding (if applicable). Guidance note 1: Geometry and material properties of the tensioner pads (i.e. pad length and separation, angle of pad groove) are required input to the product supplier for establishing maximum allowable tensioner squeeze load and minimum tensioner holding capacity. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 185 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.4.7.5 Chinese fingers, cable grips etc. shall be suitable for the product including the load capacity and used in accordance with manufacturer’s requirements. Stresses in the outer layer(s) of a flexible product, resulting from tensioner squeeze loads and product tension, generally causes the layer material (typically a polymer) to relax and creep. At low stresses, the creep effect is negligible, but increases with increasing squeeze and/or tensile load. In order to prevent excessive elongation and sudden rupture of the outer layer, potentially resulting in uncontrollable slippage of the product internals (bundle) through the tensioner (and outer layer), it is important to have control of the creep rate at maximum allowable squeeze load and installation tension (combined). See [7.4.8.6] and [7.4.8.7] for further details. endofguidancenote 7.4.8.3 It shall be ensured that a tensioner’s holding capacity is sufficient to prevent product slippage through the tensioner during installation for all planned and contingency operations including any water filled condition (if applicable). 7.4.8.4 In order to ensure that the tensioner squeeze load capacity is sufficient to support maximum product tension, the tolerance of the squeeze load shall be considered. 7.4.8.5 The minimum squeeze load (alternatively track contact length) required to prevent product slippage through the tensioner(s) shall be established by using the minimum documented and submitted friction coefficient. The material factor, γm, applied to the characteristric friction coefficient should generally be taken as 1.5. 7.4.8.6 Where applicable the control of creep effects shall be ensured by specifying the maximum allowable product tension for a specified tensioner squeeze load based on an acceptable creep rate (see guidance note to [7.4.8.7]). The material factor, γm, applied to establish maximum allowable product tension for a given squeeze load should be taken as 1.5. Guidance note: This requirement is normally applicable to flexible product and may be applicable to coated rigid pipelines. It is not applicable to uncoated rigid pipelines. Creep is the tendency of a material to slowly deform permanently as a result of internal stress. The external layer(s) of a product will typically be subjected to compressive stress from the tensioner pads and shear stress resulting from the transfer of product tension from the strength elements (e.g. armour wires) via the external layer(s) to the tensioner pads. For example, this may occur in polymer materials (e.g. external layer). endofguidancenote 7.4.8.7 Lower material factors than those in [7.4.8.5] and [7.4.8.6] may be accepted where there are well documented tests (see [5.4.4]) that account for all the items listed in [7.4.8.2]. Where the tests comply with the minimum requirements of [5.4.4], the material factor, γm, may be taken as 1.4. A further reduction may be accepted where there has been more extensive testing validated by engineering and/or it can be shown by risk assessment (see [2.4]) that the consequences of slippage/creep in the tensioner (including risk to personnel, equipment, infrastructure, product and schedule) are low or can be mitigated; in such cases the minimum acceptable material factor, γm, is 1.25. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 186 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 2: When testing the friction coefficient and creep rate (where applicable) between the externals and the tensile components on a complete product: a) The externals should be removed over a short length on either side of the test pads to ensure that the resistance measured is due to friction and/or material creep alone. b) To capture material creep, displacement transducers should be placed on the pad(s) and the bundle/tensile components to continuously log and capture minor changes in their separation. c) For a given squeeze load, product tension should be increased in steps up to at least the maximum expected installation tension. The minimum number of load steps should be 10, and minimum holding period at each load step should be at least 5 minutes. d) For a given squeeze load, the maximum allowable characteristic creep rate (where relevant) should to defined to ensure that the operation is controllable,i.e.: – that a small change in tension or squeeze load (e.g. due to uncertainties or tolerances) will not lead to a disproportionate increase in the creep rate, and – that the accumulated creep during a halt in operations, i.e. maximum standby period, will not lead to failure, e.g. rupture of the external layer. The maximum allowable tension is that associated with the characteristic creep rate divided by the material factor. e) Typically, polymer coatings soften with temperature; in such cases the test temperatiure should exceed the maximum temperature expected offshore, and it should be ensured that the product being tested is at the required temperature over the crosssection. For rigid pipe, where fully representative project specific testing using the actual product with the actual tensioner pads for a sufficient number of squeeze loads each using different areas of the product has been performed this may be considered as extensive testing provided that the results at different squeeze loads are fully consistent. endofguidancenote 7.4.8.8 Where there are contingency plans to continue the operation after the failure of one pad or one line of pads, then the capacity of these shall be omitted from the design calculations. It shall be documented that continuing to lay after these items have failed will cause no harm to the product and that the required grip can be achieved from the resulting asymetric pad configuration. 7.4.8.9 If tensioners are to be used, demonstration tests may be required to confirm the product will be unharmed during installation unless tensioning system review tests are documented as per DNVGLSTF101 [10.4.11], /42/. Guidance note: The scope and nature of such demonstration tests is to be agreed between the client and the installer, based upon current practice and previous track record of lay operations using this tensioner system and similar product properties. endofguidancenote 7.4.8.10 The tensioner system shall be qualified for the actual product dimension to be installed. 7.4.8.11 Variations in the outer diameter of the product due to production tolerances and dimensional transitions should be within the working range of the tensioner system. Guidance note: Following risk assessments, it is in some circumstances acceptable to lay products with diameter deviations out of tensioner specification. endofguidancenote 7.4.8.12 The maximum force the product handling equipment can exert shall be set and calibrated at a load point that ensures the maximum allowable squeeze load cannot be exceeded. The MWS company should: a) b) be provided with a written statement from the product supplier confirming the maximum allowable tensioner squeeze load at maximum installation tension in accordance with acceptance criteria specified in the applicable design code be provided with detailed equipment specifications including items listed in [7.4.8.2] Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 187 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: d) e) be provided with valid calibration certificates, in accordance with [7.4.13.1] for the handling machinery compression force setting, measurement and display functions be provided the intended compression settings through the installation documentation, and witness (if present), prior to the actuation of the system, the inputting of the settings into the lay system. 7.4.9 Straighteners 7.4.9.1 For rigid pipe, any pipe straightener shall be set to ensure that the out of straightness is within the tolerance(s) in the analyses for the installation and inplace condition. The settings should be proven by trial conducted at the yard/offshore. Guidance note: If proven by track record and/or engineering for a similar pipe design, the requirement for straightening trials can be waived. If proven by engineering alone, calibration trials of the analyses should be performed and attended by a competent third party. endofguidancenote 7.4.10 Stingers, ramps and lay towers 7.4.10.1 Rollers and tracks shall be faced with a material that will not damage the product. Rollers shall be in good rolling condition, both in air and subsea, with maintenance records submitted. 7.4.10.2 The height and spacing of the rollers shall be adjusted to ensure a smooth transition from the vessel to the water column. The rollers should be spaced and their heights set to maintain loads in the product within the limits given in the installation analyses. 7.4.10.3 The pipelay vessel’s stern ramp orientation, and stinger geometry, buoyancy, mass and stiffness shall be set to suit the planned lay with roller heights/openings set to suit also. 7.4.10.4 A stinger should be equipped with a monitoring systems that feeds back to the control room to confirm that the pipe is not experiencing high point or dynamic contact loads at the end of the stinger. Guidance note: Suitable monitoring systems include load cells and video cameras, preferably fitted on the last roller to monitor the clearance with the last roller. If unavailable, a full dynamic analysis is required in addition to onsite monitoring of roller reactions and stinger angle and TDP monitoring. endofguidancenote 7.4.10.5 All lay towers, lay ramps and stingers shall be equipped with tower, ramp and stinger angle indicators. 7.4.10.6 Where stingers incorporate ballast tanks, suitable indication of tank fill status shall be provided. 7.4.11 Lay chutes, lay sheaves and radius controllers 7.4.11.1 The radius of lay chutes, lay sheaves and radius controllers shall be sufficient to prevent any limit state criteria being exceeded. Any rollers shall be in accordance with [7.4.10.1]. Guidance note: The requirements in this section, [7.4.11], are generally only applicable for flexible product. The equipment’s radius is to be equal to or larger than the specified displacement controlled MBR of the product. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 188 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used c) 7.4.11.3 In cases where the product lead angle is not in line with the lay chute or lay sheave plan centre line, the lay chutes/sheaves shall have side walls to protect the MBR. The side walls shall accommodate the maximum lead angle expected during laying operations. Guidance note: The laying may be planned such that the lay vessel might need to weather vane or crab along the route to ensure that the influence of wind, waves and current does not cause a limit state to be exceeded. endofguidancenote 7.4.12 Reels, drums, carousels, baskets, tanks and turntables The structural integrity of equipment such as reels, drums, carousels, baskets, tanks and turntables shall be documented as adequate for all phase(s) of the marine operation(s). 7.4.12.1 Portable reels/drums for flexible product which will be operated on marine vessels should be of the driven spindle type. However, underroller type reels may be used if extra care is taken during installation to ensure slip and escape from the turning mechanism does not occur. 7.4.12.2 When transport is on board the installation vessel and the installation equipment, including product storage equipment, also acts as permanent/temporary seafastening, e.g. reel drive systems, the mechanical/ hydraulic capacity of the installation equipment shall be documented as sufficient for the relevant transport loads. Special attention should be given to systems depending on hydraulic pressure, gears and roller/ bearing systems exposed to high loads in a static condition. 7.4.12.3 The seafastening arrangements for product storage equipment not supported and seafastened via the installation equipment (e.g a reeldrive system) shall be documented for all phases. Guidance note: A seafastening release procedure should document that the reel is adequately secured until the reel drive system is mounted. endofguidancenote 7.4.12.4 Floors of carousels, turnables, baskets and tanks shall be levelled to prevent damage to the product when fully loaded. Guidance note: Floors may be lined with ply wood sheets to protect the product against irregularities of the floor. endofguidancenote 7.4.12.5 Partitioning of reels/drums, carousels, turntables, baskets and tanks shall be designed with sufficient strength to contain the product in the designated partition for all phases of the marine operation(s). Guidance note: For reel carousels, this applies to any adjustable flange. endofguidancenote 7.4.13 Hangoff/installation clamps 7.4.13.1 Where required, temporary product hangoff shall be well planned, using dedicated equipment only. The hangoff system should normally consist of well supported hang off collar/clamp. The equipment shall be suitable for the maximum design loads including any waterfilled condition (if applicable). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 189 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.4.11.2 Maximum contact load between product and chute/sheave/radius controller (sometimes referred to as sidewall pressure) shall be verified to be within acceptable limits specified by the product supplier. Collars for Jlay of rigid pipe are in [7.3.3.14]. endofguidancenote 7.4.13.2 The clamp’s capacity to support product tension shall account for the following, as applicable: — — — — — — — — — — the product’s squeeze load capacity number and arrangement of pads squeeze load applied by pads contact length between pads and product geometry and material properties of pads friction between pads and product externals friction between the product outer layer(s) and tensile components creep of polymer materials in the product crosssection effect of temperature, e.g. on expansion/contraction, creep rate, etc. and wet conditions including product internal annular flooding (if applicable). Guidance note 1: Geometry and material properties of the tensioner pads (i.e. pad length and separation, angle of pad groove) are required input to the product supplier for establishing maximum allowable tensioner squeeze load and minimum tensioner holding capacity. endofguidancenote Guidance note 2: Stresses in the outer layer(s) of a flexible product, resulting from tensioner squeeze loads and product tension, generally causes the layer material (typically a polymer) to relax and creep. At low stresses, the creep effect is negligible, but increases with increasing squeeze and/or tensile load. In order to prevent excessive elongation and sudden rupture of the outer layer, potentially resulting in uncontrollable slippage of the product internals (bundle) through the tensioner (and outer layer), it is important to have control of the creep rate at maximum allowable squeeze load and installation tension (combined). See [7.4.8.6] and [7.4.8.7] for further details. endofguidancenote 7.4.13.3 Minimum required squeeze load to prevent slippage between clamp and product shall be established by using the minimum documented and submitted external friction coefficient. The material factor, γm, applied to the characteristic friction coefficient should generally be taken as 1.5. 7.4.13.4 Where applicable the control of creep effects shall be ensured by specifying the maximum allowable product tension for a specified squeeze load based on an acceptable creep rate (see guidance note to [7.4.8.7]). The material factor, γm, applied to the friction coefficient can generally be taken as 1.5. Guidance note: This requirement is normally applicable to flexible product and may be applicable to coated rigid pipelines. It is not applicable to uncoated rigid pipelines. For definition of creep see guidance note to [7.4.8.6]. endofguidancenote 7.4.13.5 Lower material factors than those in [7.4.13.3] and [7.4.13.4] may be accepted where there are welldocumented tests (see [5.4.4]) that account for all the items listed in [7.4.13.2]. Where the tests comply with the minimum requirements of [5.4.4], the material factor, γm, may be taken as 1.4. A further reduction may be accepted where there has been more extensive testing validated by engineering and/or it can be shown by risk assessment (see [2.4]) that the consequences of slippage/creep in the tensioner (including risk to personnel, equipment, infrastructure, product and schedule) are low or can be mitigated; in such cases the minimum acceptable material factor, γm, is 1.25. See guidance note to [7.4.8.7]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 190 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 7.4.14 Calibration and testing 7.4.14.1 The general requirements for equipment testing and calibration in [2.10] apply. Testing and calibration of laying equipment shall be done according to DNVGLSTF101 [10.4], /42/, or equivalent. 7.4.14.2 All loading equipment controls, sensors and monitoring devices shall have valid calibration certificates. The calibration and testing of essential equipment should as a minimum be performed on an annual basis. 7.4.14.3 Unless covered by valid certificates, the following shall be done before lay operations: 1) 2) 3) 4) 5) Combined positioning system/tensioning system tests shall be done by simulating product pull, tensioning system failures and redundancy tests during pull. Any tensioner load cells should be calibrated. (as per DNVGLSTF101 [10.4.7], /42/). The A&R winch and any product support load cells should be calibrated. (as per DNVGLSTF101 [10.4.7], /42/). Equipment should be tested and calibrated to the maximum equipment capacity or alternatively up to maximum expected dynamic or accidental loads + 50%, whichever is less. During testing and calibration the complete load range should be covered. For rigid pipes: — For linear trends at least five load steps should be applied up to maximum expected dynamic loads, more steps are required when testing to maximum capacity. — Nonlinear trends require higher numbers of load steps. Cyclic loading should be considered. 6) For tensioners and A&R winches, prior to lay operations, indate calibration certificates and proof load test certificates shall be available. Failsafe operations during event of a power blackout should be demonstrated. Guidance note 1: Loss of main power and loss of signal should be tested by removing fuses or cables. endofguidancenote Guidance note 2: Calibration shall occur not more than one year in advance of the expected completion of operations. endofguidancenote 7.5 Loadout and offshore transfer 7.5.1 General 7.5.1.1 The limit states of the product (see [7.3.3]) shall not be exceeded during any phase of the load out. This shall be confirmed by analysis where necessary. See [7.3] for details on installation engineering including analysis requirements. 7.5.1.2 If required by the recognised design code or client or similar a tracking system should be implemented. Individual pipe joints shall be identified and manifested, as they are stowed into or on the marine transport vessel, to ensure traceability. 7.5.1.3 Any damage during loadout shall be made good or otherwise addressed. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 191 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.4.13.6 Where there are contingency plans to continue the operation after the failure of one pad or one line of pads, then the capacity of these shall be omitted from the design calculations. It shall be documented that continuing the operation after these items have failed will cause no harm to the product and that the required grip can be achieved from the resulting asymetric pad configuration. 7.5.2 Handling and lifting 7.5.2.1 Product handling and lifting shall be planned so that product limit state criteria are not exceeded. The requirements in the rest of this section, [7.5.2], shall be applied as appropiate. Guidance note: For bundled product see [7.9.10.14]. endofguidancenote 7.5.2.2 The outer layer of flexible product and pipeline coating shall be protected against damage that will adversely affect the inservice condition of the product. Guidance note: Protection may be by the use of smooth facings (manufacturer approved facings) on all parts coming into contact with the product, including rollers, tensioners/cable engines, reel drums and flanges. Bolts and fixtures with potential to contact the product may be recessed or protected. endofguidancenote 7.5.2.3 Use of hold back rigging (choked slings, Chinese fingers etc.) directly on the outer layer of flexible product shall be confirmed as acceptable by the product manufacturer. Similarly, the use of installation clamps should be confirmed acceptable by the product manufacturer and only be used according to their instructions. Guidance note: Normally, the use of hold backrigging directly on the product is acceptable. Incorrect use of Chinese fingers and chokes slings could result in damage/slippage of the outer layer and/or otherwise compromise the product integrity. endofguidancenote 7.5.2.4 Where flexible product is being handled, the product shall be moved over rollers or bodily lifted, without dragging, unless all the product/support interfaces are smooth (e.g. deflectors, chutes, prepared deck surfaces) and no excessive contact force is applied. Tension and minimum bend radii shall be controlled by means of lift and transfer arrangements and procedures that are proven, e.g. through analyses and/or monitoring, not to exceed the design of the product. Similar care is required during deck handling of end or midline structures. 7.5.2.5 Lifting operations of components attached to a product shall be planned to ensure the limit state criteria of the product (see [7.3.3]) are not exceeded. In particular the following should be considered: a) b) c) The relative movements between the lifted component and product. The need for additional control measures during the lift, (e.g. tugger winches [16.16.12], lifting guides [16.14] etc.). The gradual change in CoG for the lift where the component is gradually carrying more/less of the product weight, including means to compensate and control of the catenary/bend radius (e.g. through additional support rigging, change in tension etc.). Guidance note: These considerations are particularly important for components with large relative weight compared to the product itself (e.g. end terminations, inline components) See [7.4.7] for requirements to lifting equipment. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 192 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.5.1.4 Adequate stationkeeping of all vessels shall be documented. See Sec.17 and in particular [17.10] for quayside moorings. 7.5.2.7 Pipe joints shall be lifted using equipment and/or tools systems that do not damage the coatings or prepared pipe ends, such as: — — — — soft faced hooks soft slings suitable spreader bars certified electromagnets. 7.5.3 Product loadout by reeling, spooling, winding and coiling 7.5.3.1 This section applies to loadout of product by: — reeling or spooling onto horizontal or vertical reels/drums/reel carousels with back tension — winding into a rotating basket carousel/turntable without back tension — coiling into a nonrotating basket without back tension. Guidance note: See also [7.4.12] for requirements to product storage equipment (reels, drums, carousels, baskets and tanks. endofguidancenote 7.5.3.2 The complete loadout pathway including equipment shall be inspected for acceptability and set up for the actual product. Guidance note 1: Depending on the site layout the pathway can start at the manufacturing facility or storage location or spool base and ends at product storage equipment Examples of equipment to consider are reeling/spooling/winding/coiling system, tensioners, on board equipment and spooling tower roller boxes (for rigid pipelines only). endofguidancenote Guidance note 2: The following are normally included in the inspection for acceptability: — nonconforming bends (e.g. less than the product MBR) — loose/stiff rollers — sharp protrusions — coarse sliding surfaces — sections where the product can jump off the loading pathway and — sections that are out of sight. endofguidancenote 7.5.3.3 The loading pathway should be monitored continuously as a minimum at critical sections and bends. Guidance note: CCTV and/or competent personnel may be considered as suitable monitioring methods. endofguidancenote 7.5.3.4 For product storage below deck, it shall be documented that there is sufficient clearance between top layer of basket/carousel/tank and deck opening to allow for handling of the product within its design limitations (e.g. bending radius and twist). Special focus shall be given to handling of stiff end or midline structures on the product. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 193 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.5.2.6 Where long strings or stalks of rigid pipeline are being moved, they should do so on soft faced rollers or soft faced pipe racks demonstrated to be arranged so as not to over stress the pipe and to ensure no damage is feasible to the pipe coatings, with forward and backward control of the pipe movement/tension. Guidance note: Minimum and maximum height of bottom point on any catenary may be specified and monitored. endofguidancenote 7.5.3.6 A watch shall be maintained to ensure that the wake from passing vessels cannot endanger the operation. The catenary shall have sufficient length to preserve the product if the vessel moves excessively due to wake from passing traffic. 7.5.3.7 Product reeled/spooled onto reels/drums/reel carousels shall be wound under tension to prevent loose wraps. The required backtension to prevent this shall be documented. Documentation may be means of track record made available to client/MWS if required. Guidance note: For rigid pipe to be reeled/spooled see [7.9.10.16] for requirement to length required for lead and tail sections. endofguidancenote 7.5.3.8 Flexible product loaded by winding or coiling into a basket carousel, basket or tank shall be tightly packed together to minimise gaps. Gaps should be packed out to prevent movement at sea and to prevent overlying product being forced into gaps between product in underlying layers. Any packing material shall not damage the outer layer in any way that will adversely affect the inservice condition of the product. 7.5.3.9 Where product is to be coiled the manufacturer shall specify that the product is suitable for coiling and the loading procedures shall specify the coiling direction considering the armour layup. Guidance note: For a product to be coilable, it must be designed to prevent buckling and/or locking of concentric layers within the crosssection as it is twisted (360° per turn/coil). A torque balanced crosssection is typically not coilable. endofguidancenote 7.5.3.10 Suitable arrangements for storage, seafastening and protection of the end terminations shall be made and documented. See [7.6.1.3]. 7.5.3.11 Swivels use shall be evaluated based on sling nature and product nature considering torque balance. Generally swivels should be used on the tension side when pulling products using ropes or slings that are not torque balanced, and when pulling flexible products that are not torque balanced. Guidance note: In all cases inclusion of swivels in pullin/holdback systems is to be carefully evaluated with respect to the wire construction. Rotation resistant ropes are not affected when freerotating swivels are introduced into the system, while non rotation resistant and semi rotation resistant ropes will be adversely affected by freerotating swivel. When such wire ropes are loaded and unloaded, the swivel will allow the rope to rotate back and forth causing tensiontorsion fatigue of the rope. As a result these wire ropes will operate at a reduced design factor and will in addition fail from the inside out. For non rotation resistant ropes there is generally more than 30% reduction of rope MBL and endurance by a factor of about ten. endofguidancenote 7.5.3.12 The requirements for transpooling operations of flexible product between vessels are the same as for reeling/spooling quayside operations, with the following additions: — The product catenary between the two vessels shall be monitored to ensure that relative motion between the two vessels does not jeopardise specified minimum product bending radius or cause snap loads in the product. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 194 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.5.3.5 The product catenary between shore and vessel shall be monitored to prevent excessive product bending or tension in case of unsynchronised line speed onshore and on vessel, or a sudden stop in the line. Responsibility for managing the loadout catenary between shore and the vessel shall be clearly defined. Guidance note: If a spacer barge is used between the vessels to ease the catenary, the same general principles apply. Spacer barge shall be adequate against the expected berthing and/or mooring forces. endofguidancenote 7.5.3.13 Before start of loadout, any cable ends shall be sealed against water ingress or terminated by competent technicians using junction box, splice box, subsea connector or similar. The sealing or termination shall be in accordance with the cable manufacturer’s procedures and/or termination box/connector supplier specification. 7.5.3.14 Upon completion of post loadout testing, cable seals, tube fittings, end caps and pullin arrangements , as appropriate, shall be properly fitted to the product ends by competent technicians in accordance with the manufacturer’s procedures. 7.5.3.15 If any damage occurs during loadout of a flexible product, testing shall be performed to determine the extent of product damage. The scope of the testing can be agreed at the time of an incident and will depend on the type of incident. The product shall be accepted by the owner after such damage, and subsequent testing and repairs approved before continuing the operation. 7.5.3.16 When preinstalled pullin heads are fitted at the manufacturer’s premises appropriate documentation defining the load capacity shall be submitted. 7.5.3.17 Any damage to the flexible product during loadout shall be rectified. Any signs of birdcaging armour wires, kinks and buckling in the cable and any tendency for the product to try to form loops in the catenary between the loadout gantry and the lay vessel loadout chute are causes for concern and should be investigated. 7.5.4 Lifted loadouts and offshore transfer 7.5.4.1 Loaded drums should be inspected for signs of physical damage on arrival at the delivery location before loadout. If a drum is damaged then the cable in the damaged area should be inspected and, if deemed necessary, the cable should be tested. 7.5.4.2 Lifted loadouts and offshore transfer lifts from the transport vessel to the installation or lay vessel shall be in accordance with the applicable parts of Sec.16. This includes lifting of pipe joints and product stowed on reels/drums/reel carousels and in baskets or basket carousels. Guidance note: See also [7.5.2] for requirements to handling and lifting. endofguidancenote 7.5.4.3 Where pipe joints are lifted as a stack the height shall be restricted to prevent damage to pipe/ coatings and by vessel constraints. Access to the top of the pipe stack shall be arranged to minimise risk of injuries to riggers. Guidance note: See [7.5.1.2] for tracking system requirements. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 195 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — Mooring lines should be checked on a regular basis and the checking interval should be in accordance with the prevailing environmental conditions and passing marine traffic. Mooring line checks and adjustment shall be recorded in the reeling/spooling log (in addition to the vessel bridge log). — The operation should be in sheltered waters with the relative motion between the vessels minimised. Where the operation is to take place in open waters limiting environmental conditions shall be specified to prevent any limit state being excluded. 7.5.4.5 Offshore transfer lifts shall not be executed above subsea assets without due consideration for the effect dropped objects. For lifting operations taking place over a vessel side, a safe over boarding distance from any subsea assets shall be established in accordance with [5.6.6.6]. 7.5.5 Testing 7.5.5.1 This section, [7.5.5], covers the requirements for pre loadout and post loadout testing of umbilicals (including cables) or similar. It is not applicable to rigid or flexible pipelines. Guidance note: For other product types, the testing is in accordance with the recognised desing code and any contract between client and supplier. endofguidancenote 7.5.5.2 Umbilicals shall be tested before and after loadout normally in accordance with the recognised design code with the results submitted. Generally the following would be considered as the minimum testing requirements. Guidance note: See ISO 136285, /96/, for guidance. Other parties (e.g. supplier and installation contractor) may also require testing to document product integrity before/after load out. endofguidancenote 7.5.5.3 Before start of loadout, the umbilical shall be function tested at the loadout site. Guidance note 1: Normally the function tests are in accordance with ISO 136285, /96/. If the loadout site is at the manufacturer’s facility then the tests do not need to be repeated. Any tests older than three months may need to be repeated. endofguidancenote Guidance note 2: In fibre optic cables it may be acceptable to test an agreed percentage of the fibre optics unless there is an incident during load out that might have damaged the cable. endofguidancenote 7.5.5.4 After loadout, the umbilical should be function tested. Guidance note: Normally the function tests are in accordance with ISO 136285, /96/. endofguidancenote 7.5.5.5 The post loadout test procedure should be taken into account in the deck layout, as well as the reeling/spooling, loadout and transpooling procedures. Guidance note: Depending on the post loadout test scope, it can be necessary for both ends of the loaded umbilical to be accessible for testing. endofguidancenote 7.5.5.6 Post loadout test results should be compared with the FAT results and abnormalities investigated. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 196 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.5.4.4 For offshore transfer of pipe joints from pipe carrier to installation vessel, the limiting weather conditions shall be specified considering relative motion between vessels. 7.6.1 General 7.6.1.1 These requirements are valid for the transport of product on both installation and transport vessels. 7.6.1.2 General requirements for the transport are contained in Sec.11. 7.6.1.3 All products, including inline assemblies, end structures/terminations, buoyancy modules, clamps and other accessories shall be seafastened according to requirements in Sec.11. 7.6.1.4 Limit state criteria shall not be exceeded during any phase of the voyage. The effects of vessel motions should be considered when evaluating crush loads. 7.6.1.5 Temperature limitations during storage and/or transport should be considered, not least related to the preservation fluids that have been used. The need for over pressure protection of products that are filled with preservation fluids should be considered (e.g. due to effect of temperature differences). 7.6.1.6 See [7.4.12] for reel/drum/carousel/basket/turntable requirements. 7.6.1.7 The product shall have been loadedout in accordance with the applicable sections of [7.5]. 7.6.1.8 Drummed product ends shall be protected from external damage by use of wooden planks, or similar, and securely fitted between the drum flanges. 7.6.1.9 Crush loads imparted by overlying product shall be within limits set by the manufacturer. Calculations confirming crush loads are within set limits shall be submitted and shall include the effects of vessel motions which should not be less than the design environmental condition in [3.1.3]. 7.6.1.10 Unless part of the vessel’s permanent equipment, design calculations shall be submitted to demonstrate that the reel/carousel/basket/tank structure can withstand the loads imparted by product due to vessel motions. The conditions used for the calculations shall be not less than the design environmental condition in [3.1.3]. 7.6.2 Pipe joint specific 7.6.2.1 Stowing and stacking of pipe joints for transport shall be in accordance with [11.9.9] or API RP 5LW, /7/, or equivalent. 7.6.2.2 Pipe joints should be protected against corrosion. Guidance note: Plastic end closers may be fitted before loadout for long marine voyage (particularly via tropical conditions), as experience has shown that significant corrosion can occur in the pipe bore in these circumstances. endofguidancenote 7.6.2.3 Additionally to seafastening requirements in [11.9.9], where the pipe joint is bare or coated with a hard slick product such as FBE (fusion bonded epoxy) or polyethylene either: — adequate friction against axial pipe movement shall be documented or — restraint against axial movement shall be provided. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 197 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.6 Transport This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.7 Route 7.7.1 General 7.7.1.1 The intended route of the product shall be submitted showing all relevant details of the area, including but not limited to: 1) 2) 3) 4) 5) shoreline bathymetry existing and projected platforms subsea assets, and any obstructions such as: — — — — — — — — — — — — — 6) wrecks rock or coral outcrops glacier scars seabed pockmarks sand wave or mudslide areas fault lines dumping grounds including munitions unexploded ordnance (UXO) fishing anchoring naval exercise other restricted areas areas where freespanning may occur third party concession owners. Guidance note: This could be in the form of alignment sheets or similar. endofguidancenote 7.7.1.2 Drawings shall be to a suitable scale, and all locations shall be to a common coordinate system such as UTM and geodetic datum (e.g. European Datum 1950 or World Geodetic System 1984). 7.7.1.3 The route shall be clearly defined by coordinate points, straight and curved sections, kilometre points, tangent points and intersection points as necessary. All existing structures, crossed lines and the target areas or target box for the startup and laydown locations/targets shall be clearly identified. Guidance note 1: The startup and laydown targets are normally rectangular boxes whose centre is the nominal coordinate for the aslaid location of a particular pipe spool, subsea termination unit, or similar. Lateral and axial tolerances on this coordinate set in the approved design drawings define the target box size. endofguidancenote Guidance note 2: For cable lay operations this may be a route positioning list (RPL). See also DNVGLRP0360, /58/. endofguidancenote 7.7.1.4 Where applicable, plough routes should be based on surveys and should avoid wrecks, substantial obstacles, UXO, environmentally sensitive areas (such as Sabellaria worm habitats), and difficult soil conditions. Small objects may be removed, but should be avoided if practicable. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 198 Guidance note: This is of particular interest for cable laying in offshore wind farm developments where turbine installation and cable laying operations may occur in parallel. endofguidancenote 7.7.1.6 The seabed shall be prepared in accordance with the recognised design code, as applicable, to ensure that no limit state of the product is exceeded. Guidance note: See DNVGLSTF101 [10.3.2], /42/. endofguidancenote 7.8 Surveys 7.8.1 The surveys in this section, [7.8], shall be submitted. These are required for approval of the marine operation, however any additional requirements in the recognised design code shall be considered. Guidance note: More information regarding survey requirements and their purpose can be found in the following documents/sections: — For pipelines: DNVGLSTF101 Sec.3, /42/, and DNVGLSTF101 Sec.10, /42/ — For subsea cables: DNVGLRP0360 [3.4], /58/ — Submerged pipeline towing: DNVGLSTF101 [10.6.5], /42/ — Bundles: [11.32.4] of this standard. endofguidancenote 7.8.2 The survey vessel, survey equipment, the extent of survey, and survey tolerances shall be suitable for the surveys to be performed. 7.8.3 Route survey 7.8.3.1 For product tows, route surveys shall be carried out along the total length of the planned route to provide sufficient data for design and installation related activities. 7.8.3.2 Areas where permanent constructions or temporary installation activities might be restricted shall be identified. Areas can be restricted for a variety of reasons such as environmentally sensitive habitats, political reasons, fishing activity, military ranges, or unexploded ordnance (UXO). 7.8.4 Geotechnical survey 7.8.4.1 A geotechnical survey shall be carried out in sufficient detail to establish the characteristics of the seabed along the chosen pipeline route. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 199 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.7.1.5 Where applicable, existing jackup footprints shall be identified and new footprints should be accurately plotted when jackups are deployed. If the product is to be laid on the seabed without burial, this survey may be limited to confirm general seabed soil characteristics and stability and to identify rock or coral and any presence of sulphate reducing bacteria or other aggressive soil conditions. endofguidancenote 7.8.4.2 If the product is to be trenched or trenched and buried, detailed information on the soil characteristics shall be documented to justify the trenching method, trenching tool proposed and its performance to meet trenching specification in terms of trench depth and depth of cover. Guidance note: This is known as a burial assessment survey (BAS) in the cable lay industry. endofguidancenote 7.8.5 Crossing surveys 7.8.5.1 Third party cables and pipelines crossing the proposed route shall be identified. Their location and condition shall be established in detail in order that agreement can be reached on the most effective means to protect the existing line and the new line during installation and future operating conditions. Guidance note: If the existing line is buried it may have to be located by means of acoustic or magnetic tools deployed to the seabed or from prior surveys. endofguidancenote 7.8.6 Preinstallation survey 7.8.6.1 A preinstallation survey of the worksite or route may be required in addition to the route survey required for design purposes (see [7.8.3]) if: — — — — — time elapsed since the route survey is significant a change in seabed conditions is considered likely the installation site/route is located in areas with heavy marine activity new installations or facilities are present in the area seabed preparation work is performed within the route corridor after previous survey. Guidance note: The preinstallation survey can be achieved by performing a grapnel run for cable laying. This should not be used for oil and gas products. endofguidancenote 7.8.6.2 The preinstallation survey, if required, shall determine/confirm: — potential new hazards — location of wrecks, submarine installations and other obstructions such as mines, debris, rocks and boulders that might interfere with, or impose restrictions on, the installation operations — the size as well as the location of the seabed objects and infrastructure — that the present seabed conditions confirm those of the survey required in [7.8.3] and [7.8.4] — previously unidentified hazards related to the nature of the installation operations. 7.8.6.3 The extent of, and the requirements for, the preinstallation installation site survey/route survey shall be specified. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 200 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 7.8.7.1 Post lay survey(s) shall be completed to confirm the aslaid route and the visible condition of the product. This may be done either by continuous touchdown point monitoring during pipe laying or by a separate survey. In case continuous touchdown monitoring is used, product positioning shall be confirmed after completion of product installation. Guidance note: Continuous touchdown monitoring does not always identify possible horizontal curve pullout, and it can therefore be necessary to confirm the positioning after completion of installation activities. endofguidancenote 7.8.7.2 Any free spans shall be identified with their length and height assessed to determine if any support or protection is needed. Subsequent surveys may be required after trenching to confirm product disposition and condition in the trench and the final elevation profile of the product. 7.8.7.3 Further detail on the product’s elevation relative to LAT and out of straightness survey (OSS) can be needed for lines susceptible to upheaval buckling in order to determine surcharge loading or backfill required to inhibit upheaval. Following such surcharge, another survey can be required to confirm surcharge depth achieved. Guidance note: The last of the above postlay surveys, or the accumulation of them, will constitute the asbuilt survey. The results of the survey(s) are normally required to be captured on video and on asbuilt alignment sheets for issue to the client, together with comprehensive asbuilt documentation of the full construction and installation phase. Details of the installed protection, if any, are included. For power cables, an asbuilt survey might not be required if burial levels were previously recorded. In this case, vessel location can be sufficiently accurate for asbuilt records. Required accuracy of location is project specific. endofguidancenote 7.9 Lay operations 7.9.1 General 7.9.1.1 For laying operation, the requirements of [7.2], [7.3] and [7.4] apply. 7.9.2 Planning of laying operations 7.9.2.1 The requirements for planning in [7.2] apply. The planning shall consider the requirements in the rest of [7.9]. 7.9.2.2 Seabed preparation requirements in accordance with the recognised design code shall be considered and included in the planning and/or documented as completed prior to commencement of the laying operation. Guidance note: See also DNVGLSTF101 [10.3.2], /42/. endofguidancenote 7.9.2.3 The direction of lay shall be determined with consideration for: a) operational considerations Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 201 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.8.7 Postlay surveys installation and precommissioning methodology seabed structures/subsea facilities location and water depth of planned offshore jointing operations steep slopes (uphill lay/downhill lay) offshore pullin/subsea tiein/shore pull operations including end termination design, and prevailing environmental conditions. 7.9.2.4 Steep slopes 7.9.2.5 The risk of product slippage on steep slopes shall be considered, as this can lead to straightening of curves and the formation of free spans uphill of the slope, as well as axial compression or buckling at the foot of the slope. The risk of free spans at the foot of the slope due to excessive tension during uphill lay should also be considered. 7.9.2.6 On steep slopes, the need for seabed anchors should be evaluated, considering effects of tension variations both during downhill lay and in service. 7.9.2.7 The difficulty of establishing the point of contact with the seabed (touchdown) during laying on steep slopes shall be considered with respect to lay method and installation parameters. The installation procedure shall be established in such a manner as to ensure control of the catenary at all times, e.g. by use of a step bystep lay table. 7.9.2.8 End termination assemblies/inline components 7.9.2.9 Procedures for safe overboarding and lay tables for lowering and landing shall be established to ensure a safe operation for the limiting weather conditions specified for the operation. 7.9.3 Contingencies 7.9.3.1 The operation manual shall contain a set of contingency procedures, which shall be agreed between MWS, client and contractor. 7.9.3.2 Detailed contingency procedures for each critical operational step should be documented. Guidance note: For laying operations in general, typical steps requiring contingency procedures can include a) failure of dynamic positioning system b) failure of anchors or anchor lines, c) coating repair d) anode repair e) failure of tensioning system f) repair of lay equipment emergency hang off g) product becoming stuck during pullin/tiein h) ROV breakdown i) breakdown/failure of position reference systems/navigation reference system j) weather conditions in excess of operational limiting criteria k) third party marine activity and l) critical or emergency situations identified in FMEA or HAZOP studies. endofguidancenote 7.9.3.3 For power cables and umbilicals, contingency procedures should address abandonment and recovery, including contingency cutting and subsequent repair splicing (as applicable). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 202 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used b) c) d) e) f) g) Where contingency cutting and subsequent repair splicing is not possible alternative procedures can be required. endofguidancenote 7.9.3.4 For rigid pipelines, contingency procedures shall address the following (as applicable): a) b) c) d) e) dry buckle laydown and retrieval wet buckle laydown and retrieval repair accidental flooding any other abandonment and recovery situations identified in FMEA or HAZOP studies. Guidance note: Due diligence should be exercised to ensure buckling does not occur, however a small residual risk remains that the pipe will buckle during installation. Procedures and equipment are required to be in place to safely and efficiently recover from such an event. The presence of a buckle should be detected and signalled to the vessel as per [7.9.10.18]. endofguidancenote 7.9.3.5 Contingency procedures shall address the situation where lay operations are suspended, but the product is held insitu and not abandoned. The procedures shall detail how fatigue damage will be minimized at the over boarding and touchdown points. Guidance note: Fatigue damage can be minimized by paying in/out product to change the contact point/bend at the over boarding point, such that fresh product is moved into the dynamic section and the hardworked product moves to the static section. Where multiple over boarding points are possible, the most favourable shall be used, considering the direction of prevailing current. To minimize fatigue damage at the touchdown point, visual monitoring shall be maintained such that corrective action can be implemented if anything unfavourable occurs. If the lay vessel stands by with cable deployed over the lay chute or the lay sheave then the cable shall be picked up or paid out a few metres at set periods of time to prevent cable damage where the cable is stationary on the lay chute or lay sheave – freshening the nip. endofguidancenote 7.9.3.6 The schedule should include contingency time for possible repairs (e.g. of damaged outer layer/ coating). 7.9.3.7 Provision of pipeline recovery tooling (PRT), dewatering equipment and pipeline cutting tools shall be defined at the start of the project. The availability of this equipment shall be reflected in the contingency procedures. Guidance note: For major pipeline projects in deep water, it can be beneficial to have a full standby spread of pigging and air compression equipment to dewater the pipeline, to enable rapid recovery and repair of a wet buckle. endofguidancenote 7.9.4 Procedures 7.9.4.1 Procedures for laying, supported by analyses, shall be documented. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 203 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Typically the following (as applicable) are included in the procedures: a) initiation of lay b) normal continuous lay, including around curves and changes in heading c) laydown/termination of laying operation d) flooding and system pressure test e) abandonment and recovery (empty and flooded cases for pipelines) f) reeling/spooling g) trenching, ploughing and backfilling/burial h) tiein operations i) pullin to structure j) contingency procedures k) temporary conditions l) riser and spool installation m) laying of inline structures n) shore pull and offshore pull o) andfalls p) close proximity operations q) SIMOPS r) DP/mooring operations s) diver/ROV operations t) control and monitoring u) operational limiting criteria for each operation phase. endofguidancenote 7.9.4.2 Laying procedures shall cover the whole range of water depths and environmental cases up to the marginal environmental condition at which abandonment and laydown will start using the A&R winch. Lay down and recovery procedures are also required, addressing the controlled stepwise operation to abandon and return to normal lay conditions. The weather threshold required before recovery operations starting shall also be documented in the marine operation manual. 7.9.5 Stationkeeping 7.9.5.1 In accordance with [7.2.2.2], the vessel shall be documented to have sufficient station keeping capabilities to maintain its required position within the specified installation criteria (such as layback, heading etc.) for all planned and contingency operations. 7.9.5.2 For laying operations, the vessel should either be: a) b) conventionally moored with one or more pull ahead winches (see also [7.9.6]) or be dynamically positioned (see also [7.9.7]). Guidance note: Mooring equipment requirements are in [7.4.3]. Dynamic positioning system requirements are in [7.4.4]. endofguidancenote 7.9.5.3 The stationkeeping system shall have sufficient capacity to manoeuvre the lay vessel, considering: a) b) c) limiting environmental condition lay tension, and ploughing loads (if applicable). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 204 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 7.9.6.1 A mooring procedure shall be documented with every critical/congested anchor location predefined along the pipe route. For open field locations, typical anchor plans shall be submitted. The number of anchor handling vessels shall be appropriate to the proposed mooring operations. Guidance note: As lay operations involve a nearcontinuous process of moving moorings and the lay vessel is normally attended by two or more anchor handling vessels (AHV) to facilitate adjustment of the mooring pattern. endofguidancenote 7.9.6.2 A mooring analysis shall be documented to justify the mooring spread used, and identify the limiting environmental conditions for both planned and contingency operations including any standby condition. Critical configurations and load cases shall be determined for the given route and addressed, allowing for planned anchor retrieval and relay operations. Consideration shall be given to contingency cases with reference to allowable vessel offsets and anchor holding capacity. The mooring analysis shall be in accordance with Sec.17. 7.9.6.3 The mooring analysis shall include the redundancy (single point failure) requirements in [17.6.2]. The reduced stationkeeping capability after/during a mooring failure, and any effects on product integrity, shall be considered and documented. Attending anchor handling vessels may be considered for the redundancy case. 7.9.6.4 AHV specifications and anchor handling procedures shall be documented. AHV(s) shall be subject to MWS suitability survey before the start of the operations. Anchor handling vessels shall be equipped with: a) b) c) A surface positioning reference system of sufficient accuracy. High accuracy is required for anchor drops in areas with strict requirements to control of anchor position, typical within safety zone of existing installations, proximity of pipelines or areas of archeological or environmental importance. Computing and interfacing facilities for interfacing with lay vessel, trenching vessel or other anchored vessels. Latest revision of charts for the whole area of operation. 7.9.6.5 Live anchors, i.e. anchor handling vessels used for stationkeeping, may be used to manoeuvre the lay vessel. Live anchor operations shall be carefully planned and the live anchor handling procedure shall be documented. The procedure shall include anchor position drawings showing the planned positions of anchors for all phases of live anchor operations. When a DP anchor handling vessel is used as a live anchor, it shall be DP class 2 at a minimum. See [17.13.2]. 7.9.6.6 Contingency plans shall mitigate the potential impact on the product in the case of a mooring line failure. Mooring line failure can govern the limiting environmental conditions if vessel excursions exceed the permissible values for the product being laid. See [17.13.2]. 7.9.6.7 Clearances around mooring lines and anchors should comply with the requirements of Table 177. If any of the clearances specified within Table 177 are impractical because of the mooring configuration, water depth or seabed layout, a risk assessment shall be carried out and special precautions taken as necessary, noting that agreement will be required for any affected third party equipment owner’s for such risks. Guidance note: This applies to both anchor running and laid conditions. endofguidancenote 7.9.6.8 Moorings should avoid contact with subsea assets. If contact/crossing is unavoidable then: a) it shall be demonstrated that the mooring will not damage the asset Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 205 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.6 Mooring operations for product laying suitable means of protection shall be installed, and permission shall be obtained from the asset owner. 7.9.6.9 If an anchor is run out over a subsea asset, the anchor shall be securely stowed on the deck of the anchor handling vessel. In circumstances where either gravity anchors or closed stern tugs are used, and anchors cannot be stowed on deck, the anchors shall be double secured through the additional use of a safety strap or similar. 7.9.6.10 Anchors shall be deployed with the vessel as far from other assets as safely possible, given the constraints of the mooring system. Clearances between anchors/mooring line and the subsea asset shall be in accordance with [17.7]. 7.9.6.11 The anchor position, drop zone and wire catenary should be established taking into account the water depth, wire tension and wire length. Confirmation of anchor positioning after installation shall be confirmed at regular intervals depending on required accuracy and criticality, and counteractive measures taken when found required. Monitoring systems shall be considered. 7.9.6.12 Mooring and pullahead anchors shall be selected to provide the required holding capability at the limiting operating conditions in the soil conditions expected along the entire route. See [17.6]. 7.9.6.13 Each anchor shall be loaded after deployment to a tension as per mooring analysis/procedure, and position and tension shall be monitored to ensure no dragging taking place. See [17.9.2]. 7.9.7 Dynamic positioning operations 7.9.7.1 The DP footprint shall be considered when defining the lay control parameters to ensure sufficient margin is taken to ensure that this footprint is within the limits of the installation analyses/procedures. Contingency plans shall address action required in event of a DP malfunction and shall include the actions required by the product installation equipment operators. The reduced DP capability after a DP malfunction, and any effects on product integrity, shall be considered and documented. See [7.9.3]. Guidance note: In the event that the lay vessel requires a change of heading under high wind or current conditions, it not always feasible for the DP centre of rotation to remain at the product over boarding point (or equivalent remote location). Such an operation should be carefully planned to avoid vessel movement causing damage to the product, and documented in the contingency plans. endofguidancenote 7.9.7.2 Great care should be taken when choosing and prioritizing the various DP position reference systems, taking into account the specific situations and critical parameters that need controlling. Guidance note: Relative positioning system should be used when monitoring distances to other floaters and/or moving objects while absolute positioning systems would typically be important if object is to be landed in an absolute position, such as target box or when working close to a fixed platform. endofguidancenote 7.9.8 Installation monitoring 7.9.8.1 Lay monitoring a) b) The lay monitoring methods should be documented considering the actual lay operation and [7.9.8.2] to [7.9.8.5] as applicable. Also see [7.4.5]. The lay configuration and loads shall be controlled in order to ensure that these are within established limits during installation. The configuration and loads may be controlled by various means and shall Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 206 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used b) c) Guidance note: The lay configuration may be controlled by tension, stinger tip clearance and/or layback distance/touchdown monitoring. Depending on the installation vessel and type of product, the preferred method can alter. endofguidancenote c) ROV monitoring should be performed for inline structures and PLET/PLEMs during laydown and initiation operations. Guidance note: In the case of multiple structures during laydown, monitoring the lower structure close to TDP and laydown area is normally adequate. endofguidancenote 7.9.8.2 Touchdown monitoring 7.9.8.3 Where the following requirements to touchdown monitoring cannot be achieved due to operational constraints (e.g. water depth) then alternatives to ensure product integrity shall be considered: a) b) Touchdown monitoring should be accomplished by ROV or other means to ensure the configuration in the touchdown area remains within the identified limits. Touchdown monitoring shall be performed for critical operations and critical sections representing a risk to the product or existing infrastructure. Critical operations and critical sections shall be identified in the operational HAZID. Guidance note: Critical operations and critical sections can typically be — initiation — laying around curves/altering course — narrow lay corridor — crossings — laying towards counteracts, — boulder areas and — laydown. endofguidancenote c) d) e) Laying in congested areas, in the vicinity of existing installations and at crossings, shall be carried out using positioning systems with required accuracy. Measures shall be taken to avoid damage to existing infrastructure. ROV should be used to continuously monitor such operations. In order to enable continuous lay operations, adequate contingency measures for touchdown monitoring shall be established in case of primary monitoring system failure. Any ROV used shall meet the requirements of [4.5] and it shall have sufficient working range to observe the critical areas such as touchdown point, turning points etc. 7.9.8.4 Vessel monitoring 1) 2) The position monitoring systems requirements in [4.4.5] apply. Monitoring equipment for the following should also be available: — — — — — — vessel movements such as roll, pitch, sway, heave water depth vessel floating position (e.g. draught and trim) direct or indirect indication of sagbend curvature and strain laying equipment, [7.4] for vessels to be moored see [7.4.3]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 207 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used be clearly described including allowable ranges for the specific installation. Redundancy in monitoring method or contingency plans shall be available in the event of failure of monitoring equipment. 1) 2) Tension levels shall be monitored and should be recorded throughout installation to ensure allowable values are not exceeded unless suitable risk assessment and mitigations are in place. For stinger or ramp, the following (if applicable) should be monitored : — — — — product and A&R wire position with respect to the last roller or guide roller reaction loads on the roller introducing the stinger curvature roller reaction loads (vertical and horizontal), as a minimum for stinger tip stinger and ramp configuration. Guidance note: Pipeline and wire position with respect to the last roller or guide may be monitored using underwater camera(s), sonar, ROV or diver. endofguidancenote 7.9.9 Lay initiation 7.9.9.1 The procedures for initiating the lay, accounting for any end termination, shall be documented. The lay initiation procedure shall demonstrate that laying will start in the correct location. For laying operations where initiation is via transfer and pullin to a host structure the procedure shall consider the requirements in [7.9.13]. Guidance note: For subsea power cables in shallow water see DNVGLRP0360 [6.5.3], /58/. endofguidancenote 7.9.9.2 Any rigging and connection point e.g. initiation head used during the initiation shall meet the requirements of [7.4.7] 7.9.9.3 For unbonded flexible pipe risers, annulus pressure relieving vents at end fittings shall be confirmed fitted and in good condition, before overboarding the riser. 7.9.9.4 The rest of this section, [7.9.9], is applicable when the laying is initiated using an initiation point i.e. without connection to a previously installed asset. Guidance note: Piles or dead man anchors may be used as an initiation point. endofguidancenote 7.9.9.5 The initiation point design shall be in accordance with a recognised code. Guidance note: DNVGLRPE301, /48/, DNVGLRPE302, /49/, DNVGLRPE303, /50/, and DNVGLRPC212, /19/, may be considered. endofguidancenote 7.9.9.6 Where used, dead man anchors (DMA) should be documented as being stable against tilting under load. 7.9.9.7 The initiation point shall be of adequate design and have sufficient structural capacity to resist the initiation load in the direction of lay, given a lay tolerance of +/5° from the proposed lay direction. Guidance note: In general the characteristic startup tension is based on results from full dynamic analysis of the lay process. For early design the characteristic environmental loads may be taken as half the functional loads with appropriate load and material factors. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 208 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.8.5 Load monitoring Guidance note: Load tests are generally required, unless it is proven by design, soil conditions, geotechnical analysis and quality checks, that there is a sufficient margin available against the maximum characteristic bottom tension. For initiation piles, normally embedment of the pile, design and as built fab dossier are sufficient to prove the fitness of the initiation point. endofguidancenote 7.9.9.9 Calculations shall demonstrate that the length of the initiation rigging shall ensure that product landing will occur in the designated target box. The initiation wire should be tangential to the seabed, unless the initiation point is used and designed to take loads in the vertical plane. 7.9.9.10 If a diverless latch/sheave type of initiation system is used, ROV monitoring of the sheave is imperative throughout the whole initiation phase. Further, crossings between running wires and other wires, pipelines, mooring equipment etc. shall be continuously monitored. 7.9.9.11 The initiation head structure should have means of preventing or mitigating the consequences of overturning. Structures with CoG above pipeline centre shall be specially considered. 7.9.9.12 Pulling heads fitted with valves, flanges, stabs etc. (used afterwards for pigging etc.) should be protected to eliminate the risk of entrapment in the soil/seabed or designed to cope up with any possible rotation and entrapment. 7.9.10 Laying 7.9.10.1 Catenary 7.9.10.2 The method(s) of maintaining an acceptable catenary shall be documented and based on lay analyses. Guidance note: Generally it includes the allowable layback range and top tensions required to maintain a safe seabed tension at all water depths, and for all phases of the operation. endofguidancenote 7.9.10.3 For laying, the layback shall be maintained within determined limits to ensure no limit state is exceeded. 7.9.10.4 The lay vessel shall not drop back onto the catenary unless the operation is planned and laying equipment e.g. linear cable engine/tensioners can recover product from the seabed at least at the same speed as the vessel drops back. Guidance note: This type of movement, when unplanned and uncontrolled, reduces tension and increases the risk of loops being thrown in the cable and buckling in pipelines. endofguidancenote 7.9.10.5 If an unplanned drop back over the product occurs, the product shall be inspected at the seabed and tested, if deemed necessary, to ensure product integrity before the catenary is reestablished and laying continues. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 209 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.9.8 Purpose made initiation points, should be load tested to the maximum characteristic bottom tension during startup before start of lay operation. The direction of pull during test shall reflect the actual conditions during initiation. Holding time should be at least 15 minutes. 7.9.10.7 Touchdown position when laying in curves shall take account of the tendency for tension in the product during laying to pull the touchdown point closer to the installation vessel track line. 7.9.10.8 Due to potential lateral slip of rigid pipelines over the seabed at the tangent points, checks shall be performed to assure that the curve radius is acceptable. Guidance note: SLay may limit the minimum pipeline route radii, as does the proximity of any turns in the route relative to the ends of the pipeline. endofguidancenote 7.9.10.9 In order to ensure that a curve remains stable on the seabed the curve radius, R, should be greater than the minimum stable radius, i.e. where: SF TTDP Wsub μf = safety factor (reflecting the consequences of sliding) = tension at touchdown point = submerged weight per unit length = lower bound friction coefficient. Passive soil resistance can be calculated based on DNVGLRPF109, /53/, [3.4.6]. Guidance note: SF for sliding is normally taken as 1.0 unless pipelay in close proximity to existing subsea structures, in this case it is recommended to use 1.5. endofguidancenote 7.9.10.10 Tensioners 7.9.10.11 Tensioners used for laying shall be in accordance with [7.4.8]. 7.9.10.12 Tensioner track faces bearing on the pipe shall be maintained with adequate bearing area. Tensioner control systems shall be set to the limits documented in the operation manual. 7.9.10.13 During normal lay and as much as is practically possible, sufficient tensioners should be closed and utilised so that failure of one tensioner will not cause the product to slip (or at least slippage will be limited). 7.9.10.14 Where cables are installed in bundles (e.g. HVDC circuits) the difficulty in handling such cables compared to single cables shall be considered. 7.9.10.15 Rigid pipe 7.9.10.16 Where the pipe is to be reeled/spooled, sufficient line pipe shall be available for lead and tail sections for reeling/spooling onto and off the vessel and for when straightening trials are required. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 210 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.10.6 Curves Guidance note 1: These activities are not subject to MWS approval however the effect of them on the installation as whole is. In general the FJC procedure clearly: a) Reflects the manufacturer's specification, particularly for the temperature of application which is of paramount importance. b) Shows how linepipe coating is prepared to provide adequate adherence of FJC to linepipe coating and ensure continuity of protection. c) Details the method for FJC inspection. endofguidancenote Guidance note 2: Anode attachments should in general be made on circular doubler pads, matching the line pipe material and preferably welded at the neutral axis of the pipe on the reel; however welding is not always permissible for materials susceptible to HISC. endofguidancenote 7.9.10.18 Buckle detection 7.9.10.19 For laying non reeled/spooled rigid pipe in shallow water, pipe buckle detection, may be by means of a buckle sensor pulled along the bore of the pipe on a cable, located just beyond the touchdown and continuously monitored in the control room. 7.9.10.20 If a buckle detector is not used a suitable alternative shall be provided. Alternatives include but are not limited to: a) b) c) d) increased factor of safety against buckling using design guidance given in DNVGLSTF101 [10.6.7], /42/ continuous ROV monitoring at touchdown lay parameters control acoustic buckle detection. Guidance note: Some installation contractors are reluctant to use traditional inline buckle detection methods, especially in deep water installations due to the hazards introduced by breakage of the line connecting the buckle arrestor to the pipelay vessel. endofguidancenote 7.9.10.21 Bundles 7.9.10.22 Where the line is installed strapped to another load carrying line, such as a pipeline or stronger flexible, loads from the strapping/clamping shall be acceptable. 7.9.10.23 It shall be confirmed that no limit state is exceeded for all lines within the strapped bundle. Guidance note: In most cases one of the lines in the bundle will carry the installation loads as it is convenient to use only one tension system. The strapping/clamping loads and load transfer from the carried line to the carrying pipe may determine the strength requirements of the pipe. endofguidancenote 7.9.10.24 Pipeinpipe and sleeved bundles are required to be designed as a system, recognising the installation loads and processes from the outset. For these systems, the system design is most likely to be tailored to a single installation method and the detailed designer will need to define and analyse generic installation loads before finalisation of the line pipe and components’ (such as spacers, internal and end bulkheads) specifications. Before installation, the installation contractor may be required to clarify Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 211 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.10.17 Welding, nondestructive testing (NDT), field joint coating and installation of cathodic protection procedures/activities shall be documented including details of inspections and QC procedures for approval of laying operations. The field joint coating (FJC) procedure shall be documented and shall be approved as agreed between contactor, client and MWS company. 7.9.11 Abandonment and recovery 7.9.11.1 This section applies to all abandonment and recovery (A&R) operations. A&R operations shall be documented in normal and/or contingency procedures; see [7.3.3.2]. Guidance note: Abandonment and recovery operations could be: — in response to emergency situations — to enable the vessel to collect more product — as a temporary safe condition in response to a weather forecast in excess of the forecasted operational criteria. endofguidancenote 7.9.11.2 A detailed abandonment and recovery procedure is required in the operation manual, covering the full range of water depth and product weight cases that may be required over the route. This procedure shall define in stages the: a) b) c) d) e) required A&R winch tension A&R lineout layback laydown head depth, and roller support loads, where applicable to get the pipe safely down to the seabed. The analysis shall define the steps for abandonment and recovery with the aforementioned parameters and shall identify if limit states are exceeded. Where a limit state is exceeded it shall be shown that it is possible to safely abandon and recover the product. 7.9.11.3 The procedure should present the same steps with the same tensions, lineout, layback distance and head depth. 7.9.11.4 An acceptance threshold for tension should be defined for each piece of pipelay equipment/ operational phase such that in conjunction with the installation methods and risk assessment, the decision for emergency A&R is clear at the start of pipelay. 7.9.11.5 The reference point for the A&R lineout (length of wire being paid out) shall be clearly specified in the analysis/procedure. This reference shall be available or directly readable by the Superintendent or winch operators so that the tension can be reduced/increased in accordance with the steps defined in the analysis. 7.9.11.6 A&R laydown areas should be defined as it may not be possible to abandon the pipeline within the lay corridor. Areas of the route where abandonment is not possible shall be documented. 7.9.11.7 Before abandonment of a rigid pipeline, all internal equipment shall be removed from the pipeline and all welds filled sufficiently to achieve the strength determined for abandonment and recovery. If a buckle detector is being used it may be left in the line with its cable made secure to the abandonment head. The abandonment and recovery head shall be fully welded to the line and tested in accordance with relevant welding and NDT procedure. 7.9.11.8 Should it be necessary to release the A&R wire to the sea, a buoy and pennant shall be fitted to the wire for subsequent recovery. Alternatively, an ROV hooking loop may be used on the wire end. 7.9.11.9 The method of establishing the product’s condition and ensuring there has been no damage (including buckling) anywhere between the location of the touchdown point before abandonment and the Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 212 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used the detailed design analyses, incorporating further detail and the details of his own equipment into the installation analyses to confirm the designer’s generic assumptions or to perform tests to confirm design assumptions (e.g. test the centralisers to maximum expected tension). Guidance note: Generally and in particular when abandonment commenced during environmental conditions approaching the limiting criteria or in response to an emergency situation the product is to be surveyed prior to recovery. endofguidancenote 7.9.12 Temporary condition including onbottom stability 7.9.12.1 The product shall be demonstrated as adequate for other temporary conditions experienced including confirmation that the product has sufficient onbottom stability for any relevant temporary condition (e.g. untrenched, air filled, etc.) and that the on bottom roughness and free span limits are not exceeded. The applicable project specific design basis should identify the relevant recognised codes to be satisfied in this regard. Guidance note: Further information on the onbottom stability of submarine pipelines can be found in DNVGLRPF109, /53/. endofguidancenote 7.9.12.2 The aslaid product on the seabed shall be stable on the seabed in the design environment. The risk of product slippage in steep slopes should be considered. For a temporary phase with duration less than 12 months but in excess of three days, a 10year return period for the actual seasonal environmental condition should apply. An approximation to this condition is to use the most severe of the following two combinations: a) b) The seasonal 10year return condition for waves combined with the seasonal 1year return condition for seasonal current. The seasonal 1year return condition for waves combined with the seasonal 10year return condition for current. Guidance note: This is consistent with DNVGLRPF109, /53/. Where the recognised design code has other requirements these may be acceptable. endofguidancenote 7.9.12.3 The season covered by the environmental data shall be sufficient to account for uncertainties in the beginning and ending of the temporary condition, e.g. delays. For a temporary phase less than three days an extreme load condition may be specified based on reliable weather forecasts. 7.9.13 Pullin to structures 7.9.13.1 General 1) General requirements for product pullin into structures are given, with additional requirements for various pullin operations as follows: — pullin through Jtubes, see [7.9.13.2] — installation of dynamic risers (including pullin through Itubes), see [7.9.13.3]. Guidance note: Pullin is usually through Jtubes or Itubes. There are two types of Jtube/Itube pullin methods: — pullin winches mounted on the offshore structure — pullin winches mounted on the lay vessel with a sheave arrangement mounted on the offshore structure (pull back method). endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 213 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used laydown head shall be documented reflecting the nature of the abandonment and the implemented lay monitoring. Other requirements within this document to ensure product integrity shall be applied as found relevant, in particular those related to not exceeding any limit state (see [7.3.3]). 3) The operation manual shall document careful planning of close proximity operations and shall include contingency plans to be implemented in the event that the lay vessel moves out of control toward or away from a structure. Guidance note: Lay vessels typically approach close enough to offshore structures to transfer pullin aids using the lay vessel crane. endofguidancenote 4) Vessel standoff or offset at all stages of the installation shall be defined and drawn to scale in plan, and elevation if necessary, to demonstrate that the installation is clash free from any adjacent risers or moorings or other facilities and to guide the vessel crew. Such drawings shall be included in the operation manual. This shall also include different vessel headings to account for various wave directions, if applicable. 5) Clearances to nearby subsea assets should be monitored during pullin of the product. 6) Catenary geometry at these critical locations and vessel offset to achieve them shall be documented in supporting analyses of the installation. 7) Where applicable, contingency procedures for safe rapid disconnection of the installation vessel from the product shall be established and approved for the duration of physical connection of the installation vessel to the receiving installation. Procedures for recovery from circumstances such as dead ship, DP runoff or failed winches shall be established and accepted before mobilisation. 8) The pullin load shall be found through analysis, including the effects of friction, vessel motions and back tension, and any other relevant loads. 9) The strength of the Jtube/Itube, pullin aids, pullin winch, foundation and sheaves shall be confirmed capable of carrying the maximum loads placed upon it during product pullin. 10) Pullin winch and rigging capacity on the receiving installation shall have a practical margin (see guidance note) between the predicted peak pull load and the winch’s capacity at the loaded diameter under consideration, subject to any uncertainties governing assumed friction loads. Guidance note: A 10% increase (i.e. a safety factor of 1.1) would be typically acceptable for this practical margin. The nominal capacity can be stated for an empty drum whereas the peak pull load is likely to be with the drum full of wire when the winch’s capacity is lower. endofguidancenote 11) The pullin winch shall have a render setting so that excess tension in the pullin rigging caused by lay vessel movements does not over tension the pullin rigging. 12) Before mobilisation the pullin winch should be load and function tested. A commissioning report should be submitted if the testing is not witnessed by the MWS company. 13) Pullin rigging and components, including the pull head, loaded by the pullin shall be checked in accordance with the criteria in [7.4.7]. Guidance note: The design of the pull in arrangement should minimise the possibility of snagging. Sharp corners and/or protruding elements shall be avoided. Contingency plans should include actions to be taken in case of stuck product during pullin, failure of pull in winch, actions to be taken in case of topside evacuation etc. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 214 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2) Guidance note: Depending on the geometry of the pullin route (i.e. if it is not in a single vertical plane), the pullin head can be required to have equal strength across all axes. endofguidancenote 15) Messenger lines, connecting shackles and other rigging should be fully certified and graded for predicted loads. Preinstallation of messenger wires before pullin should consider asleft conditions and the risk of entanglement/damage. Guidance note: Messenger lines are used to initiate the pullin operation. It is recommended that messenger lines are marked top and bottom to ensure the correct line is connected to the pullin winch wire. endofguidancenote 16) Product shall not be pulled in by the preinstalled messenger lines. The messenger line shall be used to install the dedicated pullin lines. 17) Prior to pullin of products into Jtubes, the position of the Jtube, clamps, supports and product plus ancillaries shall be confirmed and evaluated with respect to the design. Bend restrictors shall be fitted at the correct location on the product and follow the manufacturer’s installation instructions to ensure the interface with the Jtube/Itube engages properly. Guidance note: Careful measurements and calculations are required to establish the position at which bend restrictors and product protection are to be attached, and these should be verified by an approved and proven QA/QC check process onboard the installation vessel.. endofguidancenote 18) Factors including the following shall be considered when determining the pullin operational limiting sea states and other limiting conditions: — offshore structure access/egress for pullin personnel — vessel motions and impact on crane operations for transferring pullin aids and other equipment to offshore structures — pullin tension caused by lay vessel motions — ablility to safely land the pullin head on the seabed. 19) The entry of the product into the structure shall be continuously monitored, and the pullin tension shall be within specified limits. 7.9.13.2 Pullin through Jtubes a) b) c) Jtube bell mouths can be raised above the seabed. The product MBR shall be protected in the free span between the Jtube bell mouth and the touchdown point. Protection against dropped objects at the approach to offshore structures should be provided on a project specific basis. Pullin loads shall account for the frictional soil loads from the seabed (as discussed in [7.9.15.5]), frictional loads (as discussed in d) and e)), and the backtension from the tensioners. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 215 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 14) Pullin heads or grips/Chinese fingers shall be of adequate strength for the transfer operation. Friction between the Jtube and the product shall be calculated according to the principles in [5.6.9]. Guidance note: Indicative coefficients are in Table 73. The internal coating and geometry are not accounted for in the below but should be considered if relevant Table 73 Typical upper bound design friction coefficients for Jtubes Friction interface Static coefficient Sliding coefficient Steel wire 0.8 0.5 Bare pipe or pull head 0.9 0.6 FBE (fusion bonded epoxy) coated pipe 0.5 0.4 PP (polypropylene) coated pipe 0.5 0.4 Nylon, PE (polyethylene) orpPolyurethane 0.5 0.4 Cable or umbilical 0.5 0.4 endofguidancenote e) f) If lubricant is planned to be used during pullin to reduce friction, the compatibility of the lubricant with the surfaces in question both with respect to chemical reactions and friction reduction shall be documented. Testing may be carried out in order to establish applicable friction coefficients following the principles in [5.4]. It shall be ensured that the Jtube is free of any obstacles that can cause the pulling head to get stuck during the pullin operation. Guidance note: This may be achieved by pigging the Jtube in at least in one direction, for instance during the retrieval of the messenger line. endofguidancenote g) h) i) If the clearance between the Jtube internal diameter and the pullin head is small, a gauge run with a dummy pulling head should be performed. The gauge plate should be sized slightly below the minimum Jtube bore, e.g. 95% of the I.D., according to its fabrication tolerances. Also, if the Jtube has been in place for several years, its internal condition should be assured by means of remote visual spot check inspection. For flexible product pullins, classical theory for the tension amplification around a frictional bollard and elastic beam bending theory are usually sufficient for the purpose. For rigid riser pipe, the dimensions of the Jtube are such that the pipe will be plastically strained as it passes through each bend in the Jtube, acquiring residual plastic and elastic bending after each bend, and large contact/bearing loads will set up in the middle and each side of these bends during the pullin. Analysis shall be performed to calculate the pullin loads. Guidance note: For calculation of the pullin loads for a rigid riser pipe reference may be made to A Design Basis for the Jtube Method of Riser Installation, /123/, or to Design and Installation of the Oseberg Flowline Bundle, /124/. endofguidancenote j) Cumulative rigid pipe riser ovalisation due to bending shall be checked and documented in the operation manual to ensure that local buckling or collapse is not a risk, particularly at the deepest bends in the J tube. Similarly, the riser pipe material shall be verified as suitable for the strains accumulated, including those during Jtube pullin. For a Jtube pullin after a reel lay, the pipe will be deformed plastically twice more. It is important to document the total accumulated strain and compare it with the requirement for ECA or additional tests. See [7.3.2.23]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 216 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used d) a) b) c) d) The path of the riser, cable or umbilical through the installation shall be guided through cones and smooth bores of known dimensions and tolerances, as far as practicable, to avoid hangups. Also, consideration of the approach angle offvertical or wire offset from centre of pulltubes/Itubes, etc. shall be included in the planning and procedure to avoid hangup. In the case of installation into a floating installation such as an FPSO which is free to rotate around a turret mooring, specific procedures and controls of the weathervaning shall be documented if the installation vessel is to enter the swing circle (swept envelope created by the weathervaning installation and its maximum radial excursion on its mooring system). Lift points should be properly engineered and designed according to the specific rules. Where it is necessary to attach to the line between hard points, this should be by means of purpose made clamps or by suitably sized and rated Chinese fingers. Chinese fingers should be used only for axial and minor lateral loadings after acceptance for this has been provided by the product manufacturer including design limits for such use, see [7.5.2.3]. Similarly, soft webbing strops choked around the body of the line shall only be used for minor loads and only after acceptance by the product manufacturer and according to their instructions included with the installation procedure. 7.9.14 Crossings 7.9.14.1 For all crossings identified on the crossing survey, [7.8.5], a detailed procedure shall be documented that ensures a safe crossing for both the crossing and the crossed submarine plant (pipeline or cable). The procedure shall include adequate monitoring to allow the crossing to be installed correctly. Guidance note: The key principle for crossings is to demonstrate that the existing line will be protected from harm and can continue to operate without interruption. This could include prevention of physical contact, prevention of galvanic action and electrical or cathodic protection interference. Cable or pipeline crossings are normally constructed with mattresses, rock dumping, polyurethane products or small concrete bridges. endofguidancenote 7.9.14.2 The crossing shall be designed in accordance with the recognised design code(s) for both the crossed and crossing product. 7.9.14.3 Construction and protection methods, crossing angles and operational zone dimensions shall be agreed between the respective submarine plant owners. Guidance note: Typically owners of the crossed submarine plant require that plough operations cease and restart at specified distance from the crossing point location. Jetting is normally allowed within the agreed noplough zone. endofguidancenote 7.9.14.4 Preparations for crossing of pipelines and cables shall be carried out according to a specification detailing the measures adopted to avoid damage to both installations. The operations should be monitored to confirm proper placement and configuration of the supports. Support and profile over the existing installation shall be in accordance with the accepted design. 7.9.14.5 Asbuilt records and visual and written records of the construction sequence shall be submitted to provide evidence of the conditions with respect to the crossed line. 7.9.14.6 An accurate position of the crossing shall be obtained. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 217 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.13.3 Dynamic flexible riser/umbilical installation (including pullin through Itubes) Visual monitoring and/or transponders are typically acceptable. Where the crossing is close to the final end/laydown area, the procedure should state the number of transponders (where required) to obtain an accurate positioning at the crossing area and to ensure that the pipeline will also land in the target box. endofguidancenote 7.9.15 Shore crossings/landfalls 7.9.15.1 Shore crossings are made by one of the following methods, on the surface or seabed (bottom): a) b) Pull from shore (offshore pull) Pull to shore (shore pull). Guidance note: a) Surface pull is when the pipeline is made to float on the surface assisted by floating devices such as individual buoyancy tanks. This method is commonly used for short distance crossings in a calm sea environment and for relative fast fabrication. b) Bottom pull is when the pipeline is pulled along the seabed and is often performed in a trench to mitigate the impact of lateral load due to current and wave. This method may also be performed from shore to shore, crossing a strait, bay or river. endofguidancenote 7.9.15.2 Pulls require trenching or dredging operations before or after the product is in position and backfill to stabilise and protect the product against the environment and against other traffic in the area. Guidance note: Pull in can also be done through preinstalled horizontal conduits (steel or HDPE conduits preinstalled in a trench or drilled hole). endofguidancenote 7.9.15.3 For shore crossings using horizontal directional drilling (HDD) ducts, the relevant requirements of [7.9.13] shall apply. Guidance note: HDD ducts are often required for landfall sites with sea defence systems. endofguidancenote 7.9.15.4 The pull loads shall be calculated in order to establish: — — — — required capacity of winch, tensioner or similar loads on product and installation aids the need for guiding arrangements and roller supports and corresponding design loads. Guidance note: The pull loads are essentially static forces but the product span between the seabed and the lay vessel will be dynamic. Depending upon the equipment used and the local ocean environment, it can be necessary to consider the dynamics. The maximum static pull load includes the following components: a) leading rigging friction, including in any sheaves b) leading pull head friction c) product friction on launchway, shore and seabed d) any hold back tension. endofguidancenote 7.9.15.5 A significant part of the rigging and product will rest on the seabed. Friction shall be calculated according to the principles in [5.6.9]. Also, effects of soil penetration of pullin head and product shall be Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 218 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Guidance note: Indicative coefficients are in Table 74. endofguidancenote Table 74 Typical upper bound design friction coefficients for shore crossings Conditions Breakout Running Pull wires on seabed and shore 1.0 0.85 Pipe on seabed and shore 1.2 0.85 Cable on seabed and shore 1.2 0.85 Wheel bogies on rail track 0.01 0.008 0.5 0.5 Pull wires on sleepers 7.9.15.6 The maximum onbottom nominal pipe weight should be used, accounting for any increase due to seawater absorption. Guidance note: For concrete coating, a 3% increase in weight may normally be considered. endofguidancenote 7.9.15.7 Analyses shall be performed to establish buoyancy requirements and design loads for product attachment points. In cases where buoyancy aids are used, analyses shall be performed to demonstrate the integrity of the product with an appropriate loss of buoyancy considering the buoyancy fastening plan. Seabed clearance and stability of buoyancy tanks during floating of pipelines shall be considered. 7.9.15.8 The effect of drag on product and buoyancy elements due to current and wind shall be considered. 7.9.15.9 Effects of contact loads at the entrance to a HDD duct or micro tunnel shall be considered, including stress concentrations at interface between product and pullin head, and increase in required winch tension due to friction. 7.9.15.10 Sensitivity with respect to vessel standoff distance, friction coefficients and drag should be considered in order to ensure a robust solution. 7.9.15.11 For shore pull, a design factor shall be applied to the computed total static force to account for uncertainties. Guidance note: An indicative value for this design factor is 1.3. endofguidancenote 7.9.15.12 The MBL of the pull wire should be twice the calculated factored static load. 7.9.15.13 Shackles, end fittings such as spelter sockets and other certified rigging items should have an MBL at least 30% greater than the pull wire. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 219 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used considered, if applicable, as well as required breakout force due to startup after a temporary stop in the pulling operation. — pull wire required MBL + 40 tonnes for MBL > 160 tonnes or — pull wire required MBL x 1.25 for MBL ≤ 160 tonnes. 7.9.15.15 In particular circumstances, where the available pull wire is oversized with regard to the design shore pull requirement, the design of the rest of the components can be related to the required MBL rather than the actual MBL of the pull wire. Such relaxation shall be noted in the pull in procedures and appropriate measures put in place to avoid exceeding the design pull. 7.9.15.16 In the event of the pull stopping due to a buildup of soil ahead of the pull head or on top of the product, the peak allowable pull load may be increased to 60% of the MBL of the weakest part of the launch rigging. This upper limit should be clearly stated in the pull procedure as a contingency case. It may only be used subject to accurate monitoring of the actual force required. Any such operation shall be subject to a risk assessment, see [2.4]. 7.9.15.17 Documented calculations shall justify the acceptability of the structure or equipment (i.e. walls made of sheet piles, mooring lines etc.) used for holding back tension 7.9.15.18 A representative vessel standoff distance shall be established considering: — — — — seabed topography tide vessel draft for a representative loading condition hull/seabed clearance. 7.9.15.19 If a lay vessel can approach close enough to the landfall position or in case the shore pull area is sheltered area like bay/gulf, product can be floated ashore using a pulling wire from the landfall with floats attached to the product. This is called a direct landfall. Detailed marine planning is required to ensure the lay vessel can set up close enough to the landfall position for the duration of the landfall operation. Care shall be taken in cross currents which can cause excessive tension in the product leading to loss of control of the pull in operation. 7.9.15.20 In shallow water, where the lay vessel is allowed to bottom out during low water phases of the tidal cycle then the following shall be considered: a) b) c) d) e) f) g) h) Careful planning is required to ensure the seabed is flat with no obstructions that might in anyway cause damage to the lay vessel hull. Adequate preset mooring shall be provided. The work shall be carefully planned and timed to ensure the vessel does not become trapped by falling tides. A pullahead anchor should be deployed offshore of the lay vessel A standby anchor handling vessel should be on site to assist the lay vessel if it needs to pull off the set up position in an emergency. Consideration should be given to seabed suction forces when refloating the lay vessel. Hull strength shall be adequate to withstand the loads arising. Required vessel systems shall be operable. Guidance note: It is common to float the lay vessel in on a rising tide until the lay vessel is close enough to the landfall for a pullin operation Often anchors are placed on land due to the close proximity to land of the lay vessel set up position. It is normal for an operation where it is planned for the lay vessel to bottom out for it to approach the landfall site with minimum product onboard. This requires the product to be laid from the offshore structure towards the land. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 220 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.15.14 Structural steel items such as padeyes and the load path through the pull head to the pipe should have an ultimate load capacity not less than: a) b) A shore end cable is laid by a small vessel between the landfall and a position where the main lay vessel can set up for jointing operations or, The cable is turnedover from the main lay vessel onto a small vessel. The small vessel lays the cable toward the landfall location. This method presents complications at the landfall end as the cable will need to be turnedover a second time to bring the landfall cable end to the top of the cable tank. 7.9.15.22 Landfall sites with extensive shallow water will require a bespoke solution adapted to the challenges of each landfall. A range of methods have been adopted including very shallow draught vessels and tracked vehicles with cable drums mounted on the vehicle. The combination of HDD ducts and extensive shallow water adds a high level of construction risk. 7.10 Other installation activities 7.10.1 Tiein operations 7.10.1.1 The requirements for tiein operations in DNVGLSTF101 [10.9], /42/, apply. 7.10.1.2 Above water tie in operations 7.10.1.3 For pipeline above water tieIn (AWTI) operations, procedures and engineering calculations shall be documented to demonstrate suitability of the following: a) b) c) d) e) f) g) The capacity of the lifting davits and/or cranes to be within allowable limits. The capacity of any lifting slings and lifting appliances involved in the operation to be within allowable limits. The capacity of any temporary supports for the pipeline sections during tiein operations to be within allowable limits. The capacity of the pipeline to be within requirement of pipeline capacity check according to relevant design code including all dynamic liftlowering effects. An hourly time schedule for the AWTI operation. Limiting criteria for recovery and abandonment of the pipeline sections. Vessel stationkeeping analyses. 7.10.2 Steel catenary riser installation 7.10.2.1 This section specifies the additional requirements for the installation of steel catenary risers (SCR) over those elsewhere in this Sec.7. The applicable design codes for SCR’s are API RP 2RD, /4/, and DNVGL STF201, /43/. Guidance note: Steel catenary risers require sufficient water depth for the riser to flex to follow the surface installation without overstressing and are therefore only feasible in deep water (generally greater than 500 m). They may be installed as part of the pipeline using the same type of vessels and methods as the rigid pipe laid to the location. The weight of thick walled SCRs is an issue for installation. There are only a limited number of installation vessels able to install thick walled SCRs in deep water and the number of suitable installation vessels diminishes rapidly with increasing depth and pipe wall thickness. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 221 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.9.15.21 Alternatively, a small low draught vessel can be used to preinstall a separate shore end cable when the main lay vessel cannot approach close enough for a direct landfall operation. There are two methods for implementing a preinstalled shore end installation: 7.10.2.3 SCR transfer operations shall be planned for all contingencies identified during hazard identification. Where the operation is planned based on an empty SCR, contingency procedures based on the SCR accidentally becoming flooded shall be prepared to enable the SCR to be brought into a safe condition. The installation aids shall be sized to enable the SCR to be bought into a safe condition for all planned and contingency operations. 7.10.2.4 The capacity of the SCR porch shall be adequate for all planned and/or contingency operations including the flooded SCR condition. 7.10.2.5 Where a flexible joint or taper stress joint or similar is provided at the top of the riser as the connection to the host facility: a) b) the capacity of the joint shall be acceptable for all phases of the marine operation and the joint shall be included in the analyses, procedures and operation manual. 7.10.2.6 The effects of locked in torque shall be evaluated. Guidance note: This joint is vulnerable to any locked in torque left in the pipeline and riser so the load should be determined from the installation analysis and confirmed to be within the design specification of the joint. endofguidancenote 7.10.2.7 If automatic ultrasonic testing (AUT) is employed, the procedure, equipment and personnel shall be qualified by an authorized body. Guidance note: The use of SCRs in deep water results in thick wall risers with complex welding procedure requirements for the offshore field joints. Automatic ultrasonic testing (AUT) is typically employed as part of the offshore NDT program and is considered one of the most effective methods of inspection offshore to detect critical flaw sizes as small as 0.5 mm to 1.0 mm in height, which is a possible requirement for fatigue sensitive SCR welds. See DNVGLSTF101 App.D, /42/, and DNVGLSTF101 App.E, /42/, for guidance. endofguidancenote 7.10.2.8 The planning shall consider the complexity of the handover operation and the close proximity of the pipelay vessel to the host facility. If the SCR is laid down before arrival of host facility for later recovery and handover, the lay route should be finalized considering the requirements of vessel movements and clearance issues during handover after arrival of host facility. Guidance note: Generally SCRs are installed once the host facility is in place. endofguidancenote 7.10.2.9 Additionally to any point of no return, the procedures shall identify any point of the operation where the SCR cannot be brought into a safe condition (including abandonment) without reversing the operation to that point. Where reversing the operation could be required this shall be included in the procedures. Guidance note: During assembly of the SCR, typically there will be a point beyond which the SCR cannot be abandoned (the point of no return or PNR) as it would interfere with the host platform’s field architecture (moorings, infield pipeline, wells, templates, etc.). Abandonment beyond this point will first require the SCR to be cut back (or reeled back for reellay vessels) before it is abandoned. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 222 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.10.2.2 In this application, the pipelay process is critically important to the available life of the system and its performance. Residual strains, strain history, residual torque, residual ovalisation, local stress concentrations and fatigue life consumption from the installation process are key and shall be compared to the allowances provided by the system designers. Guidance note: The key factor for the final transfer phase is to ensure an adequate weather window is in place to successfully complete the SCR assembly and its subsequent transfer to the host facility. At a deep water facility, the SCR installation can take up to five days. This is longer than currently available weather forecasts. endofguidancenote 7.10.3 Rigid spool/jumper installation 7.10.3.1 This section is applicable to transportation and installation of rigid spools/jumpers (see [1.5.2]). See DNVGLSTF101 [10.6], /42/, for guidance. 7.10.3.2 Transport and seafastening shall be in accordance with Sec.11. Guidance note: Short spools/jumpers can be accommodated and seafastened on deck by lashings or weldments and clamps as appropriate. Larger spools/jumpers can be cantilevered or carried on overside seafastenings welded to the installation vessel or to a transport vessel. endofguidancenote 7.10.3.3 Lifting of all but the shortest spools/jumpers shall be inaccordance with Sec.16 and inparticular [16.17]. 7.10.3.4 Lift point design shall consider any restrictions on welding directly to the pipe. 7.10.4 Flexible jumper and flying lead installation 7.10.4.1 The loadout, transportation and installation of flexible jumpers and flying leads shall be designed and executed in such a manner as to prevent the exceedance of any limit state, see [7.3.3]. The same principles for flexible product lay apply for these items, as described in [7.9]. 7.10.4.2 Fully certificated rigging in accordance with [16.12] shall be used. Lift points and rigging shall be checked for condition before use. The lift should be analysed and proven suitable for the environmental design criteria and vessel. See Sec.16. 7.10.4.3 The structural capacity of baskets, pallet structures or similar used to transfer the product to the seabed shall be documented as adequate. Guidance note: Valid load test certificates may be used to document adequate strength as an alternative to a full design and fabrication package. endofguidancenote 7.10.4.4 Lifting shall be inaccordance with Sec.16 and inparticular [16.17]. 7.10.4.5 It shall be clear in the procedures and drawings that the line is being installed sealed closed or freeflooding and arrangements made to suit. 7.10.5 Cable jointing and repair 7.10.5.1 Submarine power cable repair operations involve a number of complex manoeuvres that shall be carefully planned with documented procedures. The proposed repair method(s) shall be determined and Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 223 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.10.2.10 The installation time from any point of no return to final handover and hang off of the SCR onto the host facility shall be kept to a minimum. Guidance note 1: See also DNVGLRP0360 [7.6], /58/. endofguidancenote Guidance note 2: Wind farm cable repairs can be either by complete replacement of a cable or by cutting out the damaged/faulty section of cable and inserting a new section. Replacement is most likely to be used for array cables whereas inserting a new segment will most likely apply to export cables. endofguidancenote 7.10.5.2 The repair vessel shall be capable of supporting all phases of a cable repair operation. The general vessel requirements of [7.3] apply. 7.10.5.3 Repair vessels shall provide a stable working platform, have fine control when manoeuvring and be capable of holding station over the repair location for the time required to complete a cable joint. 7.10.5.4 An enclosed jointing space with sufficient room for performing a cable joint shall be provided. 7.10.5.5 Repair joints shall be qualified and type tested in accordance with a recognised design code. 7.10.5.6 Jointing personnel shall be qualified and jointers’ qualifications shall be submitted. Guidance note: It is recommended that repair joint kits are opened in a clean environment onshore, that all parts are checked against the repair joint contents list, and that a dummy assembly of the joint is done to ensure that the procedures are correct. The shelf life of compounds and/or resins should be checked and shown to be valid. endofguidancenote 7.10.5.7 Dynamic analyses of the suspended cable(s) shall be performed in accordance with [7.3.2] for the entire repair operation, from the time when the damaged cable is recovered until the repaired cable has been redeployed to the seabed. This includes the time when the catenaries are suspended from the vessel during the final splice. 7.10.5.8 If the cable is cut subsea and is not of a waterblocked design, then the potential for and the consequences of water ingress shall be considered in the procedures. Guidance note 1: If cable tension prevents the cable from being lifted to the surface the cable will need to be cut on the seabed. endofguidancenote Guidance note 2: Submarine power cables are either wet, dry or semidry designs and each has different levels of tolerance to water ingress. The cable manufacturer should be consulted if the repair strategy involves cutting the cable on the seabed. endofguidancenote 7.10.5.9 Any cable end returned to the seabed shall be secured to prevent movement due to currents. Guidance note: Typically this is achieved by attaching a chain and/or a clump weight to the cable end. endofguidancenote 7.10.5.10 The method for retrieving a cable end from the seabed shall be documented. If a surface buoy is used to aid location and recovery of the ground tackle, the buoy should have sufficient buoyancy to remain Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 224 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used included in the marine operation manual. The required personnel, tools, equipment and consumables shall be available. 7.10.5.11 The cable(s) shall be stoppered to secure points on the repair vessel, having sufficient capacity to support maximum cable tension during the cable jointing process. The stopper type shall be approved by the cable supplier, and the stopper attachment point shall be in line with the cable to prevent the stopper from exerting nonconforming forces on the cable. 7.10.5.12 If an inline joint is to be deployed over a lay chute or sheave, the mechanical strength of the joint shall be confirmed adequate for the chute’s/sheave's radius and cable tension during deployment. Extreme tensions can be generated in the cable where it enters the joint housing as the joint enters and leaves the chute/sheave. Consideration should be given to using shaped supports or a spreader beam and crane to deploy the joint over the repair chute/sheave. 7.10.5.13 In the case of an omega joint, the recovered cable shall be cut back sufficienty to ensure good cable before cutting the spare cable to length and performing the second joint. 7.10.5.14 During deployment of an omega joint, the joint and cables shall be supported to prevent damage during lowering, e.g. using a spreader beam. The joint lowering speed shall be coordinated with vessel movements to ensure the final splice is laid down on the seabed without exceeding any limit state criteria and without throwing loops or leaving sections of the cable standing clear of the seabed. The subsea lifting requirements of [16.17] apply. Guidance note 1: Deployment and landing of an omega joint is a hazardous operation during which a combination of cable slack and residual torsion in the cable can cause loops, catpaws and standing sections of cable. It is recommended that the laydown points are continuously monitored by ROVs in order to maintain control of layback and further mitigate the risk for the forming of loops, overbending, etc. endofguidancenote Guidance note 2: An omega joint typically adds an additional cable length of 23 times the water depth into a cable system. endofguidancenote 7.10.5.15 Deployment rigging shall be removed from the cable and joint after installation to avoid corrosion issues and ensure the rigging does not become entangled with cable jetting equipment or similar. 7.10.5.16 The cable catenaries formed during an omega jointing operation shall have sufficient tension to ensure the cable MBR is not jeopardised at the seabed touchdown point, but not higher than the maximum allowable tension specified in the operational procedures. 7.10.5.17 If the cable is to be trenched and/or rock dumped, the whole of the repaired section shall be protected. The protection installation shall be in accordance with [7.11] Guidance note: This can be achieved by trenching into the seabed or rockdumping. The omega joint layout should be surveyed using an inspection ROV and any loops, standing loops and/or catspaws should be recorded and if necessary an alternative protection to jetting should be developed. endofguidancenote 7.10.5.18 The repaired cable shall be tested and consideration should be given to retaining the cable repair vessel on site until the tests are complete and the cable repair is shown to be acceptable. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 225 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used at the surface in all anticipated environmental conditions. If the cable end is to be lifted by use of the rope, wire or chain to connect the buoy to the cable, the rope/wire/chain shall be designed according to the requirements for lifting rigging in Sec.16. 7.11.1 General 7.11.1.1 Any requirements to protection and/or postlay intervention shall be documented with corresponding operational procedures as applicable. Guidance note: Generally only the installation related aspects of the protection system (including the design of installation aids) are of interest to the MWS company. endofguidancenote 7.11.1.2 Limiting weather conditions for the installation operation of protection, as well as any survey operations, shall be documented and clearly stated in the operational procedures. 7.11.1.3 Deployment of protection and deployment/recovery of any associated equipment (e.g. trenching equipment) shall be managed as any overside lift in the proximity of unprotected subsea assets, see [16.17.2.13]. The lifting requirements of [16.17] apply. 7.11.1.4 The product shall be adequatly protected in accordance with the recognised design code. Varying ground conditions can require a combination of protection methods to achieve acceptable levels of protection. Guidance note: Various means of protection are employed to protect a product from excessive loads during installation and/or in service. The most common means of protection are mechanical protection systems, trenching, gravel installation/rock dumping, and installation of mattresses and grout bags. Mechanical protection systems are generally devices attached to, or structures applied over/under, the product for mechanical protection during installation and/or in service, typically designed to protect the product against abrasion or impact, e.g. from dropped objects, or to limit product bending. A mechanical protection system may be attached to and/or installed together with the product, or installed prior to and/or after the product is installed. A bend restrictor assembly attached to a product end fitting/termination or component, is an example of a mechanical protection system that is installed together with the product. Other examples are various types of abrasion/impact protection, e.g. sleeving and split pipe assemblies. Such systems will typically affect the submerged weight, bend stiffness and drag properties of the product, during installation and potentially also in service. Various types of structures and covers are examples of mechanical protection systems that are typically installed prior to or after installation of the product. Trenching is generally performed to lower a product into the seabed, typically to protect the product from dropped anchors or trawling equipment, and/or to ensure onbottom stability of the product, i.e. to prevent lateral movement as a result of wave and current action. The most common methods of trenching are ploughing and jetting, and to some extent also cutting (in partuclarly hard soils) and excavation (typically in the landfall area). The preferred method, and whether trenching is performed prior to, during or after a product lay operation, is typically a function of soil conditions, water depth, environmental conditions and cost. Required depth of burial may be governed by a number of site specific parameters such as regulatory requirements, marine activities, and geotechnical, loads from ice, seabed and tidal conditions on site. Gravel installation/rock dumping is typically a means of protecting a product in areas not suitable for trenching, e.g. in hard soils or close to seabed structures etc. It is also a means of levelling out an uneven seabed to avoid or reduce free spans and ensuring onbottom stability. Gravel installation/rock dumping generally requires the use of purpose built vessels. Mattresses placed over a product can serve as protection from dropped objects, a means of stabilising the product on the seabed, preventing abrasion, reducing erosion, or ensuring a certain separation between products at crossings. In general, installation of mattresses does not require a purpose built vessel, and is thus often a more cost effective solution than gravel installation/rock dumping, particularly in cases where the scope is limited. Grout bags are typically used to provide support and/or protection of a product at shorter free spans and exposed areas, and can, in certain applications, be an alternative to mattresses or gravel installation/rock dumping (primarily where the scope is limited). Installation of grout bags generally does not require a purpose built vessel. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 226 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.11 Protection and postlay intervention 7.11.2 Mechanical protection systems 7.11.2.1 It shall be verified that the mechanical protection system(s) meet(s) the requirements of relevant approved design reports and/or specifications. 7.11.2.2 Mechanical protection systems that are attached to and/or installed together with the product will normally affect product response, and thus loads, on both the product and the protection system itself, as well as any joints, terminations, or similar. These effects shall therefore be considered in the installation analyses to demonstrate that all relevant system loads are acceptable for the proposed installation procedure. 7.11.2.3 Installation of protective covers or structures shall be managed as any overside lift in the proximity of unprotected subsea assets. The lifting requirements of [16.17] apply. 7.11.3 Trenching 7.11.3.1 The suitability of the trenching equipment with respect to the applicable product(s) and soil conditions shall be documented (also see [7.8.4.2]). Guidance note: The term trenching equipment refers to ploughs, jetting machines, and cutters, used to generate a trench in which to lower a product, either prior to, during, or after the product laying operation. endofguidancenote 7.11.3.2 The trenching equipment monitoring system shall be calibrated and include: — devices to measure depth of pipe — a monitoring system and control system preventing horizontal loads on the pipeline or devices to measure and record all vertical and horizontal forces imposed on the pipeline by trenching equipment, and devices to measure the proximity of the trenching equipment to the pipeline, horizontally and vertically relative to the pipeline — underwater monitoring systems enabling the trenching equipment operator to view the pipeline and seabed profile forward and aft of the trenching equipment — measuring and recording devices for trenching equipment tow force — devices monitoring pitch, roll, depth, height and speed of the trenching equipment. 7.11.3.3 Jet sleds shall have a control and monitoring system for the position of the jetting arms and the overhead frame, horizontally and vertically relative to the pipeline. The location of the sled shall not be controlled by the force between sled and pipeline. Devices indicating tension in the tow line and showing the depth of the trench shall be installed. 7.11.3.4 It shall be documented that the trencher, including any guides, rollers, depressors, ploughshares, hydraulic jets, or cutters, will not damage the product or any components attached to the product (e.g. anodes) under normal and contingency operations. Special care shall be taken during trenching operations of piggy back and bundle pipelines, so that strapping arrangements are not disturbed/damaged during trenching. 7.11.3.5 It shall be documented that no limit states of the product are exceeded during all phases of the trenching operation. In particular, the transition into and out of the trench shall not induce excessive product bending or free spans. The following phases of the trenching as a minimum should also be considered: — during docking and undocking of the trencher Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 227 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.11.1.5 For requirements to trenching of rigid pipelines reference is also made to DNVGLSTF101 [10.8], /42/. 7.11.3.6 Required depth of lowering (DOL) and depth of cover (DOC), as applicable, shall be clearly stated in the operational procedures. Guidance note: To avoid confusion related to definition of burial depth, use of the following terms is recommended: — Depth of lowering (DOL) is the vertical distance from mean seabed level to bottom of product. — Depth of cover (DOC) is the vertical distance from mean backfill level to top of product. endofguidancenote 7.11.3.7 It shall be verified that the DOL and/or DOC specified in the trenching procedures are in accordance with relevant approved design reports and/or specifications. 7.11.3.8 Limiting weather conditions shall consider the deployment and recovery of trenching equipment. Guidance note: Lifting and handling of a trencher may pose a risk to the safety of personnel, the product, and the trenching equipment itself. endofguidancenote 7.11.3.9 Where it is planned to leave trenching equipment on the seabed during weather standby, the limiting weather conditions for standby shall be clearly stated in the operational and/or emergency abandonment procedures. 7.11.3.10 Loads applied to a product by a trencher, e.g. guides, depressors, or other, shall be monitored by calibrated load cells with alarms and trips on the motive power to the trencher, if applicable. These alarms shall be relayed by failsafe radio telemetry to the support vessel control center. These alarms shall be calibrated and tested in accordance with [7.4.13.1]. 7.11.3.11 For towed ploughs, the required bollard pull shall be considered for the expected conditions and the actual seabed. Consideration shall be given to the impact this can have on the ability of the DP vessel to support plough operations for both planned and contingency operations in the operational limiting criteria. Guidance note: Towed ploughs can require high bollard pulls, therefore trials are recommended to ensure that the selected plough is suitable and to verify that the support vessel can provide sufficient bollard pull or power supply for the plough to penetrate the seabed to the required depth of lowering. endofguidancenote 7.11.3.12 The towline between a plough and the support vessel shall be designed in accordance with [11.13]. 7.11.3.13 Where moving cutters are involved, product position sensors and automatic trip sensors shall be utilised to trigger alarms and cut the power to the cutters and forward thrust (if possible) in the event that the cutters come too close to the product. These sensors, the alarm and trip should be calibrated in accordance with [7.4.13.1]. 7.11.3.14 The procedures shall consider that unexpected or sudden changes in the soil may: — affect the performance of the trenching equipment — cause damage to the trencher and/or the product. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 228 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — during startup and stopping of the trenching operation — in transition zones — during any other normal and contingency operation. Buried debris and glacial rocks in clay are examples of the hazards which require constant diligence from the operators of the trenching equipment who will need to adjust or stop operations as these are encountered. endofguidancenote 7.11.3.15 If an uncontrolled drop back occurs during ploughing of a flexible product, the product shall be inspected and tested, if deemed necessary, to ensure product integrity before restarting the ploughing operation. 7.11.3.16 The method of monitoring trenching equipment seabed position and plotting of aslaid coordinates shall be considered. Guidance note: For example, trenchers can carry HPR acoustic beacons for this. endofguidancenote 7.11.3.17 Achieved DOL and DOC, as applicable, shall be documented for asbuilt purposes and to enable an assessment of the need for mitigating measures, such as an additional pass or an alternative protection method. 7.11.3.18 A post trench survey, using an active or passive tracking system (as applicable), should be performed to document achieved DOL and DOC, as applicable. Alternative methods of documenting achieved DOL and/or DOC shall be described in the operational procedures. 7.11.3.19 Seabed profiles showing product position relative to trench/seabed should be provided at regular intervals along the line to document that relevant protection requirements are satisfied. Profile intervals shall be defined in project procedures, depending on site and operational constraints. Calibration of relevant instruments shall be documented. Where applicable, a video survey record should also be made to enable detection of free spans or other anomalies. 7.11.4 Gravel installation/rock dumping 7.11.4.1 Materials used for gravel installation/rock dumping shall meet the specified requirements to specific gravity, composition and grading in order to prevent product damage due to impact or overloading in the buried condition. 7.11.4.2 Required DOC, alternatively minimum size/profile of gravel/rock berm and relative position of the product, shall be clearly stated in the operational procedures. Guidance note: For crossings both products are normally considered. endofguidancenote 7.11.4.3 It shall be verified that the acceptance criteria, e.g. DOC, size/profile etc., specified in the operational procedures are in accordance with the recognised design code. 7.11.4.4 The limiting weather conditions for gravel installation/rock dumping operations, shall consider the installation and recovery of of the fall pipe and shall be clearly stated in the operational procedures. 7.11.4.5 Gravel installation shall be performed in a continuous and controlled manner. Existing infrastructure should not be disturbed or interfered with. 7.11.4.6 The position of the bottom of the fall pipe relative to the product, seabed and any nearby seabed structures shall be controlled and monitored to ensure that the fall pipe system does not damage the product or any other subsea asset. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 229 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 7.11.4.8 A post gravel installation/rock dump survey, using an active or passive tracking system (as applicable), should be performed to document the achieved DOC. Alternative methods of documenting achieved DOL and/or DOC shall be described in the operational procedures. Guidance note: For rigid pipelines, see also DNVGLSTF101 [10.8.5.7], /42/. endofguidancenote 7.11.4.9 Seabed profiles showing product position within the gravel/rock berm should be provided at adequate intervals (normally a maximum 5 m) along the line to document that relevant protection requirements are satisfied. Calibration of relevant instruments shall be documented. Where applicable, a video survey record should also be made to enable detection of exposed product or other anomalies. 7.11.5 Installation of mattresses and grout bags 7.11.5.1 It shall be verified that mattresses and/or grout bags meet the requirements of the recognised design code. 7.11.5.2 Placing of grout bags and concrete mattresses shall be performed in a controlled manner with suitable monitoring, such that the bags or mattresses are placed as required. Restrictions on vessel movements during the operation shall be considered. 7.11.5.3 For grout bags, the following shall be clearly stated in the operational procedures: — required amount of grout bags and — any acceptance criteria related to positioning, e.g. relative to the product. 7.11.5.4 For mattresses, the following shall be clearly stated in the operational procedures: — acceptable tolerances for positioning of mattresses relative to the product and/or other components or structures — the position of a mattress and lifting frame relative to the product, seabed and any nearby seabed structures. 7.11.5.5 Any fibre ropes or slings used for lifting shall be checked to confirm fitness for purpose, noting that the fibres are degraded by ultra violet radiation from sunshine. 7.12 Product testing and precommissioning 7.12.1 Product testing and precommissioning is not typically part of the MWS scope. However it does influence other activities within the MWS scope, and possibly the warranty if a damaged product is installed undetected. Therefore MWS involvement is limited to ensuring that testing is completed and results and/or remedial actions are acceptable to relevant parties (such as owner, installation/transport contractor and/or manufacturer). Guidance note: Product testing in this refers to the testing used to confirm the product has not been damaged during the marine operations and that performance is satisfactory. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 230 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.11.4.7 Achieved DOC shall be documented for asbuilt purposes and to enable an assessment of the need for dumping additional gravel/rock. The product testing and precommissioning programme shall be in accordance with the recognised design code and include any remedial actions and hold points. The programme shall be reflected in the schedule and operation manual. 7.12.3 The testing programme shall be fully documented and agreed by relevant parties for the extent of testing at each stage of the operation, such as pre/post loadout, pre/post transport, during lay operations, and post installation. 7.13 Documentation requirements 7.13.1 Information noted in this section is what may be required to achieve MWS approval for the given operation with exact list to be agreed on a project specific basis. Other parties may have different requirements. 7.13.2 Lay vessel 7.13.2.1 For the lay vessel: a) b) c) d) General arrangement of vessel, principal dimensions and operational draught. Deck layout of all permanent and moveable equipment items. Outline specification of vessel, accommodation and machinery. Cranes – including loadradius covers, winches including abandonment and recovery (A&R) and records of maintenance. e) Stinger, Lay tower or ramp geometry and rating. f) Reel lay system or reel drive system. g) Carousels capacity and drive systems. h) Structures (PLET/ILT) handling systems. i) Tensioner capacity and settings. j) Full details of the mooring system, winches, anchors, control and monitoring system, a mooring procedures manual, mooring lines certificates and records of maintenance. k) Dynamic positioning system information. l) For DP vessels, the last annual DP trials including recommendations and closeouts, the latest DP FMEA detailing single point failures. m) ROV class and capacities. n) ROV handling system. o) Rollers, load cell arrangement. p) Video and other control and monitoring equipment. q) Weather or motion limitations for laying. r) Motion response characteristics, preferably as tabulated response amplitude operators (RAO’s) against frequency and vessel heading. s) MRUs and motion measurement system. t) Current meters. u) Where available, the latest common marine inspection document. v) Certification as appropriate, including: w) Certificate of class for hull and machinery. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 231 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 7.12.2 Registry, load line and tonnage certificates. Safety construction, safety equipment and safety radio certificate. Certificates for cranes, davits, winches, rigging and other items relevant to the operation such as DMA/ initiation cable not covered by the normal classification requirements. 7.13.3 Mooring/dynamic positioning procedures 7.13.3.1 For DP vessels, documents in accordance with [17.13]. 7.13.3.2 Mooring information required is in [17.1] to [17.12] and summarized below: a) b) c) d) e) f) g) h) i) j) General procedures for mooring and anchor handling. General anchor patterns and catenary curves during straight lay and on radius. Specific procedures for working anchors close to shore. Specific anchor patterns during startup and laydown, crossing points and where working close to existing structures and pipelines, risers, subsea assets and other prohibited zones. Command structure, communications and working frequencies, anchor movement logging procedures and proformas. Contingency procedures for bad weather, mooring failure, power failure of positioning system, etc. Details of anchor handling vessels. Vessel position survey procedures. Survey equipment calibration procedures. Survey equipment specifications. 7.13.4 Route 7.13.4.1 For the route following information shall be provided : a) b) Startup and laydown target areas. Route between the target areas, clearly showing the theoretical route, straight and curved sections, radii and tangent points, existing platform(s), pipelines, cables, and shoreline (if applicable). c) Lay corridor. d) Alignment with predominant current and wave headings. e) Shipping lanes and other restricted areas due to military or political reasons. f) Presence of any submarine exercise areas, fishing, mine fields, dredging and wrecks. g) If applicable, levels and type of fishing activity. h) Mooring line/riser crossings. i) Minimum distance from existing subsea assets. j) Minimum distance to existing fixed/floating platforms and platform approach drawings. k) Any other potential hazards or obstructions, such as mines or munitions dumping areas. l) Seabed features such as possible huge and multiple spans, coral growths, rock out crops, soft liquefiable soils, sand dunes, pockmarks, iceberg scour marks and other seafloor obstructions such as boulder fields. m) RPL. 7.13.5 Survey 7.13.5.1 A hydrographic and sidescan survey of the route for the design corridor showing: a) b) Water depth along the route and general seabed topography. Any obstacles within the proposed corridor. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 232 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used x) y) z) Any areas where freespanning is anticipated, or where scour or sand waves are anticipated. 7.13.5.2 A Geotechnical survey of the route showing: a) b) c) General seabed composition and stability. Identification of rock or coral outcrops, sand waves or mudslide areas. Sufficient subsurface information to justify trenching and/or burial procedures. 7.13.5.3 Asbuilt surveys of cables/pipelines to be crossed. 7.13.5.4 Procedures and specifications for the following: a) b) c) Prelay survey. Postlay surveys. Asbuilt survey. 7.13.6 Product design and construction as related to marine operations 7.13.6.1 For rigid pipe: a) b) c) d) e) f) g) h) i) j) k) l) m) n) o) Internal and external diameter and wall thickness. Weight in air and in water (empty and flooded). Allowable stress, strain and fatigue. Design environmental conditions. Design, operating and test pressures. Structural design during installation and commissioning load cases, stresses and buckling. Pipeline material specification. Pipeline corrosion and weight coating. field joint coatings specifications. Anode type and method of fixing. Piggyback lines. On bottom pipeline stability analysis for temporary conditions. Free spans analysis. Free spans and rectification procedures. Trenching/burial requirements. 7.13.6.2 For flexible pipe: a) Drawings and dimensions of the flexible product and all ancillary equipment and components to be installed onto it. b) Internal and external diameter and wall thickness. c) Weight in air and in water (empty and flooded). d) Allowable stress, strain, fatigue, axial compression, twist and MBR. e) Bend stiffness. f) Design environmental conditions. g) Design, operating and test pressures. h) Structural design during installation and commissioning load cases, stresses and buckling. i) Flexible pipe data sheet. j) Anode type and method of fixing. k) Piggyback lines. l) On bottom pipeline stability analysis for temporary conditions. m) Free spans analysis. n) Free spans and rectification procedures. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 233 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used c) This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used o) Trenching/burial requirements. 7.13.6.3 For cables: a) b) c) d) e) f) g) h) Operating performance specification. Weight in air and in water. Allowable stress, strain, fatigue, axial compression, twist and MBR. Bend stiffness. Design environmental conditions. Structural design during installation and commissioning load cases, stresses and buckling repair specifications. Trenching/burial requirements. Jointers qualifications. 7.13.7 Loadout and spooling 7.13.7.1 For lifted loadouts: a) b) c) Loadout procedure. Rigging design report. Stationkeeping/mooring arrangement. 7.13.7.2 For spooling/reeling: a) b) c) d) e) Spooling procedure. Spooling analysis. Rigging design report. Stationkeeping/mooring arrangement. Stationkeeping/mooring analysis (if open water location). 7.13.8 Lay operations 7.13.8.1 For all lay operations (as applicable): a) b) c) d) e) f) g) h) i) j) k) l) m) n) o) p) q) r) Laying procedure. Laying schedule covering expected durations and contingency time from safe to safe condition. Installation analysis. Operational limit. Provisions for weather forecasting. Line installation stress and fatigue calculations. Special procedures for laying and attaching piggyback line. Procedures for attachment of anodes, etc. Installation aids and their structural design. Slack and catenary management. Startup procedures and analyses. Calculations for startup sheave or pile and rigging. Touchdown monitoring procedures. Laydown procedures and analyses. Emergency laydown and recovery procedures and analyses. Contingency protection methods in the event of temporary abandonment. Contingency planning. SIMOPS. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 234 Risk management plan. Initiation rigging and lifting/pulling equipment: — — — — arrangement calculations certification showing WLL and/or MBL calculations justifying length of initiation wire [7.9.9.9]. 7.13.8.2 For all pipelay operations (as applicable): a) b) c) d) e) f) g) h) i) Buckle detection procedures. Dry and wet buckle contingencies. Stringing, welding, NDT and field joint coating procedures. Procedures and analyses for installation of hot tap tee, inline tee, wyes,pPipeline end tees and other structures in the line. Free span limitations. Precommissioning procedure including pigging and hydrotest acceptance criteria (if applicable). Design, operating and test pressures. Details of pulling heads, pig receivers, end caps, etc. Dewatering and drying procedures. 7.13.8.3 The following items shall be checked and documented for SLay and JLay of rigid pipe: a) b) c) d) e) f) g) Soil friction for route curvatures midline and in proximity to pipeline ends (see [7.9.10.8]). Local buckling strength at seabed touchdown recognising bending and hydrostatic loads and ovalisation from manufacturing tolerance and plastic bending strain from passage through the stinger (see [7.3.2.18]). Propagation buckling initiation pressure and sustained running pressure (see [7.3.2.18]). Requirement and extent of buckle arrestor provision based upon initiation and running pressures and hydrostatic pressures along the route (see [7.3.2.18]). Quasistatic pipelay analyses for the load cases combining tension ranges, water depth ranges, trim, draught, current, pipe weight and effects of concrete stiffness (where applicable) to determine critical cases for overbend stress/strain on the stinger, and sagbend stress near the touchdown (see [7.3.2.19]). Dynamic pipelay analyses for critical stress cases that determine weather limits for stress/strain in the pipe and other limit states such as pipe dynamics in the stinger due to wave motions and plastic strain history limits (see [7.3.4]). Analysis of bearing loads in the concrete weight coating (where applicable) from tensioner pads and tracks and for intercoating shear between the concrete coating and the underlying anticorrosion coating (see [7.4.8]). 7.13.8.4 The following items should be checked for reel and carousel lay of rigid pipe, in addition to those for SLay and JLay in [i)]: a) b) c) d) e) f) Linepipe steel qualification testing to be performed to confirm suitable toughness for reeling strains on the intended installation vessel. Coating qualification testing to demonstrate suitability for the strain cycles on the intended installation vessel. Minimum reelable wall thickness for linepipe or strength against local buckling at the maximum reeling strain. Total strain and requirements for ECA or additional testing. Cumulative ovalisation and partial recovery of circular section through reeling/spooling, unreeling and straightening. Local buckling strength at seabed touchdown recognising bending and hydrostatic loads and ovalisation from manufacturing tolerance and residual ovalisation from reeling/spooling. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 235 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used s) t) h) i) j) k) l) Propagation buckling initiation pressure and sustained running pressure (recognising that it is not practical to include buckle arrestors in a reeled pipe). Anode doubler plates shall be circular, matching the pipe material. Quasistatic pipelay analyses for the load cases combining tension ranges, water depth ranges, trim, draught, ramp angles, current and pipe weight to determine critical cases for peak and minimum axial tension in the product and maximum curvatures. Dynamic pipelay analyses for critical stress cases that determine weather limits for axial tension in the pipe and other limit states such as pipe dynamics in the stinger or over boarding chute/roller due to wave motions. Analysis of crushing and shear loads in the product from tensioner pads and tracks and for interlayer shear within the product. Analysis of crushing and shear loads in the product at any straps or clamps attaching to other lines or installation aids. 7.13.8.5 For all cable lay operations (as applicable): a) b) Testing procedures and schedule. Cable handling requirements. 7.13.9 Pullin through Jtubes or Itubes 7.13.9.1 For Jtubes or Itubes: a) b) Procedures. Analysis: — pullin tension — stress/MBR check or product. c) Jtubes/Itubes details: — — — — dimensions strength bend radius friction. d) Messenger line details. e) Pullin winch details including capacity of the pullin winch, winch wire and other parts (sheaves, blocks, foundations etc.). f) Pullin winch load cell calibration. g) Pullin winch operational procedure. h) Winch commissioning report. i) Drawings and details or rigging and pullin assembly. 7.13.10 Pipeline and cable crossings 7.13.10.1 For pipeline and cable crossings: a) b) c) d) Crossing procedure including inspection and monitoring (may be included in lay procedure). Overall chart of crossing location, identifying coordinates of the crossing point (UTM), crossing angle and sizes of crossed and crossing cables and pipelines. Specification of minimum cover between and above crossed and crossing cables and pipelines. Geometry of supporting structures, methods to be used for protection, seabed morphology and soil characteristics at the crossing location. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 236 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used g) Mooring procedures whilst anchors and mooring lines are in the vicinity of the crossed cable or pipeline. Check of stress and span at crossing location. 7.13.11 Shore crossing 7.13.11.1 For shore crossing: a) b) c) d) e) f) g) h) i) Pulling procedure and analysis. Governing weather criteria. Tide tables. Details of launching supports on land, vessels (such as pull barges), any special equipment, and manning arrangements. Special procedures for messenger and pull wire laying and attaching installation aids such as buoyancy tank etc. Installation aids (pull head, riggings etc.) and their structural design. Contingency protection methods in the event of temporary abandonment. Holding back tension analysis for structure or mooring lines. Dredging and pretrenching procedure. 7.13.12 Riser or subsea tiein 7.13.12.1 For riser or subsea tiein installation: a) Tiein analysis report including calculations of, maximum allowable landing speed and for riser clamps and rigging. b) Stress analysis where pipe is to be lifted for connection. c) Riser or subsea tiein installation procedures. d) Installation tolerances. e) Information of target boxes for installation. f) Details regarding tiein equipment and tiein capacities. g) Allowable tiein loads. h) Capacity of interfacing hubs/structures. i) Contingency procedures in case of tiein load limits are reached. j) Check tiein equipment, including inspection, monitoring and testing. k) Welding and NDT procedures for approval in the situation where welding will be performed under a suspended load in order to see how this is addressed. This should normally be riskassessed. l) Bolting procedures. m) Temporary hangoff procedures. n) Riser, subsea spool and/or structure configuration, weight (inair and in seawater) and CoG. o) Need for installation aids (e.g. buoyancy, lifting slings, seabed anchors, low friction plates/ gratings.) p) Need for seabed preparations, e.g. rock dumping or similar. 7.13.13 Protection and postlay intervention 7.13.13.1 For protection and postlay intervention (if applicable): a) b) c) d) e) Specification for burial. Specification of plough, trenching machine, jet sled and support vessel as applicable. Available bollard pull and tow force. Deployment/recovery procedures and analyses of plough/sled/trencher. Trenching and backfilling procedures and analyses. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 237 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used e) f) Monitoring procedures. Analysis to confirm product design allowables are not exceeded during trenching operations i.e. pickup, transitionin, normal trenching and transitionout. h) Confirming that transition in and out of the trench will not induce overlong free spans at the ends of trench. i) Protection against contact with trencher specifically for piggyback lines or gross lateral deflection. j) Protection against cutter coming in contact with or too close to product. k) Contingency procedures. l) Upheaval pipe buckling assessment. m) Seabed rock installation vessel specification and operating procedures. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 238 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used f) g) 8.1 Introduction 8.1.1 General 8.1.1.1 This section gives the MWS requirements for installing offshore wind farm infrastructure (apart from cables which are covered in Sec.7). Operators should also consider national and local regulations, which can be more stringent. Background information is in App.H. 8.1.2 Scope 8.1.2.1 This standard provides requirements and guidance for installation of offshore wind farms, in particular: — Foundations including monopiles, steel jackets, gravity bases, suction bases, floating bases including spars, TLPs and semisubmersibles. — Towers, turbines and blades to be installed on foundations. — Offshore substations, offshore converter platforms, offshore transformer station, control and other platforms, including those on jackup platforms. 8.1.3 Revision history 8.1.3.1 No main changes have been made to this section. Editorial corrections may have been made in this section. 8.1.3.2 The changes made to this section for the June 2016 edition are shown in App.A. 8.2 Planning 8.2.1 General 8.2.1.1 See Sec.2 for general planning requirements and Sec.3 for environmental conditions and criteria. 8.2.2 Tolerances and criteria 8.2.2.1 Tolerances and criteria should be agreed with the MWS company at an early stage of the project. Guidance note 1: The selection of many installation tolerances and criteria will be a tradeoff between reducing the cost of manufacture and reducing the costs of delays waiting for good weather in consequence. Manufacturers often prefer tighter installation tolerances which require better weather criteria for installation. It is generally beneficial to select the transport/installation contractors before such tolerances and criteria are fixed as they may significantly affect the installation methods, risks and costs. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 239 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 8 OFFSHORE WIND FARM (OWF) INSTALLATION OPERATIONS The MWS company normally has input to the selection to ensure that the tolerances and criteria are not so severe that there is a possibility that the equipment may never be able to be installed without taking unacceptable risks. endofguidancenote 8.2.2.2 Such tolerances may include: a) b) c) Position and orientation of monopiles, pile templates, jackets and other structures. Pile or structure verticality. Clearances between piles inside pile sleeves, including allowances for weld beads and grout keys. 8.2.2.3 Such criteria may include: a) b) c) d) e) f) g) Wind speeds (at specified heights and gust durations) for critical lifts. Any restrictions on current speeds or wave heights (and how they will be measured) for specific operations. These could include stabbing piles or jackets into templates. Degree of acceptable damage to grout keys during piling. Any restrictions on helicopter or vessel movements within the field in bad visibility or other adverse conditions. Any restrictions on transfer of people and equipment onto fixed or floating installations by various means. Requirements for disposal of any dredged materials, drilling cuttings or soil plugs removed from piles (to comply with national or international laws or conventions, and to avoid problems with other contractors). Piling operations – sound effects on sea life. 8.2.3 Vulnerable items or areas 8.2.3.1 Due to the many parties and vessels working in close proximity, it is necessary that each party understands what items are particularly vulnerable to actions by others. These items need to be identified at an early stage so that they can be considered in the relevant risk assessments. The list of vulnerable items needs to be updated and promulgated as required during the life of the wind farm. 8.2.3.2 Typical vulnerable items or areas may include: a) b) c) d) e) f) Jtube entry holes being covered with soil or debris. Changes in seabed level (from scour, dredging, jackup footprints, drill cuttings, etc.) varying the natural frequency of foundations. Scour can also affect jackup foundations, cables, anchors etc. Scour model tests may be required in areas with high current speeds and soft or sandy seabeds. Damage to grout seals and backup seals. External fittings (including anodes, Jtubes, etc.) being damaged by dropped objects, vessel collision or mooring lines. Operations of divers (vulnerable to propellers and propeller wash, noise and blast, bubble curtains, cables and dropped or lowered objects). 8.2.4 Planned moorings 8.2.4.1 Geotechnical and bathymetric surveys should determine at an early design stage if the seabed will provide good anchor holding and may determine the type of anchors that will be needed. If anchor holding is poor (leading to a high probability of dragging anchors damaging cables) then prelaid or piled anchors may be desirable. Allowable anchor locations should be agreed at the same time as the cable routes. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 240 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 2: 8.3.1 Jackups – general 8.3.1.1 Jackup legs can be a major threat to cables. The aslaid cable routes should be updated as required and properly distributed through the project in order to prevent cable damages. A suitable safe distance shall be maintained between the aslaid cable route and the intended positions of the jackup legs. This is of particular importance in OWF developments where cable laying/installation is progressing near turbine installation activities in a similar time frame. 8.3.2 Jackups in weather unrestricted operations 8.3.2.1 Jackups that are designed and classed for elevated operations in conditions in excess of those at the installation site (either all year or for particular months) shall comply with the requirements of DNVGLST N002, /39/. 8.3.2.2 The jackup can operate at a lower air gap than required for survival in a design storm as long as it is able to jackup to a safe air gap for a design storm before bad weather. Guidance note: If a breakdown prevents jacking up, then the crew may need to be evacuated. endofguidancenote 8.3.3 Jackups in weather restricted operations 8.3.3.1 Jackups that cannot comply with [8.3.2] for a specific location and season shall comply with the requirements for weather restricted operations in [2.6.5]. Guidance note: Useful practical guidance on weather restricted jackup operations is given in section 5.3 of Renewable UK Guidelines for Jack ups, /115/, but note that [2.6.7] allows a greater operational window. This is summarised as: a) Agree procedure documents which include limiting criteria, allowing for uncertainty due to monitoring and the forecasting of the environmental conditions (see [2.6.9]), for relevant decision points and identify suitable alternative jackup locations between the site and safe ports. b) The jackup is only to leave a safe location to go to the installation site on receipt of a favourable weather forecast with high confidence to cover the time (including a contingency for delays) from departure to return to a safe location. c) The jackup is to leave the installation site unless there is a confident good weather forecast to cover the remaining time on site and to return to a safe port or to elevate to a safe air gap at a suitable standby location, including a contingency for delays. d) If the jackup cannot reach a safe port or location before meeting bad weather (above the laden jacking limits of the jackup, typically about 1 m to 1.5 m significant wave height), then it should jackup to survival air gap at a suitable shallow water location and evacuate the crew if necessary. endofguidancenote 8.3.3.2 The procedures and criteria described in [8.3.3.1] shall be the subject of a risk assessment in accordance with [2.4]. 8.3.3.3 Jackups can also operate on DP or when moored afloat to save time jacking up and down and pre loading. These operations require favourable weather and shall follow the weather restricted operations requirements in [2.6.7]. The use of the crane in floating mode shall be specified in the vessel’s operation manual with the associated allowable environmental limits and approved by the classification society. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 241 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8.3 OWF installation vessels 8.3.4 Crane vessels (seagoing) 8.3.4.1 Any crane vessel or sheerlegs shall be classed for operating in the relevant area. The design and operating criteria shall be defined according to Sec.2. 8.3.4.2 Carrying a suspended load on a crane hook in transit offshore is not generally considered good practice, unless it is for very short distances in calm weather. In bad weather the load can be very difficult to control, stability is reduced and the crane can be overloaded. Approval of such operations will require agreement from the vessel’s Classification Society and a risk assessment in accordance with [2.4]. 8.3.5 Inshore crane vessels and barges 8.3.5.1 Inshore crane vessels and barges shall only be used if allowed by their class notation and: a) b) c) The MWS company has agreed procedure documents which include limiting environmental criteria for relevant decision points and identifies safe ports or locations. These criteria shall take into consideration the Alpha Factors described in [2.6.9] The vessel is only to leave a safe port or location to go to the installation site on receipt of a confident good weather forecast to cover the period from departure to safe return, including a contingency for delays. The vessel to leave the installation site unless there is a confident good weather forecast to cover the remaining time on site and to reach a safe port or location, including a contingency for delays. 8.3.6 Grounded OWF installation vessels and barges 8.3.6.1 Some vessels working in shallow water may need to be grounded at low water or over one or more tidal cycles. This can only be approved provided that: a) b) c) d) The vessel’s classification society allows such operations. The seabed is such that the vessel will not be damaged and it will not hold the vessel down when attempting to refloat. There is a method (e.g. moorings or “spuds”) for holding the vessel on location when grounding and floating off in the design conditions agreed with the MWS company at the design stage without damaging any cables or other structures or equipment. A confident good weather forecast is obtained before grounding to cover the period (including a suitable allowance for delays) until floatoff without exceeding the operational criteria. 8.3.7 Other OWF installation vessels 8.3.7.1 The following vessels usually do not require the approval of the MWS company unless their operations represent a risk for other structures or operations. a) b) c) Crew transfer or accommodation vessels with proprietary crew access arrangements. Escort and standby vessels can be needed in some areas to warn off other vessels, especially during sensitive operations or transports. Bubble curtain deployment and energising vessels which can be needed if regulations on piling noise pollution apply (see [13.10.2]). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 242 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8.3.3.4 Jackups can operate in semijackedup condition (vessel stabilised in water by a low leg preloading and a reduced draught) under good weather conditions. This condition can make it feasible to operate the jackup at critical locations where the risk of punch through is high. It will require approval by the vessel’s classification society as it is not typically a normal operating condition. 8.4 Planning and execution 8.4.1 Procedures and manuals 8.4.1.1 Technical documentation shall be completed for all operations. See [2.3] for details. In general, this should include: a) b) c) d) e) f) g) The anticipated timing and duration of each operation, including contingencies. The limiting wave states, wind speeds and currents, and where applicable any visibility/daylight, temperature and precipitation limits, as well as the sitespecific equipment or methodology prescribed for measuring each limitstate. The transport route including shelter points. The arrangements for control, manoeuvring and mooring of barges and/or other craft alongside installation vessels. Effects on and from any other simultaneous operations (SIMOPs – see IMCA M 203, /83/). Contingency and emergency plans. Requirements from the relevant MWS company standards for each individual phase. 8.4.2 Weight control 8.4.2.1 The requirements in [5.6.2] apply. 8.4.2.2 The manufacturer shall supply a weight statement with tolerance and CoG envelope for all weight sensitive items. 8.4.2.3 When a large number of virtually identical items are built with very good quality control, reduced weight contingency factors can be agreed with the MWS company based on the standard deviation from weighing of initial items, with random subsequent weighing used to confirm consistency of manufacture. 8.4.2.4 Where rigorous quality control is in place, and predictions of final weights in initial weighings are demonstrated to be accurate, a reduced requirement for weighing can be agreed with the MWS company. 8.4.3 Weather restricted operations and weather forecasts 8.4.3.1 For requirements see [2.6.7] for requirements for weather restricted operations and [2.7] for weather forecasts. 8.4.3.2 For areas with high tidal currents there can be additional restrictions on operations due to the need to wait for slack (or slacker) tides for currentsensitive operations such as: — — — — Moving jackups on or off location Stabbing piles or installing jackets, substructures or equipment on the seabed Bringing cargo vessels alongside installation vessels. Diving operations. 8.4.3.3 When high currents are combined with shallow water then additional current forces will be caused by “blockage” effects. These shallower conditions also lead to increased seabed turbulence due to wave action, Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 243 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8.3.7.2 In some cases, it may be unclear whether the approval of the MWS company is required or not for smaller vessels approaching existing structures. Planned operations should be discussed between the OWF owner, the Underwriter and the MWS company in order to identify the major risks for the existing structure and decide case by case the scope of the MWS company. 8.4.3.4 Weather forecasts shall follow the requirements in [2.7]. Forecasts for wind speed shall specify the height (to be agreed in advance) and wind speeds measured on site should be corrected to that height for direct comparison. The swell height, direction, and period should also be included, as well as the probability of precipitation, fog and lightning within the next 24 hours. The time of sunrise and sunset, and the phase of the moon can be advantageous though these will normally be found in nautical almanacs. 8.4.3.5 For subsea lifts in areas where it is known that high currents exist in the water column, infield monitoring of currents (speed and direction) should be considered to enhance the regular forecasts. The monitoring of subsea currents with acoustic Doppler or similar systems should be considered when the operational limits of ROVs, and drag on piles during stabbing can lead to operational delays. 8.4.4 Site and route survey requirements 8.4.4.1 As well as ensuring that all positional, bathymetric, soil and current surveys are performed using the same datum and coordinate systems, various requirements to ensure sufficient accuracy like the frequency of survey equipment calibration (for salinity, temperature etc.) shall be agreed. There shall be an agreed procedure for ensuring that all survey results are disseminated to all relevant parties as required. 8.4.4.2 The “as built” locations of structures, cables and subsea equipment shall be recorded accurately on charts using a common survey datum used by all parties. These charts shall be kept updated, including all jackup footprints as soon as they are made and issued to all vessels operating in the field. “No anchoring” zones shall be well marked. 8.4.4.3 In advance of the final detailed design being carried out for the foundations, the seabed material, geophysical, and geotechnical surveys of the subbottom profile should have been carried out, as well as magnetometer surveys for ferrous objects, including UXO. The Cone Penetrometer Test results and other appropriate survey details for each foundation location should be documented, to jackup vessel operators. This will allow them to carry out sitespecific assessments in accordance with ISO 199051, /102/, and to assess the possibility of scouring around jacklegs and spudcans. 8.4.4.4 Unexploded ordnance (UXO) disposal, although important, is not generally subject to a Marine Warranty and is normally excluded. However it is recommended that it will be managed in accordance with the requirements of ‘Risk Management Framework’ provided in CIRIA C754, Assessment and management of unexploded ordnance (UXO) risk in the marine environment, /13/ or similar. 8.4.4.5 Additional requirements for the cable route surveys are given in Sec.7. 8.4.5 Scour protection 8.4.5.1 If scour is a possible problem, procedures or contingency procedures shall be prepared and anti scour materials stockpiled and deployment equipment prepared for mobilisation. See [8.4.3.3] and [8.4.4.3] for information that will help in prediction of scour. Guidance note 1: “Dynamics of scour pits and scour protection”, /119/, gives the results of research into scour on early UK offshore wind farms. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 244 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used and additional contingency measures can be necessary to make allowances for accelerated scouring around jacklegs and spudcans. However suitable moorings, stabbing guides and other aids can help to reduce the sensitivity to currents and decrease downtime waiting for slack tide. Cables are generally be trenched or otherwise protected in scourprone areas. However additional precautions can be required close to Jtubes or Itubes at monopiles or platforms, especially immediately after laying. endofguidancenote Guidance note 3: Scour around jackup legs can make them more vulnerable to punchthrough and around cables can make them more vulnerable to damage. endofguidancenote 8.4.5.2 Care shall be taken when laying scour protection to ensure that bad weather and/or high currents during the installation phase do not cause damage to the lower layers. 8.4.6 Wet storage of jackets or OWF foundations 8.4.6.1 Any unpiled jackets or foundations should be able to comply with the requirements in [13.10] for the return period applicable to the operation reference period given in [3.4]. This can require any chosen location to be sheltered from high waves and currents. 8.4.6.2 A constant exclusion zone for marine traffic shall be enforced. 8.5 Loadouts of OWF components 8.5.1 Structure loadout 8.5.1.1 Loadouts shall be in accordance with Sec.10. However the following special cases apply, as applicable. a) b) c) d) Special consideration should be given to purposebuilt lifting appliances for blades. The lifting tool Certificate shall specify the maximum load and any limits regarding the overall dimensions of the lifted item and any environmental limitations (e.g. maximum wind speed). In the event of structural modifications to an item of lifting equipment, it shall be reapproved by a Recognized Classification Society before further use. Bolts used for removable lifting lugs shall generally be used one time only. In special cases, reuse can be accepted as described in [E.2] but only if initial pretensioning does not exceed 60% of the bolt yield strength and the loads during lifting have not exceeded the maximum design values. For reuse of bolts, a detailed inspection plan with regular NDT including rejection criteria and exchange intervals should be documented. As a minimum, bolts should be visually inspected after each lift and with MPI (Magnetic Particle Inspection) after every 3 lifts unless fatigue calculations accepted by the MWS company show that less frequent inspections are acceptable. Reuseable lifting lugs shall be tested in accordance with [16.9.7]. 8.6 Transport of OWF components 8.6.1 General 8.6.1.1 Sea voyages are covered in Sec.11 and road transport in Sec.9. The rest of [8.6] describes items specific to OWF components. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 245 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 2: 8.6.1.3 The requirements of [E.2] will apply for bolted connections used for seafastening. The strength of bolted connections may be assessed to DNVGLOSC101 Ch.2 Sec.11 [2], /24/, Eurocode 3 /61/ or [E.2] 8.6.1.4 Minimum clearance between cargo items to be lifted is given in [16.13.2] and [16.13.3]. 8.6.2 Transport of complete rotor 8.6.2.1 Rotors with diameters of well over 100 m may be transported horizontally (rotor axis vertical) on vessels or barges of only about 30 to 40 m beam. The voyage and installation planning shall account for the large overhangs in particular avoiding wave slam on the blades. Guidance note 1: The blades will generally be very vulnerable to wave slam, especially when the vessel rolls and/or pitches into a wave. endofguidancenote Guidance note 2: Normally the voyage and installation planning considers some or all of the following: a) The rotor being designed to safely withstand the accelerations (from [11.3]). b) Reducing to negligible the probability of wave slam on the blades by securing them well above the still water level. c) Selecting vessels that can be ballasted to reduce the motions in likely wind and wave combinations. d) Doing motion response calculations to optimise the loading and ballasting arrangements so as to minimise the probability of wave slam on the blades in likely wind and wave combinations. e) Weather routing the transport to avoid any weather that could cause wave slam on the blades. (This cannot always be practicable for some seasons and longer routes between suitable shelter points). f) Developing procedures to avoid blade collision damage when coming alongside loading quays, entering ports of shelter (as part of the weather routing) and coming alongside the offshore lifting vessel. These procedures include advance liaison with any suitable shelter points (to agree the conditions under which the transport can enter, e.g. problems when meeting other vessels in the approach channel, clearances at harbour entrance and mooring at a quay). Escort vessels may also be required to reduce the probability of collision with other shipping, especially at night. endofguidancenote 8.6.3 Transport of tall vertical cargoes 8.6.3.1 Seafastening of the transition piece flanges on barges or ships is often critical for many projects. The design of the bolted connection shall be “gap free” to avoid any bolts becoming loose. All gaps due to imperfections shall be filled in with shim plates but not more than 2 shim plates should be used at any gap. 8.6.3.2 Bolts used for seafastening shall generally be used one time only. In special cases, reuse can be accepted as described in [E.2] but only if initial pretensioning does not exceed 60% of the bolt yield strength and the loads during the transport have not exceeded the maximum design values. For reuse of bolts, a detailed inspection plan with regular NDT including rejection criteria and exchange intervals should be documented. As a minimum, bolts should be visually inspected after each transport and with MPI (Magnetic Particle Inspection) after every 3 transports unless fatigue calculations accepted by the MWS company show that less frequent inspections are acceptable. 8.6.3.3 Pretension bolts in seafastenings shall be used only once due to fatigue during voyages. 8.6.3.4 Seafastenings shall be designed to allow safe removal offshore without endangering the cargo or personnel. See also [11.9.6]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 246 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8.6.1.2 Seafastening of blades and other fragile components require special care to avoid damage from welding or locating guides. Where friction is required to resist some or all of the seafastening forces, the coefficients of friction shall be shown to be adequate in both the wet and dry states. See [11.9.2]. Guidance note: The power line catenary will change if power is shut off. endofguidancenote 8.6.3.6 High towers, when transported vertically, can be vulnerable to vortex induced vibrations. Analysis shall be carried out to evaluate the risk for the structure and the seafastening frame, see [5.6.7.4]. If required, protection devices shall be installed to reduce the risk of vibrations. 8.6.4 Other OWF wet towages 8.6.4.1 Larger Concrete Gravity Structures will generally be built in a drydock or building basin with construction often completed afloat. The MWS requirements are given in Sec.12 8.6.4.2 Smaller gravity structures may be built on barges and floated off or lifted off by crane or sheerlegs. They can also be lowered to the seabed by purposebuilt installation units. Where these are not covered by existing MWS company standards, suitable criteria can be developed by the MWS company at an early design stage. 8.6.4.3 It will often be impracticable to provide onecompartment damage stability for floating piles, transition pieces and suction anchors by introducing temporary bulkheads. In this case, a risk assessment, in accordance with [2.4], shall be carried out to determine the major causes of flooding and to reduce the risk to acceptable levels, as described in [11.10.7.3]. 8.7 Installation of OWF components 8.7.1 Monopiles and transition pieces installation 8.7.1.1 The following items shall be addressed and agreed with the MWS company: 1) 2) 3) 4) 5) 6) 7) 8) Position and orientation tolerances (see [8.2.2]). Release of seafastenings which will normally require a specific procedure, especially for tall objects transported vertically. Sea bed soil condition and scour protection requirements (see [6.5.7] and [8.4.5]) Levelling arrangements for the transition pieces. Grippers, handling and upending equipment. Onbottom stability of the unpiled Monopile in the pile gripper. Stability of the Transition Piece on the Monopile before grouting (see [13.10] for the criteria). If drilling is required for installing piles then: — Disposal of cuttings (see [8.2.2]). — Contingency plans and equipment (e.g. fishing tools) for a broken drill string. 9) Approval of grouting operations (see [H.5.3]). 8.7.2 Piling templates 8.7.2.1 Piling templates are often used to help locate piles before driving and to ensure that piles are driven vertically or at the right inclination. They are normally placed on the seabed but may be attached to the side of a jackup, with the facility to be lowered or raised and may use the jackup legs as a positioning guide. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 247 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8.6.3.5 Clearance (air draught) under any bridges or power cables shall be considered. The safe distance from live power lines shall be considered with input from the power line operator. 8.7.2.3 Special transit procedures can need to be developed to reduce the risk of collisions or grounding if the attached template increases the combined draught or beam, especially if not visible above water. 8.7.2.4 The template shall be capable of being levelled if there is a sloping or uneven seabed. Mudmats can also be needed for a soft seabed. 8.7.2.5 When templates are liable to settle in clay or silt, provision shall be made for jetting or other means to overcome adhesion during subsequent extraction. 8.7.3 Suction bucket foundations 8.7.3.1 The requirement for any seabed preparation before installation shall be determined at any early stage. 8.7.3.2 Equipment and procedures shall be documented to ensure that: a) b) c) d) e) the foundations can be safely lowered through the splash zone (buoyancy should be considered) to the seabed and located within tolerances there is no “piping” (soil erosion due to seepage) through the soil between outside and inside, or between individual compartments, if any, during installation that any out of verticality can be corrected to within the required tolerances (possibly using crane assistance) there is sufficient redundancy to allow installation to continue after flooding of any compartment or breakdown of any item of equipment. If there is insufficient redundancy a risk assessment in accordance with [2.4] should be completed. the operation should be made reversible so as to be able to extract the suction bucket foundation and relocate if there is a risk of refusal (no further penetration at maximum pump capacity). The risk of refusal should be determined from a penetration analysis using the latest soil data. 8.7.4 Jtubes and Itubes 8.7.4.1 Installing cables through Jtubes and Itubes is covered in Sec.7. 8.7.5 Turbine installation 8.7.5.1 Requirements in this standard shall apply unless novel installation techniques are proposed. 8.7.6 Towers 8.7.6.1 Installation lifting requirements are covered in Sec.16. In addition the following items shall be addressed, if applicable, and agreed with the MWS company: — — — — Access for derigging Partial bolting Lifting points certification for multiple use (loadout, installation, maintenance, decommissioning) Verification that there will be no ovalisation of structure tubular members due to local seafastening forces in higher sea states — Transport frames Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 248 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 8.7.2.2 If transported attached to a jackup then the template and its attachment shall be able to withstand the design accelerations according [11.3] as well as the hydrodynamic forces acting on the structure. Its effect on trim and stability shall also be checked. 8.7.7 Nacelles 8.7.7.1 Installation lifting requirements are covered in Sec.16. In addition the following items shall be addressed, if applicable, and agreed with the MWS company: — — — — Lift points Tugger lines arrangement Access for derigging Partial bolting. 8.7.8 Blades 8.7.8.1 Installation lifting requirements are covered in Sec.16. In addition the following items shall be addressed, if applicable, and agreed with the MWS company: — Infrared release systems which shall be shown to be reliable in releasing and, more importantly, not liable to early release from any cause — Limiting criteria. — Boom tip motions, See [16.17.3.1] 4) — Partial bolting. 8.7.9 Complete rotor assembly installation 8.7.9.1 The following aspects need special consideration: — — — — — Upending and lifting devices Tugger lines arrangement Partial bolting Horizontal and vertical movement during positioning High windage area effect on dynamic loads. 8.8 Lifting operations and lifting tools 8.8.1 Lifting operations are covered in Sec.16 and lifting tools in [16.6.2]. However, due to the high number of repetitive lifting operations carried out in the Offshore Wind Industry, special attention should be paid to the regular inspections of lifting gear. Replacement of slings and grommets as well as the provision of sufficient spares along the project will prevent project delays and offshore downtime. An inspection plan including the detailed scope of inspections and rejection criteria should be documented by the lifting operator to the MWS at the beginning of the project. Refer to [16.12] for more information. 8.9 Information required for MWS approval 8.9.1 See subsections at the end of each relevant section, e.g. lifting, voyages, etc. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 249 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — Requirements and criteria for upending from the horizontal to vertical mode. 9.1 Introduction 9.1.1 General 9.1.1.1 This section gives the requirements for objects subject to road transport on public roads, which are generally subject to national or local requirements/legislation. 9.1.2 Scope 9.1.2.1 This section gives the basic default design criteria for transport on roads, together with the information typically required for MWS approval. However additional local or technical requirements can apply. 9.1.3 Revision history 9.1.3.1 No main changes have been made to this section. Editorial corrections may have been made in this section. 9.1.3.2 The changes made to this section for the June 2016 edition are shown in App.A. 9.2 Requirements 9.2.1 Statutory requirements 9.2.1.1 Most countries have specific legislation containing criteria for transport of large items by road. These shall be obtained and complied with. 9.2.2 Loads and accelerations 9.2.2.1 Table 91 will cover most countries with published requirements for tiedown requirements. These shall apply in the absence of more stringent criteria, depending on jurisdiction or other requirements. 9.2.2.2 Possible additional limitations on wind (or road speed) shall be checked for structures where strength or stability can be an issue. Table 91 Typical road tiedown acceleration requirements Direction Requirements Transverse acceleration 0.5 g Forward acceleration 0.8 g Backward acceleration 0.5 g Vertical acceleration 1.2 g (1.0 g in some areas) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 250 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 9 ROAD TRANSPORT 9.2.3.1 All securing equipment should be in accordance with the principles and requirements of seafastening design strength in [11.9.5]. 9.2.3.2 Friction can be permitted as part of the securing system, subject to justification and where permitted by local legislation. 9.2.4 Stability 9.2.4.1 Stability in accordance with [10.5.3.15] shall be demonstrated. 9.3 Information required 9.3.1 Object information 9.3.1.1 For the object: a) b) c) d) e) Weight, CoG and envelopes considered Description and dimensions Definition of allowed lashing points on cargo, or specification of those locations which are forbidden Support point requirements and cargo general strength when transported. For multiple supports, allowance shall be made for possible loss of support due to trailer deflections Padeyes, where used as lashing points, or other lashing points on the cargo to be verified against transport design forces. 9.3.2 Trailer or SPMTs 9.3.2.1 Requirements are given in [10.5.3]. 9.3.2.2 For the trailer or SPMTs: a) b) c) d) e) f) Trailer or SPMTs specifications including lashing anchor point capacity and spine load capacity. Bending moment and shear calculations of applied load on trailer or SPMTs spine. Tyre ground pressure calculations and axle utilizations. Hydraulic grouping details and trailer or SPMTs (loaded) stability calculations. Demonstration that there is enough power/traction/braking capacity in SPMT or trucks to conduct the transport along the planned route accounting for any inclines or turns. Demonstration that stroke length is adequate to prevent grounding (cargo/trailer/SPMTs) or tyres losing contact with roadway. 9.3.3 Securing 9.3.3.1 For the securing arrangement: a) b) c) d) Details including WLL/SWL and MBL of all items in the securing system including tensioners. General arrangement drawing of the securing plan including cargo CoG location while positioned on trailer/SPMT and clearly defined required lashing angles. Design acceleration definition and justification. Securing Calculations documented and found adequate. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 251 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 9.2.3 Securing Demonstration of lashing/stopper adequacy against uplift and horizontal forces, including friction assumptions and description of friction material and description of blocking if used. 9.3.4 Route 9.3.4.1 For the route: 1) 2) Transport procedure in place which includes contingency plans for prime mover failure, schedule for arrival at way points and destination, as well as if police escort is required. Route mapped an overview of the entire route with the following: — — — — Start location and destination Critical turns planned to show no collisions with roadside obstructions. Adequate overhead clearance when passing under bridges or overpasses. Overhead power and utility lines along with relevant traffic signals and street signs, including a plan for depowering as required. — Any relevant limitations on bridge loadings — Any relevant limitations on timing. — Significant inclines and declines. 3) Permit obtained if required. 4) Max speed defined if not stipulated in a permit. Max speed to allow for trailer /SPMT levelling as needed. 5) Requirements for strength of ramps where used, allowable ground pressure should take in to consideration any limits on buried culverts, utilities etc. 6) Allowable ground pressures for the route defined. Special attention regarding ground pressure capacity should be made to areas where the route is changing ground type (e.g. asphalt to cement). Tyre and ground pressures should comply with the allowables for the entire route. 7) If the transit passes an airfield and the cargo is of sufficient height, evidence that coordination with the airfield, including any required aviation warning lights, has been included in the transport procedure. 9.3.5 Risk assessment 9.3.5.1 A risk assessment in accordance with [2.4] of the transport. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 252 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used e) 10.1 Introduction 10.1.1 Scope 10.1.1.1 This section presents the requirements for loadout operations involving transfer of heavy objects from land and onto a vessel (often a barge) either by skidding or by use of trailers. General requirements and guidance is given in sections [10.1] to [10.8]. Section [10.8] gives additional requirements and guidance for the following special cases: — — — — — grounded loadouts loadin, i.e. a reversed loadout vessel to vessel load transfers transverse loadouts site moves. 10.1.2 Other types of loadout 10.1.2.1 For loadout operations carried out by crane lifting, see Sec.16 10.1.2.2 For other load transfer operations, see Sec.15. 10.1.3 Revision history 10.1.3.1 No main changes have been made to this section. Editorial corrections may have been made in this section. 10.1.3.2 The changes made to this section for the June 2016 edition are shown in App.A. 10.2 General 10.2.1 Loadout class 10.2.1.1 Requirements to loadout equipment are defined according to loadout class. The loadout operation shall, based on tide conditions and weather restrictions, be classified according to Table 101. Table 101 Loadout (operation) class Tide range 1) Tide restricted? 2) Weather restricted? 3) Loadout Class Significant Yes No/Yes 1 Significant No Yes 2 Significant No No 3 Zero No Yes 4 Zero No No 5 Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 253 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 10 LOADOUT 1) If ballasting is required in order to compensate for tide variation, then the tide range shall be defined as significant, see also [10.2.1.2] and [10.2.1.3]. 2) If the ballast system cannot compensate for a complete tide cycle, then the loadout shall be defined as tide restricted. 3) If weather restrictions apply, then the loadout shall be categorized as weather restricted, see [2.6]. If there are no weather restrictions to the object movement/ballasting phase the loadout class may be selected accordingly. 10.2.1.2 The possibility for water level differences due to environmental effects shall be duly considered. If such effects could be significant during the loadout, then the tide range in Table 101 should normally be regarded as significant even if the astronomical tide variation is defined as zero. 10.2.1.3 For grounded loadouts, see [10.8.1], the tide range in Table 101 shall be defined as significant if ballasting is required in order to maintain ground reactions within acceptable limits. 10.2.2 Planning 10.2.2.1 General requirements for planning of marine operations are given in Sec.2. 10.2.2.2 Start and end points for a loadout shall be safe conditions and clearly defined, see [2.5]. Guidance note: A loadout from one safe to another safe condition could include many suboperations, such as “liftoff from construction supports”, “site move”, “move onto barge”, “temporary seafastening phase”, “turning of barge” and “final mooring of barge”. Hence, it should be thoroughly evaluated if it may be possible and beneficial to split the loadout into two (or more) operations with safe condition(s) inbetween, see [2.5]. endofguidancenote 10.2.2.3 Tide variation is normally a critical parameter for loadouts. Extreme tide levels and rates of change should be considered. All environmental effects that can influence tide levels, in addition to the astronomical tide variation, shall also be evaluated and duly considered. 10.2.2.4 The following should be given due attention when planning loadout operations: 1) 2) 3) 4) 5) 6) Yard layout, including position of object Transport vessel dimensions and strength Object position and support height on transport vessel Loadout route survey regarding clearances and obstructions Water depths Local environmental effects, e.g.: — the possibility of waves/swell — currents during and following the operation, including blockage effects if applicable — the possibility for squalls and/or thunderstorms; design wind speeds should account for such effects when relevant 7) Quay strength and condition 8) Loadout site soil strength and condition 9) Skidway levelness tolerances 10.2.2.5 A loadout operation could involve several construction, transport and load transfer (main) contractors/responsible parties. Interface planning should be given due attention. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 254 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Notes: 10.2.3.1 Operational risk should be evaluated and handled in a systematic way, see [2.4]. Guidance note: The risk assessment should at least demonstrate that all necessary tasks can be safely performed under all environmental conditions planned and designed for. endofguidancenote 10.3 Loads 10.3.1 General 10.3.1.1 Loads and load effects are generally defined in [5.5] and [5.6]. It shall be thoroughly evaluated if any other loads and load effects not described in Sec.5 need to be considered. 10.3.1.2 The design principles and methods described in Sec.5 shall be adhered to. 10.3.1.3 All relevant limit states as defined in Sec.5 shall be included in the design calculations/analysis. 10.3.2 Weight and CoG 10.3.2.1 Weight (W) and CoG of the object shall be determined as described in [5.6.2]. 10.3.2.2 The appropriate weights and CoGs to be used may be evaluated separately for strength and ballast purposes, see [4.3.9.2]. 10.3.2.3 Any possible CoG position shall be considered for support layouts or systems sensitive to CoG shifts, see [5.6.2]. 10.3.2.4 If there are significant uncertainties regarding weight and CoG position, sensitivity analysis should be carried out, see [5.6.14]. 10.3.3 Weight of loadout equipment 10.3.3.1 The weight of the loadout equipment (Weq) should be accurately assessed. Guidance note: Weq is the total weight of equipment and support structures which moves with the transported object. Such equipment may be support beams, grillages, skidding shoes, trailers, push/pull jacks, hydraulic power packs, etc. endofguidancenote 10.3.3.2 Any uncertainties in weight and CoG of loadout equipment shall be considered by applying conservative estimates in the loadout calculations, see however [4.3.9.2]. 10.3.4 Environmental loads 10.3.4.1 All load effects caused by tide variations shall be considered. 10.3.4.2 Load effects caused by wind and current shall be considered. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 255 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.2.3 Risk management Guidance note: Applicable loads due to waves and swell for transport vessel mooring before and after the loadout operation to be considered. endofguidancenote 10.3.5 Skidding loads 10.3.5.1 The loads required to break loose and continue moving the object can be expressed as: F1 = μ1(W+Weq) + P1 F2 = μ2(W+Weq) + P2 Where: F1 F2 μ1 μ2 W Weq P1 P2 = Required breakout load = Load required to continue moving the object = Upper bound design friction coefficient or rolling resistance for breakout, see [10.3.5.4] = Upper bound design friction coefficient/rolling resistance for the move, see [10.3.5.4] = Object weight, see [10.3.2] = Equipment weight, see [10.3.3] = Any other load occurring during breakout, see [10.3.5.2] = Any other load occurring during skidding/trailing, see [10.3.5.2] 10.3.5.2 The following load effects should be considered: — Inertial loads — Environmental loads — Loads caused by the slope of the skidding or rolling surface 10.3.5.3 If two or more propulsion systems are used then the effect of maximum possible differential push/ pull loads shall be considered. 10.3.5.4 The upper bound design friction coefficients/rolling resistance values used should not be taken less than specified in Table 102 unless adequate inservice documentation indicates that other values may be used, see also [5.6.9]. Guidance note: The indicated friction coefficients for moving include restarting after short stops during the loadout operation. Breakout friction is the maximum friction expected after an extended (construction) period with the object supported at the friction surfaces, see also [10.3.5.5]. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 256 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.3.4.3 Loadout operations should normally not be carried out in significant waves and swell conditions. Sliding surfaces Breakout Moving Steel/Steel 0.30 0.20 Steel/Teflon 0.25 0.10 Stainless steel/Teflon 0.20 0.07 Teflon/Unwaxed wood 0.40 0.10 Teflon/Waxed wood 0.25 0.08 Steel/Waxed wood 0.28 0.15 Steel wheels/Steel 0.02 0.02 Rubber tyres/Steel 0.02 0.02 Rubber tyres/Asphalt 0.03 0.03 Rubber tyres/Compacted gravel 0.05 0.05 Notes: 1) It is assumed that sliding surfaces are properly lubricated. 2) Long term effects such as adhesion, settlements, etc. are included in values for breakout. See also [10.3.5.5]. 3) The values are valid only for contact stresses lower or equal to the allowable contact stresses for the considered medium. Allowable contact stresses should be obtained from the manufacturer or from an applicable code or standard. 4) Wood should normally be surface treated by wax or by other adequate means in order to avoid that the lubrication is absorbed by the wood. Rolling surfaces 10.3.5.5 Where a structure is supported for an extended period on a skidway system, the effect of the degradation of the lubricant between the support and the skidway system should be investigated. This is particularly important where unwaxed wood is used as part of the interface as the lubricant can disperse into the wood giving higher breakout requirements than anticipated. The effects of skidway deformation shall also be considered. 10.3.6 Skew load 10.3.6.1 Skew load is the extra loading at object support points due to inaccuracies in the level of the skidways, rolling surfaces, supports, etc. Such loads shall be considered. Guidance note: Skew loads could normally be disregarded for loadout operations where the object has a 3 point support system. This could be obtained by including a reliable load equalising system. endofguidancenote 10.3.6.2 For cases without 3 point support systems skew load effects shall be determined by considering the stiffness of the object, the supporting structure, the tolerances of skidways, rolling surfaces and supports, deflections/movement of transport vessel and link beams, transport vessel inaccuracies and the operational procedure. Guidance note 1: In lieu of a more refined analysis, the skew load may be determined considering the object supported on 3 points only. It may be required to assume various possible 3 point support situations. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 257 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 102 Upper bound design friction coefficients/rolling resistance For SPMT loadouts using 4 support groups, the effect of skew loading across diagonals should be assessed to account for the possibility that the groupings may not be coplanar due to incorrect pressure in the SPMT groups, the stiffness of the structure and/ or uneven conditions beneath the SPMTs. Appropriate limitation in pressures should be defined and the structure should be checked to ensure that these limitations do not cause overstress. During the operation it should be controlled that the measured pressure variations are within 75% of the set limitations. E.g. if the limiting load (i.e. pressure) variation across a diagonal is 20% of the combined nominal value for that diagonal, the measured variation should not exceed 15%. endofguidancenote Guidance note 3: For skidded loadouts it is recommended to verify the object and supports for the following minimum deflections: — Subsidence of any single object “corner” support with respect to the other “corner” supports by 25 mm. — Subsidence of any single object support with respect to the other supports by 15 mm. Dimensional survey measurement before (and if applicable during) the operation should substantiate that the actual relative deflection will be within 75% of the deflections assumed in structural verifications. endofguidancenote 10.3.7 Other loads 10.3.7.1 Any other significant loads, not covered above should be considered in the design of the object and in the planning of the operation. Such loads may include: — — — — — Hydrostatic loads on transport vessel(s) Impact loads Local support loads on grounded vessel hulls Mooring loads Guiding loads. 10.4 Design calculations 10.4.1 General 10.4.1.1 Structures and structural elements shall be checked against the requirements in [5.2]. for the load cases in [10.3]. 10.4.1.2 Mooring system design is covered in [10.5.8]. 10.4.2 Load cases 10.4.2.1 Relevant load cases shall be selected in order to identify design conditions for the object, skidding equipment or trailers, support structures and transport vessel. Guidance note: A loadout operation consists of a sequence of different load cases. In principle, the entire loadout sequence should be considered stepbystep and the most critical load case for each specific element should be identified, e.g. 25%, 50% and 75% of travel, steps of 5 axles, half jacket node spacing, etc. as appropriate. However, the force distribution during a loadout may normally be represented by static load cases distributing the object weight and any environmental and equipment loads to relevant elements in the analyses. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 258 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 2: 10.4.2.3 For trailer loadouts, the reactions imposed by the trailer configuration on the transported object shall be taken into account. Guidance note: Support reactions for the transported object will be governed by the trailer arrangement. It should be remembered that trailer axle loads within each hydraulic group will be uniform and that the trailers spine stiffness may influence the support reactions. See also [10.3.6.2] GN2. endofguidancenote 10.4.2.4 The design load cases for link beams, link beam attachments and the quay should consider mooring forces, skidding forces and vessel movements when relevant, including any situations where the object or vessel can be jammed. 10.4.3 Quays 10.4.3.1 Allowable horizontal and vertical load capacities of loadout quays should be documented according to a recognized code or standard. 10.4.3.2 Calculations showing that the actual loads during loadout are not more than the allowable loads should be documented. Guidance note: If information about the quay is limited and it is therefore difficult to document its capacity by calculations, then an alternative approach where quay capacity is documented by historical records of previous loadouts over the quay may be considered. Detailed information about the previous loadout(s) will be needed for an adequate comparison. endofguidancenote 10.4.4 Soil 10.4.4.1 Strength and settlement calculations/evaluations for the ground in the loadout area should be documented. Guidance note: The risk of differential ground settlements which may influence the loads during loadout should be considered and minimised by means such as: — preloading of ground in loadout tracks — load spreading e.g. by concrete slabs or steel plates. endofguidancenote 10.4.4.2 Soil bearing capacity should normally be tested before construction or loadout of the object. Alternatively, relevant site investigation should be documented. 10.4.4.3 Geotechnical calculations and testing should be carried out according to a recognized standard, e.g. EN 1997 Eurocode 7, /67/. 10.4.4.4 For trailer transport, the soil strength requirements apply for the whole planned path/track plus at least 2 meters at each side. 10.4.4.5 If there is any doubt as to the soil capacity, then a loaded SPMT test drive should be done before the loadout. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 259 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.4.2.2 For skidded loadouts, analyses of the skidded object should consider the elasticity, alignment and asbuilt dimensions of the shore and vessel skidways. See also [10.3.6.2] GN3. 10.5 Systems and equipment 10.5.1 General 10.5.1.1 Systems and equipment to be used during loadout should comply with the requirements given in Sec.4. 10.5.2 Propulsion systems 10.5.2.1 Propulsion systems shall be able to break loose and push/pull the object to the final position on the transport vessel. Guidance note: Propulsion systems can for skidded loadouts be for instance wire and winch, hydraulic jacks or strand jacks. Trailer loadouts can be by selfpropelled trailers (SPMT) or trailers. Trailers can be propelled by a wire and winch system or by tractors/trucks. endofguidancenote 10.5.2.2 The propulsion system capacity for breakout shall be not less than the required breakout load (F1), see [10.3.5.1]. For objects that cannot be considered to be in a safe condition if the breakout system fails the capacity and redundancy requirements in Table 103 apply also to the breakout system. Guidance note: Adequate breakout capacity may be obtained by combining e.g. jacks with the continuous propulsion system. endofguidancenote 10.5.2.3 The propulsion system used to move the object shall satisfy requirements specified in Table 103. 10.5.2.4 Propulsion systems should act in a synchronised manner in the transfer direction. A minimum required loadout velocity shall be identified considering: — — — — Maximum allowable loadout duration Dynamic friction coefficient Length of the loadout track Conservatively estimated duration of repair work (if such work is accepted as back up), or documented installation time for back up equipment 10.5.2.5 The propulsion system shall be able to provide adequate braking capacity at any time. Required braking capacity shall be evaluated assessing conservatively the possible (combined) effects of: — Track slope, including maximum possible (accidental) inclinations of the loadout vessel — Low friction, e.g. by using (steel) wheels/rollers or surfaces with low friction — Elasticity in pull system, i.e. high elasticity (e.g. long winch wires) combined with temporary jamming could result in a “catapult effect”. 10.5.2.6 Backup propulsion system capacity should be able to compensate for the following conditions: a) Breakdown of one arbitrary selfcontained propulsion unit Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 260 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.4.4.6 For loadouts involving grounded vessel, the seabed should be evaluated with respect to topography, bearing capacity, settlement, etc. Unexpected increase in the skidding loads above the expected nominal value Guidance note: Backup capacity for accidental conditions of type a) may be achieved by: — Spare capacity in the main propulsion units — Separate backup propulsion units with sufficient capacity — Spare parts for the main propulsion units and an acceptable and proven repair/replacement time The backup capacity for conditions of type b) may be: — Spare capacity in the main propulsion units — Backup propulsion units Detailed requirements to be complied with are in Table 103. endofguidancenote 10.5.2.7 Any required modifications during the operation, e.g. removal of pull bars of the push/pull system layout should be proven feasible. Normally, layout modifications should be avoided with the object supported both at the quay and transport vessel. 10.5.2.8 A pullback system and a procedure for pulling the object back on shore shall be available for Load out Class 1. 10.5.2.9 A pullback system and procedure shall be available for Loadout classes 2 and 4 unless otherwise justified by risk assessment, see [10.2.3] and [2.4]. Guidance note: One acceptable option may be to substantiate that a retrieval system could be made operative to retrieve the object within the Operation Reference Period (TR). endofguidancenote Table 103 Propulsion system requirements Load out Class Intact System Capacity System Redundancy Requirement after breakdown of any one component 1 160% 130% capacity or repair possible within 30 minutes Required 2 140% 120% capacity or repair possible within 2 hours See [10.5.2.9] 3 120% Repair possible Not required 4 120% 100% capacity or repair possible within 6 hours See [10.5.2.9] 5 100% Repair possible Not required Pullback System Notes 1) Nominal (100%) system capacity is the load (F2) required to continue moving the object in the intact case, see [10.3.5.1]. 2) Breakdown of any one mechanical component, hydraulic system, control system or prime mover/power source shall be considered. After such a breakdown it shall either be possible to proceed with the loadout without repairing the component, or it shall be possible to repair the component within the timeframe indicated. 3) Where a pullback system is achieved by derigging and rerigging the pull on system, the time required to achieve this shall be estimated, clearly defined and duly considered. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 261 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used b) 10.5.3.1 Trailers (multi wheel bogies) should be used in accordance with the manufacturer's specifications. 10.5.3.2 The hydraulic suspension layout (linking) should be thoroughly considered. Normally a layout giving a three point support condition for the object, e.g. a statically determinate system, is recommended. However, it should be noted that a 3point support system is generally less stable than a 4point support system. 10.5.3.3 The trailer configuration should have adequate manoeuvring capabilities for the intended loadout (including site move) route. Guidance note: Where a structure cannot be loaded out directly onto a barge or vessel without turning: — Turning radii should be maximised where possible. — For small turning radii, lateral supports/restraints should be installed between the trailer and the structure/loadout support frame (LSF)/cribbage. — It should be demonstrated by the loadout contractor that the steering coordinates used in the trailers or SPMTs set up are correct, with the details of the set up coordinates contained in the procedures. — The cornering speed should be kept to a minimum to avoid the potential for loads due to lateral accelerations affecting the stability of the structure or SPMTs. Alternatively, a limiting turn speed should be specified and the stability assessed accounting for the associated loads. endofguidancenote 10.5.3.4 The trailer axle load calculations shall consider: — — — — — — — — Weight of object Weight of object supports on the trailers Weight of the trailers themselves Extreme positions of CoG Hydraulic suspension layout Maximum overturning effect caused by relevant “external” horizontal loads, see [10.5.3.7] Possible operating errors, see e.g. [10.5.3.8] Contingency situations, see [10.5.3.12]. Guidance note: It some cases it may be found beneficial to plan for possible rearrangement of the trailer after liftoff should the load distribution between the trailer groups not be as expected. endofguidancenote 10.5.3.5 The following shall be documented for the trailer axle loads calculated according to [10.5.3.4]: a) b) Maximum axle loading shall be shown to be within the trailer manufacturer's recommended limits. Trailer moment and shear force within the manufacturer’s specified limits or the global (spine) strength to be documented by calculations. 10.5.3.6 The support layout on each trailer shall ensure stability in both directions of the trailer. Guidance note: A trailer with a fully linked hydraulic suspension needs to be regarded more as a distributed load than as a support. The supports on such trailers should be checked for the vertical loading from the trailers combined with maximum “external” and “internal” horizontal loads acting on the trailers, see [10.5.3.7] and [10.5.3.8]. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 262 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.5.3 Trailers a) b) External effects, i.e. reaction loads from wind, inertia (e.g. acceleration during start and stop) and ground slope (including vessel heel/trim). Internal effects such as differential traction and steering inaccuracies. 10.5.3.8 Trailer inclinations due to improper coordination in operation of the hydraulic suspension system shall be considered. 10.5.3.9 The traction system, either the trailers are selfpropelled or pushed/pulled by trucks/winches, should fulfil the requirements in [10.5.2]. Ground surface conditions should be duly considered. 10.5.3.10 It should be documented that the trailer hydraulic suspension will work well within the stroke limits. Support heights, ground slopes/conditions and defined vessel levels/motions (see [10.6.5]) should be considered. Guidance note: Normally the planned operational stroke should be limited to 70% of the total theoretically available stroke. endofguidancenote 10.5.3.11 Contingency/repair procedures should be documented for at least: — — — — — — Hydraulic system failure Hose rupture/leakage Tyre puncture Steering problems Traction failure, see [10.5.2] Failure of power pack. 10.5.3.12 The trailer load calculations shall consider that any one axle does not take load due to e.g. tyre puncture. Guidance note: If repair is possible 10% overload could normally be accepted. For Class 1 loadout the loading should be within the stated maximum trailer loading. endofguidancenote 10.5.3.13 Link span bridge capacity shall be demonstrated by calculation, see [10.4.2.4]. 10.5.3.14 Special caution/consideration should be given to steel plates used as link span bridge between the quay and the vessel. The following should be considered when ensuring their suitability: — Vessel ballasting should be carried out to minimise the difference in level between the vessel deck and the quay. — The distance between the vessel and the quay should be minimised to avoid excessive deformation of the steel plates caused by the reactions from the trailers or SPMTs. — Effectively maintaining of the vessel position on the quay e.g. using mooring winches — Securing the plates to the vessel or quay to prevent their slippage during loadout. 10.5.3.15 Adequate global stability of the hydraulic system shall be ensured. Load cases A and B as specified in [10.5.3.16] and [10.5.3.17] shall be considered. For each of these load cases a minimum tipping angle shall be calculated. Unless otherwise justified, the minimum tipping angles for load case A shall be ≥ 7° and for load case B shall be ≥ 5°. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 263 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.5.3.7 The trailers should be properly supported to withstand horizontal loads. Such loads are caused by: The COG to be used in these calculations is the combined CoG for trailers and object. endofguidancenote 10.5.3.16 For load case A the following shall be considered: a) b) c) The most extreme possible horizontal/vertical location of the centre of gravity. When transiting on land: Any known inclination of the route increased by 2° to account for uncertainties in the route profile. When transiting on a vessel or bridge link: Any predicted inclination of the vessel and link under the design wind and ballast conditions, increased by 2° to account for uncertainties in the ballasting and wind speed. 10.5.3.17 For load case B the following shall be considered: a) b) c) d) e) The most extreme possible horizontal/vertical location of the centre of gravity. The characteristic horizontal load due wind and inertia, see [10.5.3.7] a). When transiting on land: Any known inclination of the route increased by 2° to account for uncertainties in the route profile. When transiting on a vessel or bridge link: The defined maximum acceptable level inaccuracies/ motions of the vessel and bridge link increased by 2° to account for uncertainties in the ballasting and environmental conditions Possible change of heel or trim due to hangup between the vessel and the quay, or dynamic response after release of hangup. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 264 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Any free surface liquids within the structure. Guidance note 1: Where the hydraulic support system allows for the trailer bed to be levelled horizontally to account (partly) for a known inclination, the effect of the known inclination can be reduced to account for this, provided this capability is demonstrated and contained in the procedures. This may be considered also for case A. endofguidancenote Guidance note 2: Example case: Total weight of object and trailer assembly: 300t Extreme CoG, vertical location: 10 m above ground level Extreme CoG, horizontal location: 2.5 m from tipping line Design wind load on the assembly: 11t at 12 m above ground level Known maximum route inclination: 3° Risk for hangup between vessel and quay: No Free surface effects: None Calculation for example case: Design slope: 3°+2° = 5° Load case A Virtual correction of COG: (10x300 x sin5)/300 = 0.87 m Horizontal distance from virtual COG to tipping line: 2.50.87= 1.63 m Minimum tipping angle: arctan(1.63/10) = 9.3° > 7°, i.e. OK Load case B Virtual correction of COG: (10x300 x sin5°))/300 = 0.87 m for slope 12x11/300 = 0.44 m for wind load 0.87 + 0.44 = 1.31 m in total Horizontal distance from virtual COG to tipping line: 2.5 1.31 = 1.19 Minimum tipping angle: arctan(1.19/10) = 6.8° > 5°, i.e. OK endofguidancenote 10.5.3.18 For virtual COG location as in load case A or B in [10.5.3.15], it shall be demonstrated that the structure itself is stable on the trailer bed. Where any object support reaction on the trailer gives uplift or a value of less than 25% of the static support reaction, a means of securing the object to resist the uplift shall be provided and calculations documented to show that the uplift restraint system is suitable. The restraint shall be designed to provide holddown equal to the calculated holddown force plus 25% of the static reaction. When there is no uplift, the remaining contact reaction can be taken into account. The strength of the restraints shall be assessed to LS1 (ASD/WSD method) or ULS (LRFD method). 10.5.3.19 Special attention shall be given to loadout operations where the CoG of the structure is very close to the centre of a group or grouping of trailers or SPMTs and the CoG has a low elevation. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 265 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used f) 10.5.3.21 Loadouts with high slender structures on narrow support bases, or offset from the vessel centreline, shall be subject to special attention in terms of the effects of uncertainties in ballasting and de ballasting. 10.5.4 Skidding equipment 10.5.4.1 Skid shoes, steel wheel bogies and steel rollers are in this subsection defined as skidding equipment. Any part of such equipment used for the horizontal movement of the object is defined as part of the propulsion system, see [10.5.2]. 10.5.4.2 Adequate strength and stability of skidding equipment should be documented. All possible combinations of vertical load, horizontal load and support reaction distribution should be verified. Sufficient articulation or flexibility of skid shoes shall be provided to compensate for level and slope changes when crossing from shore to vessel. Guidance note: Skidding equipment may be connected in order to reduce internal horizontal loads transferred through the object. The effect of possible rotation of skidding equipment should be considered. endofguidancenote 10.5.4.3 Skidway levelness tolerances, surface condition and side guides shall be adequate for the applied skidding equipment. Guidance note: — Sliding interfaces should be suitably lubricated unless this is not required by the supplier of any specialised equipment used for the loadout — Side (lateral) guides are normally provided along the full length of skidways. endofguidancenote 10.5.4.4 Where a vessel, because of tidal limitations, has to be turned within the loadout tidal window the design of the link beams shall be such that when the loaded unit is in its final position they are not trapped, i.e. they are free for removal. 10.5.4.5 For hydraulic suspension systems, see [10.5.3.2] and [10.5.3.10]. 10.5.4.6 The nominal computed load on winching systems shall not exceed the certified working load limit (WLL), after taking into account the requirements of [10.5.2] and [10.3.5] and after allowance for splices, bending, sheave losses, wear and corrosion. If no certified WLL is available, the nominal computed load shall not exceed one third of the breaking load of any part of the system. 10.5.4.7 The winching system should be capable of moving the structure from fully on the shore to fully on the vessel without rerigging Guidance note: If rerigging cannot be avoided, then this should be included in the operational procedures, and adequate resources should be available. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 266 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.5.3.20 For movements of the structure where slopes are expected and these cannot be compensated by stroking of the SPMTs, the stability of the group or grouping of trailers or SPMTs is to be checked accounting for the slope and the horizontal load from the structure on to the trailers or SPMTs. 10.5.5.1 The requirements for the ballasting systems are given in [4.3]. Guidance note 1: The loadout classes defined in Table 101 corresponds to the operation classes referred to in [4.3.2]. endofguidancenote Guidance note 2: Normally, vessel pumps should not be considered for the primary ballast system but may be taken into account in the backup provision endofguidancenote 10.5.6 Power supply 10.5.6.1 The power requirements in [4.3.2] shall apply for both the ballast pumps and the propulsion units during the loadout. Guidance note: Need for additional power supply to e.g. lighting and welding should be considered. endofguidancenote 10.5.7 Testing 10.5.7.1 See general requirements in [2.10] with respect to testing/commissioning, test procedures and test reporting. 10.5.7.2 Commissioning of the ballast pumps should at least include: — Capacity control — Final functional testing not more than two hours before start of the operation Guidance note: Pump capacity control should be carried out with equal or greater head and similar hose lengths as planned used during the operation. If tank ullages are used as capacity measuring means, the pumped volumes should be sufficient to obtain minimum 300 mm difference in ullages before and after pumping. endofguidancenote 10.5.7.3 For loadout operations of Class 1 a complete test run of the ballast system following the procedure for the loadout should be carried out. 10.5.7.4 The propulsion units including the spare units should be tested in both push and pull mode before the loadout operation in order to verify the estimated friction forces and functioning/capacities of the equipment. 10.5.7.5 If the considered backup necessitate replacement of equipment (e.g. pumps and propulsion units) then this should be included in the test program. 10.5.8 Mooring and fendering 10.5.8.1 General design requirements to mooring systems are given in Sec.17. Additional requirements applicable for loadouts are given below. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 267 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.5.5 Ballasting systems 10.5.8.3 Moorings for the duration of the actual loadout from quay to vessel should be designed for the limiting (design) weather conditions, see [2.6], in combination with the maximum loads from the pushing or pulling of the structure. 10.5.8.4 Mooring before and after loadout should normally be considered a weather unrestricted operation. Weather unrestricted moorings should be designed to the return periods given in Table 32 and in accordance with Sec.17. 10.5.8.5 Facilities for retensioning of mooring lines should be present and in standby during the loadout. Guidance note: Such facilities may be winches, jacks for tensioning, etc. endofguidancenote 10.5.8.6 The mooring system stiffness shall limit the movements of the loadout vessel(s) to those that are acceptable during the loadout in particular when the object is supported both on the quay and vessel. 10.5.8.7 Adequate strength, stiffness and layout of fenders should be documented. Guidance note: Fender design solutions should at least consider: — Requirement for a stiff mooring system during loadout, see [10.5.8.6] — Effect of extreme tide variations — Possible impact loads — The possibility that the vessel could “hang” on the fenders, see also [10.7.7.1]. For floating loadouts care should be taken to ensure that minimum friction exists between the vessel and quay face. Where the quay has a rendered face, steel plates should be installed in way of the vessel fendering system. The interface between the vessel and vessel fendering should be liberally lubricated with grease or other substitute which complies with local environmental rules. endofguidancenote 10.5.8.8 Friction between the vessel and support pad considered as a part of the mooring system in grounded loadouts, see [10.8.1] shall be properly documented. Guidance note: The calculations of friction effect should at least consider: — The documented lower bound design friction, see [5.6.9] — Minimum vertical load on the pad considering all relevant ballast, tide level and deck loading combinations — Any limitations due to interaction between mooring system and the friction effect endofguidancenote 10.6 Vessels 10.6.1 General 10.6.1.1 General requirements for vessel(s) are given in [2.11]. These requirements are applicable to any vessel involved in the loadout. 10.6.1.2 See section [10.9.3.2] for requirements to vessel documentation. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 268 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.5.8.2 For additional load cases to be considered, see [10.4.2.4]. 10.6.1.4 Approved tugs shall be available or in attendance as required, for vessel movements, removal of the vessel from the loadout berth in the event of deteriorating weather, or tug backup to the moorings, see also [10.7.2.4]. 10.6.1.5 For the loadout vessel the requirements in Sec.11 apply as relevant. 10.6.2 Class 10.6.2.1 Generally it is recommended that a vessel classed by a recognized classification society is used, see also [2.11]. Guidance note 1: If the vessel is not classed by a recognised classification society, then there should be particular emphasis on documentation of structural strength for the vessel, see also [2.11] and [10.6.3]. In such cases a detailed survey of the barge by the MWS company may be required. endofguidancenote Guidance note 2: If the barge will be grounded during loadout then it should be ensured that the classification society is informed and that any requirements to inspection of the vessel after grounding are adhered to. endofguidancenote 10.6.2.2 Vessels that are intended to be totally immersed during loadout should be classed for such use by a recognised classification society. 10.6.2.3 Where a loadout operation temporarily invalidate the class or load line certificate then a statement of acceptance from the classification society should be submitted, see [2.11.4.4]. 10.6.2.4 Any items temporarily removed for loadout shall be reinstated after the loadout is completed and the vessel shall be brought back into class before sailaway. Guidance note: This may apply if, for instance, holes have been cut in the deck for ballasting, if towing connections have been removed or, in some instances, after grounding on a pad. endofguidancenote 10.6.3 Structural strength 10.6.3.1 The loadout vessel global strength shall be documented for all possible ballast conditions, see also [2.11.3]. 10.6.3.2 The strength should be documented for all parts of the vessel exposed to local loads. Such parts are typically: a) b) c) d) e) f) g) Link beam/plate support area Skidway, including support area Deck plate for wheel loading Jacking system connection points Hull locally for horizontal loads from the quay Bottom structure, if grounded loadout Bollards/mooring brackets Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 269 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.6.1.3 For tugs involved in the loadout the applicable sections from [11.12] apply as relevant for the actual tug work tasks. 10.6.4.1 Sufficient stability afloat shall be ensured during loadout. Guidance note 1: Generally loadout should be performed with a minimum GM of 1 m at all stages. The accuracy requirements to ballasting will tend to increase with decreasing GM. endofguidancenote Guidance note 2: — Normally there is no requirement to document damage stability during loadout. However, it is recommended to consider if/ how incorrect operation of the ballast system may influence stability. — Due attention should be given to situations with small metacentric height where an offset centre of gravity may induce a heel or trim as the structure transfer is completed, i.e. when any transverse moment ceases to be restrained by the shore skidways or trailers. — Friction forces between the vessel and the quay, contributed to by the reaction from the pull on system and the moorings, should be given due attention. (Large friction forces may cause “hangup” by resisting the heel or trim until the pullon reaction is released, or the friction force is overcome, whereupon a sudden change of heel or trim may result.) — Due attention should be given to situations where a change of wind velocity may cause a significant change of heel or trim during the operation. endofguidancenote 10.6.4.2 For loadout operations the minimum “effective freeboard”, should for vessels be fmin=0.5 + 0.5Hmax where: fmin Hmax = Minimum effective freeboard in metres, see guidance note. = Maximum anticipated wave height in metres at the site during loadout. Guidance note: — The “effective freeboard” is defined as the minimum vertical distance from the still water surface to any opening, e.g. an open manhole or deck area where personnel access could be required. A maximum possible tide level and any possible vessel heel/ trim should be considered. Coamings/bundings at openings could be installed to increase the “effective freeboard”. — In order to use a vessel with less freeboard than defined by the load line certificate, approval from class is required. The freeboard should be sufficient to maintain the vessel’s waterplane area. — Procedures to monitor freeboard at all 4 quarters of the vessel should be in place; where this is not implemented fmin should be increased by 0.3 m. endofguidancenote 10.6.5 Loadout vessel draught and motions 10.6.5.1 Nominal values and allowable tolerances for the loadout vessel(s) level, trim and heel shall be clearly defined for all stages of the loadout. 10.6.5.2 It should be documented that the values defined according to [10.6.5.1] are adequate to prohibit unexpected effects or load effects. 10.6.5.3 Significant wave/swell induced motions of the loadout vessel are normally not acceptable during the operation, see [10.3.4.3]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 270 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.6.4 Stability afloat 10.6.6.1 A vessel (barge) handling procedure should normally be documented. The procedure should as a minimum describe: — — — — Berthing and if applicable relocation Vessel surveys e.g. onhire and offhire surveys, condition surveys Installation and inspection of moorings General watch keeping 10.6.6.2 A barge engineer familiar with operation and maintenance of the barge equipment should be present if any barge equipment is used (or considered as backup) during critical phases of the loadout. 10.6.6.3 Where relevant, precautions to avoid freezing in tanks and ballast systems shall be taken. Guidance note: Such arrangements may be heating devices (in pump rooms), additive antifreeze solution, or any other devices or actions serving the above purpose. endofguidancenote 10.7 Operational aspects 10.7.1 General 10.7.1.1 The general requirements for planning and execution of the operation in Sec.2 apply. Guidance note: The remaining paragraphs in [10.7] include some additional requirements and/or emphasise on requirements considered especially important for loadout operations. endofguidancenote 10.7.1.2 Manhole covers which are opened for ballast water transfer or other reasons shall be closed watertight as soon as practical after use. Any holes cut for ballasting purposes shall be closed as soon as practical, see also [10.6.2.3]. 10.7.2 Preparations 10.7.2.1 All structures and equipment necessary for the operation shall be correctly rigged and ready to be used. 10.7.2.2 Means (e.g. steel plates) and personnel (e.g. welders) for general repair work shall be available during the operations. 10.7.2.3 For operations or phases of operations that may be carried out in darkness sufficient lighting shall be arranged and be available during the entire operation. 10.7.2.4 Additional tugs that may be employed for critical tasks (e.g. as planned contingency measures) during the loadout operation should be nominated and comply with the requirements of section [11.12] and be available for inspection as required before the operation. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 271 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.6.6 Maintenance 10.7.3.1 Adequate minimum clearances, including clearances under water, for all phases of the operation shall be defined and properly documented by calculations and surveys before and during the operation. Guidance note: Welding/erection of “last minute” items should not be allowed without a proper recheck of the clearances. endofguidancenote 10.7.3.2 Sufficient underkeel clearance should be documented for vessel(s) during and after the loadout operation. Normally the clearance should not be less than 1.0 meters. Guidance note: If the vessel underkeel clearance is considered as critical, then the seabed should be inspected by divers or by other adequate survey method. Where there is a risk of debris, inspections should be done immediately before the vessel berthing. If confidence in the lowest predicted water levels and in the survey of the loadout area is high, then the minimum clearance requirement could be reduced to 0.5 m. endofguidancenote 10.7.3.3 The required land area and sea room shall be checked for obstacles. All obstacles that could cause damages and/or which may delay the operation shall be removed. 10.7.3.4 If relevant, adequate tug air draught shall be ensured. Guidance note: The nominal air draught should be minimum 0.5 metres. All positions, including needed access routes that may be required for the tug(s) should be considered. Possible emergency situations should be included in the considerations. endofguidancenote 10.7.4 Environmental effects 10.7.4.1 Effects caused by (unexpected) swell and tide could be of significant importance for load transfer operations and shall be duly considered. 10.7.5 Marine traffic 10.7.5.1 In areas with other marine traffic necessary precautions should be taken to avoid — possible collisions (e.g. with the object, involved vessel(s) or mooring lines) — significant wash from passing vessel(s) Guidance note: Port authority approval for the operation may be required. It may also be necessary to ask local harbour authorities to put restrictions on the marine traffic. endofguidancenote 10.7.6 Organisation and personnel 10.7.6.1 General requirements for organisation, personnel qualifications and communication are given in [2.8]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 272 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.7.3 Clearances Load transfer operations will often involve personnel that do not regularly participate in this type of operation. Personnel training and briefing are hence of great importance, see [2.8.3]. endofguidancenote 10.7.6.2 Load transfer operations may involve complicated equipment. Hence, equipment operators should have the required experience, (see [10.6.6.2] for barge engineers). 10.7.6.3 Proper working conditions for personnel shall be ensured throughout the load transfer operation. Guidance note: Load transfer operations may last for many hours or sometimes for several days and they may be carried out in areas with limited permanent facilities. Hence, the following may be important to consider: — Easy access to food, drinking water and toilets in order to allow for proper continuous work execution — Adequately sheltered/heated/cooled working location(s) for required paper/PC work during the operation — Safe access to all areas were work, including inspections, may be required. endofguidancenote 10.7.7 Loadout site 10.7.7.1 Due attention shall be paid to the possibility of the vessel “hanging” on the fenders or the quay structures, see [10.5.8.7] and [10.7.8.2]. 10.7.7.2 A level survey of the site area should be performed for loadouts with trailers to ensure that the level tolerances of the trailers will not be exceeded. 10.7.7.3 Planned trailer tracks should provide an adequate surface condition and the tracks should be marked on the ground and vessel. Guidance note: Before any loadout it should be ensured that: — pot holes are filled and compacted — debris and obstructions to the loadout path are identified and removed — the loadout path and at least 2 m either side of it is freshly graded endofguidancenote 10.7.7.4 The movement of the structure should not be stopped in areas with the potential for settlement due to e.g. consolidation or adverse weather. 10.7.8 Supports and skidways 10.7.8.1 Levels of supports (and, if applicable, skidways and temporary supports) and horizontal dimensions on the loadout vessel should be thoroughly checked to be within acceptable tolerances. 10.7.8.2 Tolerances on link beam movement shall be shown to be suitable for anticipated movements of the vessel during the operation. Guidance note: Design of link beam hinges should ensure that it is not possible for the link beams to get stuck when the last skid shoes/loadout frames are moved from link beams and onto the vessel, see also [10.7.7.1] and [10.5.8.7]. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 273 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 10.7.8.4 Suitable shims should be available on the loadout vessel for filling of gaps if required during set down. 10.7.8.5 The skidway surface condition shall be checked to be as assumed in the friction coefficient estimate. 10.7.9 Grillage and seafastening 10.7.9.1 The main requirements for the grillage and seafastening structures of the transported object are in [11.9]. 10.7.9.2 The set down procedure for the object should be documented and it should ensure that the grillage and seafastening design assumptions are fulfilled. 10.7.9.3 The seafastening should start immediately after final position of the object on the loadout (transport) vessel is confirmed. However, see [4.3.7.2]. 10.7.9.4 Before moving the vessel to another location at the same site for further seafastening, the object should be secured to the vessel/barge to withstand possible impact loads and/or any heel and trim (due to wind or onecompartment damage). This condition shall be checked with load and material factors for relevant failure mode(s) in LS1 (ASD/WSD method) or ULS (LRFD method). Guidance note: — Normally a horizontal characteristic acceleration of minimum 0.1g in any direction will be sufficient. — Friction may be considered in the calculations of necessary seafastening capacity, as described in [5.6.9]. The possibility of contaminants such as grease, water or sand (which may reduce friction between sliding surfaces) should then be assessed and duly considered. — It should be justified that impacts (e.g. between vessel and quay, ground or nearby vessels (in areas of high marine traffic density) will not cause displacements of the object that may jeopardize the integrity of the object vertical supports. — Classification society acceptance required for moving of the vessel if out of class. endofguidancenote 10.7.9.5 Final seafastening connections should be made with the vessel ballast condition as close as practical to the voyage condition. See [11.9.5] for towing section requirements. 10.7.10 Recording and monitoring 10.7.10.1 During the operation a detailed log should be prepared and kept, see [2.3.8]. 10.7.10.2 Monitoring shall be carried out according to [2.9]. 10.7.10.3 The following loadout parameters should, as applicable, be monitored and recorded before and during the operation: a) b) c) d) e) f) tide push/pull force straightness and levelness of skidding tracks inclination of link beam level and vertical deflections of the object horizontal position of the object Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 274 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.7.8.3 Nominal set down position and set down tolerances should be marked on the supports on the load out vessel. vessel draught and/or level vessel heel and trim water level in vessel tanks hydraulic pressure and stroke on any support/equalising jack, e.g. trailer hydraulic suspension. 10.7.10.4 The line and level of the skidways and skidshoes should be documented by dimensional control surveys and reports. The line and level should be within the tolerances defined for the loadout operation and skidway/skidshoe design. 10.7.10.5 Normally a remote reading sounding system should be used for tank water level control. A back up system but not necessarily remotely controlled (e.g. hand ullaging) should be provided. If access to any tank is obstructed, e.g. by seafastening supports, alternative access should be arranged. 10.7.10.6 For tidal loadouts, an easily readable tide gauge should be provided adjacent to the loadout quay in such a location that it will not be obscured during any stage of the loadout operation. Where the tide level is critical, the correct datum should be established. 10.7.10.7 It shall be possible to continuously monitor hydraulic pressures. 10.8 Special cases 10.8.1 Grounded loadouts 10.8.1.1 If the barge (or loadout vessel) is supported at the seabed during the load transfer phase then the operation is defined as a “grounded loadout”. 10.8.1.2 Seabed support pad(s) should be prepared considering: a) b) c) d) e) Any protruding elements (e.g. anodes and bilge keels) on the vessel bottom Soil bearing capacities, see also [10.4.4] Stability and global deflections of the vessel Vessel bottom local strength Required sliding resistance (friction) 10.8.1.3 Acceptable safety margins should be documented for all relevant load effects, see [10.4] and [10.6.3]. Guidance note: Maximum vessel bottom loading at the extreme low tide throughout the period should be considered. endofguidancenote 10.8.1.4 Where the margin against sliding is low mooring lines shall be maintained between the vessel and quayside when the vessel is grounded. 10.8.1.5 The plan area of the grounding pad with respect to the vessel keel shall be of sufficient extent to ensure stability of the edges of the grounding pad. Both geotechnical site investigation data and geotechnical calculations demonstrating the capacity of the grounding pad shall be documented. Guidance note: The grounding pad elevation should be defined based on the actual depth of the vessel and not the moulded vessel depth. endofguidancenote 10.8.1.6 Condition and level survey(s) of the support pad(s) shall be performed in due time before loadout. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 275 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used g) h) i) j) Guidance note: If a bar sweep survey is done, then it is recommended that this is supported by a diver’s inspection. endofguidancenote 10.8.1.8 The vessel should be positioned and ballasted onto the pad several tidal periods before the loadout to allow for consolidation and settlement. Pad loading to reflect the loadout loading condition(s) and vessel levels to be monitored during this period. Guidance note: Preloading in excess of the maximum loading during loadout may be used to reduce the required period for pad consolidation and settlement. endofguidancenote 10.8.1.9 A detailed procedure covering both positioning on the pads and the floatoff operation following the loadout shall be made. 10.8.1.10 Final skidway levels shall be measured and confirmed to be within tolerances compatible with assumptions used for structural analysis as in [10.3.6]. 10.8.1.11 Between loadout and sailaway, the vessel keel should be inspected, either by diver survey or by internal tank inspection. This is to ensure that no damage has occurred during the loadout. 10.8.2 Transverse vessel loadouts 10.8.2.1 Generally transverse loadouts are sensitive to variations in object weight and CoG as well as to inaccuracies (between theoretical and actual) moved distance, ballasting and tide levels. This shall be duly considered both in the ballast calculations and in the monitoring/control procedures. See also [10.3.2]. Guidance note: Ballasting calculations for transverse loadouts should be based on the weighed weight and CoG and include load combinations addressing weight and CoG contingencies. See also [10.3.2]. endofguidancenote 10.8.2.2 A small GM may be more critical than for an endon loadout as the heel may change significantly due to minor inaccuracies. Hence, it is recommended that the GM is as high as possible and that the moment to change the vessel heel by 0.1 m is computed (and shown in the operation manual) for all stages of the loadout. 10.8.2.3 As the vessel (accidental) heel can be significant, a braking system for the (skidded) object shall be provided. See [10.5.2.5]. 10.8.2.4 A risk assessment, see [10.2.2.5], should consider the effects of potential errors in ballasting, and of friction between the vessel and the quay. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 276 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.8.1.7 A diver or sidescan survey should be carried out shortly before the vessel is positioned. This to ensure that there is no debris in the area that can damage the vessels bottom plating. Friction between the side of the vessel and the quay may be more critical than for an endon loadout. Snagging or hangup could potentially lead to ballasting getting out of synchronisation with the move of the structure. Release of snagging load could potentially lead to instability and failures. Where a winch or strand jack system is used to pull the structure onto the vessel, the effects of the pulling force on the friction on the fenders should be duly considered. For sliding surfaces between the vessel and the quay, particular attention should be paid to lubrication and use of low friction or rolling fenders. endofguidancenote 10.8.3 Loadin 10.8.3.1 Requirements to loadout operations are generally applicable for loadin operations as well. 10.8.3.2 Special attention should be given to selecting the optimal tide phase for starting the loadin operation. Guidance note: Normally loadins are scheduled to be started on a falling tide. endofguidancenote 10.8.4 Vessel to vessel load transfer 10.8.4.1 A vessel to vessel load transfer operation is defined as the activities necessary to transfer an object between vessel(s) doing mainly a horizontal movement of the object. 10.8.4.2 Requirements to loadout operations are generally applicable for vessel to vessel load transfer operations as well. 10.8.4.3 Vessel to vessel load transfer operations could be complex involving more than two vessel(s), and different support conditions on one or more of the vessel(s). Due attention should be paid to this fact during planning, design and execution of the operation. Guidance note: For these operations measurements of the vessel(s) draught, trim and heel may not be sufficient to control the load distribution. endofguidancenote 10.8.4.4 Tide effects can be neglected for operations involving only floating vessel(s) if sufficient bottom clearance is ensured. Hence, the operation could be defined as loadout class 3 or 4. 10.8.5 Site moves 10.8.5.1 The entire route for the site move shall be clearly defined. 10.8.5.2 Any variation in ground slope along the route shall be duly considered. 10.8.5.3 It shall be ensured that condition and capacity of the ground is satisfactory along the entire route, see [10.4]. 10.8.5.4 The route should be marked up and barriered off. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 277 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 10.8.5.6 If the site move involves crossing of a road with traffic or a move on a road with traffic, then this shall be duly planned for. Guidance note: Relevant authorities should be informed and any required approvals should be in place. endofguidancenote 10.9 Information required 10.9.1 General 10.9.1.1 General requirements to documentation are given in [2.3]. 10.9.2 Design documentation 10.9.2.1 The following design documentation is normally required: — Analyses/calculations/certificates/statements adequately documenting the necessary strength and capacity of all involved equipment and structures, see also [10.9.2.3] — Documentation of civil elements (soil, quay, bollards, etc.) by e.g. engineering calculations, approved drawings or certificates, see also [10.9.2.3] and [10.9.5] — Vessel (barge) stability and (local) strength verifications, see also [10.9.3.2] — Ballast calculations covering the planned operation as well as contingency situations, see also [10.9.4] and [4.3.8.4]. — Weight report(s). 10.9.2.2 Where parameters are monitored, the expected monitoring results should be documented together with the acceptable tolerances and the contingency measure to be applied should the acceptable tolerances be exceeded. 10.9.2.3 Structural analysis report for the object to be loaded out should normally include at least: — — — — — — — Structural drawings, also of any additional loadout steelwork Description of analyses programs used Description of the structural model Description of boundary conditions Description of load cases Unity checks for members and joints Local analyses for support points, padeyes and winch connection points. 10.9.3 Equipment, fabrication and vessel(s) 10.9.3.1 Acceptable fabrication and acceptable condition of equipment/vessel(s) involved in the loadout operation shall be documented by: — Certificates — Test, survey and NDT reports — Classification documents. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 278 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.8.5.5 It shall be ensured that clearances are sufficient to all parts of the transported object along the entire route. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10.9.3.2 For the loadout vessel: — — — — — — — — — — — — General arrangement drawing Hull structural drawings, including drawings of any internal reinforcements Limitations for evenly distributed load and point loads on barge deck Limitations on skidway loadings, if applicable Equipment data and drawings Hydrostatic data (either in curves or tables) Tank plan, including ullage (or sounding) tables Instructions for air pressurised barge tanks, if used Guidelines, if applicable, for grounded barge condition Specification and capacity of all mooring bollards Details of any additional steelwork such as grillages or winch attachments Details of vessel pumping system, see also [10.9.3.6]. 10.9.3.3 For tug(s) supporting the loadout a general specification should be submitted and include information about the tugs bollard pull and towing equipment. 10.9.3.4 For trailered loadouts: — — — — — — — — — Trailer specification and configuration Details of any additional supporting steelwork, including link span bridges and attachments Allowable and actual axle loadings Allowable and actual spine bending moments and shear forces Schematic of hydraulic interconnections Statement of hydraulic stability of trailer or SPMT system, with supporting calculations For SPMTs, details of propulsion axles and justification of propulsion capacity Details of set up coordinates for the trailer or SPMT grouping Specifications of tractors if used. 10.9.3.5 For skidded loadouts: — — — — — Jack/winch specification Layout of pullon system Layout of pullback and braking systems Details of power sources and backup equipment Calculations showing friction coefficient, allowances for bending and sheaves, loads on attachment points and safety factors — Reactions induced between vessel and quay. 10.9.3.6 For the pumping system: — Specification and layout of all pumps, including backup pumps — Pipe schematic and details of manifolds and valves where applicable — Pump performance curves. 10.9.3.7 For the loadout vessels mooring: a) b) c) d) A statement showing capacity of all mooring bollards, winches and other attachments used. Mooring arrangement drawings for the loadout operation and for the postloadout condition. Mooring design calculations, see [10.5.8]. Certificates for all mooring arrangement component, e.g. wires, ropes, shackles, fittings and chains (issued or endorsed by a body approved by a recognized classification society or other certification body accepted by the MWS Company). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 279 Specification for winches, details and design of winch foundation/securing arrangements. Fender arrangement, including lubrication arrangements if applicable. 10.9.3.8 If the object is weighed, then weighing results and load cell calibration certificates shall be submitted. 10.9.4 Operation manual 10.9.4.1 An operation manual shall be prepared, see [2.3.7] for general requirements to operation manuals. 10.9.4.2 The items listed below will normally be essential for successful execution of a loadout and shall be emphasized in the manual: a) b) c) d) A detailed operational communication chart (and/or description) showing clearly the information flow throughout the operation. Monitoring procedures describing equipment setup, recording, expected readings (including acceptable deviations) and reporting routines during the operation. Detailed ballast procedures, see also [4.3.9.5] and [10.9.4.4]. Operation bar chart showing time and duration of all critical activities. Guidance note: The operation barchart should include the following as applicable: — Mobilisation of equipment — Testing of pumps and winches — Testing of pullon and pullback systems — Barge movements — Initial ballasting — Structure movements — Loadout operation — Trailer removal — Seafastening — Remooring — Decision points. endofguidancenote 10.9.4.3 The manual should highlight metocean conditions/directions to which the operation is sensitive. 10.9.4.4 The manual should include ballasting information as follows: 1) 2) Planned date, time and duration of the loadout, with alternative dates, tidal limitations and windows Ballast calculations for each stage showing: — — — — — — — — Time Tidal level Structure position Weight on quay, link beam and vessel Ballast distribution Vessel draught, trim and heel Pumps in use and pump rates required Moment required to change heel and trim Standard — DNVGLSTN001. 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Requires a valid subscription to be used e) f) Stages to be considered should minimum include: — — — — 4) Start condition with structure entirely on shore A suitable number of intermediate steps 100% of weight on vessel Any subsequent movements on vessel up to the final position Stages requiring movement or reconnection of pumps should be clearly defined. 10.9.4.5 The manual should include contingency plans for all eventualities identified during risk assessment process, including as appropriate: — — — — — — — — — — — — Pump failure Mains power supply failure Jackwinch failure Trailer/skidshoe power pack failure Trailer/skidshoe hydraulics failure Trailer tyre failure Tractor failure Failure of any computerised control or monitoring system Mooring system failure Structural failure Deteriorating weather Quay failure. 10.9.5 Site 10.9.5.1 For the loadout location: — Site plan, showing loadout quay, position of object, route to quay edge, position of mooring bollards and winches used, reinforced areas etc. — Section through quay wall — Drawing showing heights above datum of quay approaches, object support points, vessel, link beams, pad (if applicable) and water levels (the differential between civil and bathymetric datums should be clearly shown) — Statement of maximum allowable loadings on quay, quay approaches, wall, grounding pads and foundations — Specification of capacity for all mooring bollards and other attachment points used — Bathymetric survey report of area adjacent to the quay and passage to deep water — Bathymetric survey of pad (for grounded loadouts) — Structural drawings of skidways and link beams, with statement of structural capacity, construction (material and NDT reports) and supporting calculations — Method of fendering between vessel and quay, showing any sliding or rolling surfaces and their lubrication. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 281 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 3) 11.1 Introduction 11.1.1 General 11.1.1.1 This section covers MWS requirements for sea voyages which include: a) b) c) d) dry towages of objects on barges transport of objects on selfpropelled vessels wet towages of objects floating on their own buoyancy, including floating or submerged pipes or similar. Location moves of jackups (approval of the locations is covered in DNVGLSTN002, /39/). 11.1.1.2 It does not normally cover “standard” or “routine” cargoes such as bulk liquids, bulk solids, refrigerated cargoes, containers or vehicles (on ferries) or supply vessels unless they are subject to marine warranty. 11.1.2 Scope 11.1.2.1 This section covers the requirements for: — — — — — — — — — — — Motion response Design and strength Floating stability Transport and tug selection Towing equipment Voyage planning Pumping and anchoring equipment Manning Multiple tows Additional requirements for specific asset types Information required for MWS approval. 11.1.3 Revision history 11.1.3.1 The following changes have been made to this section: — — — — — — — — — — — General: Editorial changes to improve clarity. [11.6]: Section modified for both DNV GL and DNV ship motions. [11.7.1.2]: New clause to clarify checks for green water loads. [11.7.2.1]: New clause including new guidance note for using LRFD approach with ASD/WSD default motions added. Table 114: Table modified to allow linear interpolation for case 14. [11.7.3.1]: New clause stating load and resistance factors to be applied. [11.7.3.2]: Clause modified to clarify requirements for selfweight. [11.7.3.2]: New guidance note for using ASD/WSD approach with LRFD default motions added. [11.9.2.4]: Clause modified to clarify requirement related to effect of vibrations on friction including new guidance note. [11.9.2.8]: New clause for minimum seafastening for sheltered waters included. [11.9.5.15]: Guidance note modified for clarity. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 282 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used SECTION 11 SEA VOYAGES — — — — — — — — — — — — — — — — — — — — — [11.9.5]: Section modified to update requirements for lashing seafastenings. [11.9.5.33]: Clause modified to clarify acceptable conditions for welding. [11.9.9.6]: Clause modified to include requirement to provide safe access. [11.10.1.1]: Clause modified to clarify calculations related to stability. [11.10.1.2]: New clause to clarify calculation of metacentric height. [11.10.1.5]: New clause related to air cushion. [11.10.1.6]: New clause related to loose solid ballast. [11.10.4.3]: Clause modified to include text related to air escape that was previously in [6.2.1]. [11.12.1.7]: Clause modified to account for high density traffic zones. [11.12.2]: Section modified for bollard pull requirements. [11.12.2.14]: New clause for short towlines. [11.12.2.15]: New clause for shallow water included. [11.12.11.2]: Clause modified to clarify burning and weld gear requirements. [11.13.4]: Section modified as previous [11.13.4.4] now [11.13.4.1]. Acroymns used updated for consistency with the rest of the document. [11.13.6]: Section modified to clarify the use of Kenter shackles. [11.13.13.1]: Clause modified to include text related to retrival of towing gear. [11.13.14]: Section modified to make inspection terminology consistent with lifting section. [11.13.14.3]: Clause modified to include text related to equipment in the splash zone. [11.13.14.4]: Clause modified including new guidance note. [11.13.14.6]: New clause to clarify nonsocket terminations. [11.13.14.7]: Clause modified to change requirement for resocketing to 2.5 (two and a half) years. [11.14.1.2] Clause modified as references updated (definition remains the same) and new guidance note included. [11.17.4.1]: Clause modified to change GMDSS radio to DSC VHF radio. [11.17.5.1]: Clause modified to include requirement to sound signals. [11.20.3.3]: Clause modified to make acroymns used consistent with the rest of the document. [11.21]: New section on specifics for inland waterways. [11.26.2.7]: Clause modified to cover all potential situations. [11.26.2.11]: Clause modified to remove requirement for qualification testing [11.26.3.1]: Clause modified to clarify monitoring requirements. Table 1120: Table modified to make friction coefficients consistent with elsewhere in document. [11.26.3.13]: Clause modified for consistency with elsewhere in document. [11.26.4.2]: Clause modified to ensure tow route is clear. [11.26.4.4]: New guidance note to clarify loss of buoyancy requirement. [11.26.8.2]: Clause modified to clarify survey package requirements. [11.27.2]: Section renamed. 11.1.3.2 The changes made to this section for the June 2016 edition are shown in App.A. 11.2 Towage or transport design/approval flow chart 11.2.1 The flow chart in Figure 111 shows the steps in the approval process and references the sections in this standard. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 283 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — — — — — — — — — — — — — — This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 111 Voyage design/approval flowchart 11.3 Motion response 11.3.1 General 11.3.1.1 Design motions shall be derived by means of motion response analyses, from model tank testing, or by using the default equivalent motion values shown in [11.4]. 11.3.1.2 See [3.2] for design sea states. The range of periods associated with the extreme sea state shall be in accordance with [3.4.11]. 11.3.2 Vessel heading and speed 11.3.2.1 The analyses shall be carried out for zero vessel speed for a range of headings. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 284 Normally head, bow quartering, beam, stern quartering and stern seas should be considered. endofguidancenote 11.3.2.2 Additionally, the analysis should be carried out for nonbeam sea cases for the maximum service speed of the vessel or the maximum speed that can be maintained in the design sea state. Where this cannot be handled directly by the software, a zero speed analysis can be carried out with the range of probable peak wave periods, Tp, adjusted for the speed of the vessel as follows: where: Tp, lower Tp, upper VSHIP θ = Lower Tp for zero forward speed = Upper Tp for zero forward speed = ship speed in m/s = ship’s heading in degrees (0° = head seas, 180° = stern seas). 11.3.3 Effects of low GM and waterplane area 11.3.3.1 Any effects of low GM giving wind heeling should be considered 11.3.3.2 Where there are large changes in waterplane area that can cause heaveinduced roll the effects shall be quantified by analysis and/or model tests. 11.3.4 Effects of free surfaces 11.3.4.1 For motions analyses, free surface corrections to reduce metacentric height (GM) and hence to increase natural roll period should not be considered. The effect of any reduction in GM shall, however, be considered in intact and damage stability calculations. 11.3.4.2 RAO’s for vessels with roll reduction tanks (for example) are permissible if this is the actual loading condition and the roll damping effects are documented (say by model tests) 11.3.5 Effects of cargo immersion 11.3.5.1 The effect of cargo immersion on the motion response should be considered. Guidance note: Cargo immersion increases the GM and damping. The increase in GM reduces the natural roll period. endofguidancenote 11.3.6 Motion response computer programs 11.3.6.1 Motion response programs and their application are discussed in [5.6.12.1] 6) to 9). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 285 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.3.7.1 Model tests can be used to derive design motions, provided the tests pass the usual review of overall integrity, see [5.4.2]. Generally, for voyage analyses, the model test results should present the standard deviation of the relevant responses. The standard deviation of the responses should then be multiplied by , where N is the number of zeroupcrossings, to obtain the most probable maximum extreme (MPME) in 3 hours, which is required for design. This applies to Gaussian responses, however where the response is significantly nonGaussian then alternative methods should be used. Guidance note: The individual measured maxima from model tests should generally not be used in design as these vary between different realisations of the same sea conditions, and are therefore unreliable for use as design values. However, the maxima from a series of tests can be analysed statistically to determine a design value. The number of tests in the series should be sufficient to achieve stable results. Most wave frequency motion responses can be considered as Gaussian responses. endofguidancenote 11.3.7.2 Maximum values of global loads, motions or accelerations from model test results can be used provided ten similar realisations, or greater, are carried out to ensure that variations between individual tests are accounted for. The mean and standard deviations of the maxima should be calculated. The design value should be the mean plus two standard deviations. 11.3.7.3 Scale effects should also be accounted for by increasing the design values by a further 10% or a mutually agreed value. 11.4 Default motion criteria – general 11.4.1 If neither a motions study nor model tests are performed, then for standard configurations and subject to satisfactory marine procedures, default motion criteria given in [11.5] to [11.7] may be acceptable. 11.4.2 When criteria in [11.5] or [11.6] are used the criteria adopted shall be applicable to the actual case in question. The associated loading and strength calculations shall also be used and not those in [5.6] and [11.9.1]. 11.5 Default motion criteria – IMO 11.5.1 For smaller cargoes, IMO Code of Safe Practice for Cargo Stowage and Securing, /87/, may be acceptable Guidance note: Smaller cargoes are typically under 100 tonnes weight. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 286 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.3.7 Results of model tests 11.6.1 For ships the default motion/acceleration criteria from classification society rules may be acceptable e.g. DNVGLRUSHIP Pt.3 Ch.4 Sec.3, /35/, and DNV Rules for Classification of Ships, /15/, Pt.3 Ch.1 Sec.4, B600, B700 and B800. 11.6.2 Where accelerations from DNVGLRUSHIP Pt.3 Ch.4 Sec.3, /35/, are used then the following should be considered: — The assumptions in DNVGLRUSHIP Pt.3 Ch.1 Sec.2 [3.2], /35/, shall apply. — The heavy object accelerations consider the “normal” behaviour of the vessel captain, i.e. extreme weather conditions are avoided if possible and any extreme vessel motions are reduced by adequate vessel manoeuvring. — The vessel GM influences the transverse accelerations significantly and it should be ensured that it is within the analysed value throughout the transport. As this can be difficult to ensure, it is recommended that a conservative value is applied and that GM < B/13 is normally not considered. — Likewise, if not known, the Cb factor shall be chosen conservatively. — DNVGLRUSHIP Pt.3 Ch.4 Sec.3 [3.3] (Envelope Accelerations) of /35/ shall apply and not DNVGLRU SHIP Pt.3 Ch.4 Sec.3 [3.2] (Accelerations for dynamic load cases). 11.6.3 If the cargo is to be carried on a vessel classed to DNV Rules for the Classification of Ships, /15/, then Pt.3 Ch.1 Sec.4 may be used. The following should be considered: — The factor for active roll damping should not be used. — The heavy object accelerations consider the “normal” behaviour of the vessel captain, i.e. extreme weather conditions are avoided if possible and any extreme vessel motions are reduced by adequate vessel manoeuvring. — The vessel GM influences the transverse accelerations significantly and it should be ensured that it is within the applied value throughout the transport. As it may be difficult to ensure this, it is recommended that a conservative value is applied and that a GM < B/13 is normally not considered. Likewise, if not known, the Cb factor shall be chosen conservatively. — The referenced part of the DNV ship rules that states the simplified accelerations are valid only for ships with a length L > 100 m. For ships with length greater than or equal to 100 m it is normally acceptable to multiply the accelerations from the DNV Rules (al, at, av, apz and arz) by the values shown in [11.6.4] below. For ships with length of 50 m or less a value of 1.0 shall be assumed for all TPOP. For ships with length between 50 m and 100 m, linear interpolation of the 50 m and 100 m values may be used. 11.6.4 The accelerations obtained from both DNV Rules (al, at, av, apz and arz) and DNV GL Rules (ax‐env, ay‐env 8 and az‐env) for the Classification of Ships are based on loads at the 10 probability level, and are therefore conservative for marine operations. Reduced accelerations may be applied to represent the maximum expected accelerations for the actual operation. The reduction factors given in Table 111 may be used: Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 287 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.6 Default motion criteria – ships Duration in days (TPOP) Worldwide 1) Harsh conditions 2) TPOP ≤ 7 7 < TPOP ≤ 30 30 < TPOP ≤ 180 180 < TPOP 0.67 0.67 0.80 1.00 0.67 0.80 0.90 1.00 Notes: 1) Where a voyage passes through area(s) of harsh conditions for a part of the voyage, then the time spent in the harsh conditions area(s) shall be addressed separately from the rest of the voyage which may be treated as worldwide. 2) Voyage entirely in an area with harsh conditions; such areas include the North Atlantic, Norwegian Continental Shelf and Northern North Sea outside the summer season. For transports that can seek shelter in the case of forecasted extreme weather conditions and will do so according to the operation procedure and within the reliable forcast period, TPOP ≤ 7 days may be applied. 11.6.5 For both ASD/WSD and LRFD, loads due to these accelerations (which may be reduced according to Table 111), shall be combined as shown in Table 112 or Table 113, as applicable: Table 112 Load cases for accelerations based on DNV ship rules ax ay Head sea 1 (mainly pitch) al 0 Head sea 2 (mainly pitch) al 0 Beam sea 1 (mainly roll) 0 at Beam sea 2 (mainly roll) 0 at Oblique/quartering 1 0.6al 0.6at Oblique/quartering 2 0.6al 0.6at Load case az Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 288 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 111 Reduction factors as a function of voyage duration This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 113 Load cases for accelerations based on DNV GL ship rules ax ay Head sea 1 (mainly pitch) ax‐env 0 g+ az‐env‐pitch Head sea 2 (mainly pitch) ax‐env 0 g az‐env‐pitch Beam sea 1 (mainly roll) 0 ay‐env g+ az‐env‐roll Beam sea 2 (mainly roll) 0 ay‐env g az‐env‐roll Oblique/quartering 1 0.6ax‐env 0.6ay‐env g+ az‐env Oblique/quartering 2 0.6ax‐env 0.6ay‐env g az‐env Load case az Where: az‐env is the envelope vertical acceleration in m/s2, at any position: Where: apitch‐z = apitch(1.08x – 0.45L) aroll‐z = aroll y All as defined in the DNV GL ship rules. az‐env‐pitch is the envelope vertical acceleration in head seas, in m/s2, at any position: azenvroll is the envelope vertical acceleration in beam seas, in m/s2, at any position: 11.6.6 The strength assessment (of all items, including steel structure, welds, bolted connections and lashings) shall be as follows: — WSD Method: The loads due to the combinations given in [11.6.5] shall be assessed as an LS1A or LS2A condition (see [5.9.7] and Table 57 to Table 59 therein). — LRFD Method: The loads due to the combinations given in [11.6.5] shall be taken as characteristic loads i.e. assessed using the normal load factor(s) applied to the environmental accelerations and the gravity loading and the normal resistance factors. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 289 11.7.1 Alternative design methods 11.7.1.1 Where the ASD/WSD approach is used for structural checks the values in [11.7.2] apply. For LRFD the criteria in [11.7.3] apply. 11.7.1.2 Where green water loads are expected these shall be added to the loads due to the motions in [11.7.2] and [11.7.3]. 11.7.2 ASD/WSD default motion criteria 11.7.2.1 LS2 checks may be used for the default motion criteria in Table 114 subject to the requirements of [11.7.2.2]. Guidance note: LRFD checks in accordance with [5.9] may also be acceptable if the loads resulting from the motions in Table 114 are considered as characteristic loads and appropriate ULS load factors are applied. The requirements of [11.7.2.2] still apply. endofguidancenote 11.7.2.2 The default motion criteria shown in Table 114 shall only be applied in accordance with the following: 1) 2) 3) 4) 5) Vessels to have typical geometry for their type. For example, vessels with high freeboard are excluded because they will not experience deckedge immersion, and consequent damping. The cargovessel interface shall have friction coefficients no less than those of typical of unlubricated steelsteel interfaces, however see [11.9.3.1]. Roll and pitch axes shall be assumed to pass through the centre of floatation. Gravity and heave shall be assumed to be parallel to the global vertical axis, see [5.6.12.1] 8). Phasing shall be assumed to combine, as separate load cases, the most severe combinations of — roll +/ heave — pitch +/ heave. 6) For Cases 7 and 8, the departure shall be limited to a maximum of Beaufort Force 5, with an improving forecast for the following 48 hours. The voyage duration including contingencies, should not be greater than 24 hours. 7) For Cases 9 and 10, the criteria stated is given as general guidance for short duration voyages as there are too many variables associated with weather routeing. The actual criteria should be agreed with the MWS company, taking into account the nature of the vessel or barge and cargo, the voyage route, the weather conditions which can be encountered, the shelter available and the weather forecasting services to be utilised. 8) For Case 11, the design loading in each direction shall be taken as the most onerous due to: — a 0.1g static load parallel to the deck, or — the static inclination caused by the design wind, or — the most severe inclination in the onecompartment damage condition. 9) The additional heel or trim caused by the design wind (with a default value of 52 m/sec or 100 knots) should be considered. For most voyages, it is permissible to omit the effects of direct wind load when computing the forces on the cargo (see [5.6.15] and [5.6.16]). If the total effect of the wind on the cargo due to direct loading and wind heel are more than 10% of the loads from the default motion criteria, then they shall be added. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 290 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.7 Default motion criteria – specific cases Table 114 Default motion criteria (ASD/WSD approach) Nature of Voyage Weather unrestricted (these values to be used unless cases 7 to 15 apply) Case 1) LOA (m) B (m) L/B 1) Block Coeff 1 > 140 & > 30 n/a < 0.9 2 > 76 & > 23 n/a Any ≤ 76 or ≤ 23 ≥2.5 3 4 5 6 ≤ 76 or ≤ 23 < 2.5 < 0.9 2) Roll Pitch 10 20° 10° 0.2 g 10 20° 12.5° 0.2 g 15° 0.2 g 2) ≥0.9 < 0.9 Full cycle period (secs) 10 2) ≥0.9 10 Single amplitude 30° 25° 30° 30° 25° 25° Heave 0.2 g Weather restricted operations in non benign areas for a duration <24 hours (see [11.7.2.2] 6). For L/B < 1.4 use unrestricted case. 7 Any ≥2.5 Any 10 10° 5° 0.1 g 8 Any < 2.5 ≥1.4 Any 10 10° 10° 0.1 g Weather restricted operations in benign areas, as defined in [3.6], (see [11.7.2.2] 7). For L/B < 1.4 use unrestricted case. 9 Any ≥2.5 Any 10 5° 2.5° 0.1 g 10 Any < 2.5 ≥1.4 Any 10 5° 5° 0.1 g Inland and sheltered water voyages (see [11.7.2.2] 8)]). For L/B < 1.4 use unrestricted case. 11 Any ≥1.4 Any Static Independent leg jackups, weather unrestricted tow on own hull. For L/B ≥ 1.4 use unrestricted Cases 1 to 6 12 n/a > 23 < 1.4 n/a 10 20° 20° 0.0 Independent leg jackups, 24hour or location move. For L/B ≥ 1.4 use Case 7 or 8 as applicable 13 n/a > 23 < 1.4 n/a 10 10° 10° 0.0 Mattype jackups, weather unrestricted tow on own hull. For L/B ≥ 2.5 the pitch angle can be reduced 3) to 8° 14 n/a > 23 < 1.4 n/a 13 16° 16° 0.0 Mattype jackups, 24hour or location move. 15 n/a > 23 n/a n/a 13 8° 8° 0.0 Equivalent to 0.1 g in both directions 0.0 Notes: 1) B = maximum moulded waterline breadth, L = waterline length. n/a = not applicable 2) Block coefficient = 0.9 is the cutoff between bargeshaped hulls (>0.9) and shipshaped hulls; see [11.6] for alternative criteria for shipshaped hulls. 3) Linear interpolation may be used between 16° at L/B = 1.4 and 8° at L/B = 2.5. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 291 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 10) Where default motion criteria are used the effects of ballasting to counteract wind heel shall be ignored. 11.7.3.1 Loads due to the accelerations given in this section shall be checked using the load and resistance factors given in [5.9.8]. 11.7.3.2 The characteristic accelerations given in Table 115 to Table 117 can normally be applied to a standard “North Sea Barge” (300’ × 90’ × 20’) and bigger barges for the wave heights shown (either design values or OPLIM for weather restricted tows). The transverse/longitudinal accelerations include the gravitational component due to roll/pitch angle. Guidance note: ASD/WSD checks in accordance with [5.9] may also be acceptable if loads due to the accelerations given in Table 115 to Table 117 are considered as design loads and the LS1 load and permissible usage factors in [5.9] are applied. endofguidancenote 11.7.3.3 If the effect of rotational inertia is negligible, the accelerations can be calculated at the CoG of the cargo. If not, they should be calculated at carefully selected “mass locations” on the cargo, in order to include the effect of rotation. 11.7.3.4 If accelerations corresponding to an OPLIM are used, an appropriate OPWF shall be defined for the planned tow duration and procedure. 11.7.3.5 Table 115 can also be used for smaller barges with B > 20 m and L > 50 m for most normal cargoes and configurations. However for unusual towages it would be prudent to check with analysis or model testing. 11.7.3.6 For barges smaller than a “North Sea Barge”, the limiting wave heights in Table 116 and Table 117 shall be reduced by multiplying them by the factor which is the lesser of: L/LNSB or B/BNSB using the same units (feet or metres) where: L is the length of the barge and LNSB is 300’ (91.4 m) B is the breadth of the barge and BNSB is 90’ (27.4 m) 11.7.3.7 Alternatively, the limiting wave heights (6 m and 4 m) can be used, if the accelerations from Table 116 and Table 117 are divided by the same factor 11.7.3.8 All 3 cases (roll/quartering/pitch) in Table 115 to Table 117 should be considered. In each case, all possible combinations of directions of the indicated ax, ay and az accelerations shall be taken into account. Wind force should be added. However it can be acceptable to omit the quartering case based on engineering judgement if agreed with the MWS company. At least the seafastening forces and maximum vertical support reaction should be evaluated. 11.7.3.9 Gravity shall be assumed to be normal to the vessel’s deck. 11.7.3.10 The following key applies to Table 115 to Table 117: x y = distance from barge mid ship d = distance used for calculating az in quartering sea, z ay = height above waterline. = distance from barge centreline = transverse acceleration parallel with barge deck Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 292 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.7.3 LRFD default motion criteria This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used ax az = longitudinal acceleration parallel with barge deck = acceleration normal to the barge deck. Table 115 Weather unrestricted criteria worldwide (LRFD approach) Acceleration/wind force Roll Case Quartering Pitch Case 0.50 g 0.40 g 0 0.017 g/m 0.013 g/m 0 ax at waterline (wl) 0 0.15 g 0.25 g ax incr. each metre (z) above waterline 0 0.005 g/m 0.007 g/m 0.20 g 0.15 g 0.10 g ay at waterline ay increase for each metre (z) above waterline az at centre (C) barge az incr. each metre (y, d or x respectively) from C Wind pressure 0.017 g/m 0.012 g/m 2 2 1.0 kN/m 1.0 kN/m 0.007 g/m 1.0 kN/m 2 Table 116 Criteria for Hs ≤ 6 m for larger barges (LRFD approach) Acceleration/wind force Roll Case Quartering Pitch Case 0.37 g 0.28 g 0 0.017 g/m 0.013 g/m 0 ax at waterline (wl) 0 0.12 g 0.17 g ax incr. each metre (z) above waterline 0 0.004 g/m 0.006 g/m 0.20 g 0.15 g 0.10 g az incr. each metre (y, d or x respectively) from C 0.017 g/m 0.011 g/m 0.006 g/m Wind pressure 0.5 kN/m ay at waterline ay increase for each metre (z) above waterline az at centre (C) barge 2 0.5 kN/m 2 0.5 kN/m 2 Table 117 Criteria for Hs ≤ 4 m for larger barges (LRFD approach) Acceleration/wind force Roll Case Quartering Pitch Case 0.26 g 0.20 g 0 0.017 g/m 0.013 g/m 0 ax at waterline (wl) 0 0.08 g 0.12 g ax increase for each metre (z) above waterline 0 0.003 g/m 0.004 g/m 0.15 g 0.12 g 0.08 g ay at waterline ay increase for each metre (z) above waterline az at centre (C) barge az incr. each metre (y, d or x respectively) from C Wind pressure 0.017 g/m 0.009 g/m 2 2 0.3 kN/m Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS 0.3 kN/m 0.004 g/m 0.3 kN/m 2 Page 293 11.8.1 The incident weather shall be considered to be effectively omnidirectional, as stated in [11.3.2]. No relaxation in the design sea states from the bowquartering, beam and sternquartering directions shall be considered for: a) b) c) d) e) f) Any voyage where the default motion criteria are used, in accordance with [11.4], or similar Single tug towages, or voyages by vessels with nonredundant propulsion systems (see [11.8.3]). Any voyage where the design conditions on any route sector are effectively beam on or quartering, of constant direction, and of long duration, see guidance note Any towage in a Tropical Revolving Storm area and season Any unmanned towage Any transport where the vessel does not have sufficient redundant systems to maintain any desired heading in all conditions up to and including the design storm, taking account of the windage of the cargo. Guidance note: For c) examples are crossing of the Indian Ocean or Arabian Sea in the SouthWest monsoon. endofguidancenote 11.8.2 When the relaxation exclusions in [11.8.1] do not apply, relaxation in the nonhead sea cases can be considered for: 1) 2) Manned, multiple tug towages, where after breakdown of any one tug or breakage of any one towline or towing connection, the remaining tug(s) still comply with the bollard pull requirements of [11.12.2]. Voyages by selfpropelled vessels with redundant propulsion systems. A vessel with a redundant propulsion system is defined as having, as a minimum: — — — — — 2 or more independent main engines 2 or more independent fuel supplies 2 or more independent power transmission systems 2 or more independent switchboards 2 or more independent steering systems, or an alternative means of operation of a single steering system (but excluding emergency steering systems that cannot be operated from the bridge) — the ability to maintain any desired heading in all conditions up to and including the design storm, taking account of the windage of the cargo and assuming the failure of any one component. 11.8.3 Any vessel not complying with all the requirements in [11.8.1] and [11.8.2] shall be considered non redundant. 11.8.4 For voyages by selfpropelled vessels a survey should be performed to confirm the propulsion system redundancy is acceptable. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 294 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.8 Directionality and heading control If there is any doubt as to whether or not a vessel can be considered to have a redundant propulsion system the survey should be performed at an early stage of the project. endofguidancenote 11.8.5 In general, where a relaxation is allowed in accordance with [11.8.2], Table 118 is a guide to the acceptable sea state values. This should be confirmed by the MWS company as being acceptable on a casebycase basis. Table 118 Reduced sea state v heading Incident angle (Head Seas = 0°) Applicable Hs, as % of design sea state (adjusted as appropriate) 0° to ± 30° 100% ± (30° to 60°) Linear interpolation between 100% and 80% ± 60° 80% ± (60° to 90°) Linear interpolation between 80% and 60% ± 90° 60% ± (90° to 120°) Linear interpolation between 60% and 80% ± 120° 80% ± (120° to 150°) Linear interpolation between 80% and 100% ± (150° to 180°) 100% 11.8.6 For any voyage where a relaxation is allowed in accordance with [11.8.2] and [11.8.5], a risk assessment in accordance with [2.4] shall be carried out. Guidance note: For any voyage where a relaxation is allowed in accordance with [11.8.2] and [11.8.5] having an independent Cargo Owner’s Representative is on board to witness events could be beneficial. The representative should be qualified to discuss with the Master weather conditions forecast and encountered, routeing advice received and avoidance techniques adopted. endofguidancenote 11.8.7 Such relaxation shall only apply to considerations of accelerations, loads and stresses. It shall not be applied to considerations of stability. 11.8.8 For any voyage where a relaxation is allowed in accordance with [11.8.2] and [11.8.5], the voyage manual shall contain, in a format of use to the Master: a) The limitations on critical parameters see guidance note Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 295 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: c) d) e) Procedures for monitoring and recording of critical parameters, possibly by accelerometers on barges with radio links to the lead tug(s) Procedures for heading control Results of the risk assessment, and any recommendations arising Contingency actions in the event of any breakdown. Guidance note: Critical parameters should be observable or measurable by the Master. endofguidancenote 11.8.9 The Master shall confirm that he can accept that the effects of these restrictions are practicable and acceptable. 11.9 Design and strength 11.9.1 Computation of loads 11.9.1.1 The loads acting on grillages, cribbing, dunnage, seafastening and components of the cargo shall be derived from the loads acting on the cargo, according to Sec.3, Sec.5, and [11.3], as applicable. Guidance note: Care should be taken in cases where the cargo has be designed for service loads in the floating condition, but is being dry transported. Its centre of gravity can be higher above the roll centre in the drytransport condition than in any of its floating service conditions. Even though the voyage motions can appear to be less than the service motions, the loads on cargo components and shiploose items can be greater. endofguidancenote 11.9.1.2 The loads shall include components due to the distribution of mass and rotational inertia of the cargo. Guidance note: This is of particular importance in the calculation of shear forces and bending moments in the legs of jackup units and similar tall structures. endofguidancenote 11.9.1.3 If the computed loads are less than the “Minimum allowable seafastening force” shown in Table 119, then the values in the Table shall apply. Guidance note: A simplified example of cribbing/seafastening calculations is shown in [K.7]. endofguidancenote 11.9.2 Friction – general 11.9.2.1 Friction forces on the cargo supports/cribbing may be allowed to contribute to a reduction in the seafastening design loads provided that the entire load path, including the potential sliding surfaces, are documented as being capable of withstanding the loading generated. 11.9.2.2 Uncertainty in the load distribution between (seafastening) members and friction forces shall be taken properly into account. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 296 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used b) Force/load distribution between friction supports and seafastening can be calculated (assessed) by comparing deflection needed to mobilize friction with seafastening stiffness. If this is not done the following precautions should be implemented: — Seafastening members should be designed to tolerate possible “overloading”, see [11.9.2.3]. — In FLS, friction should not be used to reduce the seafastening loads in any sea state up to the sea state giving seafastening load without friction equal to the ULS characteristic load with friction. endofguidancenote 11.9.2.3 The magnitude of restraint loads, especially if caused (entirely or partly) by friction effects, could be difficult to calculate accurately. Hence, the following precautions should be taken: — Avoid if possible designs/layouts that cause restraint forces. — Minimize restraint forces as a result of ballasting to transport condition, see [11.9.5.32] — The end connection of seafastening elements with significant restraint forces should be made stronger than the element itself. — A thorough evaluation of “worst case distribution” of restraint forces between seafastening elements should be carried out. Reasonably conservative assumptions regarding force distributions should be considered in FLS calculations. Deformation loads on the cargo due to the waveinduced bending and torsion of transport vessel shall be considered. 11.9.2.4 The reduction in the effectiveness of friction restraint due to vibrations caused by wave slamming on the vessel hull and/or on overhanging cargo shall be assessed. Guidance note: Other slamming effects are given in [5.6.5.4] c). endofguidancenote 11.9.2.5 For cargoes with weight less than 1000t and/or unusual high volume (potential buoyancy) weight relationship the possible effect of buoyancy (and green water, see [5.6.5.5]) should always be evaluated on a case by case basis. 11.9.2.6 FLS calculations shall be based on the actual (linear elastic) stress (range) distribution. Hence, the effect of friction and restraint forces (vessel deflection) on the stresses shall be adequately calculated. See [5.6.11]. 11.9.2.7 For voyages in open water, the minimum seafastening capacity, without considering friction, shall be sufficient to resist the accelerations shown in Table 119. If the effects of vibrations and hull beam deflections can be proved to be insignificant, consideration can be given to reducing this requirement. Table 119 Minimum seafastening capacity as a function of Cargo Weight, W W < 1000t 1000t ≤ W < 5000t 5000t ≤ W < 20000t 20000t ≤ W < 40000t W≥40000t Transverse 0.15g Linear 0.10g Linear 0.05g Longitudinal 0.10g Linear 0.05g Linear 0.03g Direction/Weight 11.9.2.8 For voyages in sheltered inland water, the minimum transverse seafastening capacity shall be taken as 0.1g plus the effect of any heel, but need not exceed the requirements of Table 119. 11.9.2.9 For very short duration moves in sheltered water, such as turning a vessel back alongside the quay after a loadout, then friction can be allowed to contribute. The entire load path, including the potential sliding surfaces, shall be demonstrated to be capable of withstanding the loading generated, including Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 297 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.9.2.10 Where friction is considered, see [5.6.9], the characteristic friction coefficient shall be documented and a material factor applied to find the design friction coefficient. The effects of lubricating fluids or similar shall be considered when establishing the design friction coefficient. Friction shall not be used to reduce the design loads when the potential friction interfaces are steelsteel, unless the friction surfaces can be guaranteed to remain dry. Guidance note: The following maximum upper bound design friction coefficients for calculation of favourable friction forces can/should normally be considered: — Steel to steel, wet: 0.0 — Steel to steel (wet and dry) if vibrations (see [11.9.2.4]) can occur: 0.0 — Steel to steel dry: 0.1 — Steel to wet timber: 0.2 — Steel to dry timber or rubber (wet or dry): 0.3 — Timber to timber: 0.4 It is assumed that the friction surfaces are free from oil or other lubricating fluids. endofguidancenote 11.9.2.11 Where the cargo is supported on cribbing alone, the friction contribution may be determined using a simplified approach provided that a mean design friction coefficient of 0.2 is found applicable according to either [11.9.3.2] for ASD/WSD or sections [11.9.4.4] and [11.9.4.5] for LRFD. In such cases the assumed friction coefficient shall not exceed the value given in Table 1110, as a function of the cargo weight and overhang. Table 1110 Max allowable upper bound design friction coefficients Cargo weight, W, tonnes Maximum cargo overhang W<1,000 1,000 <W< 5,000 5,000 <W< 10,000 10,000 <W< 20,000 20,000 ≤W Maximum allowable coefficient of friction None 0.10 0.20 0.20 0.20 0.20 < 15 m 0 0.10 0.20 0.20 0.20 15 – 25 m 0 0 0.10 0.20 0.20 25 – 35 m 0 0 0 0.10 0.20 35 45 m 0 0 0 0 0.10 > 45 m 0 0 0 0 0 Guidance note: The friction coefficients can be interpolated as a function of Maximum Cargo Overhang using the actual maximum overhang value. endofguidancenote 11.9.2.12 Friction forces shall be computed using the normal reaction between the vessel and cargo compatible with the direction of the heave.sin(theta) term used in computing the forces parallel to the deck in [5.6.15.3]. Thus, when heave.sin(theta) increases the force parallel to the deck, it also increases the Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 298 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used collision with nearby vessels in areas of high marine traffic density. Where friction is applied for this case, any seafastenings shall have sufficient flexibility to allow the friction to develop. — When heave adds to the selfweight reaction the total normal reaction shall be reduced by 10% to allow for adverse phasing. — When heave reduces the selfweight reaction, the normal reaction shall be taken as weight less heave as any effects of phasing will cause an increase in the normal reaction. 11.9.3 ASD/WSD friction 11.9.3.1 When using the ASD/WSD method, friction shall NOT be used if the loadings are computed in accordance with the default criteria in [11.4] and [5.6.16], except as allowed by [11.9.9]. 11.9.3.2 When using the ASD/WSD method, friction effects can be incorporated to reduce seafastening requirements for cargos supported on timber cribbing, subject to the following: 1) 2) Loadings are computed in accordance with [5.6.12] to [5.6.15]. For wood cribbing less than 600 mm high, with a width not less than 300 mm, the friction force due to the friction coefficient permitted in Table 1110 can be assumed to act in any direction relative to the cribbing provided that: — the cribbing is reasonably well balanced in terms of the proportion in the foreaft and transverse directions, AND — each of these groups is reasonably well balanced about the cargo CoG in plan. 3) Provided that the conditions in [2)] are met, for cribbing heights between 600 mm and 900 mm, with a width not less than 300 mm, then the percentage computed friction force at right angles to the longitudinal axis of a cribbing beam shall not exceed (900 H)/3%, where H = the height of cribbing above deck, in mm. In the direction of the longitudinal axis of a cribbing beam, the full friction force can be used. 4) For wood cribbing over 900 mm high, or with a width less than 300 mm, no friction force shall be assumed to act in a direction at right angles to the longitudinal axis of a cribbing beam. 5) If greater cribbing friction is required than available according to [3)] and [4)], stanchions can be fitted to provide transverse cribbing restraint. Where such stanchions are fitted, they should be designed to carry loads due to a friction coefficient of 0.5 (to ensure they are able to carry loads due to upperbound friction assumptions). 6) The underlying assumption in the approach given above is that the seafastenings have sufficient flexibility to deflect in the order of at least 2 mm in the horizontal direction of loading without failing. This will be reasonable in most cases, but when this is not the case the more detailed approach given in [7)] shall be used. 7) As an alternative to [2)] through [5)], a more detailed approach can be used. In such cases, the friction coefficient permitted in Table 1110 can be doubled, provided that the distribution of loading between the seafastenings and cribbing friction accounts for the relative flexibility of the cribbing and seafastenings. The angle between the loading direction and the grain of the cribbing shall be taken into account, e.g. when the loading is perpendicular to the grain the cribbing is more flexible. The arrangements shall be such as to ensure that the required lateral load can be carried by the combination of friction and seafastening reactions BEFORE the seafastenings are overstressed. Where stanchions are used, they shall comply with [5)]. 11.9.4 LRFD friction 11.9.4.1 When using the LRFD method, friction can be used if the loadings are computed in accordance with the default criteria in [11.4] and [5.6.16] Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 299 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used normal reaction and viceversa. When the provisions of [5.6.15.4] b) and c) are used, the normal reaction should be determined conservatively, as follows: 11.9.4.3 Design loading on the seafastening can be reduced by considering relevant friction effects on the cribbing, see [11.9.7]. 11.9.4.4 Where friction on the cribbing is considered, see [5.6.9], the characteristic friction coefficient shall be documented and a material factor applied to find the design friction coefficient. Guidance note: In the areas and directions where full friction effect could be mobilized a design friction coefficient of 0.3 can normally be applied between wood and steel on cargo. Any special effects (e.g. wood treating, type of surface treatment on cargo, and risk of oil/ lubricant present) that can reduce the friction significantly should be evaluated. endofguidancenote 11.9.4.5 Due to low wood shear stiffness and strength, friction forces transverse to the cribbing (soft wood) boards should only be accounted for if properly documented. Guidance note: If a thorough evaluation including cribbing shear stiffness and seafastening design (stiffness) has not been carried out the following apply: a) For cribbing with H (height)≥1.5B (breadth) zero contribution should be considered from friction in the transverse cribbing direction. b) For cribbing with H < 1.5B contribution from friction in the transverse direction could be considered with (1.5B – H)/1.5B x 100%. c) Normally 100% contribution from friction could be considered in the longitudinal cribbing direction. However, see [11.9.2.2]. d) The mean design friction coefficient considered should in any case not exceed 0.2, but see [11.9.2.11]. endofguidancenote 11.9.5 Seafastening design 11.9.5.1 Introduction. This section covers requirements for seafastenings which in this context, includes any grillage, dunnage, cribbing or other supporting structure, roll, pitch and uplift stops, and the connections to the barge or vessel. This section also applies to fastenings for land transport though with different accelerations. Guidance note: Grillage and seafastening design is influenced by the loadout method. — Cargoes floated over a submersible barge or vessel, are frequently supported by timber cribbing or dunnage to distribute the loads and allow for minor undulations in the deck plating. — Cargoes lifted onto the transport barge or vessel are either supported on timber cribbing/dunnage or grillage depending on type and size of cargo. — Cargoes loaded by skidding normally remain on the skidways, and are seafastened to the skidways and/or vessel. — Cargoes loaded out by trailers normally need a grillage structure higher than the minimum trailer height. endofguidancenote 11.9.5.2 Design Principles. The grillage elements, including shimming plates, shall be used to distribute a concentrated deck load to a sufficient number of loadcarrying elements. The grillage or cribbing height shall allow for any projections below the cargo support line. 11.9.5.3 Seafastenings shall be designed to withstand the global loadings from the transported objects rotation (overturning) and sliding in any direction as computed in Sec.5 and the additional requirements of this section. Their strength shall be assessed using the applicable checks in [5.9]. Normally seafastening calculations should be provided for any item heavier than 5 tonnes. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 300 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.4.2 When using the LRFD method the following approach shall be used if friction effects are to be incorporated to reduce seafastening requirements. Guidance note: The effect of global loads on local strength should be considered; e.g. a buckling check of vesselstiffened panels for support loads from cargo should include the stresses caused by hull bending moments and shear forces. endofguidancenote 11.9.5.5 Grillage and seafastening shall be designed (and installed) taking into account all the physical limitations implied by the load transfer procedures/methods both to and from the transport vessel(s). Guidance note: Typical physical limitations could be related to: — available heights — strict tolerances, etc. imposing requirements for the erection/welding sequence, see also [11.9.5.10] — loadout trailer layout — needed space for (operation of) loadout systems, e.g. pumps, hoses, pull/push units — set down tolerances and shimming requirements — cutting/handling offshore — securing of object before lift, see [11.9.5.7] — possible need for set down of the object again and reinstate seafastening offshore. endofguidancenote 11.9.5.6 The design calculations shall include any positioning tolerances for the transported object on the grillage including, if applicable, effect of vessel hull beam deflections. Guidance note: Positioning tolerances should be included in the loadout procedure. endofguidancenote 11.9.5.7 Seafastening design for offshore or inshore installation operations should allow for easy release and provide adequate support and horizontal restraints until the object can be lifted clear of the vessel, or launched as applicable as described in [11.9.6]. 11.9.5.8 Elements providing horizontal and/or vertical support after cutting/removal of seafastening shall be verified for characteristic environmental conditions applicable for the installation operation. 11.9.5.9 Wave entry (slamming) and exit loads shall be considered for overhang cargo in the seafastening and cargo design (see [5.6.5.4]). See also [11.9.2.5] for uplift due to buoyancy. 11.9.5.10 Vessel global deflection both due to waves and redistribution of ballast may impose significant loads on grillage elements and seafastening. Both additional horizontal and vertical loads shall be considered, see [11.9.5.32] 11.9.5.11 For special precautions to seafastening after back loading offshore see DNVGLRPN102, /55/. 11.9.5.12 If reinstating of the transport seafastening may be required offshore this should be taken into account in the design and in the cutting/release procedure. 11.9.5.13 Seafastenings shall be designed to accept deflections of the barge or vessel in a seaway, principally due to longitudinal bending. In general, longitudinal bending should be considered for the cases described in [5.6.11]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 301 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.5.4 The seafastening and grillage design shall duly reflect the structural strength limitations of both the objects and transport vessel. Where longitudinal bending is a consideration, suitable seafastening designs include: a) Chocks which allow some movement between the vessel and cargo b) Pitch stops at one point only along the cargo, with other points free to slide or deflect longitudinally c) Vertical supports at only 2 positions longitudinally d) An integrated structure of vesselseafasteningscargo, capable of resisting the loads induced by bending and shear. endofguidancenote 11.9.5.14 The (assumed) force distribution in seafastening and grillage shall correspond to the considered reaction forces for vessel and transported object strength verifications. 11.9.5.15 Possible uplift due to overturning of the object and/or relative deflections shall be prevented by seafastening where required. See also [5.3.4]. Guidance note: Uplift seafastening is always required if the object overturning moment is greater than the object restoring moment in the “worst” applicable ASD/WSD or ULS load combination. If uplift is predicted when the restoring moment due to gravity is reduced by 15% then uplift restraints should be provided to resist, as a minimum, an overturning moment equal to 15% of the restoring moment due to gravity. The need for prohibiting calculated “local” uplift should be evaluated in each case. If not prohibited the effect of “gaps” and redistribution of reaction loads should be taken into account. endofguidancenote 11.9.5.16 Additionally, for towed objects which can have permanently installed modules with piping or other connections between them, there should be adequate flexibility in the connections to avoid overstress. In long modules carried as cargo, internal pipework should be similarly considered. Guidance note: It should be noted that the voyage wave bending condition can be more severe than the operating condition. endofguidancenote 11.9.5.17 When required by [5.6.11.2], and in the absence of more detailed information, it should be assumed that the vessel will incur bending and shear deflection as if unrestrained by the cargo; the seafastenings and the object should be checked assuming quasistatic vessel hogging and sagging due to a wave of length, Lw, equal to the vessel length, and height: where Lw is in metres. 11.9.5.18 Seafastenings should generally be welded steel. For smaller cargoes, chain, wire or webbing lashings with suitable tensioning devices can be acceptable and shall meet the requirements in [11.9.5.19] to [11.9.5.26]. Guidance note: Smaller cargoes are typically less than 100 tonnes for wire and chain seafastening and 50 tonnes for webbing lashings. endofguidancenote 11.9.5.19 Seafastening – Lashings: Chain binders, ratchets or turnbuckles shall be tensioned before departure to spread the load between the seafastenings and secured so that they cannot become slack. Lashings should be inspected regularly and after bad weather to ensure that tension is maintained. All mechanisms shall be adjustable without release unless there is sufficient redundancy. Wire lashings and webbing lashings should not be used for unmanned voyages since they can loosen and are difficult to inspect regularly, see also [11.9.5.27]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 302 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Guidance note: A skew load factor of 1.5 is considered adequate if lashings carrying the same (quasistatic) load component between them have approximately the same stiffness and similar means of pretensioning. If not, a conservative assessment should be conducted to estimate the applicable skew load factor(s). endofguidancenote 11.9.5.21 Calculations of characteristic loads in lashing seafastening shall take into account cargo CoG, support lay out, friction and location/direction/stiffness of each lashing. In indeterminate seafastening arrangements the loads can be calculated based on a quasistatic load distribution combined with an appropriate skew load factor, see [11.9.5.20]. Guidance note: Applicable design friction coefficients are listed in [11.9.2]. endofguidancenote 11.9.5.22 Unless motions have been calculated in accordance with [11.5] (IMO code), then if the equipment certificate states the MBL the following applies: — For ASD/WSD the maximum design load computed using the applicable load factors from Table 57 shall be less than the applicable value from Table 1111: — For LRFD the maximum design load shall be less than the design resistance where the design resistance is the certified MBL divided by the relevant material factor, see [5.9.8.5]. Table 1111 Allowable design load as a function of MBL Maximum allowable design load to DNV GL or DNV class rules, see [11.6] Item type Maximum allowable ASD/WSD design load LS1A LS2A LS1 LS2 Certified steel wire ropes and chains 0.46MBL 0.61MBL 0.46MBL 0.61MBL Polyester ropes 0.42MBL 0.56MBL 0.42MBL 0.56MBL 0.34MBL 0.46MBL 0.34MBL 0.46MBL Ropes and webbing straps of 1) other fibre materials 0.27MBL 0.37MBL 0.27MBL 0.37MBL Shackles, turnbuckles, D links, etc. 0.35MBL 0.47MBL 0.35MBL 0.47MBL HMPE and Aramid ropes 1) Notes: 1) For fibre ropes subject to a robust certification process, other material factors may be considered acceptable; however the maximum allowable design load should not be taken to be greater than that permitted for polyester ropes. 2) These allowables apply to both new and used items, provided that used items are inspected and found to be in good condition, and that the manufacturer does not specify reduced capacity for reuse. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 303 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.5.20 Possible skew loads in lashings due to uneven pretensioning and length/stiffness variations in statically indeterminate seafastening arrangements shall be taken into account. The design loads for lashings should be multiplied by a skew load factor not less than 1.5 if skew load effects are not accurately calculated. a) b) It may be acceptable to use the above requirements where the MBL is taken as the breaking load (or similar) specified in the code. Where a) does not apply the characteristic load shall be less than the stated capacity (typically given as WLL or SWL). 11.9.5.24 When the motions have been calculated in accordance with [11.5] (IMO code), then strength of lashing equipment shall be assessed in accordance with IMO requirements. 11.9.5.25 The good practice for lashings and similar devices in the IMO Code of Safe Practice for Cargo Securing and Stowing, /87/ should be followed if relevant. 11.9.5.26 Lashing equipment (chains, wires, shackles, turnbuckles etc.) shall have certificates, giving the ultimate capacity, WLL or SWL, issued or endorsed by a body approved by a Recognized Classification Society or other certification body accepted by the MWS company. Certificates should be revalidated at intervals of not more than 4 years and identify the equipment to which they apply. Each item is to be visually inspected prior to each use by a responsible person. 11.9.5.27 Synthetic webbing should only be used for smaller cargoes on manned voyages. Where synthetic webbing ratchet straps are used, then: a) b) c) d) e) f) Dlinks and shackles shall be used instead of hooks (which can unhook) The straps shall be in good condition, with no rips or abrasion damage. They shall not have been, or be likely to be, subject to chemical degradation or excessive sunlight (ultraviolet radiation). Note that different types of synthetic materials (e.g. nylon or polyester) have very different resistance to acids, alkalis, UV radiation, ripping and abrasion. Material design has also improved over the last few years. There shall be no sharp edges to damage the straps. If sharp edges are protected by rubber or similar materials then the materials shall be properly secured. The fittings shall be of the correct shape and size to ensure that the straps are not damaged Straps shall not be knotted or twisted through more than 90° unless allowed in the certification. The strength of synthetic webbing doubled around a Dring is reduced. This reduction shall be taken into account; it can be documented by testing. 11.9.5.28 If chains are used, and it is not properly documented otherwise, then: 1) 2) Chains should not be bent around edges with diameter less than 4 times the chain diameter. 2 times the chain diameter may be acceptable for up to 90° edges. The effective MBL of doubled chains that are bent more than 90° around connection points should be reduced as indicated below: a) b) c) Point with diameter equal or less than 2 times (1.5 times if bend 90° or less) the chain pitch (inside length of links): 50% Point with diameter equal or greater than 4 times (3 times if bend 90° or less) the chain pitch: 10% (skew load between the two legs included) Point with diameter greater than 2 (1.5) times and less than 4 (3) times the chain pitch: Linearly between a) and b). 11.9.5.29 Seafastening welded: Connections to the deck of a barge or vessel should be carefully considered, particularly tension connections. Calculations should be documented to justify all connections. It should not be assumed, without inspection, that underdeck connections between deck plating and stiffeners or bulkheads are adequate especially in the region of tension connections, see [5.3.4]. 11.9.5.30 It is not generally acceptable to land tubular seafastenings, liable to tension, on deck via a doubler plate. A gusset connection should be used, landing on an underdeck member of suitable strength in accordance with [5.3.4]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 304 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.5.23 For equipment in accordance with a recognised code where the certificate states a capacity other than the MBL then: 11.9.5.32 So far as is practical, seafastening connections should be made after loadout with the barge or vessel in the voyage ballast condition, or a condition giving a similar longitudinal bending situation. If not practical, then the additional stresses which can be caused by the change in ballast condition shall be considered. 11.9.5.33 Adequate weather protection and heating and drying should be used to ensure the quality of seafastening welds made in wet conditions, see also [5.9.7.5], [5.9.8.4] 5) and [5.10.2.2]. 11.9.5.34 Where a lift is made onto a vessel offshore, the seafastenings should be designed accordingly, normally by means of guides or a cradle, which will hold the cargo whilst it is being seafastened. 11.9.5.35 Items of the cargo which are vulnerable to wave action, wetting or weather damage shall be suitably protected. Guidance note: This can require provision of breakwaters or waterproofing of sensitive areas. endofguidancenote 11.9.5.36 Internal seafastenings shall be provided to prevent items moving inside structures or modules. See also the caution in guidance note to [11.9.1.1] for dry transport. 11.9.5.37 Guide posts should not be used for seafastenings unless specifically designed for that purpose. 11.9.6 Seafastenings to be removed offshore 11.9.6.1 For cargoes that will be installed offshore, the seafastenings should be capable of being released in stages, such that the cargo remains secure for all anticipated angles and motions. The release of seafastenings, and the removal of any one object, should not disturb the seafastenings of any other object. Guidance note: For lifts, see [16.16.9.5] for the design of the restraints/seafastenings that remain after all cutting has been completed. For other operations, 10° is normally sufficient. endofguidancenote 11.9.6.2 Where the installation is in an area more benign than that for which the seafastenings were designed then, subject to the agreement of the MWS company, some seafastenings can be removed after entering that area and before the Installation Certificate of Approval is issued. In this case, unless weather routed: a) b) The remaining seafastenings shall be designed for the design criteria for the installation area and the route to a sheltered area if required, and The seafastenings to be removed early shall be clearly marked as such. 11.9.6.3 Removal of seafastenings shall not normally start until the Installation Certificate of Approval has been issued. This requirement can be relaxed in special circumstances subject to a risk assessment in accordance with [2.4]. The seafastenings to be removed early shall be clearly marked as such and identified in the seafastening removal procedures. 11.9.7 Cribbing 11.9.7.1 Where the cargo is supported on wooden cribbing or dunnage, rather than steeltosteel supports, then sufficient plan area and height of material should be provided to distribute the loads to ensure that the Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 305 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.5.31 Seafastenings shall not be welded onto fuel oil tanks or oil cargo tanks, unless the tanks are empty, and gas free certification has been obtained. Guidance note: Cribbing designed to pick up structural members in the underside of larger transported objects e.g. MOUs, the vessel deck, or both, and fixed to the deck of the vessel, should not normally be less than 200 mm high. endofguidancenote 11.9.7.2 A minimum clearance of 0.075 m, after accounting for vessel deflections, should be provided between the lowest protrusion of the cargo and the deck of the barge or vessel. Guidance note: Where the dimensions and locations of protrusions from the cargo are well documented the minimum clearance can be reduced. endofguidancenote 11.9.7.3 Unless it can be demonstrated that the cargo, vessel and cribbing (without crushing), can withstand 2 a greater pressure, the nominal bearing pressure on the cribbing should not exceed 2 N/mm for softwood. The nominal bearing pressure on the cribbing should be calculated taking into account the deadweight of the cargo plus the loads caused by the design environmental loadings. 11.9.7.4 The selected timber should withstand the computed cribbing pressures without crushing. Localised crushing to accommodate cargo and cribbing imperfections is permissible. Guidance note: A satisfactory arrangement can consist of hardwood for the main cribbing structure, topped by a soft packing layer, typically 50 mm thick. endofguidancenote 11.9.7.5 In the case of a random or herringbone dunnage layout supporting a flatbottomed cargo, without 2 taking into account the strong points, then the maximum cribbing pressures should not exceed 1 N/mm , subject to consideration of the overall allowable loads on the deck of the vessel and the underside of the cargo. 11.9.7.6 For cargoes floated on and/or off a grounded or partially grounded transport barge or vessel, the cribbing should be designed to withstand: — line loads during initial phases of contact or final stages of separation and — trim or heel angles during onload and offload. Minimum angles of 5º should be considered. 11.9.8 Cargo strength requirements 11.9.8.1 The cargo shall meet the requirements in Sec.5 for the loads imposed during the voyage. Additionally the cargo shall be shown to have adequate strength to withstand the local cribbing/grillage and seafastening loads, see [11.9.5]. 11.9.8.2 Any additional loadings caused by any overhang of the cargo over the side of the transport vessel, buoyancy forces and wave slam loadings shall be included. 11.9.9 Securing of pipe and other tubular goods 11.9.9.1 This section refers to the transport of tubulars, including line pipe, casing, drill pipe, collars, piles, conductors, marine risers and similar, hereafter called “pipes”, on vessels and barges. Transport of drill pipe, collars etc. on jackups is covered in [11.28.11]. The design of securing shall consider the following: — the type of vessel, Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 306 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used underside of the cargo and to the deck of the transport vessel are not overstressed. The loads shall include the static loadings and the design environmental loadings as shown in [11.3] and Sec.5. 11.9.9.2 For these types of cargoes, friction can be assumed to resist longitudinal seafastening loads (i.e. from pitch), and [11.9.1.1] and [11.9.1.3] do not apply. The design friction coefficients shall be in accordance with [5.6.9] and should not exceed the coefficients in Table 1112. Table 1112 Typical upper bound design friction coefficients for pipe stowage Materials in contact Friction coefficient Concrete coated pipe concrete coated pipe 0.5 Concrete coated pipe – timber 0.4 Timber – timber 0.4 Uncoated steel – timber 0.3 Polypropylene coated pipe timber or rope dunnage 0.3 Polypropylene coated pipe Polypropylene coated pipe 0.15 Uncoated steel uncoated steel 0.15 Epoxy coated pipe – timber 0.1 Epoxy coated pipe epoxy coated pipe 0.05 11.9.9.3 Where sand can be present between the friction surfaces, the friction coefficient should be considerably reduced. 11.9.9.4 Friction coefficients (both wet and dry) for other materials should be justified or the beneficial effects of friction should be ignored. 11.9.9.5 Generally, pipes should be stowed in the fore and aft direction. 11.9.9.6 Where pipes are stacked in several layers, the maximum permissible stacking height shall be established, in order to avoid overstress of the lower layers. Safe access shall be provided to minimise risk of injuries to riggers. Guidance note: Reference can be made to API RP 5LW “Recommended practice for transportation of line pipe on barges and marine vessels”, /7/. endofguidancenote 11.9.9.7 Smaller diameter pipes such as drill pipe can be stacked without individual chocking arrangements and restrained transversely by means of vertical stanchions. Timber dunnage or wedges shall be used to chock off any clearance between the pipes and the stanchions. The stanchions, taken collectively, shall be capable of resisting the total transverse force computed. a) b) For weather restricted operations, and 24hour or location moves of jackups, the stack can be secured by means of transverse chain or wire lashings over the top, adequately tensioned. Provided it can be demonstrated that sufficient friction exists to prevent longitudinal movement, no end stops need be provided. For weather unrestricted operations, including voyages of jackups, steel strongbacks should be fitted over the top layer, and each stow (group of pipes) set up hard by driving wooden wedges between the strongbacks and the top layer of pipe. End stops or bulkheads shall be provided. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 307 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — the nature of the cargo, — the duration of the towage or voyage and — the weather conditions expected. a) b) For weather restricted operations, provided it can be demonstrated that adequate friction exists to prevent longitudinal movement, no end stops need be provided. For weather unrestricted operations, steel strongbacks should be fitted over the top layer, and each stow set up hard by driving wooden wedges between the strongbacks and the top layer of pipe. End stops or bulkheads shall be provided. Guidance note: This is likely to apply to concrete coated pipe, but uncoated or epoxy coated pipe should be treated with caution. endofguidancenote 11.9.9.9 Larger diameter pipes (e.g. piles) are often individually chocked, and end stops provided. Unless proven that the piles cannot roll out of the chocks further restraints shall be provided. Guidance note: It may be possible to provide end stops at one end only. Further restraints to retain the pipes could be individual wire or chain lashings, stanchions or strongbacks. endofguidancenote 11.9.9.10 In all cases for the transport of coated line pipe, the transport and securing arrangements shall be designed so that the coating will be protected from damage. The manufacturer’s and/or shipper’s recommendations should be followed. 11.9.9.11 Where end stops are provided for pipes with prepared ends, the end preparation shall be protected. Guidance note: Protection could be either by protectors on the pipe, or by wood sheathing on the end stops. endofguidancenote 11.9.9.12 When open ended pipes are carried as deck cargo and the pipes could become partially filled with water, care should be taken to ensure that: a) b) the vessel’s stability shall meet the requirements of [11.10] with including the effects of entrapped water, and the deck and pipe layers shall not be overstressed. Guidance note: Where the requirements are not met a possible solution is to seal the pipe ends of at least the lowest level of the stack. endofguidancenote 11.9.9.13 Where the trim and stability booklet includes suitable example loading conditions these should be considered. 11.9.10 Inspection of welding and seafastenings 11.9.10.1 Principal seafastening welds shall be visually checked and the weld sizes confirmed against the agreed design. 11.9.10.2 Nondestructive testing (NDT) shall be carried out on the structural members of the seafastenings. Specific requirements for weld inspection are given in [5.10.2.3]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 308 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.9.8 Line pipe on pipe carrier vessels can be stacked between the existing stanchions/crash barriers, on the wooden sheathed deck. Timber dunnage or wedges should be used to chock off any clearance between the pipes and the stanchions. 11.9.11 Use of second hand steel seafastenings 11.9.11.1 When second hand steel seafastenings are used, any wastage caused during previous removal(s) or use should not affect its fitness for purpose. There should be sufficient documentation to ensure the traceability of the steel and in particular documentation relating to the grade of steel. 11.9.11.2 There should be NDT inspection reports to demonstrate no cracking or lamellar tearing in critical areas. Guidance note: Areas to consider included regions of previous fabrication, old welds, burnt off attachments etc., endofguidancenote 11.9.11.3 Should sufficient documentation of the type of steel (e.g. EN10025) be unavailable, coupon testing is acceptable to determine the steel type. The guaranteed minimum properties of this type of steel shall be used. Guidance note: Tested values should not be used as they may not be representative of the rest of the steel. endofguidancenote 11.9.12 Fatigue 11.9.12.1 See [5.9.4] for requirements for fatigue analysis. 11.9.12.2 The FLS design waves (and wind) should be carefully selected based on a “worst case scenario” regarding weather conditions during the voyage. Guidance note: For calculating the maximum expected fatigue damage for a voyage it is recommended that weather conditions are selected that do not have more than 10% probability of being exceeded with regards to cumulative fatigue damage. endofguidancenote 11.9.12.3 A reasonably conservative exposure time should be selected for calculating the maximum expected transport fatigue damage. Guidance note: The following exposure times should normally be considered: — For transports from one sheltered location to another: 1.5 x TPOP ; when TPOP exceeds 30 days, TPOP + 15 days can be considered. — For transports to offshore (wave exposed) location ample time should be added to account for the maximum expected waiting time, including possible return(s) to an inshore holding location. endofguidancenote 11.9.12.4 Fatigue damage should be calculated for representative sea state directions relative to the vessel. The spacing between analysed wave headings should not exceed 45°. Symmetry may be considered. 11.9.12.5 The most probable (percentage) exposure time for each sea state direction relative to the vessel should be selected for calculating the maximum expected transport fatigue damage. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 309 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.10.3 Any faulty welds discovered shall be removed or repaired in accordance with a qualified weld repair procedure and qualified welders and retested. For transports with sailing routes for which there are no predominant sea state directions relative to the vessel the exposure time and analysed directions can be selected according to the below table. Where applicable, symmetry can be considered to reduce number of load cases/directions. Sea direction Representing range Head H Port Q Port Beam S Port Q Stern S Stbd Q. Stbd Beam H, Stbd Q 337.522.5 22.567.5 67.5112.5 112.5157.5 157.5202.5 202.5247.5 247.5292.5 292.5337.5 0 45 90 135 180 225 270 315 10 15 15 10 10 10 15 15 Analysed direction Exposure in % Where H and S denote head seas and stern seas respectively and Q denotes quartering (45°) seas. endofguidancenote 11.9.12.6 For fatigue critical transports, it is recommended to maintain control of the (anticipated) fatigue damage during the transport. This is especially important if the assumed stress range distribution could be unconservative. Guidance note: Fatigue damage could be controlled by regular inspections and/or by verifying that the actual fatigue stress range is less critical than the stress range applied in the calculations. The stress range could be controlled by setting up systems that compare the actual to the applied: — exposure time — wave scatter diagram considering relative vessel/sea directions — vessel motions, e.g. calculated vs MRU readings — member loads/stresses. endofguidancenote 11.9.12.7 Whenever relevant, mitigation actions to avoid excessive transport fatigue shall be defined. Guidance note: Potential mitigation actions include: heading control and/or weather routing. Regular inspections combined with repair possibilities could/should also be considered. endofguidancenote 11.9.13 Vortex shedding 11.9.13.1 All voyages should be checked for windinduced Vortex Induced Vibration (VIV), see [5.6.7.4]. Where the potential is identified, mitigating measures shall be taken. Guidance note: Typical items that can be susceptible include: — slender members in jackets that will be submerged in the inplace condition and which are therefore not checked for inplace VIV, or — singletube jackup legs (which can be fitted with spoilers to prevent VIV). endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 310 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.9.14.1 Special cases can be considered for the towage of vessels with a Load Line Exemption Certificate or for objects with no classification such as caissons and vessels with expired classification such as a demolition towage. In such special cases the object shall be in seaworthy condition, and therefore an inspection shall be carried out in order to verify if the structural strength and watertight integrity of the tow is approvable for the intended voyage. As such, the MWS company can require one or more of the following: a) b) c) d) e) An extended, in depth, survey of the vessel structure involving one or more specialist surveyor(s). Facilities for a closeup survey of inaccessible parts of the hull structure may be required. Thickness determination (gauging) of specified areas of the vessel structure. This survey may be in limited areas or extend over large parts of the hull structure. Such surveys shall be carried out by a reputable independent company. An existing survey report may be acceptable provided that it is not more than 1 year old, and there is no evidence of damage or significant deterioration since that date. A MWS company review of classification society approved scantling drawings. Calculations to show that the structural strength of particular local areas of the vessel is adequate. The extent of the calculation required to be determined by the results of the surveys and drawings review. A dry dock survey of the vessel can be necessary should there be any doubt as to the condition of the tow. 11.10 Floating stability 11.10.1 General 11.10.1.1 Freetrimming stability programs can give misleading results unless “freetwist” or equivalent is used. Two examples when this may occur are: (i) where hull geometry causes significant trim relative to the heel angle, such as, in the case of a triangular shaped jackup; (ii) where there is an asymmetric waterplane area, such as, during offload of a floating cargo aligned obliquely to the longitudinal axis of a transport vessel. In such cases, fixed trim can be used for stability calculations provided a sufficient number of axes of rotation (azimuth) are considered, thereby allowing the minimum GZ to be identified for each azimuth/ heel angle combination. Consideration should be given to the selection of the range and increment in azimuth angle by refining the increment until no significant changes in results are apparent. 11.10.1.2 Whether using fixed or free trim, metacentric height (GM) should be calculated from the initial slope of the righting arm (GZ) curve rather than from the second moment of waterplane area. 11.10.1.3 The lightship data used in the stability calculations shall accurately reflect the current status of the unit. Guidance note: It is common practice to maintain a lightship alteration log to record minor iterations to light ships with modification/mutations over a period of time from previous light ship survey. The weight and position of additions or removals in excess of 100 kg (220 lb) should be recorded in the log. The details would typically include; — Date the modification was made — A description of the item — Weight (positive value for weight addition, negative value for removal) — Vertical Centre of Gravity (VCG) — Longitudinal Centre of Gravity (LCG) — Transverse Centre of Gravity (TCG) — Reference to modification, project or approval number as applicable endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 311 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.9.14 Condition of unclassed tows 11.10.1.5 The consequences of the escape of air from any air cushion shall be evaluated where applicable. 11.10.1.6 Loose solid ballast shall be prevented from moving and, where submerged, shall be protected against dispersal by wave or current or towing action. 11.10.1.7 During towing, all watertight doors and openings on and underdeck on both the tug(s) and tow shall be closed at all times. Where vessels are fitted with remote indication of watertight door position, this shall be confirmed as operational. 11.10.1.8 The towed asset and tug(s) should have a systematic programme for the assurance that such openings are closed prior to and throughout towing operations, and these arrangements referenced as necessary in the tow plan. 11.10.1.9 The effects of free surface shall be considered in all stability calculations. These shall include: a) b) c) the effects of free surface liquids in unit and cargo, residual free surface due to incomplete venting, such as can occur if ballasting when trimmed any Air Cushion Effect from air trapped or introduced below any part of the hull which produces additional buoyancy. The Air Cushion Effect is in addition to the Free Surface Effect from all standard closed tanks. It reduces stability due to the compressibility of the air. 11.10.1.10 Vessels shall comply with the mandatory parts of the IMO Intact Stability Code 2008, /89/, and the IMO International Convention on Load Lines, Consolidated Edition 2005 /90/. 11.10.1.11 Multivessel combinations can be considered as one vessel providing that the strength of the combination meets the requirements of Sec.5. 11.10.1.12 Any cases where stability or damage IMO Intact Stability Code 2008, /89/, requirements cannot be met should be agreed with the MWS company at an early stage. 11.10.1.13 The MWS company will generally accept the stability of ships and MOUs when they are operated within the limits accepted for Class by a Recognized Classification Society. 11.10.1.14 Requirements for the different asset types in transit are given in Table 1113. Table 1113 Stability requirements for different asset types in transit Jackup Intact range Semisub Cargo on ships and barges See [11.10.2] 40° Wind overturning (intact) See [11.10.3] Damage (general) See [11.10.4] Damage (specific) See [11.10.5] See [11.10.6] Jacket wet tow See [11.10.7] Compartmentation and watertight integrity See [11.10.8] Draught and trim See [11.10.9] GBS 1) [11.10.7] 1) See [6.2] Notes: 1) Subject to agreement with the MWS company once full details are known Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 312 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.10.1.4 The stability calculations shall also take into consideration any addition or removal of mooring chain from the system that will impact the final loads during passage/departure and arrival conditions. 11.10.2.1 This section does not cover stability of GBSs (for which see [6.2]) or selffloating structures (if not MOU, barge or ship shaped) for which the criteria should be agreed with the MWS company once full details are known. 11.10.2.2 Where there is a significant difference between the departure, arrival or any intermediate condition, then the most severe should be considered, including the effects of any ballast water changes during the voyage. 11.10.2.3 The initial apparent metacentric height, GM0, shall be greater than 0.15 m and should be greater than 1.0 m. The calculation of GM0 shall include adequate margins for computational and other inaccuracies. 11.10.2.4 The intact range of stability, about any horizontal axis, defined as the range between 0° inclination and the smallest angle at which the righting arm (GZ) becomes negative shall not be less than the values shown in Table 1114. When assessing the range of stability, downflooding does not need to be taken into account provided that the watertight and weathertight requirements of [11.10.8] and [11.28.6] are met. Table 1114 Intact stability range Vessel or towed object, type and size Intact range Large and medium vessels, LOA > 76 m and B Large cargo barges, LOA > 76 m and B Small cargo barges, LOA < 76 m or B Small vessels, LOA < 76 m or B 1) 1) 1) 1) > 23 m > 23 m 36º 36º < 23 m 40º < 23 m 44º MOU’s including jackups and semisubmersibles To satisfy [11.10.3] Vessels and barges in inland and sheltered water (in ice areas) 36º Vessels and barges in inland and sheltered water (out of ice areas) 24º Notes: 1) B = maximum moulded waterline beam. 11.10.2.5 Requirements for objects which do not fall into the categories shown in Table 1114, which are nonsymmetrical, or which have an initial heel or trim which is not close to 0º, shall be agreed with MWS company. 11.10.2.6 Alternatively for barges, if maximum amplitudes of motion for a specific towage or voyage can be derived from model tests or motion response calculations, the intact range of stability shall be not less than: 15+(15/GM)+θ where GM is in metres and θ = the maximum amplitude of roll or pitch caused by the design sea state as defined in [3.2], plus the static wind heel or trim caused by the design wind, in degrees. 11.10.2.7 Additional requirements for jackups are given in [11.28.6]. 11.10.2.8 Cargo overhangs shall generally not immerse as a result of inclination from a 15 m/s wind in still water conditions (but see [11.19.28.3] for ice areas) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 313 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.10.2 Intact stability (apart from GBS’s and floating jackets) 11.10.2.10 In areas and seasons prone to icing of superstructures, the effects of icing on stability shall be considered as described in [11.19.28]. 11.10.3 Wind overturning (intact condition all units) 11.10.3.1 For the intact condition, the area under the righting moment curve shall not be less than 40% in excess of the area under the wind overturning arm curve (30% for column stabilised units). The areas shall be bounded by 0º inclination, and the dynamic angle (defined as the angle at which this condition is met). The dynamic angle shall be less than both the second intercept and the downflooding angle as shown in Figure 112. 11.10.3.2 The wind velocity used for intact wind overturning calculations for the survival condition shall be the 1minute design wind speed, as described in [3.2]. In the absence of other data, 52 m/s (100 knots) shall be used. A 36 m/s (70 knot) wind can be used for operating conditions as long as the unit can always change to a survival condition within an adequate time scale. Figure 112 Wind overturning criteria (intact case) 11.10.4 Damage stability background (all except for columnstabilised) 11.10.4.1 This section gives the common requirements for damage stability before the specific requirements for jackups in [11.10.5] and others in [11.10.7] 11.10.4.2 The wind velocity used for overturning moment calculations in the damage condition shall be 26 m/s (50 knots) or the wind used for the intact calculation if less. It shall be applied in the most critical direction. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 314 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.10.2.9 Subject to [11.10.2.8], [11.10.4.4], [5.6.2.5] and [11.19.24.2] (for ice areas), buoyant cargo overhangs can be assumed to contribute to the range of stability requirement of [11.10.2.4], but see [5.6.2.5] e). a) b) c) d) e) All piping and ventilation systems within the 1.5 m penetration in damaged compartments shall be assumed damaged. Positive means of closure shall be provided to preclude the progressive flooding of other spaces which are intended to be intact. Damage shall be assumed to extend from the baseline upwards without limit. The distance between effective watertight bulkheads or their nearest stepped positions which are positioned within the assumed extent of horizontal penetration should not be less than 3 m; where there is a lesser distance, one or more of the adjacent bulkheads shall be disregarded. The consequences of water ballast escaping from any compartments above the waterline, or the escape of air from any air cushion shall be evaluated where applicable. Where damage of a lesser extent than in [a)] to [d)] results in a more severe condition such lesser extent shall be assumed. 11.10.4.4 If buoyancy of the cargo has been included to meet intact stability requirements, then loss of cargo buoyancy or flooding of cargo compartments, shall be considered as a damage case, as appropriate. 11.10.4.5 The extent and adequacy of the precautions necessary for a particular towage shall be assessed on a casebycase basis. 11.10.4.6 Transports on multiple vessels. When cargo is transported on multiple vessels it shall be demonstrated that the flooding of any one compartment of any vessel cannot cause the damaged vessel to change its heeling or trim angle relative to the overall heeling or trim of the combined vessel assembly. In other words, the damaged vessel should not pivot around any of the reaction points between it and the cargo or between it and another vessel, thus losing contact at another reaction point. 11.10.5 Damage stability for jackups 11.10.5.1 All units shall have positive stability about any horizontal axis with any one compartment flooded or breached. 11.10.5.2 The residual range of damage stability (ignoring downflooding and wind inclination) about any axis from the angle of loll to the maximum angle of positive stability shall be not less than (7º + 1.5 x angle of loll) with a minimum of 10º as shown in Figure 113. 11.10.5.3 The downflooding angle shall be greater than the first intercept (the angle of loll plus wind inclination, with the wind speed in [11.10.4.2]). 11.10.5.4 Where a mat is fitted, the damage shall generally be assumed for either hull or mat. Simultaneous damage shall be assumed if any part of the mat is within 1.5 m of the waterline or upper hull and the mat extends less than 1.5 m horizontally outside the upper hull. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 315 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.10.4.3 All units (except for those covered in [11.10.7.1]) shall have positive stability about any horizontal axis with damage caused by an assumed minimum penetration of 1.5 m from any external plating, between effective watertight bulkheads, with the following: 11.10.6 Damage stability for column stabilised units 11.10.6.1 Damage shall be considered for 2 separate cases, A and B for any transit or operating draught and for the most critical horizontal axis and wind direction. 11.10.6.2 Case A (including wind heel using the wind speed in [11.10.4.2]) covers damage on exposed portions of columns, underwater hulls and braces on the periphery of the unit. (Exposed means outboard of a line through the centres of the periphery columns). The damage shall be assumed to have a horizontal penetration of 1.5 m and a vertical extent of 3 m occurring at any level between 5 m above and 3 m below the transit or operating draught being considered. The following shall be assumed damaged: 1) 2) 3) Any horizontal flat between these levels. All piping and ventilation systems within the 1.5 m penetration in damaged compartments shall be assumed damaged. Positive means of closure shall be provided to preclude the progressive flooding of other spaces which are intended to be intact. Any vertical bulkheads within the following distances of another which is considered intact: — 3 m, or — column perimeter/8 measured around the outer skin at the waterline (when within a column) if greater than 3 m. 11.10.6.3 The inclination at the first intercept (the angle of loll plus wind heel) for any axis shall be less than 17º and less than the downflooding angle. 11.10.6.4 The residual range of stability from the first intercept to the second (ignoring downflooding, but see [11.10.8.2]) shall be not less than 7º. 11.10.6.5 The righting arm at some inclination before downflooding or the second intercept (if less) shall be at least twice the Wind Heel Arm (shown as WHA in Figure 114) at the same angle. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 316 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 113 Damage stability for jackups 11.10.6.6 Case B covers flooding of any compartment adjacent to the sea, or with pumps, or with machinery with salt water cooling. No wind heel need be included. a) b) The angle of loll shall be less than 25º for any axis. The residual range of stability from the angle of loll to the downflooding angle shall be not less than 7º. Figure 115 Damage stability for column stabilised unit (Case B) 11.10.7 Damage stability (apart from jackups and column stabilised) 11.10.7.1 Except as described in [11.10.7.2] and [11.10.7.3], the unit should have sufficient reserve stability in a damaged condition to withstand the wind heeling moment using the wind speed in [11.10.4.2] superimposed from any direction and the damage as described in [11.10.4.3]. In this condition the final waterline, after flooding and wind heel, should be below the lower edge of any downflooding opening as shown in Figure 116. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 317 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 114 Damage stability for column stabilised unit (Case A) 11.10.7.2 Onecompartment damage stability is not always achievable without impractical design changes, for the wet towages of the following and similar structures: — — — — — Concrete gravity based structures, particularly when towing on the columns Submerged tube tunnel sections Bridge pier caissons Outfall or water intake caissons Monopiles, transition pieces (TPs) and suction bases for wind farm foundations. 11.10.7.3 For those structures listed in [11.10.7.2], or similar, damage stability requirements can be relaxed, provided the towage is a oneoff towage of short duration, carried out under controlled conditions, and suitable precautions are taken, which can include: — Areas vulnerable to collision should be reinforced or fendered to withstand collision from the largest towing or attending vessel, at a speed of 2 m/s. — Projecting hatches, pipework and valves are protected against collision or damage from towing and handling lines. — Emergency towlines are provided, with trailing pickup lines, to minimise the need for vessels to approach the structure closely during the tow. — Emergency pumping equipment is provided. — Potential leaks via ballast or other systems are minimised. — Ballast intakes and discharges, and any other penetrations through the skin of the vessel or object, shall be protected by a double barrier system, or blanked off. — Vulnerable areas are conspicuously marked and Masters of all towing and attending vessels are aware of the vulnerable areas. — A guard vessel is available to warn off other approaching vessels. — A risk assessment in accordance with [2.4] shall be carried out. 11.10.7.4 The relaxations allowed by [11.10.7.2] and [11.10.7.3] do not apply in iceaffected areas, where the vessel or structure should comply with [11.19.28]. 11.10.7.5 The damage stability recommendations of this section do not apply to transport of cargos on flagged trading vessels, sailing at the assigned ‘B’ freeboard or greater. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 318 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 116 Damage stability (apart from jackups and columnstabilised) The ‘B’ freeboard is the minimum freeboard assigned to a Type B vessel, which is generally defined as any vessel not carrying a bulk liquid cargo. Reduced freeboards can be assigned to a Type B vessel over 100 m in length, depending on the arrangements for protection of crew, freeing arrangements, strength, sealing and security of hatch covers, and damage stability characteristics. See the IMO International Convention on Load Lines, Consolidated Edition 2005, /90/, for further details. endofguidancenote 11.10.8 Compartmentation and watertight integrity 11.10.8.1 All external openings below the static intact and any onecompartmentdamaged waterlines from [11.10.3] to [11.10.7] with wind applied in the most onerous directions, but no waves, shall be fitted with watertight closing appliances in operable condition. 11.10.8.2 Weathertight closing appliances in operable condition shall be fitted to all external openings that are not required to be watertight by [11.10.8.1] and are below either: — the static intact waterline at the dynamic angle (the smallest angle at which the area ratio in Figure 112 is satisfied), or — 4 m above all required static onecompartmentdamaged waterlines. All horizontal axes should be considered with the wind applied in the most onerous direction for each case. 11.10.8.3 Where the watertight integrity of any tow is in question, particularly for demolition tows, part built ships and MOU’s, it shall be checked by visual inspection, chalk test, ultrasonic test, hose test or air test as considered appropriate by the attending MWS company surveyor. 11.10.8.4 Hatches, ventilators, gooseneck air pipes and sounding pipes shall be carefully checked for proper closure and their watertight or weathertight integrity confirmed. Where such equipment could be damaged by sea action or movement of loose equipment, then additional precautions shall be considered. 11.10.8.5 Outboard accommodation doors shall be carefully checked for proper closure and their watertight or weathertight integrity confirmed. All dogs shall be in good operating condition and seals shall be functioning correctly. 11.10.8.6 Watertight doors in holds, tween decks and engine room bulkheads, including shaft alleyway and boiler room spaces, shall be checked for condition and securely closed. 11.10.8.7 Any watertight doors required to be opened for access during the voyage, shall be marked, on both sides, “To be kept closed except for access” or words to that effect. In some cases a length of bar or pipe can be required to assist opening and closing. 11.10.8.8 Portholes shall be checked watertight. Porthole deadlights shall be closed where fitted. Any opening without deadlights that can suffer damage in a seaway shall be plated over. 11.10.8.9 Windows which could be exposed to wave action shall be plated over, or similarly protected. 11.10.8.10 All tank top and deck manhole covers and their gaskets shall be in place, checked in good condition, and securely bolted down. 11.10.8.11 All overboard valves shall be closed and locked with wire or chain. Where secondary or backup valves are fitted for double protection, they shall also be closed. 11.10.8.12 Closure devices fitted to sanitary discharge pipes, particularly near the waterline, shall be closed. Any discharge pipe close to the waterline not fitted with a closure device, can need such a facility incorporated, or be plated over. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 319 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.10.8.14 All other spaces shall be sounded before departure. It is recommended that all spaces should be either pressed up or empty. Slack tanks should be kept to a minimum. 11.10.9 Draught and trim 11.10.9.1 For vessels and barges with a load line certificate, the draught shall not normally exceed the appropriate load line draught, without flag state exemption, except for temporary onload and offload operations under controlled conditions. 11.10.9.2 The draught should be small enough to give adequate freeboard and stability, and large enough to reduce motions and slamming. Typically, for barge towages, it will be between 35% and 60% of hull depth, which is usually significantly less than the load line draught. 11.10.9.3 For barges and large towed objects, such as FSUs, the draught and trim should be selected to minimise slamming under the forefoot, to give good directional control, and to allow for the forward trim caused by towline pull. 11.10.9.4 For guidance, and for discussion with the Master of the tug, the tow should be ballasted to the minimum draughts and trims for barges in Table 1115. Table 1115 Minimum recommended draught and trim for barges Length of Towed Vessel Minimum Draught Forward Minimum Trim by Stern 30 m 1.0 m 0.3 m 60 m 1.7 m 0.6 m 90 m 2.4 m 0.8 m 120 m 3.1 m 1.0 m 150 m 3.7 m 1.2 m 200 m plus 4.0 m 1.5 m 11.10.9.5 Where barges with faired sterns are fitted with directional stabilising skegs, it can be preferable to have no trim. However allowance should be made for trim caused by the towline force and there should be adequate freeboard at the bow (and possibly a breakwater) to minimise damage from “green water” coming over the bow. 11.10.9.6 For towed shipshaped units (where LOA is the overall length of the unit in metres) the forward draught should be greater than: for LOA≥200 m 2.0 m+ 0.015 x LOA for LOA <200 m as for barges in Table 1115 but in both cases the mean draught shall not be less than the minimum Class approved ballast draught. Slamming pressure under the forefoot estimated for the metocean criteria for the tow route shall be less than the bottom design pressure. For directional stability, a minimum aft trim of 0.75% of LOA is normally recommended. 11.10.9.7 Draught should be carefully selected for FSU’s etc. that will have deeper inoperation draughts than for towage. This can give higher accelerations in the installed modules etc. when under tow. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 320 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.10.8.13 All holds, void spaces and engine room bilges shall be checked before departure and should be pumped dry. 11.10.9.9 Draught marks forward and aft shall be easily readable and, if necessary, repainted in the area above the waterline. 11.10.9.10 Where the tow is unmanned, and in order that the tug can monitor any increased draught during the towage, a broad distinctive line of contrasting colour should be painted around the bow approximately 0.5 m above the waterline. 11.11 Transport vessel or barge selection 11.11.1 Selection criteria 11.11.1.1 In addition to the requirements in [2.11], the transport barge or vessel selection, including identification of any necessary repairs or upgrades, should be undertaken considering the following: a) There shall be adequate deck space for all the cargo items planned, including room for seafastenings, access between cargo items, access to towing and emergency equipment, access to tank manholes, installation of cargo protection breakwaters if needed, and for lifting offshore if required. b) The barge or vessel shall have adequate intact and damage stability with the cargo and ballast as planned, including any requirement for ballast water exchange. c) The barge or vessel as loaded shall have sufficient freeboard to give reasonable protection to the cargo. d) If a floating loadout is planned, there shall be sufficient water depth to access and leave the loadout berth and for the loadout to be carried out in accordance with Sec.10. e) If a submerged loadout is planned, the barge or vessel can be submerged, within its Class limitation, so as to give adequate clearance over the deck, and adequate stability at all stages, within the water depth limitations of the loadout location. f) There shall be adequate pumping capacity to comply with [11.15], or be suitable for the use of additional pumping equipment. g) Submersible barges. Barges that can be totally immersed in the intact condition should be classed as submersible barges. Submersible barges are normally classed as such by a RCS (Recognized Classification Society). h) The deck strength shall be adequate, including stiffener, frame and bulkhead spacing and capacity, for loadout and transport loads. i) For a vessel, securing of seafastenings shall not need welding in way of fuel tanks. j) For a barge, it shall be properly equipped with main and emergency towing connections, recovery gear, pumping equipment, mooring equipment, anchors, lighting and access ladders. k) The motion responses as calculated shall not cause overstress of the cargo. l) All required equipment and machinery shall be in sound condition and operating correctly. m) The barge or vessel shall possess the relevant, in date, documentation as set out in Table B2. n) Unclassed barges shall be subject to appropriate projectspecific structural, equipment and machinery checks. They shall have a valid load line, or load line exemption, certificate. Guidance note: To ensure compliance with [2.11], the charterer is advised to have a suitability survey and an onhire survey of the barge or vessel carried out before acceptance of the charter. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 321 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.10.9.8 It can be preferable to tow structures such as floating docks at minimum draught with zero trim, in order to minimise longitudinal bending moments. 11.12.1 General 11.12.1.1 The tug(s) selected should comply with the minimum bollard pull requirements shown in [11.12.2], and should also comply with the appropriate Category in Table 1116. The appropriate category should be agreed with the MWS company. Table 1116 Tug categories Category ST – Salvage Tug U Unrestricted Used for Single tug towages in benign or nonbenign weather areas. They shall have very good seakeeping qualities including good propeller immersion in bad weather. These qualities are unlikely to be satisfied with a Length Over All (LOA) less than 40 m and a displacement of less than 1,000 tonnes. C Coastal Towages in benign weather areas or staged tows R1 Restricted Assisting in multitug towages R2 Restricted Benign weather area towages R3 Restricted Assisting in multitug towages in benign weather areas 11.12.1.2 Vessels in all categories shall be of such a design to allow them to operate safely and effectively in their designated areas and shall be purposebuilt for towing operations or be of a multipurpose design having towing capability. 11.12.1.3 The length and normal operating draught of the vessel shall be adequate to maintain propeller effectiveness and reduce slamming in heavy weather conditions. 11.12.1.4 Vessels in category ST, U, C and R1 shall have a raised forecastle with a height of at least 2 m above the freeboard deck. The forecastle shall be of such a design to ensure minimum water retention. 11.12.1.5 The tug(s) used for any towage to be approved by the MWS company should be inspected by a MWS company surveyor before the start of the towage. The survey shall cover the suitability of the vessel for the proposed operation, its seakeeping capability, general condition, documentation (including ice classification if applicable), towing equipment, manning and fuel requirements. 11.12.1.6 Where the tug does not have a bollard pull test certificate giving the static continuous bollard pull, issued or endorsed within the last 10 years by a body approved by a Recognized Classification Society or other certification body accepted by the MWS company, then it can be calculated as follows: 1) 2) for tugs under 10 years old without a bollard pull certificate, the bollard pull can be estimated as 1 tonne/100 (Certified) BHP (Brake Horsepower) of the main engines. Icebreaking tugs can be less than this and the MWS company should be consulted. for tugs over 10 years old, without a bollard pull certificate less than 10 years old, can be the greater of: — the certified value reduced by 1% per year of age since the BP test, or — the value from 1) above reduced by 1% per year of age greater than 10. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 322 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.12 Tug selection — Act as a guardship, to protect the tow, and advise approaching vessels that they can be running into danger — In the event of mechanical failure or towline breakage, assist in removing the failed tug from the towing spread. In this case it is desirable for all the main tugs to have towing connections forward and appropriate rigging deployed. See [11.18.7.5] for procedure for tug breakdowns in multitug tows. — Take over the duties of the failed tug — Provide any other required assistance in an emergency. 11.12.2 Bollard pull requirements 11.12.2.1 The minimum towline pull required (TPR) shall be calculated based on the towing route (including available sea room) and procedures. In all cases, an assessment should be made that a reasonable speed can be achieved in moderate weather. The TPR calculations shall include the wind, wave drift and current (i.e. relative speed between towed object and water) forces and should be calculated for all relevant combinations of wind, wave and current directions relative to the towed object. Guidance note: Further guidance may be found in DNVGLRPN103 Sec.7, /56/. endofguidancenote 11.12.2.2 Table 1117 summarises the different conditions to be considered. The conditions are described in more detail in the indicated sections. Table 1117 Meteorological criteria for calculating TPR (towline pull required) Section Condition Hs(m) Wind (m/sec) Current (m/sec) [11.12.2.3] Standard 5 20 0.5 [11.12.2.3] Benign weather areas [11.12.2.4] Limited sea room [11.12.2.5] Weather restricted towage [11.12.2.6] <24 hour staged tow or <24 hour jackup move [11.12.2.7] Sheltered from waves As agreed with the MWS company but not less than: 2 15 0.5 Design Design (1 hour mean) 0.5 or predicted current if greater To document that the tow will maintain forward speed under all possible weather conditions and to render probable that the tow can be carried out within TPOP 3 15 0.5 or predicted current if greater As agreed with the MWS company. 11.12.2.3 For weather unrestricted towages where adequate sea room can be achieved within the departure weather forecast and maintained thereafter, the TPR shall be computed for zero forward speed against the following acting simultaneously: 1) For nonbenign areas: — 5.0 m significant sea state, and — 20 m/s wind, and — 0.5 m/s current, or the maximum predicted surface current if greater. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 323 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.12.1.7 Additional tug(s) can be required for high value tows or towages through areas with limited sea room or through high density traffic zones, to carry out the following duties: For benign weather areas, the criteria for calculation of TPR shall be agreed with the MWS company and generally these should not be less than: — 2.0 m significant sea state, and — 15 m/s wind, and — 0.5 m/s current. Guidance note: If the tow route passes through an area of continuous adverse current or weather, a greater TPR may be required and agreed with the MWS company. endofguidancenote 11.12.2.4 For towages which pass through an area of restricted navigation or manoeuvrability, outside the validity of the departure weather forecast and which cannot be considered a weather restricted operation, the Towline Pull Required (TPR) should be computed for zero forward speed against the following acting simultaneously: — the design wave height see [3.4.8] (but such towages should not be attempted if the design wave is more than 5 m significant), and — 1 hour design wind speed (see [3.4.6]), and — 0.5 m/s current, or the maximum predicted surface current if greater. 11.12.2.5 For weather restricted towages, the TPR shall be the greater of the TPRs calculated for the following sets of environmental conditions: 1) to document that the tow will maintain forward speed under all possible weather conditions: — the OPLIM significant wave height, OPLIM < 5 m (i.e. such towages should not be attempted if the design wave is more than 5 m significant) — the tenminute sustained wind velocity of 1.2 times the OPLIM wind speed and — a one year return period current + 0.5 m/s. 2) to render probable that the tow can be carried out within TPOP: — the OPWF significant wave height — the tenminute sustained wind velocity of the OPWF wind speed and — a one year return period current + the required forward speed to obtain TPOP. Guidance note 1: Where weather restricted towages pass through an area of restricted navigation or manoeuvrability increases to the above environmental conditions can be required. endofguidancenote Guidance note 2: The alpha factor to be applied is the same as used in the structural checks. endofguidancenote 11.12.2.6 For towages which are planned to take less than 24 hours (including jackup moves and every stage of a staged tow) and have adequate marine procedures, the following reduced criteria, acting simultaneously, may be used for the calculation of TPR: — 3.0 m significant sea state, and — 15 m/s wind, and — 0.5 m/s current, or the maximum predicted surface current if greater. 11.12.2.7 For towages partly sheltered from wave action, but exposed to strong winds, the criteria shall be agreed with the MWS company. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 324 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 2) where: Teff (BP × Teff)/100 Σ = the tug efficiency in the sea conditions considered, % = the contribution to TPR of each tug = the aggregate of all tugs assumed to contribute. 11.12.2.9 Only those tugs connected so they are capable of pulling effectively in the forward direction shall be assumed to contribute. Stern tugs shall be discounted from the calculation in [11.12.2.8]. 11.12.2.10 Tug efficiency, Teff, depends on the size and configuration of the tug, the sea state considered and the towing speed achieved. In the absence of alternative information, Teff can be estimated for good oceangoing tugs according to the following equation: where: LOA = tug length overall in metres (using 45 m for LOA > 45 m) BP = Static continuous bollard pull in tonnes (with BP > 20 tonnes, and using 100 when BP >100 tonnes) = significant wave height (with 1 m < Hs < 5 m). Hs Guidance note: Towing vessels will generally have very low efficiencies with Hs > 5 m since they should be protecting their towing gear. Towing Teff in all sea states. vessels with less seakindly characteristics will have significantly lower values of endofguidancenote 11.12.2.11 These efficiencies given in [11.12.2.10] are shown graphically in Figure 117 for tugs of LOA > 45 m in different significant wave heights up to 5 m. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 325 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.12.2.8 The effective continuous static bollard pull (BP) of the tug(s) proposed shall be greater than or equal to TPR as shown by: This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 117 Tug efficiencies in various wave heights (tug LOA ≥ 45 m) 11.12.2.12 The resulting effective bollard pull in different wave heights for tugs with LOA ≥ 45 m and LOA = 20 m is shown in Figure 118. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 326 11.12.2.13 The curves for 20 m LOA tugs do not imply that they are approvable for towages in the given wave heights but are shown to demonstrate the effect on assumed efficiency. See also [11.12.1.1]. 11.12.2.14 Short towlines: The effect of backwash from the towed object shall be taken into account when short towlines are used. If short towlines have to be used, care shall be taken to avoid high shock loading due to lack of adequate towline catenary, especially in bad weather. Guidance note: DNVGLRPN103 [7.2.8], /56/, shows how to estimate the effects of interaction between propeller thrust and the towed object with short towlines. In an extreme case (a very wide and deep towed structure) the backwash may be greater than the towline force. This effect has been observed in tank testing and full scale operations. endofguidancenote 11.12.2.15 Shallow water: Allowance shall be made for the additional towing resistance in shallow water. Guidance note: Cd values will be increased (doubled for draft = 0.9 x water depth). See Fig. 20 of OCIMF Guidelines and Recommendations for Safe Mooring of Large Ships at Piers & Sea Islands 1978, /131/, for details. For small underkeel clearances the endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 327 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 118 Effective bollard pull v wave heights for tug LOA = 20 m and ≥ 45 m 11.12.3.1 The main and spare towing wires, pennants and connections shall be in accordance with [11.13.3]. 11.12.4 Tailgates/stern rails 11.12.4.1 Where a towing tailgate or stern rail is fitted, the radius of the upper rail shall be at least 10 times the diameter of the tug’s main towline, and adequately faired to prevent snagging. 11.12.5 Towline control and seabed clearance 11.12.5.1 Where a towing pod is fitted, its strength shall be shown to be adequate for the forces it is likely to encounter. It should be well faired and the inside and ends shall have a minimum radius of 10 times the towline diameter. 11.12.5.2 Where no pod is fitted, the after deck should be fitted with a gog rope, mechanically operated and capable of being adjusted from a remote station. If a gog rope arrangement is fitted then a spare shall be carried. Where neither a towing pod nor gog rope is fitted, then an alternative means of centring the tow line should be provided. 11.12.5.3 On squaresterned tugs, it is preferred that mechanically or hydraulically operated stops be fitted near the aft end of the bulwarks, to prevent the towline slipping around the tug's quarter in heavy weather. 11.12.5.4 Tug masters should be cognizant of the towline catenary at all times, but particularly in shallow water to avoid towline abrasion or snagging on the sea floor. Ideally this should be by monitoring the water depth, towline tension and the deployed towline length from the tug stern combined with a method of calculating the towline maximum depth below sea level. 11.12.5.5 The minimum static clearance between the towline and the seabed should be 10% of the water depth with a minimum of 5 m in exposed waters or 2 m in sheltered or calm water. 11.12.6 Workboat 11.12.6.1 A powered workboat shall be provided for emergency communication with and transfer to the tow, and shall have adequate means for launching safely in a sea state associated with Beaufort Force 4 to 5. An inflatable or RIB can be acceptable provided it has flooring suitable for carriage of emergency equipment, including the portable pumps in [11.12.10] to the tow. 11.12.7 Communication equipment 11.12.7.1 In addition to normal Authorities’ requirements, the tug shall carry portable marine VHF and/ or UHF radios, for communication with the tow when tug personnel are placed on board for inspections or during an emergency. Spare batteries and a means of recharging them shall be provided. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 328 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.12.3 Main and spare towing wires and towing connections 11.12.8.1 Tugs shall be provided with: — all necessary navigational instruments and uptodate charts (for which an IMOapproved electronic chart display and information system (ECDIS) is acceptable), and — publications that can be required on the particular towage, including information for possible diversion ports and their approaches. 11.12.9 Searchlight 11.12.9.1 The tug shall be fitted with a searchlight to aid night operations and for use in illuminating the tow during periods of emergency or malfunction of the prescribed navigation lights. The searchlight(s) should provide illumination both forward and aft, thereby allowing the tug to approach the tow either bow or stern on. 11.12.10 Portable pump 11.12.10.1 On any tow outside coastal limits, the tug shall carry at least one portable pump, equipped with means of suction and delivery and having a selfcontained power unit with sufficient fuel for 12 hours usage at the pump’s maximum rating. The pump shall be suitable for the requirements outlined in [11.15.2] to [11.15.4] but cannot be considered to be a substitute for the pump(s) required in [11.15.2] as it may be difficult to deploy in bad weather. The methods and feasibility of deployment should be considered. 11.12.11 Additional equipment 11.12.11.1 Antichafe gear should be fitted as necessary. Particular attention should be paid to contact between the towline and towing pods, tow bars and stern rail and any other sharp edges (e.g. in the gap between hull and rollers) that could damage the towline. 11.12.11.2 All tugs should be equipped with burning and welding gear for use in emergency. If this is not possible then burning and welding gear should be accessible on the tow or other tugs. 11.12.12 Bunkers and other consumables 11.12.12.1 The tug should carry fuel and other consumables including potable water, lubricating oil and stores, for the anticipated duration of the towage, taking into account the area and season, plus a useable reserve of at least 5 days’ supply (excluding any unpumpable). For tows likely to take more than 20 days the reserve should be increased to 7 days. 11.12.12.2 If refuelling enroute is proposed, then suitable arrangements shall be made before the towage starts, and included in the towing procedures (see [11.14.7]). 11.12.13 Tug manning and accommodation 11.12.13.1 Vessels in all categories shall be manned to meet the minimum requirements laid down by Statutory Regulations or those required by State or Port Authorities. 11.12.13.2 Manning levels for vessels in all categories shall be subject to the requirements of a specific towage. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 329 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.12.8 Navigational equipment 11.12.13.4 In addition, consideration shall be given to the fact that in an emergency situation, two or more of the tug crew can need to board and remain on the tow for an extended period. This should be taken into account when approving the manning level of a tug. 11.12.13.5 Category ST. To satisfy category ST, certified accommodation and lifesaving appliances shall be provided for a minimum of twelve (12) persons. 11.12.13.6 Vessels in category ST shall, when engaged in towing operations, carry a minimum of five (5) certificated officers. These should be the Master, two (2) Deck Officers and two (2) Engineer Officers. 11.12.13.7 Categories U, C and R1. To satisfy categories U, C and R1, certified accommodation and life saving appliances shall be provided for a minimum of eight (8) persons. 11.12.13.8 Vessels in categories U, C and R1 shall, when engaged in towing operations, carry a minimum of four (4) certificated officers. These should be the Master, one (1) Deck Officer and two (2) Engineer Officers. 11.12.13.9 Vessels in Categories R2 and R3 shall, when engaged in towing operations, carry a minimum of three (3) certificated officers. These should be the Master, one (1) Deck Officer and one (1) Engineer Officer. 11.13 Towing equipment 11.13.1 Flowchart 11.13.1.1 Figure 119 is a flowchart for determining the required strength of the towing gear for a specific tug. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 330 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.12.13.3 Where vessels are required to undertake long duration towages, difficult towages or where the tow is unmanned, they shall have adequate certified accommodation to enable manning levels to be increased. Any increase in manning levels shall be subject to the limitations of the regulations relating to life saving appliances. This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Figure 119 Flowchart for determining towing gear required strength and lengths 11.13.1.2 Towage should normally be from the forward end of the barge or tow via a suitable bridle as shown in [K.1]. The components of the system are: — — — — Towline connections, including towline connection points, fairleads, bridle legs and bridle apex Intermediate pennant Bridle recovery system Emergency towing gear, see [11.13.13]. 11.13.1.3 Where there is a case for towing an object or vessels by the stern, the decision should be based on the results of a risk assessment in accordance with [2.4]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 331 The following could be favourable to tow by the stern: — Partbuilt or damaged ships, or any structure when the bow sections could be vulnerable to wave damage. — Partbuilt ships, converted ships or FPSOs without a rudder or skeg, or with a turret or spider fitted forward, where better directional stability can be obtained if towed by the stern. — Any structure with overhanging or vulnerable equipment near the bow, which could be vulnerable to wave damage, or could interfere with the main and emergency towing connections. endofguidancenote 11.13.1.4 If two tugs of different sizes are to be used for towing, then either: — the larger tug should be connected to the bridle, and the smaller tug to a chain or chain/wire pennant set to one side of the main bridle or — two bridles can be made up, one for each tug. 11.13.1.5 For two balanced tugs, the bridle can be split and the tugs should tow off separate bridle legs, via intermediate pennants. This approach should not be used for tows with rectangular bows. 11.13.1.6 For any systems in [11.13.1.4] and [11.13.1.5], a recovery system should be provided for the connection point for each tug. 11.13.1.7 For tows where a bridle is not appropriate, such as multiple tug towages, then unless agreed otherwise with MWS company each tug should tow off a chain pennant and an intermediate wire pennant. 11.13.2 Number of towlines 11.13.2.1 Table 1118 gives the minimum number of towlines for each category of tug. Table 1118 Tug wire requirements Category Main Wire Spare ST – Salvage Tug Two (on separate winch drums) One U – Unrestricted One One C – Coastal One One R1 – Restricted One Not applicable R2 – Restricted One One R3 – Restricted One Not applicable 11.13.3 Strength of towline and towline connections (outside ice areas) 11.13.3.1 The Minimum Breaking Loads (MBL) of the main and spare towlines, and the ultimate load capacity of the towline connections to the tow including each bridle leg, shall be related to the continuous static bollard pull (BP) of the actual tug to be used. Table 1119 gives the minimum required breaking load of the towlines and wire intermediate pennants (BP, MBL and ULC are in tonnes) but see [11.13.4.4] for shorter towlines. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 332 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Continuous Bollard Pull (BP) Benign Areas Other Areas BP < 40 tonnes 2.0 x BP 3.0 x BP 40 ≤ BP ≤ 100 tonnes 2.0 x BP (220 BP) x BP/60 BP > 100 tonnes 2.0 x BP 2.0 x BP 11.13.3.2 For tugs with very large bollard pulls (typically over 280 tonnes) it can be difficult to satisfy the requirements of Table 1119 due to problems in safely handling the large towlines required. In these cases the effective towing bollard pull for selecting the towline MBL can be reduced to not less than 280 tonnes provided that: — — — — the the the the vessel is fitted with towline tension monitoring, tug Master is in agreement, reduction is documented in the towing procedures and Certificate of Approval, tug master shall take extra care in bad weather to protect the towline. and if practicable: — the winch should be adjusted to pay out at 80% of the towline MBL, and — the engines should be mechanically or electronically limited to produce a maximum static bollard pull of not more than 50% of the towline MBL (i.e. the effective bollard pull). 11.13.3.3 For specific towages in benign weather areas and in deep water that allows long towlines to be deployed, the effective towing bollard pull in [11.13.3.2] can be further reduced to not less than 250 tonnes after agreement with the MWS company. 11.13.3.4 The Ultimate Load Capacity (ULC), in tonnes, of towline connections to the tow, including each bridle leg, connectors (apart from shackles and bridle apex which are covered in [11.13.8]), chain pennants, and fairleads, where fitted, shall be not less than: — ULC = 1.25 x required towline MBL for the actual tug (for MBL ≤ 160 tonnes) or — ULC = required towline MBL for the actual tug + 40 (for MBL > 160 tonnes). 11.13.3.5 See [11.13.4.4] for shorter towlines and [11.13.6.2] for bridle apex angle≥90º. 11.13.3.6 See [11.13.14.3] when bridles and pennants cannot be inspected annually. 11.13.3.7 Any towline connections below or near the towing waterline shall be designed to fail without allowing flooding. 11.13.3.8 A certificate to demonstrate the MBL of each towline shall be submitted. MBL can be obtained by testing, or by showing the aggregate breaking load of its component wires, with a spinning reduction factor. This certificate shall be issued or endorsed by a body approved by a Recognized Classification Society or other certification body accepted by the MWS company. 11.13.3.9 Fairleads, where fitted, shall be designed to take — transverse loadings from any likely tug pulling direction, and — loadings along the line of the towline caused by a chain or shackle being caught in the fairlead using the loads given in [11.13.3.4]. 11.13.3.10 Where no fairleads are fitted, the towing connections shall be similarly designed. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 333 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Table 1119 Minimum required towline breaking loads (RTBL) 11.13.3.12 Where towing connections or fairleads can be subjected to a vertical load, the design shall take account of the connection or fairlead elevation, the proportion of bridle and towline weight taken at the connection or fairlead, and the towline pull, at the maximum pitch angle computed. 11.13.3.13 It should be noted that the above requirement represents the minimum values for towline connection strength. It can be prudent to design the main towline connections to allow for the use of tugs larger than the minimum required. 11.13.3.14 In particular circumstances, where the available tug is oversized with regard to the Towline Pull Required (TPR see [11.12.2]), and the towline connections are already fitted to the tow, then the towline connections, fairleads and bridle (but not the towline itself, pennants, stretchers or shackles between the towline and bridle) can be related to the required BP rather than the actual BP but should allow for the effective length of the towline used. Such relaxation shall be with the express agreement of the Master of the tug, and shall be noted in the towing procedures and Certificate of Approval. It shall not apply for towages in ice areas (see [11.19.23]). 11.13.4 Relationship between towline length and strength 11.13.4.1 The deployable length shall not include the minimum remaining turns on the winch drum, and the distance from the drum to the stern rail or roller. One full strength wire rope pennant which is permanently included in the towing configuration can be considered when determining the deployable length. 11.13.4.2 Except in benign areas and for sheltered water towages, the minimum deployable length in metres of each of the main and spare towlines (L) shall be determined from the “European formula”: except that in no case shall the deployable length (as defined in [11.13.4.1]) be less than 650 m, apart from coastal towages within a good weather forecast when this can be reduced to 500 m. 11.13.4.3 For benign areas, the minimum deployable length in metres shall be not less than: except that in no case shall the deployable length (as defined in [11.13.4.1]) be less than 500 m. 11.13.4.4 The towline MBL as shown in [11.13.3.1] shall be increased if required to allow L to comply with [11.13.4.1] or [11.13.4.2]. In such cases the ULC for the bridle, fairleads and towing connections [11.13.3.4] may need to be correspondingly increased. 11.13.5 Towline connection points 11.13.5.1 Towline connections to the tow shall be of an approved type. They should be capable of quick release under adverse conditions, including to allow a fouled bridle or towline to be cleared, but shall also be secured against premature release. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 334 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.13.3.11 If a fairlead or towing connection is to be used either with or without a bridle, it should be designed for both cases. A typical bracket design is shown in [K.3]. endofguidancenote 11.13.5.2 Towline connections and fairleads shall be designed to the requirements of [11.13.3.4]. 11.13.5.3 Sufficient internal/underdeck strength shall be provided for all towline connections and fairleads. 11.13.5.4 Where fitted, fairleads should be of an approved type, located close to the deck edge. They should be fitted with capping bars and sited in line with the towline connections, to prevent side load on the towing connections. 11.13.5.5 Where the bridle might bear on the deck edge, the deck edge should be suitably faired and reinforced to prevent chafe of the bridle. 11.13.5.6 Where towing connections are of a quickrelease type, then the fairlead design shall allow all the released parts to pass easily through the fairlead. 11.13.6 Bridle legs 11.13.6.1 Each bridle leg should be of stud link chain or composite chain and wire rope. If composite, the chain should be of sufficient length to extend beyond the deck edge and prevent chafing of the wire rope. 11.13.6.2 The angle at the apex of the bridle should normally be between 45° and 60°. If it exceeds 90° (or if either leg is more than 45° to the centreline of the tow) then the strength of the bridle legs, fittings and towing connections shall be increased to allow for the increased resolved load in the bridle from the towline force. 11.13.6.3 The end link of all chains should be a special enlarged link, not a normal link with the stud removed. If there is no enlarged link at the end of the chain connected to the towing bracket, a new Kenter or similar joining shackle may be used provided that care is taken to ensure that the retaining pin cannot come out under tow and that the Kenter is in a more or less static position. 11.13.6.4 All wire ropes shall have hard eyes or sockets but not aluminium or alloy ferrules. 11.13.7 Bridle apex 11.13.7.1 The bridle apex connection should be a towing ring or triangular plate or an enlarged bow shackle. Any towing ring or shackle shall have documented evidence that they have been designed and certified for this type of loading. The triangular plate shall not allow any shackle to rotate (see [K.9.1]). The minimum MBL or ULC of the bridle apex connection should be at least that required for shackles in the bridle as described in [11.13.8]. Guidance note: A triangular plate is also known as a Delta, Flounder or Monkey Plate endofguidancenote 11.13.8 Shackles 11.13.8.1 The documented MBL of shackles forming part of the towline (including any shackle between the towline and the bridle apex) shall be at least 130% of the required MBL of the towline to be used. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 335 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.13.9 Intermediate pennant or surge chains 11.13.9.1 An intermediate wire rope pennant can be fitted between the main towline and the bridle or chain pennant. All wire rope pennants shall have hard eyes or sockets, and be of the same lay (i.e. left or right hand) as the main towline. Guidance note: Its main use is for ease of connection and reconnection. endofguidancenote 11.13.9.2 A synthetic spring, if used, should not normally replace the intermediate wire rope pennant. 11.13.9.3 The length of the wire pennant should be such that it can be handled on the stern of most tugs without the connecting shackle reaching the winch. Longer pennants can be needed in particular cases. Guidance note: For barge tows, pennants are normally 10 m to 15 m long. endofguidancenote 11.13.9.4 The MBL of the wire rope pennant shall not be less than that required for the main towline. 11.13.9.5 Any “fuse” or “weak link” pennant shall have a strength not less than that required for the towline. Guidance note: MWS companies do not normally recommend the use of a “fuse” or “weak link” pennant. endofguidancenote 11.13.9.6 A surge chain can be used, especially in shallow water when a long towline catenary cannot be used, to provide shock absorption. If a surge chain is supplied then the MBL shall not be less than that of the main towing wire. The surge chain shall be a continuous length of welded stud link chain with an enlarged open link at each end (see [11.13.6.4]). A method of recovery of the chain shall be provided in case a tow wire breaks. The length of the surge chain should allow recovery by the tug when the weight of bridle and chain is at the limit of the recovery system in [11.13.11]. 11.13.10 Synthetic springs 11.13.10.1 Where a synthetic spring is used, its MBL shall be at least 1.5 times that required for the main towline. It shall be in good condition and its use shall be in line with the requirements of the manufacturer, especially with regards to storage and safety factors. Synthetic springs have a limited life due to embrittlement and ageing, and shall be stored to protect them from wear, solvents and sunlight. See [11.19.16] for towages when icing can occur. 11.13.10.2 If used, a synthetic spring should normally be connected between the main towing wire and the intermediate pennant, rather than connected directly into the bridle apex. 11.13.10.3 All synthetic springs shall have hard eyes. A synthetic spring should be a continuous loop with a hard eye at each end. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 336 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.13.8.2 The MBL or ULC of the bridle apex and shackles forming part of the bridle shall be not less than 130% of the required MBL of the connected parts. See [1.1.12] if the MBL of any equipment is not known. This is generally preferable to a single line with an eye splice each end due to the reduced strength from splicing. endofguidancenote 11.13.11 Bridle recovery system 11.13.11.1 A system shall be fitted to recover the bridle or chain pennant, to allow reconnection in the event of towline breakage. The recovery system should consists of a winch and a recovery line connected to the bridle apex, via a suitable lead, preferably an Aframe. Guidance note: The preferred type of bridle recovery system is shown in [K.1]. endofguidancenote 11.13.11.2 The recovery winch shall be capable of handling at least 100% of the weight of the bridle, plus attachments including the apex and the intermediate pennant. It shall be suitably secured to the structure of the tow. Except for very small barges, the winch should have its own power source. Sufficient fuel should be carried, including a reserve. Guidance note: A wellsized recovery winch can also be useful for initial connection of the towline. endofguidancenote 11.13.11.3 If the winch is manually operated, it should be fitted with ratchet gear and brake, and should be geared so that the tow bridle apex can be recovered by 2 persons. 11.13.11.4 Should no power source be available, and manual operation is deemed impractical, then arrangements shall be made, utilising additional pennant wires as necessary, to allow the tug to reconnect. 11.13.11.5 The MBL of the recovery wire, shackles, leads etc. shall be at least 6 times the weight of the bridle, apex and intermediate pennant. The winch barrel should be adequate for the length and size of the wire required. 11.13.12 Towing winches 11.13.12.1 Tugs in all categories shall be provided with at least one towing winch, (two towing winch drums for category ST). 11.13.12.2 The towing winch and its connection to the vessel shall be strong enough to withstand a force equal to the actual MBL of the tow wire acting at its maximum height above deck, without overstressing either the winch or the deck connections 11.13.12.3 If the power for the towing winch is supplied via a main engine shaft generator during normal operating conditions, then another generator shall be available to provide power for the towing winch in case of main engine or generator failure. 11.13.12.4 If a multidrum winch is used, then each winch drum shall be capable of independent operation. 11.13.12.5 The towing winch drum(s) shall have sufficient capacity to stow the required minimum length of the tow wire(s). 11.13.12.6 A spooling device shall be provided such that the tow wire(s) is effectively spooled on to the winch drum(s). Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 337 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.13.12.8 The winch shall be fitted with a mechanism for emergency release of the tow wire. 11.13.12.9 There shall be an adequate means of communication between the winch control station(s) and the engine control station(s) and the bridge. 11.13.12.10 If there is only one towing winch then the crew shall be able to demonstrate that a spare tow wire can be safely run onto the towing winch within 6 hours of a towline break in bad weather. 11.13.13 Emergency towing gear 11.13.13.1 Emergency towing gear shall be provided in case of towline failure, bridle failure or inability to recover the bridle. The method of retrieving the emergency towing gear should be deployed as soon as practical and safe after commencement of the voyage unless it can be safely deployed from the tow in case of an emergency during the voyage. 11.13.13.2 The emergency towing gear should be fitted at the bow of the tow and consist of either a separate bridle and pennant or a system as shown in [K.2]. Precautions should be taken to minimise chafe of all wire ropes. 11.13.13.3 For a bridle arrangement the same strength requirements as the main bridle shall apply. 11.13.13.4 If a system as shown in [K.2] is to be used the following shall apply: a) b) c) d) e) f) The towing connection should be on or near the centreline of the tow, over a bulkhead or other suitable strong point Closed fairlead should be provided The emergency pennant should be at least 80 m, with hard eyes or sockets. See guidance note. An extension wire to prevent the float line chafing on the stern of the tow should be provided. A float line, to extend 75 m to 90 m abaft the stern of the tow should be provided Conspicuous pickup buoy, with reflective tape, on the end of the float line should be provided. Guidance note: The pennant is preferably in one length. The pennant length can be reduced for small barges and in benign areas endofguidancenote 11.13.13.5 The strength of items [a)] and [b)] above should be as for the main towline connections, as shown in [11.13.3.4]. The MBL of the handling system, items [d)] and [e)] above should be not less than 25 tonnes (with shackles stronger by a factor of 1.3), and shall be sufficient to break the securing devices or lashings. 11.13.13.6 If the emergency towline is attached forward, it shall be led over the main tow bridle. It should be secured to the outer edge of the tow, outside all obstructions, with soft lashings, or metal clips opening outwards, approximately every 3 m. 11.13.13.7 If the emergency towing gear is attached aft, the wire rope should be coiled or flaked near the stern, so that it can be pulled clear. The outboard eye should be led over the deck edge to prevent chafe of the float line. 11.13.13.8 For towage of very long vessels, alternative emergency arrangements can be approvable but any arrangement shall be agreed with the Master of the tug to ensure that reconnection is possible in an emergency. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 338 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.13.12.7 The towing winch brake shall be capable of preventing the towing wire from paying out when the vessel is towing at its maximum bollard pull and shall not release automatically in case of a power failure. 11.13.13.10 The connection of the float line to the pennant line or extension wire, and at the connection of the float line to the buoy should have swivels. 11.13.13.11 The following reconnection equipment should also be considered, and placed on board if the duration and area of the towage demand it: a) b) c) Heaving lines Line throwing equipment Spare shackles. 11.13.14 Certification and inspection 11.13.14.1 Valid certificates (less than 5 years old) shall be submitted for all towing gear hardware (e.g. chains, wires and shackles) from the towing winch to the towing connections. Certificates shall be issued or endorsed by bodies approved by a Recognized Classification Society or other body accepted by the MWS company. For Delta plates, less than 5 years old, calculations agreed with the MWS company in advance can be acceptable instead of certification. Guidance note: It is preferable for certificates to detail any proof load testing (individual or batch) that has been performed. Where certification is not submitted or attainable for minor items the MWS company can recommend that oversized equipment be fitted. endofguidancenote 11.13.14.2 Apart from towing bridles or pennants connected to underwater connections (such as on semi submersible pontoons) all towing gear hardware shall be subjected to a documented thorough examination by a competent person not more than 12 months before use and shall be visually inspected before each use. Any significant wear or damage shall be repaired and thoroughly examined again before use or the item replaced. The competent person may require applicable testing in accordance with a recognised code e.g. MPI and/or UT and/or proof load testing. 11.13.14.3 For any towing gear that cannot be thoroughly examined annually, an inspection regime shall be agreed in advance with the vessel operator. Higher safety factors shall be agreed to allow for corrosion, fatigue and longer times between examinations. The maximum age for such equipment shall be 5 years from new and typically the safety factors should be increased by an extra 20% per year after the first year. Special attention should be paid to any gear that spends time in the splash zone as it is subject to accelerated corrosion. Guidance note: For example a submerged bridle pennant with a 5 year planned life, rated for a 100 tonnes BP tug, the required MBL would need to be increased from 240 tonnes by a factor of 1.8 to 432 tonnes. endofguidancenote 11.13.14.4 Towlines shall not be in use longer than 100,000 nautical miles, of which no more than 50,000 miles shall have been in adverse weather conditions (nominally > Beaufort Force 6). Within 5 years from new or from any previous similar test about 10 m to 12 m of towline shall be cut out and break tested or proof loaded to 1.5 x BP without yielding. Max towline life shall be 5 years if not adequately documented in a towline log. Tow wires shall be terminated with hard eye thimbles or closed sockets. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 339 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.13.13.9 Whatever the arrangement agreed, precautions shall be taken so no chafe can occur to the floating line when deployed. Guidance on recording of towing operations can be found in IMO “Guidelines for Safe Ocean Towing”, /138/. See also “Guidelines for Offshore Marine Operations (GOMO)” /69/, section 12.2.3.3. endofguidancenote 11.13.14.5 Anchor handling “work” wires should generally not be used for towing due to the high probability of damage. The only exception is when the wire log shows only very light use and after a thorough examination of the whole wire by an independent competent person appropriately certified to do such inspections. 11.13.14.6 Tow wires shall be terminated with hard eye thimbles or closed sockets. Hard eye thimbles shall be formed by an acceptable type of mechanical splice except where formed at sea in an emergency situation. 11.13.14.7 The closed socket (normally spelter type) if used to form the towline termination shall be renewed at intervals not exceeding 2.5 (two and a half) years (excluding time before fitting when new on the tug), irrespective of the condition of the socket and its wire. Except when resocketed at sea for (temporary) contingency reasons socketing shall only be done by a certified specialist, approved by a Recognized Classification Society. Renewed means the wire cropped back to steel that shows no sign of deterioration and the use of either a new socket or one which has undergone rigorous NDT. 11.13.14.8 Aluminium or alloy ferrules shall not be used on any pennant or towline. 11.13.14.9 The MWS company surveyor can reject any items that appear to be unfit for purpose, or are lacking valid certification. 11.13.14.10 Table 1120 summarises the required expiry times for the above certificates and inspections shown above. Table 1120 Certificate and inspection document requirements Time since issue of original certificates and either revalidation or reissue of original certificates Time since thorough examination by a competent person (unless new) <10 years Not applicable. See [11.12.1.6] Delta plates, master links and shackles <5 years < 12 months Pennants, bridles and towlines <5 years < 12 months Submerged bridles <5 years See [11.13.14.3] Lashing equipment <4 years < 12 months <2.5 years excluding time before fitting when new < 12 months Item Bollard pull Spelter sockets 11.13.15 Access to tows 11.13.15.1 Whether a tow is manned or not, suitable access shall be provided. This can include at least one permanent steel ladder on each side, from main deck to below the waterline. 11.13.15.2 Where practical, ladders should be recessed, back painted for ease of identification, be clear of overhanging cargo, and faired off to permit access by the tug’s workboat. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 340 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Guidance note: For example, a pilot ladder on each side or over the stern, secured to prevent it being washed up on deck, can be accepted for short tows or where it can be deployed from a manned tow. endofguidancenote 11.13.15.4 Objects with high freeboard (e.g. over about 10 m) should have stairways. Where stairways are not practical ladders should have resting platforms every 10 m and be enclosed, except within 5 m of the towage waterline. 11.13.15.5 Where practical, a clear space should be provided and appropriately marked, with access ladders if necessary so that, in an emergency, men can be landed or recovered by helicopter. Guidance note: If it is required to land a crew on board before entering port, for instance to start pumps and reduce draught, then a properly marked and certified helideck or landing area would be an advantage. endofguidancenote 11.13.15.6 A boarding party shall be appropriately equipped such as survival suits, lifejackets and communication equipment. 11.13.15.7 Unmanned tows should have lifesaving appliances on board, appropriate to the hazards a boarding party could experience. 11.13.15.8 Notwithstanding the potential for piracy in some areas, means of boarding shall still be available. 11.13.16 Damage control and emergency equipment 11.13.16.1 When the length and area of the towage demand it, the following equipment should be carried on the tow in suitable packages or in a waterproof container secured to the deck: a) b) c) d) e) f) g) h) i) j) k) l) m) n) o) p) q) r) Burning gear Welding equipment Steel plate various thicknesses Steel angle section various sizes and lengths Plywood sheets – 25 mm thick Lengths of 3” x 3” (75 mm x 75 mm) timber Caulking material Sand and cement (suitably packaged) Nails various sizes Wooden plugs – various sizes Wooden wedges – various sizes A selection of tools, including a hydraulic jack, hammers, saws, crowbars, Tirfors. Portable coamings 60 cm minimum height, with a flange and boltholes to suit the manhole design. The top should be constructed to avoid damage to hoses and cables A sounding tube extension, of 60 cm minimum height, threaded so that it can be screwed into all sounding plug holes Sounding tapes Firefighting equipment as appropriate Personal protection equipment gloves, goggles, hard hats, survival suits etc. Emergency lighting. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 341 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.13.15.3 Alternatives can be accepted if it can be demonstrated that they will provide a safe and reliable means of access during the towage. 11.14.1 General 11.14.1.1 The following requirements apply to the way in which the towage or voyage shall be conducted. The Certificate of Approval is based on agreed towage or voyage arrangements, which shall not be deviated from without good cause, and where practical with the prior agreement of the MWS company. Deviations should follow the MOC and/or contingency plans within the towing/transport manual/procedures. 11.14.1.2 Towages and voyages in the Arctic and Antarctic waters, as defined in SOLAS, /139/, Chapter XIV (Safety measures for ships operating in polar waters), shall comply with the mandatory IMO Polar Code, /130/. Guidance note: The maximum extent of Arctic and Antarctic waters are shown in Figure 1 and 2 of IMO Resolution A.1024(26), /94/ or IMO Polar Code, /130/. endofguidancenote 11.14.1.3 Planning of the voyage or towage shall be carried out in accordance with the requirements of the IMO International Safety Management Code, /92/. 11.14.1.4 All towages shall start on a reliable good weather forecast (see [11.14.4]) 11.14.1.5 The critical depth contours for grounding, allowing for roll, pitch and heave in the worst expected weather conditions (typically less than BF8/9) at LAT, should be plotted in advance. For sea room calculations in [11.14.2], the contours should be the underkeel clearance in a 1 year return storm. 11.14.1.6 The route should be planned to avoid passing too close upwind or upcurrent of any platforms or other isolated obstacles, especially for single tug tows. 11.14.1.7 The required sea room and the basis for its calculation should be included in the towing procedures/manual for the guidance of the tug captain(s)/towmaster. 11.14.1.8 The actual tow route can safely deviate from the planned route if the weather forecasts are favourable as long as the tow can obtain the required sea room before bad weather is likely to arrive. Guidance note: In many cases in rough weather areas and seasons the required sea room can be many hundreds of miles. It may be impractical to plan a route with adequate sea room and so a staged towage can be required (in which there is a commitment to seek shelter or jackup at a standby location on receipt of a bad weather forecast). However a staged towage may be impracticable due to the problems of finding suitable places of shelter or safely approaching them on a lee shore. endofguidancenote 11.14.1.9 If stretchers are used then their fatigue life (typically about 3 days in bad weather for a new stretcher) shall be shown to be adequate. 11.14.2 Sea room 11.14.2.1 Unless a tow’s sea room, for the case in [11.14.2.2] to [11.14.2.5] is greater than both of the following, the tow should be considered to be “higher risk” and the underwriters informed as in [1.1.6]: — 75% of the required sea room within 1 day after the end of the reliable goodweather period of the departure forecast, and Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 342 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.14 Voyage planning Guidance note: Adequate sea room is typically defined as the distance that a disabled transport or tow in bad weather can safely drift, without grounding. endofguidancenote 11.14.2.2 Case 1 In bad weather (outside good weather forecast periods): The required sea room is the distance drifted whilst the significant wave height is greater than 5 m in a storm for that section of the towage including the effect of any associated currents. The design storm for determining required sea room should be at least the 1 year return after the end of a good weather forecast. Guidance note 1: A method of calculating the sea room is described in [K.9.2]. endofguidancenote Guidance note 2: A 1 year storm has been selected as many storms will not blow towards the nearest shoals. endofguidancenote 11.14.2.3 The drift distance when lying broadside to the wind and waves should be used if it is greater than that with bow or stern to wind. 11.14.2.4 It shall be assumed that the tugs develop negligible effective pull in waves over 5 m significant height, unless it can be shown that the actual tugs can safely do so without overloading their deployed towing gear in the relevant water depths. Guidance note: Most tugs cannot develop significant bollard pull without overloading their towing gear in weather much more than BF 8 (typically 20 m/s wind, 5 m sig wave height) since tugs should normally be in “survival mode” if caught in these conditions. endofguidancenote 11.14.2.5 For effective bollard pull to be included in the required sea room calculation, the results of towline tension monitoring should show that the towline yield stress is not exceeded in the relevant weather and towing conditions. The following details should be documented: — — — — — significant wave heights and periods, water depths, towline deployed lengths other relevant towline properties and that the stretcher fatigue life is adequate for the towage including the duration of a 1 year return storm if a stretcher is needed to reduce the shock loads in the towing equipment because of inadequate water depth to deploy enough towline to provide a suitable catenary. Guidance note 1: Towline yield stress is typically about 40% of the wire break load. endofguidancenote Guidance note 2: These results can also be used to validate towline dynamic simulations to extrapolate the results for other conditions. endofguidancenote 11.14.2.6 Case 2 When approaching a potential lee shore (with a good weather forecast): The required sea room is the distance drifted in the worst acceptable forecast conditions during the time taken to replace and reconnect a broken towline and/or disabled tug. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 343 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — 100% of the required sea room within 3 days after the end of the reliable goodweather period of the departure forecast (a reduction can be agreed for short periods during the duration of the tow). See Figure K12 for an example of sea room requirements against time taken to reconnect for a range of weather conditions. endofguidancenote 11.14.2.7 The acceptable forecast conditions should be included within the towage procedures/manual for a particular case. These shall be determined by applying the appropriate Alpha factor to the theoretical limit to allow for uncertainties in the forecast. 11.14.2.8 Approaching a potential lee shore should only be attempted without a good weather forecast if there is no practicable alternative in an emergency situation. Guidance note: An additional (connected) tug can be used to guard against a towline breakage or disabling of a single tug when approaching or leaving a lee shore. endofguidancenote 11.14.2.9 The same philosophy should be followed when transiting “choke points” with limited sea room, or with a high collision risk, with the tow waiting for a suitable good weather window before committing to the approach. 11.14.3 Routeing and piracy 11.14.3.1 Routeing procedures shall be agreed with the Master before the start of the voyage, taking into account: — — — — — the transport vessel or tug’s capacity, fuel consumption, the weather and current conditions, normal good navigation and seamanship and where possible avoiding the potential for piracy. 11.14.3.2 Antipiracy procedures shall be included in the towing/transport manual/procedures unless there is a low risk of piracy. 11.14.3.3 Where antipiracy measures are warrantable the requirements should be advised to the MWS. Guidance note 1: Piracy is prevalent in many areas and these vary with time. Guidance on mitigation of piracy can be found in: a) “BMP4 Best Management Practices for Protection against Somalia Based Piracy” (or later version). This can be downloaded from websites of sponsoring organisations including http://www.intertanko.com/Topics/Security/Security/BMP4 forProtectionagainstSomaliaBasedPiracy/ While this guidance was created to address the Somalian situation, this document’s good practice should be considered for any high risk area. b) Website http://www.lmalloyds.com/LMA/Underwriting/Marine/Joint_War_Committee/lma/underwriting/marine/JWC/ Joint_War.aspx (Lloyd’s Market Association/Joint War Committee website). This also gives current piracy risk areas. c) IMO website http://www.imo.org/OurWork/Security/SecDocs/Pages/MaritimeSecurity.aspx (then select “Piracy”) d) IMB Piracy Reporting Centre website http://www.iccccs.org/piracyreportingcentre e) Flagstate, vessel insurance and P&I club requirements. The MWS company should be advised by the insured at an early stage if there are any relevant insurance warranty requirements. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 344 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: Key mitigations of piracy include: a) Awareness of the sea areas and ports affected by piracy and armed robbery and, at the very least, ensuring proper all round vessel lookouts are in place and maintained, using every means possible, while in these areas. Previous incidents of piracy clearly demonstrate that slow vessels (typically less than about 18 knots) or tows, especially with low freeboards (typically less than about 8 m) or easy access over the side or stern, are particularly at risk. b) Maintaining sufficient distance from land throughout the voyage can help to reduce this risk and also ensures there is sufficient sea room in case of emergency. However, given that attacks now regularly occur many miles from the coastline (up to 1,500 nautical miles), it is essential vessels considering transiting these areas prepare well in advance for the possibility of an attack. c) Careful consideration by Masters of their route and the risks and implementation at an early stage all necessary measures to reduce the likelihood of their vessel becoming a target. A full route analysis should be conducted taking into account previously reported incidents of piracy, as part of the passage planning process. endofguidancenote 11.14.4 Weather routeing and forecasting 11.14.4.1 Staged voyages shall have a commitment to seek shelter (or jackup at a standby location) on receipt of a weather forecast in excess of the operational limiting criteria incorporating an Alpha factor. A staged voyage shall have sufficient suitable ports of shelter (or standby locations) along the route. 11.14.4.2 The voyage shall proceed in stages between shelter points, not leaving or passing each shelter point unless there is a suitable weather forecast for the next stage. Subject to certain safeguards, each stage can, be considered a weather restricted voyage. 11.14.4.3 In such cases the towage route shall be planned to incorporate a series of shelter points, meaning sheltered locations where the tow can safely ride out severe weather. It can also be necessary to identify suitable bunker ports. These requirements can conflict with the requirement for adequate sea room, and such conflicts shall be resolved. 11.14.4.4 Weather routed voyages shall only be approved if the sea room requirements in [11.14.2] can be achieved and the vessel’s speed enables it to avoid weather in excess of the operational limiting criteria. 11.14.4.5 Forecasts – General: Requirements for weather forecasts for voyages should be in accordance with [2.7] and shall be agreed with the MWS company in advance. Guidance note: These are particularly important for weather restricted voyages (either staged or weather routed) for which the strength or stability will not meet the weather unrestricted environmental criteria. endofguidancenote 11.14.4.6 Arrangements shall be made for receiving suitable weather forecasts throughout any voyage from a reputable source. If appropriate, a weather routeing service, provided by a reputable company, should be arranged before the start of the towage or voyage. The utilisation of a weather routeing service can be a requirement of the approval and shall be used for weather routed voyages. 11.14.4.7 Forecasts – Departure: For any towage, the weather conditions for departure from the departure port or any intermediate port or shelter area shall take into account the capabilities of the tug, the marine characteristics of the tow, the forecast wind direction, any hazards close to the departure port or shelter area and the distance to the next port or shelter area. Assistance from local pilots should be considered. 11.14.4.8 Weather forecasts for the departure area should be started at least 48 hours before the anticipated departure date and be level A or B as in Table 216. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 345 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 2: Table 1121 Typical maximum initial towage departure weather forecasts Type of tow Maximum wind Unusual tows with large wind area 15 knots (BF 4) “Standard” tows 20 knots (BF 5) “standard” tows with small wind areas and a towing master familiar with the type of tow and the towing route 25 knots (BF 6) 11.14.4.10 Additionally the longer term forecast shall enable the tow to obtain adequate sea room (or reach a safe sheltered area) before bad weather can arrive. 11.14.4.11 Towages approaching a potential lee shore or areas with restricted sea room shall obtain a favourable weather forecast before reducing their sea room requirements. 11.14.5 Departure 11.14.5.1 Before departure, a departure condition report for the tow or vessel shall be submitted by the owners or their agents, to the Master and the MWS company surveyor. This report should contain as a minimum: — — — — — — — — — The documentation referred to in Table B2 as appropriate Lightship weight Tabulation and distribution of ballast, consumables, and cargo, including any hazardous materials Calculated displacement and draughts Actual draughts and displacement A statement that the longitudinal bending and shear force are within the allowable seagoing limits Calculated VCG Calculated GM and confirmation that it is within allowable limits GZ Curve and confirmation that it is within allowable limits. 11.14.5.2 In the departure condition, the tow shall have acceptable stability with proper allowance made for any slack tanks. 11.14.5.3 If no stability documentation is available then it can be necessary to perform an inclining test to check that the GM is satisfactory. Calculations can be needed to establish righting and overturning lever curves. 11.14.5.4 It shall be verified that the tow floats in a proper upright attitude and at a draught and trim appropriate to the calculated weight and centre of gravity. 11.14.5.5 The Certificate of Approval shall be issued on agreed readiness for departure and receipt of a suitable weather forecast. 11.14.6 Ports of shelter, shelter areas, holding areas 11.14.6.1 Ports of shelter, or shelter areas on or adjacent to the route, with available safe berths, mooring or holding areas, shall be agreed before departure and all necessary permissions obtained. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 346 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.14.4.9 Towage departures should take place with forecasts of good visibility, allowing for the effects of fog, rain and snow, especially if the tow master is unfamiliar with the area. Unless otherwise justified the forecast wind speeds should not exceed the values in Table 1121 for the first 24 hours of the towage. 11.14.7 Bunkering 11.14.7.1 Bunkering ports, if required, shall be agreed before departure. 11.14.7.2 If it is not practical to take the tow into port, then alternative arrangements shall be agreed and included in the approved towage procedures. Unless agreed otherwise the requirements of [11.12.2], shall apply at all times: Guidance note: Possible alternative arrangements include: — Where the towage is by more than one tug, each tug in turn can be released to proceed to a nearby port for bunkers, subject to a favourable weather forecast. The remaining tug(s) should meet the requirements of [11.12.2], or some other agreed criterion. — Relief of the towing tug by another suitable tug, which itself is considered suitable to undertake the towage, so that the towing tug can proceed to a nearby port for bunkers. — Bunkering at sea from a visiting vessel, subject to suitable procedures and calm weather conditions. endofguidancenote 11.14.8 Assisting tugs 11.14.8.1 Assisting tugs shall be engaged at the start of the towage, at any intermediate bunkering port and at the arrival destination, as appropriate. 11.14.9 Pilotage 11.14.9.1 The Master shall engage local pilotage assistance during the towage or voyage, as appropriate. 11.14.10 Log 11.14.10.1 A detailed log of events shall be maintained during the towage or voyage. 11.14.11 Inspections during the towage or voyage 11.14.11.1 Unless the tow is manned, it should be boarded on a regular basis by the crew of the tug, particularly after a period of bad weather, in order to verify that all the towing arrangements, condition of the cargo, seafastenings and watertight integrity of the tow are satisfactory. Suitable access shall be provided see [11.13.15]. 11.14.11.2 For manned tows, and selfpropelled vessels, the above inspections should be carried out on a daily basis as relevant see also [11.17.5]. 11.14.11.3 Any adjustable seafastenings or lashings shall be retensioned as necessary. 11.14.12 Reducing excessive movement and shipping water 11.14.12.1 The Master should take any necessary measures to reduce excessive movement or the shipping of water which can damage the cargo, cribbing or seafastenings. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 347 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.14.6.2 Where such shelter points are required as part of a weather restricted operation, as described in [2.6.7], they shall be capable of entry in worsening weather. This can entail changes of course and/or speed. endofguidancenote 11.14.13 Notification of unusual or abnormal events 11.14.13.1 After departure of an approved towage or voyage, notification shall be sent to the MWS company regarding any unusual or abnormal events, or necessary deviation from the agreed towing procedures. 11.14.14 Diversions 11.14.14.1 Should any emergency situation arise during the towage or voyage which necessitates diversion to a port of refuge, then the MWS company shall be advised. The MWS company will review and advise any mooring requirements and on the validity of the existing Certificate of Approval for continuing the towage or voyage depending on the circumstances of the case. A further attendance at the port of refuge may be required in order to revalidate the Certificate of Approval. 11.14.15 Responsibility 11.14.15.1 The towmaster is responsible for the overall conduct of a tow, and towing arrangements during the towage. Similarly the master of the transport vessel is responsible for the overall conduct of the voyage. Nothing in this document shall set aside or limit the authority of the Master who remains solely responsible for his vessel during the voyage in accordance with maritime laws. 11.14.15.2 If any special situations arise during the voyage and it is not possible to comply with any specific recommendations, agreed procedures or International Regulations, then such measures as appropriate for the safety of life and property shall be taken. The MWS company shall be informed as soon as practical of any such circumstances. 11.14.16 Tug change 11.14.16.1 The tug(s) approved for any towage, as noted on the Certificate of Approval, shall be the only tug(s) approved for that specific towage and should remain with the tow throughout the towage. Should it be required to change the tug(s) for any reason, except in emergency or where special arrangements have been agreed for bunkering, the replacement tug shall be approved by the MWS company and a new Certificate of Approval issued. 11.14.17 Hazardous materials 11.14.17.1 The carriage of hazardous materials should be avoided, unless it can be shown that the materials are effectively controlled. For unmanned voyages, hazardous materials should be stowed accounting for the limited remedial actions available in the case of inadvertent release. Guidance note: Hazardous substances can be considered as materials which, when released in sufficient quantities or improperly handled, have the potential to cause damage to the asset, personnel or the environment through chemical means or combustion. endofguidancenote 11.14.17.2 All hazardous materials shall be transported and stored in accordance with the IMO IMDG (International Maritime Dangerous Goods) Code, /88/. The properties of such material are contained in the COSHH (Control of Substances Hazardous to Health) data sheets. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 348 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.14.18 Ballast water 11.14.18.1 Voyage planning shall account for any need to change ballast water, including all local laws, before or at the arrival port. Guidance note: Vessels can need to change ballast water before or at their arrival port for operational reasons (loading/discharging). There can be local laws that will have an impact on these activities. In the U.S.A. there are numerous state laws that cover these operations. The IMO Ballast Water Convention of 2004 (Resolution A.868(20)), /86/, requires the monitoring and recording of ballasting and deballasting operations. Vessels flagged in signatory states are required to have on board and to implement a Ballast Water Management Plan. This plan is specific to each vessel and the record of ballast operations can be examined by the Port State Authorities. endofguidancenote 11.14.18.2 The necessary ballast plan and records should be submitted to any attending MWS company surveyor. 11.14.19 Restricted depths, heights and manoeuvrability 11.14.19.1 The clearance requirements for each towage should be assessed, taking into account — — — — environmental conditions, length of areas of restricted manoeuvrability, any course changes within the areas of restricted manoeuvrability, cross section of areas of restricted manoeuvrability in relation to underwater area/shape of the base structure, and — capability of the tugs. 11.14.19.2 The clearances in [11.14.20] to [11.14.21] are the generally acceptable minimum values. Any reduction of these shall be agreed with MWS company at an early stage and it shall be proven that the reduced values give an acceptable level of risk. 11.14.19.3 Calculation of clearances shall account for the effects of — — — — — — — — — — — — — Roll, pitch and initial heel and trim, heave, towline pull, inclination due to wind, tolerance on bathymetry (which can be over 10 m on old surveys) changes in draught of the transport vessel or towed object, differences in water density, tidal height variations, squat effects, deflections of the structure errors in measurement surge (negative for underkeel clearances and positive for air draught), and any protrusions below the bottom of the asset. 11.14.19.4 For areas where the underkeel or side clearance is critical, a survey that is not older than 3 months should be documented. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 349 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.14.17.3 Where identifiable hazardous material is found on board before a voyage taking place, it should be controlled either through isolation or removal ashore. 11.14.19.6 The survey requirements can be relaxed if it can be shown that the on board bathymetry measurement systems and position management systems have sufficiently high precision. 11.14.19.7 Passages through areas of restricted manoeuvrability and passing under bridges and power cables should not generally take place in darkness. 11.14.19.8 For areas where it is not feasible to deploy adequate towline length, e.g. due to restricted water depth, weather restrictions shall be defined (to reduce peak loads due to relative motions of tug and tow). See also [11.12.2.14]. 11.14.20 Underkeel clearances 11.14.20.1 The underkeel clearance shall be not less than the greater of one metre or ten percent of the maximum draught (with a maximum of 3 m) accounting for the items listed in [11.14.19.3]. The underkeel clearance can be reduced in very benign conditions after agreement with the MWS company. 11.14.20.2 Underkeel clearances for departure from drydocks or building basins are covered in [12.6]. 11.14.20.3 If sections of the passage are tidally dependent, safe holding areas should be identified in the vicinity with adequate sea room and water depth to maintain the minimum underkeel clearance at low tide. Any delay time waiting for the tide shall be included in the overall planning. 11.14.20.4 Immediately before critical sections of the passage the tidal level shall be confirmed by measurement. 11.14.20.5 Where an air cushion is used to reduce draught then the following shall be considered: a) b) Any conceivable loss of air not increasing the draught by more than the reserve on underkeel clearance, and The recommendations contained in [12.6.2] on air cushions. Guidance note: Use of air cushions is generally only acceptable to reduce draught to assist in crossing localised areas of restricted water depth. endofguidancenote 11.14.21 Air draught 11.14.21.1 When passing under obstructions, the overhead clearance shall be calculated accounting for the items listed in [11.14.19.3] excluding squat and shall be greater than one metre plus dimensional tolerances. 11.14.21.2 Where clearance is limited then a dimensional survey of the barge/vessel and structure shall take place just before sailaway in order to ensure that the required clearance exists. 11.14.21.3 For power cables the minimum allowable clearance shall be specified by the transmission company (but not be less than 1 m) and be measured to the lowest possible catenary position. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 350 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.14.19.5 Where the survey report in [11.14.19.4] is not available, the tow route shall be surveyed with a width of 5 times the beam, with a minimum of 500 m. Sidescan sonar and bathymetric data should be documented. The equipment used shall be of a recognized industry standard. The spacing between depth contour lines should be appropriate for the purpose. Current surveys should be made in restricted parts of the tow route. Power cables need a 'spark gap', as well as a physical clearance. endofguidancenote Guidance note 2: The catenary of the power cable will change depending on the electrical load being carried in the cable. endofguidancenote 11.14.21.4 The actual clearance shall be confirmed with all appropriate authorities including those responsible for the obstruction. 11.14.21.5 Immediately before the passage the tidal level shall be confirmed by measurement unless the calculated overhead clearance from [11.14.21.1] is greater than two metres plus dimensional tolerances at HAT (Highest Astronomical Tide). 11.14.22 Channel width and restricted manoeuvrability 11.14.22.1 The minimum channel width along any inshore legs of the tow route with the underkeel clearance and air draught required in [11.14.20] and [11.14.21] should be three times the maximum width of the towed object plus allowances for yaw and sway. Additional channel width can be required — in exposed areas — if there are significant cross currents — for tugs on either side to assist in manoeuvring if required. 11.14.22.2 Narrower channels may be agreed with the MWS company on a cases by case basis for ideal conditions (e.g. sheltered straight short channels and no tight time restrictions). 11.14.22.3 Side clearances for departure from drydocks or building basins are covered in [12.7]. 11.15 Bilge and ballast pumping systems 11.15.1 Pumping arrangements – general 11.15.1.1 For classed vessels, the drainage system and (bilge) pumps should as a minimum comply with the Rules of the Classification Society. 11.15.1.2 Tugs towing outside coastal limits shall also comply with [11.12.10]. 11.15.1.3 The general requirements in [4.2] shall be applied as applicable. 11.15.2 Pumping arrangements emergency 11.15.2.1 Emergency pumping arrangements shall be installed and operable on for any vessel to deal with any leakage after collision, grounding, structural failure or other accident. The requirements in [11.15.3] apply to: a) b) Towed vessel or barge Unclassed vessels or those operating outside their conditions of class. 11.15.2.2 For other wet tows, the need for and specifications of the emergency pumping systems shall be determined by a risk assessment in accordance with [2.4] considering the requirements in [11.15.3]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 351 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note 1: The risk assessment would also normally consider the details of the towage and the extent and availability of any installed system. Examples of other tows are selffloating objects, MOU’s, FSU’s and disabled ships, endofguidancenote 11.15.2.3 Some relaxation can be possible, as agreed with the MWS company, on a casebycase basis, for a towage considered as a weather restricted operation. 11.15.2.4 Whether or not a tow is manned, the emergency pumping system shall be available at short notice and deliver pumping times and capacities shown in [11.15.3.5] to [11.15.3.7]. Guidance note: For an unmanned tow, short notice is considered to start after boarding (which could be by helicopter). endofguidancenote 11.15.2.5 Where a tow is not manned, then the tug master and chief engineer shall be aware of the available pumping system. Members of the tug crew shall be familiar with the systems, and be able to board the tow and run the pumps at short notice. Procedures for pumping shall be known and available, including any restrictions arising from considerations of stability or hull stresses, and any vents, which shall be opened before pumping starts. 11.15.3 Pumping system requirements emergency 11.15.3.1 Vessels should have one of the following systems to meet the capacity requirements of [11.15.3.5] to [11.15.3.7], able to pump into and from all critical spaces (as defined in [11.15.3.2]) in order of preference: — Two independent pump rooms or one protected pump room, as described in [11.15.3.3] and [11.15.3.4] — An unprotected pump room with an independent emergency system that can pump out the pump room — A system of portable pumps. 11.15.3.2 A critical space is defined as any tank or compartment which: 1) when flooded or emptied, at any stage of the voyage, can lead to: — noncompliance with intact or damage stability criteria, or — noncompliance with structural load limits, or — heeling or trimming that can prevent the tow from continuing its passage safely and free from obstructions in shallow water, or — maximum allowable transit draught being exceeded. 2) can be required for ballasting/deballasting so that the barge or vessel can safely continue its passage after any single compartment is damaged. 11.15.3.3 Independent pump rooms should have separate power supply, pumps, control and access. Each pump room should be able to work into all spaces. 11.15.3.4 To be considered protected, a pump room, and any compartment required for access, should be separated from the bottom plating by a watertight double bottom not less than 0.60 m deep and from the outer shell by other compartments or cofferdams not less than 1.5 m wide. 11.15.3.5 The total capacity of the fixed and portable pumps should be such that any one wing space (or other critical space as defined in [11.15.3.2]) can be emptied or filled in 4 hours for an unmanned tow, or 12 hours for a manned tow. Any time required for connection or warmup should be included in the pumping times shown. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 352 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used Guidance note: 11.15.3.7 Whatever type of pumps are fitted or supplied, sufficient fuel shall be carried for at least 72 hours continuous operation. 11.15.3.8 If portable pumps are used then either they should be portable enough to be moved around the vessel (and cargo) by two men, or enough pumping equipment should be carried so that any critical compartment can be reached. 11.15.3.9 Each portable pump should be able to pump out from the deepest space (with portable coaming installed). Portable submersible pumps shall be able to fit through tank manholes. Guidance note: This requires submersible pumps for vessels over about 6 m depth, due to suction head. endofguidancenote 11.15.3.10 Any compressed air system should have a compressor on board and available, connected into the permanent lines. Guidance note: The use of a vessel compressed air system may not be practicable for all these or emergency cases, especially if manhole covers have been removed, or the vessel is holed above the waterline. endofguidancenote 11.15.4 Pumping arrangements – nonemergency 11.15.4.1 In addition to the emergency pumping arrangements described in [11.15.2], suitable pumping arrangements shall be provided for all planned (including contingency) ballasting operations. Guidance note: Generally the following ballasting operations should be considered (as applicable): a) Ballasting before, during and after loadouts b) Ballasting to the agreed departure condition and subsequent ballasting to towing condition c) Restoration of draught and trim before/during/after discharge (e.g. lift off from barge offshore) d) Adjusting draught or trim due to shallow waters or air draught restrictions e) (De)Ballasting to change draught at end of towage (e.g. reducing draught to enter port) f) Trimming to allow inspection and repair below normal waterline. g) Correction of unintended flooding h) Deballasting after accidental grounding i) Access to flooded compartment (e.g. pump or anchor winch room). endofguidancenote 11.15.5 Watertight manholes 11.15.5.1 If manholes to critical compartments are covered by cargo then either alternative manholes should be fitted, or cutting gear should be installed and positions marked for making access. Welding gear and materials shall be carried to restore watertight integrity. 11.15.5.2 Where the vessel is classed, the owner should inform the classification society in good time of any holes to be cut or any structural alterations to be made. 11.15.5.3 Access shall always be available to pump rooms and other work areas. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 353 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.15.3.6 Except where there is a protected pump room, at least two pumps shall be provided. 11.15.5.5 Suitable tools shall be provided for removal and refastening of manhole covers and sounding plugs. All manhole covers shall be properly secured with bolts and gaskets, renewed as necessary. 11.15.5.6 Portable coamings to suit the manhole design shall be carried, if required for operation with water on deck, as in [11.13.16.1] m). 11.15.6 Sounding systems 11.15.6.1 Sounding of and pumping into or from critical spaces (as defined in [11.15.3.2]) in severe weather should be feasible. The following shall be provided on all critical spaces: — — — — Pumping system Watertight manholes Portable coamings Sounding plugs, extensions and tapes or rods. An additional remote sounding system can be needed for compressed air ballasting systems — Vents to all compartments. 11.15.6.2 For vessels or barges with compressed air ballast systems, gauges shall be provided in lieu of sounding pipes. 11.15.6.3 A sounding plug shall be installed in each compartment (in manhole covers if necessary) to avoid removing manhole covers. Sounding tapes and chalk shall be carried on board the tow. 11.15.6.4 For spaces that will be sounded regularly, a tube and striker plate should be available. 11.15.7 Vents 11.15.7.1 All compartments connected to a pumping system shall have vents fitted. The vents should be of an approved, automatic, selfclosing type. If not automatic, then the vents should be sealed for towage with wooden bungs or steel blanks, but with a 6 mm diameter breather hole fitted. Guidance note: This will give audible warning or reduce pressure differentials in event of mishap, and compensate for temperature changes. The breather hole can be drilled into the gooseneck of the vent or through the wooden bung used to close the vent. endofguidancenote 11.16 Anchors (and alternatives) and mooring arrangements 11.16.1 Emergency anchors 11.16.1.1 Emergency anchors have traditionally been required to reduce the risk of a tow running aground if a tug is disabled or a towline broken. However in many cases the disadvantages (described in [K.5]) associated with using such anchors can outweigh the advantages. 11.16.1.2 If a tow passes through an area of restricted sea room, a comparative risk assessment should be performed to determine the preferred arrangements. [K.5] sets out topics to be taken into account in this risk assessment. One possible outcome can be the provision of suitably sized extra tugs for some sectors of the tow. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 354 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.15.5.4 For each manhole position, ladders to the tank bottom shall be provided. 11.16.1.4 For jackup platforms, see also [11.28.16]. 11.16.2 Size and type of anchor 11.16.2.1 For classed vessels and barges, the anchor(s) fitted in accordance with Class requirements should be acceptable unless there is deck cargo. Guidance note: For open deck vessels and barges, the anchor is designed to hold the vessel or barge only and does not account for deck cargo windage. endofguidancenote 11.16.2.2 In other cases the minimum weight of the emergency anchor should be 1/10 of the towline pull required (TPR) for the tow, as defined in [11.12.2]. A high holding power anchor with antiroll stabilisation should be used. 11.16.3 Anchor cable length 11.16.3.1 The effective length of anchor cable should be greater than 180 m, and should be mounted on a winch. If the cable runs through a spurling pipe, or other access, to storage below decks, then the pipe or access should be capable of being made watertight. 11.16.4 Anchor cable strength 11.16.4.1 For cable on a winch, or capstan, which can be paid out under control, the MBL of the cable should be 15 times the weight of the anchor, or 1.5 times the holding power of the anchor if greater. 11.16.4.2 For cable flaked out on deck, the MBL of the cable should be 20 times the weight of the anchor, or twice the holding power if greater. Guidance note: The increase from the requirements in [11.16.4.1] is to allow for the extra shock load. endofguidancenote 11.16.4.3 The last few flakes of cable on deck should have lashings that will break and slow down the cable before it is fully paid out. 11.16.5 Attachment of cable 11.16.5.1 The inboard end of the cable should be led through a capped fairlead near the vessel centre line and be securely fixed to the vessel. Precautions should be taken to minimise chafe of the cable. 11.16.5.2 The MBL or ULC of the connections of the cable to padeye or winch, and padeye or winch to the vessel structure should be greater than that of the cable. 11.16.5.3 For towed ships, and tows with similar arrangements, the anchor cable(s) shall be properly secured, with the windlass brake(s) applied. Any additional chain stopper arrangements that are fitted shall be utilised, or alternatively, removable preventer wires should be deployed. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 355 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.16.1.3 The same requirements apply for towed ships, including demolition towages. See [11.23.3]. Where such towages may need to wait for a few days on arrival at the end of a voyage before documentation is completed then, if this is in a highcurrent area, anchoring or mooring arrangements can be required. 11.16.6 Anchor mounting and release 11.16.6.1 If there is no suitable permanent anchor housing the anchor should be mounted on a billboard, as shown in [K.4], at about 60° to the horizontal. 11.16.6.2 The anchor should be held on the billboard in stops to prevent lateral and upwards movement. It should be secured by wire rope and/or chain strops that can be easily released manually without endangering the operator. 11.16.6.3 The billboard should normally be mounted on the stern. It should be positioned such that on release the anchor will drop clear of the vessel and the cable will pay out without fouling. 11.16.6.4 For any system, it shall be possible to release the anchor safely, without the use of power to release pawls or dog securing devices. If the anchor is held only on a brake, an additional manual quick release fastening should be fitted. 11.16.6.5 The anchor arrangement should be capable of release by one person. Adequate access shall be made available. 11.16.7 Mooring arrangements 11.16.7.1 All vessels and floating objects should be provided with at least four mooring positions (bollards/ staghorns etc.) on each side of the vessel unless it is impracticable to moor them, e.g. because of draught limitations. 11.16.7.2 If fairleads to the bollards are not installed then the bollards should be provided with capping bars, horns, or head plate to retain the mooring lines at high angles of pull. Suitable chafe protection should be fitted as required e.g. to the deck edge for low angles of pull. 11.16.7.3 At least four mooring ropes in good condition of adequate strength and length should be provided. Guidance note: Typically the mooring ropes are about 50 mm to 75 mm diameter polypropylene or nylon, and each 60 m to 90 m long. endofguidancenote 11.16.7.4 Mooring ropes should be stowed in a protected but accessible position. 11.16.7.5 Objects with very large freeboard such as FSUs should be fitted with mooring and towing connection points along the side, at a convenient height above the towage waterline. The connection points should not damage, or be damaged by, attending vessels. Guidance note: These can provide a more convenient connection for mooring lines and harbour tugs than bollards at deck level. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 356 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.16.5.4 Spurling pipes into chain lockers should be made watertight with cement plugs, or another satisfactory method. 11.17.1 General 11.17.1.1 Manning of tows should generally be limited to those where early intervention by a riding crew can be shown to reduce the risks to the tow, for example tows of MOU’s, passenger ships and RoRo vessels. 11.17.1.2 Where a riding crew is carried on a tow for commissioning and/or maintenance, sufficient marine personnel shall be included to operate the equipment listed in [11.17.4] and to carry out the duties in [11.17.5]. Guidance note: A riding crew can be carried on an FPSO or FSU for similar reasons. endofguidancenote 11.17.1.3 Riding crew carried on any dry transport shall be within the carrying vessel’s Flag State limits for life saving appliances; any exceedance of the Flag State limit shall be approved by the Flag State in advance. Guidance note: There is sometimes a requirement for a riding crew on a dry transport to maintain or commission systems or to carry out general maintenance. endofguidancenote 11.17.1.4 The transport contractor shall provide the MWS company documented flag state approval for the proposed number of riding crew. The underwriters should also be informed if a large riding crew is proposed. Guidance note: The transport contractor should therefore obtain this Flag State approval in good time. endofguidancenote 11.17.1.5 The health and safety of the riding crew shall be ensured at all times. 11.17.1.6 A risk assessment shall be carried out, in accordance with [2.4], to demonstrate the acceptability of the proposed arrangements. 11.17.2 International regulations 11.17.2.1 Accommodation, consumables, lifesaving appliances, pumping arrangements and communication facilities with the tug shall comply with International Regulations. 11.17.3 Riding crew carried on the cargo 11.17.3.1 Where a riding crew is carried on the cargo, for instance a maintenance crew on a drytransported jackup rig, additional precautions shall be considered including: — Access to/from the cargo/rig forward and aft, and to the evacuation or escape area(s) — The cargo/rig’s life rafts and lifeboats should be relocated and the falls lengthened, if necessary, so that on launching they will land in the water. — A firewater supply should be made available to the cargo/rig. — The cargo/rig’s and vessel’s alarm systems should be linked, so that an alarm on the cargo/rig is repeated on the vessel, and vice versa. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 357 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.17 Manned voyages 11.17.4.1 Notwithstanding the requirements of SOLAS, /139/, and any or all international regulations for Life Saving Appliances and FireFighting Equipment, the minimum complement of safety and emergency equipment carried aboard the tow shall be as follows: — Certified life rafts located on each side of the tow, clear of any possible wave action, provided with means of launching and fitted with hydrostatic releases. The life raft or life rafts on each side of the tow shall be capable of taking the full crew complement. Adequate means of access to the water shall be provided — 4 lifebuoys, two located on each side of the tow and including two fitted with selfigniting lights and two with a buoyant line — Approved life jackets to be provided for each crew member plus 25% reserve — If appropriate, a survival suit to be provided for each crew member — First aid kit — Firefighting equipment, which can consist of an independently powered fire pump with adequate hoses, and portable fire extinguishers as appropriate. — 6 parachute distress rockets and 6 hand held flares — A daylight signalling lamp and battery — 2 portable VHF radios, fitted with all marine VHF channels, with appropriate battery charging equipment — Hand held GPS (Global Positioning System) receiver — DSC VHF radio — Charts covering the route — An EPIRB (Emergency Position Indicating Radio Beacon) emergency transmitter — 2 SARTs (Search and Rescue Radar Transponder) — Heaving line(s) and/or line throwing apparatus if appropriate. 11.17.4.2 All members of the riding crew shall be adequately trained in the use of the safety equipment. At least 1 crew member shall possess the appropriate radio operator’s licences. 11.17.5 Manned routine 11.17.5.1 The riding crew shall take the following actions during the towage: — — — — — — — — — Maintain a daily log and include all significant events Inspect towing arrangements and navigation lights Inspect all seafastenings and any other accessible, critical structures Tension any adjustable seafastenings or lashings as necessary Check soundings of all bilges and spaces Monitor any unexpected or unexplained ingress of water Pump out any ingress of water Maintain regular contact by radio with the tug, reporting any abnormalities Ensuring that the required sound signals are made during restricted visibility. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 358 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.17.4 Safety and emergency equipment 11.18.1 Definitions 11.18.1.1 This section expands on the definitions in Table 13 for multiple towages: 11.18.1.2 Double tow – 2 tows each connected to the same tug with separate towlines. One towline is of sufficient length that the catenary to the second vessel is below that of the first. 11.18.1.3 Tandem tow – 2 (or more) tows in series behind 1 tug, i.e. the second and following tows connected to the stern of the previous one. 11.18.1.4 Bifurcated tow the method of towing 2 (or more) tows, using one tow wire, where the second (or subsequent) tow(s) is connected to a point on the tow wire ahead of the preceding tow, and with each subsequent towing pennant passing beneath the preceding tow. 11.18.1.5 Two tugs (in series) towing one tow – where there is only 1 towline connected to the tow and the leading tug is connected to the bow of the second tug. 11.18.1.6 More than 1 tug (in parallel) towing one tow – each tug connected by its own towline, pennant or bridle to the tow. Figure 1110 Multiple towage types (not to scale) Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 359 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.18 Specific for multiple towages 11.18.2.1 Compared with single towages, multiple towages have additional associated problems including those of: — Manoeuvring in close quarter situations, especially at the start and end of a tow. — Reconnecting the towlines after a breakage — Maintaining sufficient water depth for the longer and deeper catenaries required. 11.18.2.2 With the exception of the cases described in [11.18.1.6], multiple towages can only be approvable in certain configurations, areas and seasons, and subject to a risk assessment. 11.18.2.3 When approval is sought, then full details of the operation, including detailed drawings, procedures and equipment specifications shall be documented. An initial assessment of the method will then be made, and if the basic philosophy is sound, recommendations can be made for the approval process to continue. 11.18.2.4 Approval can be declined if any doubt exists as to the viability of the operation proposed. 11.18.2.5 For those multiple towages that are approvable, each tow shall be prepared as described in this standard. 11.18.2.6 Additional factors can be applied to the towing arrangements, so that the probability of breakage is further reduced. 11.18.2.7 The bollard pull requirement of the tug shall be according to the number and configuration of the tows connected. The Towline Pull Required (TPR) should be the sum of those required for each tow. The towing arrangements on each tow shall have sufficient capacity for the Bollard Pull (BP) of the tug(s). 11.18.2.8 The tug shall be equipped as in [11.13], although additional or stronger equipment and longer towlines can be necessary. Where longer towlines are required, these can be formed by the utilisation of pennant wires of no less Ultimate Load Capacity than the main tow wires. 11.18.2.9 Where the towing configuration requires the use of 2 towlines from 1 tug, a third tow wire shall be carried on board the tug, stowed in a protected position, whence it can be safely transferred at sea to either towing winch. 11.18.2.10 Consideration should be given to including (surge) chain or a stretcher to improve the spring, or to provide the required catenary in any towing arrangement. 11.18.2.11 If a synthetic stretcher is included in any towing arrangement, it shall comply with [11.13.10]. A spare stretcher shall be carried aboard the tug for each stretcher utilised in the towing arrangement. 11.18.2.12 For multiple tows being towed behind a single tug, special arrangements shall be made on the deck of the tug to separate the towlines. Guidance note: This requirement is because the tows can yaw in different directions. endofguidancenote 11.18.2.13 Special procedures shall be agreed and included in the towing manual for reconnection. Guidance note: It is particularly difficult to reconnect to a tow that has broken loose when another tow or tows are connected to the same tug. endofguidancenote Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 360 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.18.2 General 11.18.3 Double tows 11.18.3.1 These should only be considered when: a) b) c) the area is benign the towage duration is short and covered by good weather forecasts Where there is sufficient water depth along the tow route to allow for the catenary required for the second tow. 11.18.3.2 The tug should be connected to each tow with a separate towline on a separate winch drum. It shall also carry a spare towline, stowed on a winch, or capable of being spooled onto a winch at sea. 11.18.4 Tandem tows 11.18.4.1 These should only be considered when in very benign areas or in ice conditions where the towed barges will follow each other. 11.18.4.2 In ice conditions the towlines between tug and lead tow and between tows will normally be short enough for the line to be clear of the water. Procedures shall be in place to avoid tows overrunning each other, or the tug. 11.18.5 Bifurcated tow 11.18.5.1 This method should only be considered when in extremely benign areas, and additional safety factors with respect to the capacity of the towing arrangements shall be agreed with MWS company. 11.18.6 Two tugs (in series) towing one tow 11.18.6.1 The first tug should be smaller and connected to the bow of a larger, less manoeuvrable second tug. Guidance note: This arrangement is used to improve steering/manoeuvring. endofguidancenote 11.18.6.2 This configuration should only be considered when: a) b) All the towing gear (towline/pennants/bridles/connections etc.) between the second tug and the tow is strong enough for the total combined bollard pull The second tug is significantly heavier than the leading tug (to avoid girding the second tug). 11.18.7 Multiple tugs to one tow 11.18.7.1 Each tug should have a separate towline to the vessel (via bridles or pennants as required). 11.18.7.2 Consideration should be given to matching the size and power of the tugs. If 2 tugs are towing they should normally be sister vessels and/or with similar propulsion and equipment. The difference in Bollard Pull should normally be within 10% of that of each other. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 361 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.18.2.14 Due to the difficulties that will be encountered if a towline breakage should occur, the number of crew on the tug should be increased over that required for a single tow. 11.18.7.4 The use of eccentric bridles can be advantageous but care shall be taken to avoid chafe. 11.18.7.5 The following procedures shall be in place: — One tug shall be nominated as the lead tug and the tow plan shall describe the lead tug’s roles and requirement to lead manoeuvres. — A communication protocol shall be established. — The tow plan shall describe tow wire length and separation of vessels to avoid tow wire entanglement and/or collision, in particular in cases of a tug loss of propulsion and/or steering. — There shall be a minimum separation distance prescribed once underway and enough sea room is available. Guidance note: The minimum separation distance should normally be 100 m. endofguidancenote 11.18.7.6 Emergency procedures shall address the loss of a tug's power, in particular if the middle tug in a threetug spread blacks out and can be overridden by the tow with catastrophic consequences. Suitable emergency procedures and tow equipment shall be available to mitigate such a possibility. 11.19 Specific for towing in ice 11.19.1 General 11.19.1.1 This section sets out the special technical and marine aspects and issues not covered elsewhere in this standard for the approval of the towage of ships, barges, MOU’s and any other floating structure towed in icecovered waters. 11.19.1.2 It is recognized that towing in icecovered water is a unique marine operation and that all vessels and towages in ice are different making this standard general in nature. Each approval will depend on the result of an indepth review of the towing manual as well as an equipment inspection/attendance by a MWS company surveyor to identify any particular problems that can exist for the specific vessel(s) and towage in question. 11.19.1.3 Structural safety and towing performance will require careful consideration of the size and shape of the tow, especially with respect to the beam of the tow in comparison to the beam of the tug and the shape of the bow of the tow. The beam difference will affect the level of ice protection provided by the tug to the tow, as well as the ice interaction and towing resistance caused when the beam of the tow is greater than that of the tug and/or of any independent icebreaker support. In addition, special towing techniques used in ice and manoeuvrability restrictions caused by the ice require that experienced personnel plan and execute the tow. 11.19.1.4 Except as allowed by [11.9.14], any vessel that is operated and/or towed in ice shall be in Class with a Recognized Classification Society and have a current Load Line Certificate. 11.19.1.5 After complying with the requirements of [11.19.1.1] to [11.19.1.4], the MWS company can deem that the vessel/object is unfit for tow and decline to issue a Certificate of Approval. For example, the towage of any tow which is damaged below the waterline, is suspected of being damaged below the waterline or has suffered other damage or deterioration which could affect the structural strength and/or watertight integrity will not be approved for towage in ice. Alternatively, the vessel/object can only be considered fit for tow after specified repairs and suitable ice strengthening has been carried out. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 362 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.18.7.3 There should not be more than 3 tugs, except for the towage of very large objects, such as FPSOs and concrete gravity structures, and for manoeuvring at either end of a towage. 11.19.2.1 The tug(s) and towed vessel shall have an appropriate ice classification or equivalent for transit through the anticipated ice conditions identified in the towing manual and verified by the MWS company. See [K.10] for more information 11.19.3 Towage without independent icebreaker escort 11.19.3.1 Where no independent icebreaker escort is identified in the towing manual for the intended voyage, the tug and tow shall be of appropriate ice classification and power to maintain continuous headway in the anticipated ice conditions. When a tow is anticipated to take more than three (3) days (the maximum for a reasonably accurate weather/ice forecast) or longer in ice conditions that includes a concentration of five (5) tenths or more of limiting ice types, the towing manual shall indicate the location of the nearest icebreaker support and the anticipated time before independent icebreaker assistance (Coast Guard or Commercial) can be provided. 11.19.3.2 With the exception of a vessel pushed ahead (pushtowed), the ice classification requirement for the towed object can be considered for reduction if it is determined that the tug has a higher than necessary level of ice classification and can protect the tow from potentially damaging ice interaction. 11.19.4 Conventional ice towing operations 11.19.4.1 The tug shall have sufficient power and hull strength (ice classification) to be capable of safely maintaining continuous towing headway through the worst anticipated ice conditions including, if necessary, the breaking of large diameter floes and deformed ice with no requirement for ramming. 11.19.4.2 The towing manual shall show that the towage should not be subjected to ice pressure. 11.19.5 Closecouple ice towing operations 11.19.5.1 Closecouple towing is an operation that allows a specially designed icebreaker to combine towing and icebreaking assistance. The stern of the icebreaker has a heavily fendered ‘notch’ into which the bow of a ship is pulled by the icebreaker’s towline. The towline remains attached and the icebreaker steams ahead, usually with additional power provided by the towed vessel in the notch. In this way an icebreaker can tow a lowpowered and low ice classed ship quickly (up to 3 times faster than conventional towing in ice) and safely (better protection of the towed vessel and less risk of collision due to overrunning) through high concentrations of difficult ice. For closecouple towages: — The beam of the icebreaker shall be more than that of the towed ship in order to avoid shoulder damage to the towed vessel and excessive towline stress and: — The icebreaker is fitted with a constant tension winch or equipment that will reduce the effects of shock loading: — The bow of the towed ship shall be compatible with the notch design of the icebreaker. Preferably the entrance of the towed ship is not so sharp as to apply excessive force on the stem when going straight ahead. Freedom of movement of the towed ship’s bow can cause manoeuvring difficulties as well as applying heavy side forces on the towed ship’s bow when turning. The bow should not be so bluff that Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 363 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.19.2 Vessel ice classification 11.19.6 Pushtow operations 11.19.6.1 PushTow operations should be carried out using either rigid connection (composite unit) or flexible connections (a pushknee erected at the stern of the pushed vessel). Where the design and ice strength of the tug and tow is acceptable, especially when experiencing ice pressure, consideration should be given to pushing rather than towing in ice. Guidance note: Pushing enables headway to be maintained and to remove the stress from the towline. Push towing can also be more efficient. endofguidancenote 11.19.6.2 Where the pushtowing technique is to be used, the pushed vessel shall have acceptable ice strengthening, particularly in the bow and shoulder areas. 11.19.6.3 The ice classification of a tug that is engaged in a ‘pushtow’ operation with no independent icebreaker support can be reduced if: — the vessel being pushed has appropriate ice classification and strength for unescorted transit in the anticipated ice conditions and: — the beam of the pushed vessel is greater than that of the tug. The beam of the pushed vessel should be at least one third greater than that of the tug to allow suitable manoeuvring for a flexible connection and: — the connection between tug and tow is of suitable strength for emergency stops and: — the towing manual shows that the ‘pushtow’ will not enter, or be exposed to, an area where ice pressure can be encountered of sufficient severity to stop the continuous forward progress of the pushtow without independent icebreaker assistance. 11.19.7 Towage operations with independent icebreaker escort 11.19.7.1 The ice classification requirements indicated in [K.10] for the tug(s) and towed vessel(s) can be considered for reduction if it is determined that appropriate icebreaker escort assistance is provided for the duration of the tow in ice and that: — The icebreaker(s) has sufficient capability to allow the towage to maintain continuous headway through all of the anticipated ice conditions and, — The icebreaker(s) has a beam equal to, or greater than, the tug and tow combination or: — The icebreaker(s) is fitted with suitable and operational equipment such as azimuthing main propulsion units or compressed air systems that are capable of opening the track wider than the beam of the escorted towage in the anticipated ice conditions or: — More than one icebreaker will be used to provide a broken track equal to, or wider than, the beam of the tug and tow combination. 11.19.8 Manning 11.19.8.1 In addition to [11.12.13] concerning manning, special consideration should be given to the number, qualification and experience of personnel required on the navigating bridge to ensure safe navigation Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 364 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used all the force is concentrated in localized areas. In addition the towed ship cannot have a bulbous bow because the underwater protrusion could damage the icebreakers propellers and: — The displacement and freeboard of the towed vessel should not be so disproportionate with that of the icebreaker that the manoeuvring characteristics of the icebreaker are seriously compromised: — The anticipated ice conditions should not require ramming or passage through areas where high levels of ice pressure can be experienced without independent icebreaker assistance. 11.19.8.2 The master in charge of a tow (towmaster) should typically have at least 3 years’ experience of towing in ice conditions similar to those anticipated for the proposed towage. Other navigating officers on tugs involved in a towage in ice should also have previous experience of towages in ice. 11.19.9 Multiple towages 11.19.9.1 Multiple towages in ice are subject to the requirements set out in this section regarding ice classification, equipment and suitable propulsion power as well as the general provisions (particularly those in [11.18]). However, only in exceptional circumstances of very light ice and/or very low ice concentration (trace) will a Double Tow (see [11.18.3]) or a Bifurcated Tow (see [11.18.5]) be considered for approval. An indepth risk assessment would be required and the risks shown to be acceptable. 11.19.9.2 In addition to the provisions in [11.19.9.1] for towages using more than one tug or multiple tows: 1) 2) 3) To avoid collision or overrunning each tug shall have a quick release and reset system as described in [11.19.11.1] and [11.19.11.2]. The most experienced tug Master shall be designated as the towmaster and give directions to the other vessels. All other tug Masters and senior navigating officers involved in the multitug towage should have an appropriate level of experience of towing in ice and be familiar with the associated difficulties and hazards. A multitug towing manual that does not include independent icebreaker escort assistance shall demonstrate clearly why it is not considered necessary. As an acceptable example, the tow could be configured such that one or more tugs with the capability to perform ice management (escort duties) can be released, and the remaining tug(s) have sufficient BP to continue making towing progress. In some circumstances a towing manual can include the contingency of releasing one or more tugs that are towing in the conventional manner to pushtow provided that: — — — — the towed vessel is appropriately ice strengthened: the towed vessel is appropriately designed and strengthened in the pushing location(s): the tugs are designed and adequately fendered for pushing: such action would only be considered in a high ice concentration where there is no influence by sea or swell. 11.19.9.3 When two tugs are towing in series as described in [11.18.6] in an ice infested area, the towing connections on the foredeck of the second tug shall be strong enough for any shock loading that may result from the lead tug to breaking through ice floes of varying thickness. 11.19.9.4 For a tandem tow (as described in [11.18.4.2]) where the presence of ice increases the potential for rapid changes to the towing speed, good fenders shall be in place between each unit in the tow due to the close connection. Guidance note: This is sometimes referred to as icecoupled. endofguidancenote 11.19.10 Towing equipment 11.19.10.1 The towing techniques that are used in ice typically require a short distance between the tug and tow to increase manoeuvrability and so that the propeller wash from the tug can assist in clearing ice accumulation around the bow of the towed vessel. Because of the short towing distance and reduction of towline catenary it is necessary for the towing arrangement to be suitable for the additional stress that can be experienced. The stress on the towing arrangement can vary considerably with: Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 365 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used including steering and engine control, lookout, operation of searchlights and, emergency operation of the towing winch abort system. It is for these reasons that additional provisions concerning towing equipment strength, type and configuration are necessary. 11.19.11 Additional equipment requirements for towing in ice 11.19.11.1 In addition to [11.12.5] a tug involved in towing in ice infested waters shall be fitted with an operational towline quick release/reset system (towwire abort system) when: — towing in ice that could rapidly reduce towing speed or — a tug is involved in a multiple tow or — a tug is involved with a multitug tow. 11.19.11.2 The towline quick release system should be capable of immediate winch brake release for pay out of towwire as well as winch brake reset from the navigation bridge and the winch control station (if different). 11.19.11.3 With reference to [11.12.9], a tug involved in a towage in ice should be fitted with at least two searchlights that can be directed from the navigation bridge. 11.19.11.4 As required by [11.12.11.2] and [11.13.16], every tug that is towing in ice shall be equipped with burning and welding gear for ice damage control and repair. 11.19.12 Strength of towline 11.19.12.1 With reference to [11.13.3.1] for a tug that is planning a conventional single towline towage in ice the towline MBL should be as follows: Table 1122 Minimum towline MBL in ice Bollard Pull (BP) MBL (tonnes) BP ≤ 40 tonnes 40 < BP ≤ 150 tonnes BP > 150 tonnes 2 × BP+60 11.19.12.2 An exception can be made for short tows in very thin ‘new’ ice or in very low concentrations (<3/10ths) of medium or thick ‘rotten’ ice. In these circumstances the towline MBL should be computed as shown for a ‘nonbenign’ tow in [11.13.3.1]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 366 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used — the thickness and concentration of ice as well as ice pressure, — the difference in beam between the tug and tow resulting in ice interaction on the shoulders of the towed vessel and ice accumulation in front of the tow as well as the use and effectiveness of independent icebreaker escort and — large heading deviations due to manoeuvring through and around ice and — unintentional tug interaction with heavy ice floes which can result in shockloading to towing components due to whiplash and the tow taking charge. 11.19.12.4 The strength of all other towing connections and associated equipment should be appropriately calculated as in [11.13.3.4]. 11.19.12.5 Further, ALL tugs involved in a towage in ice shall carry a spare towwire of the same length and strength as the main towwire that is immediately available on a reel to replace the main towwire. In addition, there shall be enough competent personnel, equipment and spares on board to crop and resocket the main towwire at least once. 11.19.13 Special cases of reduced towwire strength 11.19.13.1 The minimum size of towwire that is typically used by icebreaking tugs of 160t BP for close couple towing is for example, 64 mm EIPS rove through a multiple sheave floating ‘Nicoliev Block’ system. In this system a single bridle wire, usually of the same size and strength as tug's main towwire, is made fast to each bow of the vessel being towed. The towwire goes from the towing winch to the floating block on the bridle and back via a fairlead to a towing damper on the tug. For larger powered tugs, the towwire can be doubled up again by passing the wire through a standing block on the tug’s deck and around a second sheave on the floating block before it is made fast to the towing damper. This makes the bridle wire the ‘weak link’ in the system and because of this an icebreaking tug shall carry sufficient spare bridle wires, typically at least 6. 11.19.13.2 To meet the minimum towline strength criteria a tug that has an appropriate bollard pull can, in exceptional circumstances, be considered for approval of a conventional towage in calm waters containing ice using two towlines provided that: — Each of the two independent towlines is a minimum of 90% of the required strength and — Each towwire is on a separate towing winch that can be adjusted, quick released and reset independently from the other and — Each towwire meets the requirements of a single towwire in terms of minimum length, construction etc. and — Each towline has a monitoring system to enable load sharing. 11.19.14 Towing winches 11.19.14.1 Towing winches shall be provided due to the typical manoeuvring restrictions and hazards that are inherent to towing in ice. Guidance note: Towing hooks do not allow for the rapid adjustment of towline length. endofguidancenote 11.19.14.2 Each towing winch should have sufficient pull to allow the towline to be shortened under tension. The navigating bridge and winch operator should be provided with continuous readouts of towline length deployed and towline tension. 11.19.14.3 Winch controls and winch operating machinery should be suitably protected from environmental conditions, particularly low temperatures that can result in winch malfunction. 11.19.14.4 Towing winches shall have a quick release and reset system as described in [11.19.11.1] and [11.19.11.2]. Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 367 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be made. Requires a valid subscription to be used 11.19.12.3 Consideration should be given to use of low temperature lubricants in the manufacture of towlines for use in polar regions to reduce the probability of breakage. 11.19.15.1 A chain bridle is typically used for a towage in ice with a chain pigtail connected to a ‘fuse wire’ or directly to the towline. In some circumstances where high shock loads are anticipated, an extralong chain pigtail can be considered appropriate. Wire pennants and bridles are sometimes used for small barge and vessel tows, especially when the closecouple or icecouple towing technique is anticipated. 11.19.16 Synthetic rope 11.19.16.1 Synthetic rope shall not be used in a towing system for an inice towage, therefore [11.13.9.2] and all parts of [11.13.10] do not apply in ice transits or in very low temperatures where icing can occur. Guidance note: Synthetic rope is prone to rapid cutting both internally by ice crystals and externally by ice edges. endofguidancenote 11.19.17 Bridle recovery system 11.19.17.1 In addition to the requirements of [11.13.11.1]: — To reduce direct ice interaction and disconnection of the bridle recovery wire, the wire should be lightly secured to one leg of the bridle and the end shackled onto the apex or a chain link close to the apex of the triplate. — The fuel mentioned in [11.13.11.2] for a motorized recovery winch shall be appropriate for the anticipated temperatures. 11.19.18 Emergency towing gear 11.19.18.1 For all towages in ice the emergency towing gear should be fitted and arranged to tow from the bow unless it can be shown that the object being towed is designed for multidirectional towing. With reference to [11.13.13], special arrangements can be required for the emergency towing gear, especially on an unmanned tow proceeding in ice. 11.19.18.2 The emergency tow gear arrangement shall not be susceptible to being cut and lost or snagged by ice and pulled clear of retaining soft lashings or metal clips, especially in high concentrations of ice. Guidance note: For example, an intermediate wire can be attached to the end of the emergency towwire and lightly secured to a pole extended astern at least 5 m. The eye of the intermediate wire is suspended above the surface of the ice approximately 1 m above the aft working deck of the tug where it can be captured for connection to a tuggerwinch wire. The float line and pickup buoy are shackled to the emergency towwire in the same way as described in [11.13.13.4] but remain coiled on the deck of the tow for deployment once the tow arrives in open water. endofguidancenote 11.19.19 Access to tows 11.19.19.1 With reference to [11.13.15], whether a tow is manned or not, suitable access shall be provided. For towages in ice, a permanent steel ladder should be provided at the stern from the main deck to just above the waterline. As discussed in [11.13.15.2], ladders, particularly side ladders should be recessed to avoid ice damage. A tug workboat should carry suitable equipment to deice recessed access arrangements Standard — DNVGLSTN001. Edition September 2018, amended January 2020 Marine operations and marine warranty DNV GL AS Page 368 This copy of the document is intended for use by Klijn, Peter at Subsea 7 Limited only. Downloaded 2020-04-30. No further distribution shall be ma

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