Pipeline Overlaying Specification
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Table of Contents
1
Purpose ......................................................................................................................... 4
2
Definition and Abbreviation ............................................................................................ 4
3
2.1
Use of Language .................................................................................................... 4
2.2
Abbreviation ............................................................................................................ 5
References .................................................................................................................... 6
3.1
Codes and Standards ............................................................................................. 6
3.2
Conflicting Requirements ........................................................................................ 8
4
Client/Company Authorities and Manufacturer/Supplier Responsibilities ........................ 8
5
Documents..................................................................................................................... 9
6
Base Material and Equipment Requirements ............................................................... 10
6.1
Unloading, Handling and Storing........................................................................... 10
6.2
Base Pipeline ........................................................................................................ 10
6.3
Surface Condition ................................................................................................. 11
6.4
Welding Equipment ............................................................................................... 11
6.5
Welding Consumables .......................................................................................... 12
6.6
Welding Gas ......................................................................................................... 12
6.7
Production Welding ............................................................................................... 13
6.8
Chemical Properties and Tests ............................................................................. 13
6.9
Mechanical Properties and Tests .......................................................................... 14
6.9.1
Tensile Tests ................................................................................................. 14
6.9.2
Flattening Tests ............................................................................................. 15
6.9.3
Guided-Bend Tests ........................................................................................ 15
6.9.4
Fracture Toughness Tests ............................................................................. 16
6.9.5
Hardness Test ............................................................................................... 16
6.9.6
Special Tests ................................................................................................. 17
6.10
Defects, Disbonding and Surface Treatment ......................................................... 19
6.11
Repair ................................................................................................................... 19
6.12
Finishing ............................................................................................................... 20
6.13
Dimensions, Weight and Length of Overlayed Pipeline ......................................... 21
6.14 Manufacturing Procedure Specification (MPS) / Manufacturing Procedure
Qualification (MPQ) ......................................................................................................... 22
6.15
Overlaying Welding ............................................................................................... 23
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6.15.1
Welding Procedure Specification (WPS)/ Procedure Qualification Record (PQR)
24
6.15.2
Welding Variables .......................................................................................... 26
6.16
6.16.1
Visual Testing (VT) ........................................................................................ 28
6.16.2
UltraSound Testing (UT) ................................................................................ 29
6.16.3
Dye Penetrant Testing (PT) ........................................................................... 31
6.17
7
Nondestructive Inspection ..................................................................................... 27
Shipment, Packing, Marking ................................................................................. 31
Installation and Operation of Overlayed Steel Pipelines ............................................... 32
7.1
Welding Requirements .......................................................................................... 32
7.2
Welding Procedure Specification (WPS) / Procedure Qualification Report (PQR) . 32
7.3
Welder Performance Qualification (WPQ) ............................................................. 34
7.4
Surface Preparation .............................................................................................. 34
7.5
Joint Configuration ................................................................................................ 35
7.6
Preheating ............................................................................................................ 37
7.7
Welding Equipment ............................................................................................... 37
7.8
Welding Consumables .......................................................................................... 37
7.9
Backing Gas ......................................................................................................... 38
7.10
Chemical Properties and Tests ............................................................................. 38
7.11
Nondestructive Inspection ..................................................................................... 39
7.12
Hydrostatic Tests .................................................................................................. 39
7.13
Defects and Repair of Defects .............................................................................. 39
7.14
Flow assurance requirements ............................................................................... 40
7.15
Pipelaying Requirements ...................................................................................... 41
7.16
Pigging Requirements........................................................................................... 41
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1 Purpose
This document specifies minimum technical requirements and gives recommendations for the
manufacture, installation, operation, inspection, testing, and shipping of seamless and welded
corrosion resistant CRA overlayed steel pipelines. This document is solely meant for use of
CRA overlayed pipelines in subsea applications and as such, the CRA overlay material to
which this document primarily applies is UNS N06625. At Client/Company’s discretion, this
document may also be used for other CRA overlay materials, but some requirements may
then require review by Client/Company’s welding subject matter expert, to determine if
revisions are needed.
Overlaying as defined above are not acceptable for preventing SSC for the backing material,
which shall be fully compliant with NACE MR0175/ ISO 15156.
In the scope of this specification the CRA layer thickness shall not be included in the design
to add to mechanical strength.
This Specification is not applicable to:
Clad pipelines manufactured from metallurgically bonded clad plate;
Lined pipelines;
Buttering for weld preparations;
Weld overlay for hard surfacing.
The Manufacturer/Supplier and installation Contractor shall inform the Client/Company of any
deviation from the requirements of this document which is considered to be necessary in order
to comply with referred standards.
All MPSs and WPSs in production phase shall be qualified using tests demonstrated in
specified Code/Standard and all additional tests specified in this specification.
Overlaying is mostly applicable to equipment and piping, there are uncertainities about its
application in the pipelines. Furthermore based on the client’s previous experiences in south
pars, there was also negative feedback on its use in the topside piping. Overlaying was not a
recommded procedure as specified in the letter PPL1400/FRZA/182. However this
specification is generated based on the client instruction due to the limitations in supplying the
pipes using roll bonding method. Limitations such as the dilution, pigging limitations, flow
assurance issues, quality control concerns were raised to client both in a mutual meeting and
also addressed in the present document.
2 Definition and Abbreviation
2.1
Use of Language
Throughout this specification, the words “will”, “may”, “should”, “shall” when used have
meaning as follows:
•
“will” is used normally in conjunction with a request from CONSULTANT.
•
“may” is used where alternatives are equally acceptable,
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•
“shall” is used where a provision is mandatory
•
“should” is used where a solution is preferred
2.2
Abbreviation
ANSI
ASTM
AVC
AWS
BEDD
BS
ClSCC
CRA
CS
CVN
DNV
FBH
GMAW
GTAW
H2
H2S
HFW
HIC
HSC
ILI
IP
ISO
ITP
MFL
MIP
MPQ
MPS
MTR
NACE
NDT
O2
OP
PAW
pH2S
PMI
PQR
PREN
PT
PWPS
QA
ROV
RT
American National Standards Institute
American Society for Testing and Materials
Automatic Voltage Control
Alliance for Water Stewardship
Offshore Basic Engineering Design data
British Standard
Chloride Stress Corrosion Cracking
Corrosion Resistant Alloy
Carbon Steel
Charpy V-notch
Det Norske Veritas
Fusarium Head Blight
Gas Metal Arc Welding
Gas Tungsten Arc Welding
Hydrogen
Hydrogen Sulfide
High Frequency Welding
Hydrogen Induced Cracking
Hydrogen Stress Cracking
In-Line Inspection
Intelligent Pigging
International Organisation of Standardisation
Inspection and Test Plan
Magnetic Flux Leakage Inspection
Manufacturing and Inspection Plan
Manufacturer Product Qualification
Manufacturing Procedure Specification
Material Test Reports
National Association of Corrosion Engineers
Non-Destructive Technology
Oxygen
Operational Pigging
Plasma Arc Welding
H2S Partial Pressure
Positive Materials Identification
Procedure Qualification Record
Pitting Resistance Equivalent Number
Dye Penetrant Test
Preliminary Welding Procedure Specification
Quality Assurance
Remote Operated Vehicles
Radiography Test
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SAW
SMAW
SMYS
SOHIC
SS
SSC
SSPC
UT
VI
VT
WPQT
WPS
3
Submerged Arc Welding
Shielded Metal Arc Welding
Specified Minimum Yield Strength
Stress Orientated Hydrogen Induced Cracking
Stainless Steel
Sulfide Stress Cracking
Society for Protective Coatings
Ultrasonic Test
Visual Inspection
Visual Test
Welder Performance Qualifications Test
Welding Procedure Specification
References
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references the latest edition of the referenced document (including any amendments)
applies.
It shall be the Manufacturer/Supplier’s responsibility to acquire all of the applicable documents
referenced in this specification. Contractor shall be familiar with their requirements and comply
with their provisions as related to this specification.
3.1
Codes and Standards
The design codes and standards shall be as indicated below and /or stated on the equipment
data sheet: It shall be noted that documents of phase 19 of South Pars Gas Client/Company
have been used in this document. The latest revision Up to 2022 of the following codes,
standards and specifications shall be used unless otherwise indicated by the CLIENT.
API 5L
API 5LD
ASME Sec II Part C
ASME Sec V
ASME Sec IX
ASNT-TC-1A
ASTM A263
ASTM A264
Line Pipe
Specification For CRA Clad or Lined Steel Pipe
Specifications for Welding Rods, Electrodes, and Filler
Metal
Nondestructive Examination
Qualification Standard for Welding, Brazing, and Fuzing
Procedures; Welders; Brazers; and Welding, Brazing, and
Fusing Operators - Welding, Brazing and Fusing
Qualifications
Recommended Practice on Personnel Qualification and
Certification in Nondestructive Testing
Standard Specification for Stainless Chromium Steel-Clad
Plate
Standard Specification for Stainless Chromium-Nickel
Steel-Clad Plate
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ASTM A265
ASTM A380
ASTM A578
ASTM A751
ASTM B499
ASTM E1212
ASTM E18
ASTM E353
ASTM E384
ASTM G28
AWS A5.32
BS EN 10204
BS EN ISO 15614
DNV OS F101
EN ISO 14175
ISO 17637
ISO 2178
ISO 3452
ISO 5817
ISO/TR 9769
NACE MR0175/ ISO 15156-2
Standard Specification for Nickel and Nickel-Base AlloyClad Steel Plate
Standard Practice for Cleaning, Descaling, and
Passivation of Stainless Steel Parts, Equipment, and
Systems
Standard Specification for Straight-Beam Ultrasonic
Examination of Rolled Steel Plates for Special
Applications
Standard Test Methods and Practices for Chemical
Analysis of Steel Products
Standard Test Method for Measurement of Coating
Thicknesses by The Magnetic Method: Nonmagnetic
Coatings on Magnetic Basis Metals
Standard Practice for Establishing Quality Management
Systems for Nondestructive Testing Agencies
Standard Test Methods for Rockwell Hardness of Metallic
Materials
Standard Test Methods for Chemical Analysis of
Stainless, Heat-Resisting, Maraging, and Other Similar
Chromium-Nickel-Iron Alloys
Standard Test Method for Microindentation Hardness of
Materials
Standard Test Methods for Detecting Susceptibility to
Intergranular Corrosion in Wrought, Nickel-Rich,
Chromium-Bearing Alloys
Welding Consumables-Gases and Gas Mixtures for
Fusion Welding and Allied Processes
Metallic Products - Types of Inspection Documents
Specification and qualification of welding procedures for
metallic materials. Welding procedure test
Submarin Pipeline Systems
Welding Consumables - Gases and Gas Mixtures for
Fusion Welding and Allied Processes
Non-Destructive Testing of Welds - Visual Testing of
Fusion-Welded Joints
Non-Magnetic Coatings on Magnetic Substrates Measurement of Coating Thickness - Magnetic Method
Non-destructive testing. Penetrant testing
Welding - Fusion-Welded Joints in Steel, Nickel, Titanium
and Their Alloys (Beam Welding Excluded) - Quality
Levels for Imperfections - Fourth Edition
Steel and Iron - Review of Available Methods of Analysis
Petroleum, Petrochemical, and Natural Gas Industries —
Materials for Use in H2S -Containing Environments in Oil
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
NACE MR0175/ ISO 15156-3
NACE TM 0177
SSPC-SP 5
3.2
and Gas Production - Part 2: Cracking-Resistance Carbon
and Low Alloy Steels, and the Used of Cast Irons
Petroleum, Petrochemical, and Natural Gas Industries —
Materials for Use in H2S -Containing Environments in Oil
and Gas Production - Part 3: Cracking-Resistant CRAs
(Corrosion-Resistance Alloys) and Other Alloys
Laboratory Testing of Metals for Resistance to Sulfide
Stress Cracking and Stress Corrosion Cracking in H2S
Environments
White Metal Blast Cleaning NACE No- 1, NACE 1
Conflicting Requirements
In the event of conflict between this specification and other specifications, data sheets,
applicable codes and references, the most onerous requirement shall take precedence, and
the Manufacturer/Supplier shall notify the Client/Company in writing.
4
Client/Company Authorities and Manufacturer/Supplier Responsibilities
The Client/Company shall be permitted to witness all chemical testing, mechanical testing,
non destructive testing and equipment calibration, and to inspect all overlayed pipelines.
Client/Company shall be given a minimum two weeks notice prior to Manufacture Procedure
Qualification Testing with a minimum two days notice for each process start. Sufficient notice
(at least 14 days) shall be given of the time at which the production run is to begin. If any
inspections are performed off-line or at a third party’s facilities, sufficient notice (at least 7
days) shall be given of the time at which inspection is to begin.
The Manufacturer/Supplier shall inform the Client/Company within 48 hours of any intentional
or unintentional manufacturing changes that could affect constructability of the pipelines.
The Client/Company shall have free entry at all times to all parts of the Manufacturer/Supplier's
works that will concern the manufacture, testing, inspection, quality control and shipping of the
overlayed pipelines.
The Client/Company shall have the option to examine all materials rejected for any reason.
All failed materials shall be retained until examined by the Client/Company. The
Manufacturer/Supplier shall ensure that rejected materials are removed from production and
not used for project pipe and fittings.
The Manufacturer/Supplier shall allow the Client/Company to inspect each pipeline after
manufacture and testing are completed but prior to loading for shipment at a clean, safe
location.
The Manufacturer/Supplier shall take all reasonable precautions to ensure that all external
surfaces are free from imperfections that might interfere with the future efficient application of
coating and result in an inordinate number of holidays.
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5
Documents
The documentation shall be based on the Manufacturer Quality Management System and
shall include all quality assurance and quality control procedures applicable to the scope of
work. Documentation requirements are listed in the DNV OS-F101 Section 12.
The Quality Plan shall show the organization and methods of the quality assurance and quality
control systems employed by Manufacturer for manufacture and supply of the pipeline and
shall be in accordance with ISO 9001 and supplemented with the requirements given in ASTM
E1212 and DNV OS-F101 Section 2. The quality system shall ensure that all the requirements
of this specification are achieved.
In addition to above documents, the following documents shall be submitted for
Client/Company approval:
a. Welding procedure specifications and qualification reports that, in addition to requirement
of ASME Sec IX and this specification, include the following:
•
•
•
•
•
•
Details of pipeline preparation for welding, including blasting, cleaning, and degreasing.
Welding procedures and qualification forms as required in Section 6.15.1.
Deposited weld metal typical composition, as required in section 6.8.
Details of equipment, and procedures used for all non-destructive inspections including
calibration details, references and acceptance limits. Details of repair welding
procedures, as indicated in section 6.16 and 6.11.
Any exceptions taken to these specifications.
Details of buttering (if any).
b. A weld map that defines procedures (and any alternates) applicable to overlay welding as
well as the NDT requirements. Typical weld maps defining the applicable combinations of
base material/internal overlay and diameters/thickness of the pipeline are acceptable.
c. A positive materials identification (PMI) plan in accordance with project Specification.
d. A plan to confirm material traceability for all pipelines to which corrosion resistant alloy
(CRA) cladding will be applied.
e. Consumable material test reports (MTR).
f. A list of sub-vendors to be used.
g. A QA Plan, including procedures for QA of subcontractors, as specified in section 4.
h. Manufacturing Procedure Specification (MPS).
i. Manufacturing Procedure Qualification (MPQ).
j. Manufacturing and Inspection Plan (MIP).
k. Inspection and Test Plan (ITP)
All testing and inspection activities shall be detailed in Manufacturer’s Inspection and Test
Plan.
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The Manufacturer/Supplier shall furnish a report giving the results of each test required by this
document. The Manufacturer/Supplier shall document that all pipelines overlayed under this
document meets the requirements of NACE MR0175/ISO 15156.
The Manufacturer/Supplier’s Quality Assurance plan shall be submitted with the proposal for
Client/Company and will be a major consideration in the evaluation of the bid. The
Manufacturer/Supplier’s QA Plan shall include the following:
a. Chronological listing of manufacturing steps/control area (e.g., order entry, material
receiving, heat treatment, weld shop, machine shop, assembly area, final shipping).
b. Controlled activities with critical variables (e.g., for heat-treating operations that the critical
variables may include chemistry, temperature, time).
c. Work instructions and acceptance criteria (e.g., material specifications, heat-treating
procedures, welding procedures, manufacturing acceptance tests).
d. Inspection plan detailing the particular Manufacturer/Supplier-required quality control steps
and hold points for each part, sub-assembly, and assembly.
e. Corrective action plan, which details the act of correcting problems and their causes during
manufacturing activities.
f. Documents of compliance with ISO 9001 series and supplemented with the requirements
given in ASTM E1212 and DNV OS-F101 Section 2.
6
Base Material and Equipment Requirements
6.1
Unloading, Handling and Storing
Materials shall be received, handled and stored in accordance with a procedure to be issued
by Manufacturer/Supplier for Client/Company approval.
Manufacturer/Supplier shall exercise all reasonable precautions to ensure that no damage to
components resulting from unloading and handling while in Manufacturer/Supplier’s custody
and control. The contact surfaces of any lifting components that will come into contact with
CRA overlay shall be CRA, Stainless Steel, or soft non-metallic material. Alternatively, lifting
shall be performed using wide straps.
As each component is unloaded, Manufacturer/Supplier shall visually examine the component
for damage. Any damaged components found upon receipt by Manufacturer/Supplier shall be
segregated from the remainder of the shipment and noted on the receiving report as to the
type and extent of damage. Client/Company shall require Manufacturer/Supplier to replace
and repair any issued components that are subsequently found to be damaged and which
were not reported by Manufacturer/Supplier as being damaged upon receipt.
6.2
Base Pipeline
The base pipeline material shall be seamless or longitudinally welded and shall conform to
API 5L (45th Ed.), product specification level PSL 2, annex H and all applicable annexes,
NACE MR0175/ISO15156 and project document, except as specified otherwise. Seam weld
of base pipeline shall be subjected to 100% RT as per ASME Sec. IX using a system capable
of detecting both longitudinal and transverse defects prior to overlaying. Overlayed pipelines
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furnished to this specification shall met all the requirement of API 5L (45th Ed.), PSL 2, annex
H and all applicable annexes, NACE MR0175/ISO15156 and project document.
6.3
Surface Condition
All surfaces to be overlayed shall be clean and smooth prior to any overlaying. Pipeline Internal
surfaces to be overlayed shall be free from paint, oil, dirt, scale, oxides, and other foreign
material detrimental to weld integrity.
Surfaces to be overlayed shall be blasted in accordance with NACE No 1 SSPC-SP5,
machined or ground to clean, bright metal prior to application of overlay.
Overlayed surfaces shall be protected from marring or abrasion in lifting, handling or clamping.
Chipping tools, slag picks, brushes, and similar tools which have been previously used on
carbon and low alloy steels shall not be used on CRA surfaces. Only austenitic stainless steel
or high nickel alloy tools shall be used. Grinding, sanding, and cleaning tools used on CRA
materials shall be iron and sulphur free, and not previously used on any carbon steel surfaces.
6.4
Welding Equipment
Welding equipment and tools shall comply with DNV OS-F10 Appendix C and the following
additional requirements:
•
Welding equipment using wave form control features shall include a meter which
displays instantaneous energy or power.
•
IVA calibration certificates valid for the period of use.
•
IVA calibrated instrumentation shall be available during qualification and production in
order to measure welding parameters, such as current, voltage, welding speed, pre-heat and
inter-pass temperatures.
•
The manufacturer, model and type of equipment shall be identified in the PQR.
•
Mechanised welding equipment shall be capable of maintaining the welding head(s) at
a fixed position in relation to the workpiece during the entire welding process.
Certificates showing that equipment calibration is valid for the period of use shall be available.
Mechanized welding systems shall be subject to pre-qualification approval of Client/Company.
Manufacturer shall demonstrate that they have a track record of producing weld overlay
products with the same equipment to meet the requirements of this specification.
Manufacturer’s equipment shall be capable of maintaining the welding head at a fixed position
relative to the work piece during the entire welding procedure. The design of the welding head
suspension shall be sufficiently robust to ensure that the temperature fluctuation, or any other
external influence during the overlay process, does not negate the arc stability.
Manufacturer shall demonstrate in pre-qualification that their mechanized welding system is
capable of producing weld overlay with consistent bead width and alignment and complete
fusion of adjacent beads throughout the maximum length of pipeline to be overlaid.
Mechanized welding equipment shall be fitted with AVC.
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The welding equipment shall be fitted with a camera so that the welding operator can
continuously view the arc during the course of welding, and assist in accurate placement of
re-start location and repairs (if approved).
During welding procedure qualification and production welding, welding equipment shall be
operated in conjunction with Client/Company-approved data logging facilities capable of
recording all the essential variables associated with the arc-including:
•
Wire feed speed
•
Travel speed
•
Wire voltage and current (for hot wire process)
•
Arc Time
The equipment shall record all parameters for each weld pass at a minimum rate of once per
20 seconds. The torch position associated with each measurement shall also be recorded.
This data shall be readily retrievable for monitoring and statistical analysis purposes, and shall
form part of the component data package. Other systems for arc monitoring/data logging may
be proposed, subject to approval of Client/Company.
6.5
Welding Consumables
The welding consumable used to deposit the CRA overlay shall be Nickel Alloy 625 wire (UNS
N06625) as per ASME Sec. II, Part C, SFA-5.14 for the classification ERNiCrMo-3. Test
certificates shall be supplied prior to commencing production welding in compliance with BS
EN 10204 (Type 3.1). The test certification shall include chemical testing of each individual
batch or heat for all elements specified in ASME Sec. II, Part C, SFA-5.14 for the classification
ERNiCrMo-3. The iron content in the welding fillers shall not exceed 1.0%.
The storage and handling of all welding consumables shall be in accordance with a
Client/Company approved procedure. Specific precautions shall be adopted to avoid
contaminations of Alloy 625 welding consumables and probable fluxes that may affect the
integrity of the finished product. welding consumables identification, trade name and batch
shall be maintained during the entire welding operation. Any consumables that cannot be
properly identified or are damaged or contaminated in any way shall be removed from the
manufacturer site.
Clad material shall be kept dry and covered in a well ventilated, weather protected location.
6.6
Welding Gas
Shielding gas for welding of Alloy 625 shall be 99.995% Argon and shall not contain hydrogen.
Gases employed for shielding and purging shall comply with AWS A5.32 or EN ISO 14175.
The gas containers shall be clearly labelled with the grade and brand name as specified in the
WPS. Gases shall be held in the containers in which they are supplied and stored, with
adequate support, in a secured area.
Gas mixtures that have been proven to be satisfactory, as a result of procedure approval tests
and previous production welding in similar application may be acceptable upon approval of
the Client/Company. Gases shall be pre-mixed and bottled by the Manufacturer/Supplier and
shall have certificates of compliance.
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All gases used shall conform to the requirement of ISO 14175. The moisture content of any
gas or gas mixture shall correspond to a dew point of -30°C or lower, and shall be stated on
the certificates. For all welding, the shielding gas shall precede arc initiation by the time
specified on the WPS (pre-flow) and remain on and be held over the weld pool (post flow) for
at least 5 seconds after the arc is extinguished.
Supply and control of shielding gas shall comply with a Client/Company - approved procedure.
6.7
Production Welding
The weld overlay process shall be automatic hot wire GTAW. Other processes such as
mechanized GMAW or PLASMA may only be used if approved by Client/Company.
There shall be at least two passes.
6.8
Chemical Properties and Tests
The Manufacturer shall furnish a report containing the heat analysis of each pipeline and heat
of material used in the manufacture of the CRA layer for pipeline furnished on the purchase
order.
Overlay material shall be welded using UNS N06625 filler metal and consumables in
accordance to ASME Sec. II, Part C, SFA-5.14 for the classification ERNiCrMo-3.
One test from each of two lengths of pipeline from each lot size as indicated in Table 2 of API
5LD shall be analyzed for product analyses. Both the CRA layer and the backing steel shall
be analyzed. The results of the analyses shall be provided to the Client/Company.
Chemical analysis of overlayed layer shall be performed on the final overlay surface (aswelded or machined, as appropriate). The overlay thickness where the chemical analysis is
taken shall be the minimum thickness qualified by the WPQT and shall in no case be less than
3mm.
Samples for chemical analysis shall be removed from:
•
An area of the test weld representing the highest interpass temperature
•
A stop/start location
•
Any regions of autogenous welding undertaken as a part of the stop/start process
The required chemical analyses for the qualification of overlay welding, as determined by heat
or deposit analyses, shall be based on UNS N06625 material, as defined in Table 3 of API
5LD. Methods and practices relating to chemical analysis shall be performed in accordance
with ASTM A751, ASTM E353, or ISO/TR 9769.
The analysis shall be done by energy dispersive X-ray spectroscopy at a point located in the
middle of the overlay bead, approximately 1 mm below the surface. If overlay welding is done
with more than one bead, each bead shall be analysed separately. As a minimum the analysis
shall include the elements specified in UNS N06625. The values measured shall be consistent
with a dilution of the filler metal composition by less than 20%. The iron content shall not
exceed 5% at 2.5 mm from the base metal interface.
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The dilution shall be established by a comparison of the alloy content of the weld deposit
against that shown on the welding consumable test certificate and by a direct measurement
of the combined thickness of the backing steel and CRA layer.
Where a comparison of the alloy content is made, the values obtained from the deposit shall
not be less than 85% of the values shown on the welding consumable test certificate.
Additionally, and when requested by Client/Company, a chemical analysis shall be performed
at an overlay thickness equal to the end of design life remained CRA thickness as determined
by Client/Company erosion analysis and specified in purchase order document. The Fe
content shall not exceed 10% at this location.
When agreed and specified on the purchase order or datasheet, the chemical composition of
any CRA overlay may be further restricted by specification of a minimum pitting resistance
equivalent number (PREN) (% Cr + 3.3 % Mo + 16 % N) or PREW [% Cr + 3.3 (% Mo + 0.5
% W) + 16 % N] value. If this is the case, the actual values shall be reported on the material
test certificate. Otherwise, the minimum PREN shall be 46. Also, every weld overlay shall be
subject to PMI to ensure the use of the correct weld consumables.
The chemical properties of the backing material, including the composition, chemical analysis,
recheck analysis, and test reports, shall conform to API 5L (45th Ed.), Section 9.2 and NACE
MR0175 / ISO 15156.
Confirmation of cleanliness of the clad surface shall be performed (i.e., no iron contamination
of the overlay). This may include a pre-approved procedure showing control of possible areas
of contamination or using a copper/copper-sulphate solution (reference section 7.2.5.3 of
ASTM A380) on completion of the process.
Also abovementioned tests shall be conducted for qualification of MPS and WPS.
A test ferequency of one per 25 overlayed pipeline shall be tested to fully fulfilment chemical
analysis requirements of this specification.
6.9
Mechanical Properties and Tests
The weld overlay test pieace for qualification of MPS and WPS shall be wide and long enough
to allow the required number of test specimens considering the probability of retesting. The
weld overlay shall be continuous around the circumference.
The grade of the backing pipeline shall conform to all of the mechanical test requirements of
API 5L (45th Ed.), PSL 2, Section 9.3, NACE MR0175 / ISO 15156 and project specification.
Moreover following tests shall be conducted as a part of qualification of WPS and MPS and
results shall be submitted for Client/Company approval.
6.9.1
Tensile Tests
Tensile test orientation shall be as shown in API 5L (45th Ed.), Figure 5. The test specimen
may be either full section, strip specimen, or round-bar specimens as per API 5L (45th Ed.),
Section 10.2.3. The CRA layer shall be removed from all specimens. The type, size,
orientation of the specimens, and removal of the CRA layer shall be reported.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
6.9.1.1 Testing Frequency
Tensile tests shall be made at the frequency shown in API 5L (45th Ed.), Table 18.
6.9.1.2 Longitudinal Tensile Tests
Longitudinal tensile tests shall be conducted in accordance with API 5L (45th Ed.), Section
10.2.3.
6.9.1.3 Transverse Tensile Tests
Transverse tensile tests shall be conducted in accordance with API 5L (45th Ed.), Section
10.2.3.
6.9.1.4 Seam Weld Tensile Tests
For longitudinally welded pipelines, weld tensile tests shall be conducted in accordance with
API 5L (45th Ed.), Section 10.2.3. The tensile test shall only sample the weld seam in the
backing steel.
6.9.1.5 Control Tensile Tests
One tensile test shall be made as a control for each heat of backing steel material used by the
Manufacturer for the production of overlayed pipeline. A record of such tests shall be available
to the Client/Company. For welded pipelines, these tensile tests shall be made on either the
skelp, plate, or the finished pipeline at the option of the Manufacturer/Supplier.
6.9.1.6 Retests (Tensile)
Retests shall be performed as required in API 5L (45th Ed.), Section 10.2.12.
6.9.2
Flattening Tests
6.9.2.1 Electric Welded Backing Material
Flattening tests shall be performed for electric weld pipeline used as the backing pipe per API
5L (45th Ed.), Figure 6 during the manufacturing of the mother pipeline.
Acceptance criteria for flattening tests shall be as specified in API 5L (45th Ed.), Table 18.
Retests shall be performed as required in API 5L (45th Ed.), Section 10.2.12.
6.9.2.2 Seamless Backing Material
section of pipeline not less than 63.5 mm in length with the CRA layer left on the test specimen
shall be flattened cold between parallel plates in two steps as described in section 7.9.2 API
5LD (46th Ed.).
6.9.3
Guided-Bend Tests
The requirements of section 10.2.4.6 and Table 18 of API 5L (45th Ed.) shall be met for base
pipeline.
Longitudinally welded backing pipelines shall be tested by the 4 guided-side bend test after
overlaying. The test specimen shall be sampled perpendicular to welding direction. For
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thickness <25 mm, the test specimen width shall be equal to full thickness of base material
and overlay. For thickness >25 mm, amount of base material sampled shall be at least 5 times
the overlay thickness. Central portion of specimen shall include material from as close as
possible to start/stop area for the welding head that is depositing the first layer of cladding on
CS substrate. The thickness of specimen shall be 10 mm. Edges shall be rounded to radius 1
mm. The CRA layer shall remain.
Specimens shall be bent approximately 180° in a jig. The dimension of the former (mandrel)
used for guided-bend tests shall be a maximum of six times the nominal thickness of the
backing material.
No open discontinuity exceeding 1.5 mm, measured in any direction, shall be permitted in the
overlayed layer, and no open discontinuity exceeding 3 mm shall be permitted along the
approximate weld interface. Buckle tears originating from the edge of specimen may be
disregarded if not associated with obvious defects, as approved by Client/Company.
Retests shall be performed as specified in API 5L (45th Ed.), Section 10.2.12.
6.9.4
Fracture Toughness Tests
Fracture toughness of the backing steel shall be determined using Charpy V-notch impact
tests, as specified in API 5L (45th Ed.), PSL 2, Section 10.2.3.3, as a minimum, at the test
frequency stated in API 5L (45th Ed.), Table 18 for the Charpy test of pipeline body and seam
weld. The CRA layer shall be removed by machining prior to the test.
Unless otherwise stated on the purchase order, each set of full size tests shall satisfy the
requirements of API 5L (45th Ed.), Sections 9.8.1 and 9.8.2.
Unless otherwise stated on the purchase order, the test temperature shall be stated in API 5L
(45th Ed.), Sections 9.8.1, 9.8.2, and 9.8.3.
As permitted by API 5L (45th Ed.), Section 9.8.1.1, energy ratios for sub-size specimens shall
be 0.75E (3/4 size) and 0.5E (1/2 size) for 10 mm (0.394 in.) × 7.5 mm (0.295 in.) and 10 mm
(0.394 in.) × 5 mm (0.197 in.) specimens where E is the required energy, respectively.
Shear requirements in API 5L (45th Ed.), Section 9.8.2 shall be met on the backing steel.
6.9.5
Hardness Test
For hardness specified using a Vickers scale, testing shall be in accordance with ASTM E38411. For hardness specified using a Rockwell scale, testing shall be in accordance with ASTM
E18-14. As shown in Figure 1, a hardness survey shall consist of two traverses, according to
Table 1. Samples shall be taken from stop/start locations and from the region of highest
interpass temperature.
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Figure 1. Hardness survey path for overlayed pipeline.
Table 1. Hardness survey traverse for overlayed pipeline
Traverse
C and D
Hardness Survey
1 mm on either side of the carbon steel base metal to overlay alloy weld
interface
No individual value in the backing steel material shall exceed 248 HV10 and overlayed
material shall have maximum hardness of 345 HV10 in all locations unless otherwise agreed.
Also requrements of NACE MR0175 / ISO 15156 shall be met.
If any result exceeds the applicable limit, the result shall be reported to the Client/Company
and two additional shall be cut from the same pipeline for testing. If either of these samples
results in hardness values in excess of the above limits, this pipeline shall be rejected and all
pipelines.
6.9.6
Special Tests
6.9.6.1 Metallographic Examination
Two through-thickness samples shall be prepared for metallographic evaluation. Each sample
shall be prepared to a polished finish and suitably etched to reveal the microstructure of the
Alloy 625 overlay. The HAZ of overlaying welding shall be free from grain boundary carbides
and nitrides at 400X magnification. Micro cracking at the fusion line is not permitted.
Also, macrographs shall be provided at minimum 5X magnification and shall be supplied with
the documentation. The macro samples shall show sound welding without any defects and
show a sound weld merging smoothly into the base material and meeting Quality level C of
ISO 5817.
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Samples shall be taken from stop/start locations and from the region of highest interpass
temperature.
6.9.6.2 Corrosion Testing
Corrosion testing of the CRA weld overlay shall be performed in accordance with ASTM G48
Method A at 50°C for 24 hours and ASTM G28 Method A on a full thickness sample taken
from the test item in the final heat treated condition. The maximum weight loss shall be 4 g/m²
squared with no pitting on the exposed faces at 20x magnification and maximum 1mm/year
corrosion rate. Material sensitisation testing is not required during production.
6.9.6.3 Tests for CRA Overlaying Bond Strength
Special bond shear strength tests shall be performed. Typical tests for bond shear strength
include those found in ASTM A264-12 and ASTM A265-12. Selection of the test method and
acceptance criteria shall be by agreement. The test shall be carried out on one per 25 pipelines
during the manufacturing process. The minimum acceptable bond shear strength shall be 250
MPa.
As an alternate to the bond shear strength and by agreement between the Client/Company
and the Manufacturer/Supplier, a flattening test may be conducted. Acceptance limit of clad
separation or crack length shall be specified by agreement between the Client/Company and
the Manufacturer/Supplier.
6.9.6.4 Residual Magnetism
The residual magnetism shall be recorded at both ends of each finished pipeline and shall not
exceed 15 Gauss. Magnetism levels higher than this value shall require the pipe end to be
demagnetized until the level is reduced below 15 Gauss.
6.9.6.5 Hydrostatic Tests
Hydrostatic testing shall be in accordance with API 5L and project specification unless
modified herein. All pipeline shall be tested after overlaying and prior to inspection. Each
length of pipe shall withstand, without leakage, a hoop stress equal to 95% of specified
minimum yield strength (SMYS) of the backing steel calculated on the basis of the minimum
wall thickness of the backing steel. During the test, the pressure shall not be permitted to
exceed the minimum test pressure by more than 5%. The minimum holding time for all sizes
shall be 10 seconds following stabilization of the pressure.
6.9.6.6 Other Special Tests
Full-scale strain simulations shall be considered to validate the proposed installation method
for overlayed pipeline. Test programmes shall include repeat bend cycles to simulate dynamic
installation conditions. The CRA overlay layer of the tested pipelines shall be 100% visually
inspected and dye penetrant tested. Girth welds shall be 100% examined by RT or UT.
A thermal-cycling trial shall be considered to simulate the application of external anti-corrosion
and insulation coatings where applicable, and demonstrate that the overlaying layer will resist
thermal expansion buckling.
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Prosperities and details for abovementioned tests will be provided by Client/Company.
6.10 Defects, Disbonding and Surface Treatment
Defects shall be repaired as follows.
a) Backing Steel:
The weld repair of backing steel is prohibited.
b) CRA Layer:
Defects in the CRA layer and disbonded areas considered as defects may be repaired
by agreement between the Client/Company and the Manufacturer/Supplier.
Disbonding, as defined in ASTM A263, A264, and A265 is totally prohibited.
The corrosion-resistant behavior of the CRA layer is adversely affected by poor surface
condition. Therefore, any surface residues resulted from overlaying process of the
CRA layer shall be removed by blasting, pickling, brushing, or a combination of these
methods.
6.11 Repair
There shall not be more than three welding repairs per overlayed pipeline. Repair welding
procedures shall be single wire only and shall be fully qualified in accordance with the
requirements of this specification.
Repair welding procedures shall be separately qualified and subject to the same NDT and
destructive testing as the overlay procedure.
All repair procedures shall be submitted to the Client/Company for written approval prior to
their use. The Client/Company shall be informed of all repairs. Any single defect may be
repaired only once.
Weld repairs of the base metal that are not associated with the weld overlays are not allowed.
Repair welding procedures for pipeline, undertaken using pipeline cladding equipment, shall
be qualified in pipeline at least 1m from the end of the two different pipelines. Location of
mechanical and chemical analysis test pieces shall be agreed with Client/Company prior to
qualification.
Weld repair performed on weld overlay machined to the final thickness shall be separately
qualified.
Grinding shall be performed in accordance with procedures approved by Client/Company. A
maximum of 10% of pipeline may be repaired by grinding using stone. Ground areas shall be
smoothly contoured to the surface of the pipeline at a minimum 4 to 1 slope. Ground areas
shall have the final wall thickness measured by Ultrasonic Testing and shall be recorded (i.e.
Wall Thickness, Joint Number, Location on the Joint, etc.).
These ground areas shall not interfere with non-destructive testing at the pipeline mill or during
fabrication/installation (i.e. AUT of girth welds).
When permitted, manual repair welding of pipeline and other components shall be qualified at
the maximum reach inside the component at which the production repair will take place.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
Weld repair performed on weld overlay machined to the final thickness shall be separately
qualified.
6.12 Finishing
The metal surfaces shall be sufficiently clean and smooth to permit non-destructive
examination. All loose scale shall be removed and pitting and rough surfaces removed by
grinding. The Manufacturer/Supplier shall remove by grinding all mechanical marks and
abrasions, such as cable marks, roll marks, and scores. Imperfections such as scabs, seams,
laps, tears and slivers shall be eliminated.
The pipeline shall contain no dents that affect both the outside surface and the inside surface.
Dents on the outside surface shall be limited to a depth exceeding 2 mm for pipeline body or
exceeding 1 mm for pipeline ends, provided it is repaired, and provided that the dent is an
indentation that does not affect the pipeline ID contour. Pounding out or jacking out dents is
not permitted. Dents with gouges are not acceptable, regardless of depth and shall be repaired
by grinding.
The internal surface of the overlayed pipeline shall be sufficiently smooth that it does not
interfere with proper interpretation or radiographs or ultrasonic examination signals.
Any pipeline ends showing laminations shall be cutback and re-beveled. After re-beveling, the
pipeline end shall be inspected using surface NDT and ultrasonic inspection techniques over
a distance from the pipeline end equal to that specified in the UT procedure, to ensure that no
further laminations are present. The carbon steel portion of the bevel shall be inspected using
MPI as per Appendix D DNV OS F-101, whilst the CRA shall be inspected using Dye Penetrant
testing in accordance with ASME V, Article 6.
Acceptance criteria for magnetic testing are that any indication greater than 5 mm in length
shall be removed by re-beveling. Acceptance criteria for UT are that any sub-surface planar
imperfection exceeding 6 mm in any direction shall be rejected. Any Dye Penetrant indication
exceeding those permitted in section 6.16.3 shall be rejected and referred to Client/Company
for resolution.
On items which are to be cut and re-beveled, cutting shall be performed by oxy-fuel and/or
plasma equipment, or by other processes, such as a Robertson lathe, submitted to and
approved by Client/Company. The cut end shall be machined or ground back with a minimum
of 3 mm from the cut edge in order to remove the heat affected zone resulting from the thermal
cutting and to have smooth surfaces free of scale. Special care shall be taken to remove
internal burrs resulting from cutting.
Re-beveled pipeline shall be subjected to feroxyl testing of the CRA material. Any evidence of
iron contamination of the CRA liner requires removal of the pipeline section as a cylinder.
Where by a direct measurement of the combined thickness of the backing steel component
and CRA layer, the combined thickness of the backing steel and CRA layer minus the original
thickness of the backing material (before it the CRA layer was applied) shall be at least 80%
of the total thickness of the CRA layer (including the penetration into the backing pipeline) as
measured from a macro specimen.
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All pipelines shall be delivered with clean external and internal surfaces. final washing in clean
water with chloride ion content (mass fraction) of less than 200 mg/l is recommended. At the
end of the cleaning cycle, the pipeline shall be completely dry.
6.13 Dimensions, Weight and Length of Overlayed Pipeline
Dimensions and tolerances shall be as per Purchase Order, drawings, project specifications
or data sheets.
In the scope of this specification the CRA layer thickness shall not be included in the design
to add to mechanical strength and shall not be considered pipeline wall thickness calculations.
Unless otherwise agreed to, the minimum overlay thickness shall be 3.0 mm (-0, +0.5mm).
The overlay thickness at each pipeline end, defined as the last 150 mm shall be increased to
minimum 4.5 mm to accommodate finish machining. The thickness after machining shall be
3.0 mm (-0, +0.5mm).
The Manufacturer/Supplier shall provide for the Client/Company’s approval a procedure for
measuring the wall thickness of the overlay cladding and base material. Each pipeline shall
have a dimensional check to verify compliance with approved drawings.
Pipelines shall be furnished in the backing steel material sizes and wall thicknesses provided
in API 5L (45th Ed.), Table 9, project specification or as specified on the purchase order.
The plain-end weight, Wpe, shall be calculated using Equations below:
𝑊𝑝𝑒 = [0.02466(𝐷 − 𝑇)(𝑇)] + [0.02466(𝐷 − 2𝑇 − 𝑡)(𝑡)(𝐹)]
Where:
Wpe is the plain-end weight, rounded to the nearest 0.01 kg/m;
D is the outside diameter, rounded to the nearest 0.1 mm for sizes less than 457 mm, and 1
mm for sizes 457 mm and larger;
T is the specified wall thickness of base material, rounded to the nearest 0.1 mm;
t is the specified wall thickness of CRA layer, rounded to the nearest 0.1 mm;
F is the correction factor for 625 alloy which shall be in accordance to API 5LD.
The outside diameter of the final product shall be within the tolerances specified in Table.
Inside diameters are governed by the outside diameter, wall thickness, and CRA layer
tolerances. As an alternate, when agreed upon between the Client/Company and the
Manufacturer, pipeline sizes may be furnished based upon an inside diameter.
The diameter tolerances at pipeline ends shall apply to the nominal internal diameter.
Tolerances on internal diameter are as indicated in Table 2.
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Table 2. Dimention tolerance of overlayed pipeline
Diameter
Pipeline Body
Out-of-roundness
Pipeline Body
The pipeline body outside diameter shall be Out-of-roundness for pipe body shall not
controlled to a tolerance of ±0.75 % for exceed 1.5 % D [max 10 mm].
seamless pipeline; and +0.75 %, –0.25 % for
welded pipeline with a maximum deviation
from the nominal OD of ±3.2 mm.
Pipeline Ends
Pipeline Ends
The tolerance on the inside diameter for Out-of-roundness of pipe ends [100 mm (4
distance of 100 mm (4 in.) from the end of in.)] shall not exceed 1.0 % D [max 5mm] of
the pipe shall be ±1.0 mm
nominal OD
Pipeline Body and Ends
Local irregularity of inside surface shall be
less than 0.5 % D [max 2 mm] measured by
internal radius gauge encompassing a 200
mm (8 in.) length of arc
Wall Thickness Tolerance
Backing Steel
CRA Layer
As per API 5L (45th Ed.)
–0, +0.5 mm
Weight Tolerances
As per API 5L (45th Ed.), Section 9.14.
Change weight to mass per API 5L (45th Ed.), Section 9.11.2.
Unless otherwise ordered, pipelines shall be furnished with ends J beveled to an angle of 20°
to 30°, +5°, –0° with curvature radius of 3.2 mm, measured from a line drawn perpendicular
to the axis of the pipeline, and with a root face of 2.1 mm ± 0.3 mm.
6.14 Manufacturing Procedure Specification (MPS) / Manufacturing Procedure
Qualification (MPQ)
Prior to commencement of work, Manufacturer/Supplier Manufacturing procedure
specifications shall be prepared and qualified for the manufacture of weld overlaid
pipelines and shall be submitted for Client/Company approval.
At least one pipeline of each size and manufacturing location shall be manufactured in
accordance with the agreed MPSs and be subjected to all of the production inspection
and testing required by this specification plus the additional testing defined below:
•
The welded layer shall be inspected by radiography for longitudinal and transverse
defects along its full length, or by manual or automatic UT procedures, whichever is
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•
•
•
•
•
applicable for the production pipeline, and assessed against the requirements of this
specification.
MPI shall be performed on 100 % of the backing steel pipeline OD surface of the external
carbon steel weld seam.
The complete internal surface shall be visually inspected. For sizes less than 406.4 mm
(16 in.), an endoscope or video camera shall be used unless other methods are available
to perform this inspection.
The ultimate tensile strength, elongation, and reduction of area shall also be reported.
Where the maximum design temperature is above 100 °C, transverse and all tensile
tests shall be carried out at the maximum design temperature. Refer to DNV OS F-101,
Section 5, Figure 2 for guidance.
All Mechanical and Chemical tests specified is Sec. 6.8 through Sec. 6.9.6.6 of this
specification.
The manufacturing procedure specification (MPS) shall be as per Annex B of API 5LD (46th
Ed.). The MPSs shall also incorporate all elements necessary for weld overlaying as detailed
in this Specification. The MPSs shall give details of all stages of manufacture including all
factors that influence the quality and reliability of production as detailed in the project
specifications and Codes and Standards referenced in section and this Specification.
The MPSs shall include corrosion test procedures for qualification of the weld overlayed
pipeline according to this specification. Test rings may be used if approved by
Client/Company.
The MPS shall be qualified separately for each pipeline diameter and wall thickness.
The MPQT shall demonstrate that the requirements of this Specification and the base material
specification are satisfied with respect to composition, mechanical properties, dimensional
tolerances and quality.
Mechanical testing and NDT shall be conducted on the MPQ test pipeline in accordance with
this specification.
For pipelines where welding head angle, electrode position and other manufacturing variables
do not change per diameter, Manufacturer/Supplier may propose for qualification to cover a
range of diameters.
6.15 Overlaying Welding
All production welding shall be automatic. Repair welding may be manual or semiautomatic.
The weld overlay process shall be automatic hot wire GTAW. Other processes such as
mechanized GMAW or PAW may only be used if Manufacturer/Supplier can demonstrate a
history of use and previous qualification data, to the satisfaction of Client/Company.
Welding, fabrication and the associated quality assurance activities shall comply with the
requirements of DNV OS-F101 Appendix C unless modified by this Specification. Weld repairs
of the base metal that are not associated with the weld overlays are not allowed.
During the production, an internal camera inspection technique shall be used to maintain a
full-time monitoring and inspection. During manufacture using mechanized equipment, the
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recorded welding parameters shall be periodically audited for a minimum of two welding
stations per day.
If the weld overlay is being applied within 150 mm of future girth weld, the weld overlay
procedure shall be such that the adjacent girth weld (to be performed by others) can be
inspected with sufficient accuracy by ultrasonic methods.
Contractor shall take necessary precautions to prevent arc burns between the ground clamp
and the pipeline. All “stray welds” or ground clamp arc burns shall be considered arc burns
under this Specification. No arc burns, or repairs to arc burns, shall be permitted within 150
mm of the pipeline end.
The use of autogenous welding techniques shall not be allowed unless Manufacturer can
demonstrate that the process can be adequately controlled in production and is approved by
Client/Company. If autogenous welding cannot be avoided during the start/stops or wire
changes, this shall be minimized by strict control of procedures. Arc energy shall not be
increased during autogenous welding and this shall be fully qualified welding procedure
qualification. the use of autogenous welding shall only be allowed once per location.
6.15.1 Welding Procedure Specification (WPS)/ Procedure Qualification Record (PQR)
The manufacturer shall prepare welding procedure specifications (WPS) for overlaying or
repairing welds on forms in accordance with ASME Sec. IX and, in addition to all applicable
essential and non-essential variables of ASME Sec. IX and DNV OS F-101, shall contain the
following information:
•
material specification of base materials;
•
welding process;
•
wall thickness range for which the procedure is valid;
•
geometry of weld;
•
welding position;
•
filler metal name/type/classification;
•
filler metal size/diameter per pass/layer;
•
wire feed speed (not applicable to SAW or electroslag welding);
•
the approximate depth of each weld run;
•
flux name/type/classification;
•
name/type/specification/composition of gases;
•
gas shielding flow and gas backing flow rates;
•
number and sequences of passes;
•
welding current and voltage range and polarity (if pulsed current welding techniques
are used, full details of the pulse shape, duration, and frequency shall be listed);
•
if hot wire welding techniques are employed, full details of the associated parameters
shall be listed;
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•
travel speed for each pass and permitted range;
•
heat input range;
•
minimum preheat/maximum interpass temperatures;
•
post-weld heat treatment (if any);
•
method of cleaning and cutting.
Only the Client/Company approved weld procedures shall be used.
All overlaying process shall be done in accordance to a qualified welding procedure. Any
change in essential variables beyond qualified range is highly prohibited.
Prior to any WPQT a pWPS shall be prepared and shall include details of equipment type and
Manufacturer. Following qualification testing, the pWPS shall be revised to a ‘production’ WPS
to reflect the parameters recorded during qualification. The revised WPS shall state the
parameters for each layer and the arc energy shall be calculated using the actual recorded
values of current, voltage and travel speed.
Qualification of WPS shall be in accordance to the requirements of BS EN ISO 15614-7 (2019)
or DNV OS-F101 Appendix C E400 and the additional requirements of this Specification.
Qualification shall also meet the requirements stated in NACE MRO175/ISO 15156. For all
tests, equipment type and manufacturer shall be recorded on the PQR. Test coupons shall
not be used.
The WPQT shall be subject to 100% VT (with camera where applicable), PT (with camera
where applicable) and UT as specified for production in accordance with this specification.
The NDT procedures for WPQT shall be qualified and subject to approval by Client/Company.
All pWPSs, WPSs, and PQRs shall be submitted for approval by Client/Company prior to
commencement of production.
Each WPS shall be qualified by a single set of PQR(s) each comprising the same combination
of process and consumables of the WPS intended for. Combinations of PQR with different
consumables and different processes to PQR shall not be accepted, nor the use of
combination of previously qualified WPSs.
Consumable brand name shall be an essential variable. Any change in the brand of welding
consumables after Client/Company approval of the WPS shall perform a requalification of the
modified WPS.
Where wave form controlled welding is being employed the heat input shall be calculated
using the methods detailed in Appendix H of ASME Sec IX.
Repair welding procedures shall be qualified by a PQR simulating the repair method. Repair
welding procedures shall be qualified in pipeline at least 1m from the end of the two different
pipelines. Location of mechanical and chemical analysis test pieces shall be agreed with
Client/Company prior to qualification.
Local weld repair or local build up for the purposes of increasing the thickness of the weld
overlay as an aid to girth weld fit-up shall be fully qualified and shall be subject to approval.
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This procedure shall be qualified on the minimum thickness of overlay for which the procedure
can be used in production. This overlay thickness shall be specified in the WPS.
Welding procedure qualification shall be performed using with the maximum interpass
temperatures experienced in production. For Tandem Head Welding without forced cooling,
the interpass temperature shall be the lowest temperature measured on the outside surface
between the two welding heads.
For automated pipeline overlay welding processes the WPQT shall include first and surface
layer stop/start simulations, and the first layer stop/start location areas shall be subjected to
metallographic examination, hardness testing, and chemical analysis.
Qualification of overlay welding operators’ performance shall be in accordance to ASME Sec.
IX. NDT shall comprise of 100% VT, PT and UT as per the WPQT. Previous welder
qualifications may be acceptable pending satisfactory documented evidence and
Client/Company approval.
A certified Welding Engineer or equivalent shall be employed in the staff to overlook the
welding operations. The Engineer shall have a minimum of Master of Science degree in
Metallurgy or Materials or Welding and five years of related experience.
Production welding shall include interpass and preheat temperatures and be monitored during
CRA weld overlaying for conformance to the limits specified in the weld procedure
specification (WPS).
6.15.2 Welding Variables
All essential and non-essential welding variables of ASME IX and DNV OS-F101 Table C-2
shall apply. In addition, the essential variables listed below shall apply.
For welding materials, the Consumable Manufacturer and product number shall be essential
variables. If a separate flux is used, the lot shall be an essential variable.
Base Materials
•
•
•
•
•
•
o
o
A change of component production route
A change of heat treatment condition
For pipeline overlay welding each individual nominal diameter shall have a separate
WPQT
Method of surface preparation
Any change in grade (deliberate additions of Cr, Mo, Ni, V, Nb) or SMYS
A change in WPQT test material as follows:
For linepipe with C>0.12% and C-Mn or low alloy steel forgings an increase in CEIIW
>0.02 greater than that qualified
For linepipe with C≤0.12% an increase in PCM >0.02 greater than that qualified
Filler Metals
•
•
•
A reduction in the number of CRA layers
A change in wire size
Change in brand name
Position
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•
Any change in positions
Gas
•
•
Any change in Argon purity
If using commercially-pure Argon, then trade name is not an essential variable. For other
gas or gas mixture, any change in trade name, manufacturer, or composition limits
outside that recorded on the WPS.
Electrical Characteristics
•
•
•
•
A change in welding current, arc voltage and travel speed outside the range qualified or
±10% of the mean qualified
Any change in arc energy outside of the range in the approved WPS (Manufacturer shall
identify the method of calculation for each process in the PQR)
For pulsed current welding, a change in the pulse frequency, pulse shape, and max/min
current recorded in the WPS
For GTAW, the addition or deletion of the hot wire process.
Technique
•
•
•
•
•
•
•
•
•
•
•
Any increase in bead width
Any change to frequency of mechanized weave
Any change to dwell time at the side of any mechanized weave
Any increase of arc energy where autogenous welding is using during start/stop process
Any increase in the number of autogenous welding passes (where use of autogenous
welding is approved)
A change of wire feed speed outside the range qualified
A change of head angle, electrode spacing from bottom or top dead center and direction
of ration for 1G rotation welding
A change of electrode spacing or orientation for welding procedure utilizing multiple
electrodes
Any change in step distance between passes
The WPQT shall be undertaken using the same equipment as used in production
A change to the number/spacing of welding heads
Interpass Temperature
•
•
•
An increase over that qualified
Method and amount of forced cooling
Any change in method or position of measurement from that qualified
Location
Any change to manufacturing location. Manufacturer shall request prior approval from
Client/Company to use the same WPS/PQR at multiple sites.
6.16 Nondestructive Inspection
Each Manufacturer/Supplier shall furnish, for approval, a description of the procedures and
equipment they propose to use for each inspection operation required herein and for any
additional inspections. This description shall include details of calibration procedure, reference
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
standards and acceptance limits. The Manufacturer/Supplier shall demonstrate to the
satisfaction of the Client/Company the effectiveness of all equipment and procedures prior to
the commencement of work.
In the case of any conflict between criteria mentioned herein and Codes/Standards
acceptance criteria, the stricter criteria shall be considered.
All non-destructive testing (NDT) shall be performed by a third-party company.
All works shall be performed by ASNT-TC-1A Central Certification Program (ACCP) Level II
operator at a minimum.
Preparation of NDT procedures and execution of all NDT shall be carried out under the
responsibility of Level 3 personnel and shall be performed by personnel holding at least Level
2 qualifications. All NDT procedures shall be submitted to Client/Company for review and
approval.
At any circumstances the imperfection depth shall not exceed that which makes the cladding
thickness less than the minimum thickness specified in applicable data sheets.
A defect/indication mapping procedure, utilizing radial, circumferential and longitudinal
measurement from a fixed datum point, shall be submitted for Client/Company approval for
each NDT process. This shall enable accurate recording and location of weld
defects/indications.
All pipelines having repetitive imperfections shall be segregated and the Client/Company
informed of the extent and cause of the imperfections. The Manufacturer/Supplier shall inform
the Client/Company of actions taken to prevent the imperfections.
6.16.1 Visual Testing (VT)
Prior to weld overlay of base material all pipelines to be welded shall be subject to VT to
ensure freedom from scale, laps, oxide, non-metallics, grease or other contaminants that may
affect the welding process.
All overlayed pipelines shall be 100% visually examined per API 5L (45th Ed.), Section 10.2.7
and the requirements of ASME Sec V, Article 9.
Visual examination shall be carried out in a sufficiently illuminated area; minimum 1000 lx. If
required to obtain good contrast and relief effect between imperfections and background
additional light sources shall be used. For direct examination the access shall generally permit
placing the eye within 600 mm of the surface to be examined and at an angle of not less than
approximately 30°. in locations such that viewing is restricted, examination shall be
undertaken with the aid of a high definition camera.
A sufficient amount of tools, gauges, measuring equipment and other devices shall be
available at the place of examination.
The objects to be examined shall be cleaned to remove all scale and processing compounds
prior to examination. The cleaning process shall not injure the surface finish or mask possible
imperfections.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
The carbon steel shall be free of defects as defined in API 5L (45th Ed.), Section 9.10 and the
CRA layer shall be free of cracks and arc burns. Other imperfections in the CRA layer shall
not exceed a depth of 0.8 mm.
Generally, the following shall be categorized as defects and shall not be allowed:
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•
•
•
•
•
•
•
•
Inter-run lack of fusion (missed edge)
Missing first or subsequent layer
Oxidation or surface breaking inclusions
Unfused wire
Autogenous welding (unless qualified for start/stops or cosmetic repairs)
Poor stop/ start profile
Excessive bead width
Surface blistering or cracking
Craters or blownholes
Porosity of any diameter
Reports shall be provided in accordance with ISO 17637 including identification of the testing
procedure used.
6.16.2 UltraSound Testing (UT)
100% of all overlayed pipelines shall be subjected to an ultrasonic examination using
procedures capable of locating defects within the backing steel or the overlaying layer and to
detect overlay thickness, discontinuities, lack of fusion and un-bonded areas. Both shear wave
for radial or through wall defects and compression wave for laminar defects at the bond line
techniques shall be used.
Ultrasonic examination shall also be made at the pipeline ends and at intervals along the
length for cracks, laminations, inclusions and disbondment.
All UT procedures shall include scan plans and be approved by Client/Company.
This inspection shall be done according to ASTM A578/A578M and the requirements of ASME
Sec V, Article 4. The Manufacturer/Supplier’s written procedures shall be submitted to the
Client/Company for approval. The acceptance criteria for the bond line shall be according to
ASTM A578/A578M, Level C. Also, any area where one or more discontinuities produce a
continuous total loss of back reflection accompanied by continuous indications on the same
plane (within 5% of the material thickness) that cannot be encompassed within a 25 mm
diameter circle is unacceptable.
Scanning coverage shall be along 25 mm centers along the entire length of the pipeline. The
location of the equipment shall be at the discretion of the manufacturer.
6.16.2.1 Wall thickness measurement
On the overlayed pipelines measurement shall take place from the outside wall. The wall
thickness of each pipeline shall be measured over its full length, prior to the weld overlaying
process, from the outside diameter at a minimum of 4 locations around the circumference at
a pitch of 150 mm. After the pipeline has been overlaid a thickness check shall be carried out
at the same location as the initial thickness check and shall demonstrate that the clad layer is
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
the minimum specified in accordance with the requirements of this specification and
datasheets. In addition, the pipeline shall be scanned using a helical pattern which ensures
that a minimum of 25% of the outside surface of the pipeline is covered. Results shall be
recorded and be traceable to each pipeline. Due consideration shall be given to the
measurement of the clad thickness after machining to ensure that the minimum clad thickness
is retained. When requested by Client/Company, the thickness of the clad layer shall be
verified by electromagnetic (inductive or adhesive force) methods or by other techniques
agreed by Client/Company. Measurements shall be made from the clad side over a grid
pattern in such a way that at least 25% of the surface is covered.
The accuracy of the clad thickness measurement shall be better than 0.2 mm and shall be
carried out in accordance with ISO 2178 or ASTM B499.
6.16.2.2 Fusion interface
On overlayed pipelines 100% UT for fusion zone integrity shall be performed along the full
length of pipeline, and the surface condition of the material shall permit at least two successive
back-wall echoes to be distinguished when the probe is placed on any area free from internal
imperfections.
The UT procedure shall be qualified prior to use. A calibration block shall be manufactured for
this purpose for each diameter and overlay thickness combination made from the actual base
material with overlay deposited according to the same WPS as the actual overlay and
minimum specified thickness.
The sensitivity shall be based on echoes reflected from a 3.2 mm FBH in reference blocks
drilled from the weld overlaid side. The 3.2 mm FBH shall be placed approximately at the
fusion line between overlay and base material. If the testing shall be performed of machined
overlay, the scanning surface shall be machined to the same surface requirements as the
overlay. All reference blocks shall be marked with an identification that relates to the specific
application of each block.
Amplitude calibration shall be performed by maximizing the signal amplitude from the 3.2 mm
FBH and adjusting the signal to 80% ±5% full screen height. This shall be the reference level.
Acceptance criteria shall be:
•
•
•
No loss of back wall echo;
No single echo from an indication shall exceed 60% of the echo reflected from 3.2 mm
FBH in reference blocks;
No multiple indications exceeding 50% reference reflector. Multiple indications are
defined as two or more indications within 10mm of each other in any direction.
Inspection shall include examination for lack of inter-run fusion between the weld layers.
Defects shall be ground out, re-welded and re-tested to meet the acceptance criteria above.
For all other overlaid components inspection procedures shall identify methods for 100%
checking of fusion zone integrity for each type of component with acceptance criteria as per
Section 610 of DNV OS-F101 Appendix D.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
6.16.3 Dye Penetrant Testing (PT)
In addition to UT, the weld overlay surface including weld ends (overlay/CS interface) shall
100% be examined by the liquid penetrant method, in accordance with ASME Sec. V, Article
6, and ISO 3452. The surface to be examined and all adjacent areas within 25 mm shall be
dry and free of any dirt, grease or other extraneous matter that could interfere with the
inspection. An indication of an imperfection may be larger than the imperfection that causes
it; however, the size of the indication shall be the basis for acceptance evaluation.
The penetration and developing times shall be long enough to allow effective detection of the
smallest indications. Where access permits, PT shall be undertaken visually by approved
inspectors. Viewing conditions shall be minimum 1000 lx at the area of interest.
In addition to acceptance criteria of mentioned Codes and Standards following shall be meet:
•
•
•
•
No linear indications.
No rounded indications greater than 1.5 mm diameter.
No more than three (3) rounded indications in a pipeline separated 1.5 mm or less
(edge-to-edge).
A rounded indication is one of circular or elliptical shape with a length equal to or less
than three times its width.
6.17 Shipment, Packing, Marking
Overlayed pipeline shall be bare and free of oil, grease, lacquer, antifreeze (from UT couplant)
and other contaminants such as chlorides, which adversely affect coating adhesion. There
shall be no stickers and/or tape applied to the pipeline for any purpose. End protectors that
prevent buildup of moisture in the pipeline are recommended.
Tools used to handle overlayed carbon steels shall never be in contact with the clad part,
unless it is CRA materials dedicated tool. In that case, it shall never be in contact with the
carbon steel part. Handling devices containing copper or copper alloys shall not be used.
Hooks shall not be used.
No over storage or deck loads are permitted.
overlayed pipelines shall not be nested one diameter inside another.
In order to reduce damage to the internal cladding and bevels, Manufacturer shall use
hookable end caps or Client/Company approved equivalent.
If in-transit fatigue cracks are detected after shipment, Client/Company reserves the right to
reject the entire shipment until an absence of fatigue cracking is proven on the entire shipment
by an agreed upon NDT method.
All dimensional tolerances and surface conditions specified shall apply to the pipelines
conditions as received by the Client/Company at the shipping destination. The
Manufacturer/Supplier shall prepare a shipping proposal and shall include a detailed shipping
plan.
The Manufacturer/Supplier shall submit loading instructions and diagrams for Client/Company
approval.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
Pipelines shall be furnished bare and free of all mill coating and shall be furnished with no tags
or placards attached. No die stamping, hot or cold, shall be permitted. The
Manufacturer/Supplier shall provide the Client/Company with a marking and identification plan
for all pipelines. Mill traceability shall be maintained for all sections of the pipelines and all
operations. Marking and coding plans shall be submitted as part of the
Manufacturer/Supplier’s Quality Assurance (QA) plan.
Details of Shipment, Packing and Marking will be finalized in next stages of project.
7
Installation and Operation of Overlayed Steel Pipelines
7.1
Welding Requirements
Welding shall be carried out using a process or combination of processes that has been fully
qualified according to the requirements of this specification.
Requirements stated in DNV OS-F101 Appendix C Section G and H and NACE MR 0175/ISO
15156 shall be considered together with the following sections.
Welding shall be done by manual, semi-automatic or automatic welding.
Welding processes using filler metal shall be used for all root and hot passes.
All welds shall be a continuous operation and multi-pass.
The minimum interpass temperature shall not be less than the minimum preheating
temperature. The maximum interpass temperature shall be limited to the one recorded in the
qualified welding procedure and shall not be higher than 150 °C.
Post-weld heat treatment shall not be performed, unless specifically requested.
The root and hot pass shall be welded using GTAW. Shielded Metal Arc Welding (SMAW)
shall be used for filler and capping.
At least, the root and the hot passes shall be completed prior to stop welding. When required
by the WPS, the weld area shall be preheated before the welding starts again.
Wide welding beads are not allowed. Stringer bead welding techniques should be used.
Vertical welding shall be performed in uphill direction only.
If, for any reason, lay-barge production is halted, welding shall continue until all partially
completed joints have been completed.
Welders and the work shall be properly shielded when weather conditions are such that high
winds, rains are presents.
7.2
Welding Procedure Specification (WPS) / Procedure Qualification Report (PQR)
Welding Contractor shall produce separate welding procedure specifications for each
proposed production welding and repair welding procedure. The welding procedure
specifications shall be reviewed and approved by Client/Company prior to the start of
procedure qualification testing or production welding.
Preliminary welding procedure specification (PWPS) shall be proposed to Client/Company for
review and/or approval before starting the welding procedure qualification.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
All welding procedure qualifications shall meet the requirements stated in DNV OS-F101
Appendix C Sections D, E and F and all applicable requirements of NACE MR0175/ISO
15156. As a minimum, the procedure specifications shall contain the information set forth in
DNV OS-F101- Appendix C Section D.
Any change of essential variables listed in the above specified standards requires a new
qualification. A qualified welding procedure remains valid as long as the essential variables
are kept within acceptable limits specified DNV OS-F101 Appendix C Section D and following
sub sections.
Destructive and non-destructive testing for welding qualification purposes shall be carried out
in accordance with DNV OS-F101 Appendix C Sections E and F.
Laboratory tests in accordance with NACE TM 0177 method C shall be carried out on samples
to ascertain the weld resistance to SSC. The acceptance criteria for the test specimens shall
be “no cracking”.
All qualification test welds shall be made on project pipeline material. More than one test weld
may be required for procedure qualification in order to provide enough material for all of the
mechanical tests. The pipeline nipples used to make-up the weld shall be at least one and
one-half pipeline diameters in length. These nipples shall be taken from pipeline heats that
exhibit the highest carbon equivalents.
All information shown on the PQR, such as amperage, voltage, travel speed, heat input,
PWHT time and temperature, as applicable, shall be actual data as recorded using calibrated
instruments.
The WPS shall additionally specify the following:
•
•
•
•
minimum period of backing-gas application prior to commencement of welding;
minimum period of backing-gas application during welding;
minimum period of backing-gas application after welding;
description of the back-purge dam type and method.
The addition or deletion of a second filler wire in the GTAW process shall constitute an
essential variable. A change from hot to cold wire addition or vice versa shall also constitute
an essential variable.
A change from a stringer pass technique to an oscillating technique in the root and hot pass,
or vice versa, shall constitute an essential variable.
A reduction in the time for establishing the back purge prior to welding shall constitute an
essential variable.
A reduction in the number of passes deposited before discontinuing back-purging shall
constitute an essential variable.
Client/Company approval of Welding Contractor procedures and processes shall not relieve
Welding Contractor from the obligation to perform Work in accordance with this Specification.
Welding procedures from previous work, whether or not of a similar nature, shall not be
acceptable.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
Welding Contractor shall perform the testing required qualifying the welding procedure in the
presence of Client/Company.
Qualification of the welds shall be performed simulating the location, where welding will take
place. The test welds shall be made using the same equipment as that to be used for
production. Welding Contractor shall provide all necessary plant, equipment, consumables
and expendables to perform the weld procedure qualifications.
All qualification welds shall be performed using a Client/Company reviewed and/or approved
arc data monitoring system. All parameters shall be monitored and recorded during
qualification welding. The pipelines used for weld procedure qualification shall be selected
with maximum CEV and PCM by Client/Company. NDT of test welds shall be performed not
less than 24 hours following completion of welding.
Welding Contractor shall qualify welding procedures within the consumable manufactures
recommended parameter ranges for each consumable used. Qualification of welds outside
the recommended parameters shall be cause for rejection of the procedure.
PQR shall include all non-destructive, mechanical and corrosion tests results.
All welding procedures and PQRs shall be approved by Client/Company/Contractor prior to
start of any welding activity covered under those procedures.
7.3
Welder Performance Qualification (WPQ)
Welders qualification shall be carried out in accordance with DNV OS-F101 Appendix C
Section B. Welder qualification shall lapse after a period of six months without production
welding experience. Welders shall be qualified to actual pipeline diameter. The qualification
test shall not be performed on production joints unless otherwise approved by
Client/Company.
Re-qualification of welders or operators shall be performed by Welding Contractor if any
change is made to the essential variables of the welding procedure which necessitates
requalification of the welding procedure.
Client/Company reserves the right to require requalifying of welders or welding operators if
repair rates are encountered in production welding by any one or more operators, which in
Client/Company’s opinion are excessive. In the event of excessive repair rates, a course of
remedial action will be agreed between Client/Company and Supplier.
7.4
Surface Preparation
All surfaces to be welded shall be fully dried. Heating shall be used to remove moisture and
to warm up the metal to a temperature of at least 40°C over a 200mm wide band centred on
the weld location.
Surface to be welded shall be cleaned and free of paint, oil, dirt, scale, oxides and other foreign
material detrimental to the welding. The welding preparation of CRA overlayed steel shall be
cleaned by an organic solvent which does not contain chlorine compounds. The surrounding
area shall be free of contaminants such as oil, grease, etc.
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7.5
Joint Configuration
The weld end shall be J groove beveled utilizing mechanically operated cold-cut machining
only as shown in Figure 2 and fit-up as shown in Figure 3. Class 2 or 3 Consumable insert
may be used in lieu of open root welding. Welding Contractor shall monitor bevel dimensions
by means of gauges.
Welding bevel shall be performed with accuracy and suitable tools to guaranty the proper
chamfer tolerance specified in the WPS. Bevel preparation size and pipeline support material
removal on root bevel shall be verified by suitable means.
After new bevel preparation, a new lamination check by ultrasonic and magnetic particle or
dye penetrant testing shall be performed.
Bevels shall be cleaned for a distance 40 mm (inside/outside) by power tools to a bright finish
prior to lining up the pipeline.
Prior to welding of pipeline components, internal misalignment shall not exceed 1 mm.
The alignment of pipeline ends shall minimize the offset between the surfaces and allow for
contraction during welding. To achieve satisfactory alignment the clamp must be capable of
removing the out of roundness. Misalignment shall be minimized by rotation of the pipelines
to obtain the best fit or by other similar methods.
Internal line-up clamps shall be used when possible and shall not be removed until 100% of
the root run and hot pass are completed. Client/Company retains the right but not necessarily
the obligation to allow welding Contractor to demonstrate to Client/Company’s satisfaction that
the minimum deposit of root pass weldment is sufficient to avoid over stressing the incomplete
weld during static and dynamic loading resulting from the movement or laying of the pipeline
lengths.
When external line-up clamps are used the equipment shall be reviewed and/or approved by
Client/Company prior to welding.
Internal line-up clamps shall have stainless steel or CRA contact shoes to prevent
contamination of the overlayed layer.
Hammering or heating shall not be used for correction of misalignment. Spacer tools shall be
used to check final fit-up. Strong-backs shall not be used.
Adjacent stops and starts shall be staggered by a minimum of 25 mm.
The use of tack welds shall be subject to Client/Company review and Approval.
In girth welding of seam welded HFW and SAW pipeline, longitudinal seam welds shall be
offset by about 90°. Orientation of the seams shall be in the upper half of the pipeline, if
possible.
Welding shall be continuous as far as possible and no joint shall be accepted when subjected
to interruptions not covered by the welding procedure qualification.
Where simply machining the weld end does not result in an extended root face (TIG lip) that
consists of only the cladding material, the fabricator shall add weld metal to the end on the
inside diameter and on the end of the pipeline sufficient to ensure that the extended land is
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overlaying material. The consumables and techniques used shall be such that the surfaces
that will be exposed to the working fluid in the pipeline in service are of the chemical analysis
equal to overlaying material.
Buildup of the weld end shall be made with UNS N06625 filler metal that matches the
corrosion-resistance or other critical properties of the overlaying material. 100% of any weld
buildup shall be examined shall be examined before field welding using same NDT procedure
of the field welding.
Any pipeline length showing evidence of end area lamination on the pipe bevels shall be
removed from the welding station and Client/Company’s representative shall immediately be
notified in writing. The pipeline length shall be cut back until the laminated section is removed
and rebeveled. After rebeveling, the pipeline end shall be ultrasonically inspected over a
distance of 100mm from the bevel, in accordance with ASME IX Section V, to ensure that no
further laminations are present.
Figure 2. Weld end preparation details and fit -up for internally overlayed pipeline that
will be welded from the outside of the pipeline .
Figure 3. Fit-up tolerance on internally clad pipeline .
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
7.6
Preheating
Preheating may be necessary to keep the hardness as per NACE MR0175/ISO 15156, based
on the carbon equivalent and PCM of the pipeline base material and properties of overlay
material. Nevertheless, if preheating has to be performed it shall be limited to a temperature
of 50-60°C and applied from the beginning of the welding process.
Preheat shall be applied around the entire periphery of the pipelines or the part being joined
using electrical resistance heaters in order to obtain a satisfactory temperature distribution.
Digital contact thermometers or thermal crayons shall be used at a distance of 100mm from
weld area for checking the preheat temperature.
Preheat temperature shall also be measured, immediately prior to the commencement of
welding, around the entire joint while welding is being performed.
Preheat temperature for repair welds will be 50°C above preheat temperatures required for
production welds.
7.7
Welding Equipment
Welding equipments shall meet the requirements stated in DNV OS-F101 Appendix C Section
B.
All welding shall be performed using Client/Company reviewed and/or approved equipment of
a type which has proved to be reliable and suitable for the work being performed. Welding
Contractor shall ensure and demonstrate that all welding machines are properly grounded to
avoid the occurrence of stray arcs. Welding Contractor shall provide ground clamps of a
design reviewed and/or approved by Client/Company and shall ensure only insulated
electrode holders are used.
Current certification/calibration certificates for all testing equipment shall be submitted by
Welding Contractor to Client/Company for review and/or approval prior to use. Welding
Contractor shall maintain a system for calibration control for all equipment.
Independent means shall be provided by Welding Contractor and reviewed and/or approved
by Client/Company for the accurate monitoring of all welding parameters during qualification
and production welding, including, but not limited to, current, voltage, welding speed, heat
input, preheat, interpass temperature, process-wire feed speed, gas flow rate and gas
composition.
Tools such as earthing clamps, grinding wheels and wire brushes that are used on overlayed
pipelines shall be segregated and only used on those materials to avoid iron contamination of
the overlayed surface. These tools shall be the same as CRA overlay material or stainless
steel. Grinding discs shall be fit for stainless steel.
7.8
Welding Consumables
Welding consumables shall meet the requirements stated in DNV OS-F101 Appendix C
Section C including sour service requirements. The welding consumables shall be selected
taking into consideration the reduction of alloying elements by dilution of iron from base
material.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
The chemical composition of the filler metal shall be selected so that the corrosion resistance
of the deposited root and hot passes match or exceed that of the cladding. The fill and cap
pass filler metal shall match the yield strength of the base material.
For root and hot pass, filler metal shall be as per ASME Section II, Part C, SFA-5.14 for the
classification ERNiCrMo-3. The iron content in the welding fillers shall not exceed 1.0%.
SMAW low-hydrogen electrodes (defined as less than or equal to 5 ml of hydrogen per 100 g
of deposit weld metal) shall be used for filling passes and repair welds of non-overlayed
section of pipeline. low alloy steel consumables shall not exceed the 1.0% nickel restriction.
Coated electrodes shall be stored in the original packages or containers until issued for use.
Once an original container is opened, the consumable shall be kept free from contamination
until it is used up or its exposure life is reached. Maximum exposure time and maintenance of
covered electrodes shall be per manufacturer‘s recommendation; with the exception of
reconditioning of moisture contaminated coated electrodes shall not be permitted. All
contaminated consumables shall be discarded.
Consumables for welding of CRA overlayed pipelines shall be segregated from carbon steel
consumables. They shall be stored and handled in accordance with the Manufacturer’s
recommendations.
All welding consumables shall have individual marking.
Storage and handling of CRA overlayed pipelines shall be such that contact with other
materials is minimized. Lifting gear, clamps and rollers shall be of stainless steel or coated.
7.9
Backing Gas
To prevent oxidation or contamination during arc welding of the root run and hot pass, a back
shielding gas according to section 6.6 shall be applied. The use of hydrogen in the
backing/shielding gas is not permitted.
The back-purge shall be initiated for sufficient time before commencement of the welding
operation to ensure that the backing environment contains no more than 0,05 % of oxygen.
This time shall be determined during the welding of the test pieces.
The shielding gas back-purge shall normally maintained throughout the welding operation,
however when the thickness of the weld is sufficient to prevent oxidation of the root and hot
pass by subsequent passes, back-purging may be discontinued. This shall be verified during
the welding of the test pieces and shall be approved by Client/Company.
7.10 Chemical Properties and Tests
For CRA overlayed steel pipeline, a chemical analysis shall be performed on the approval test
weld, at a point on the centreline of the root pass, 1 mm below the surface. The complete
chemical analysis shall meet the requirements of the section 6.8.
The Client/Company may specify corrosion tests to demonstrate adequate corrosion
resistance of the weld in service.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
7.11 Nondestructive Inspection
Requirements for methods, equipment, procedures, acceptance criteria and the qualification
and certification of personnel for visual examination and non-destructive testing (NDT) shall
be according to requirements of DNV OS-F101.
Zones of coverage shall be arranged so that the entire contour of the weld groove and entire
volume of deposited metal is interrogated.
All pipeline welds will be 100% inspected visually. Visual inspection shall be according to DNV
OS-F101, Appendix D.
All pipeline girth welds shall be inspected using 100% radiographic testing and 10% dye
penetrant testing as per DNV OS-F101 Appendix D. Acceptance criteria shall be in
accordance with DNV OS-F101 Appendix D. It is recommended that radiographic testing is
supplemented with automatic ultrasonic testing in order to enhance the probability of detection,
characterization and sizing of defects. In this case an automated UT inspection procedure
shall be prepared and qualified in accordance with DNV OS-F101 Appendix E by
demonstrating that all significant flaw indications in the calibration block are located.
NDT for test welds shall be performed not less than 24 hours following completion of welding.
Radiography shall be performed using ultrafine-grain film.
Lack of fusion and lack of penetration in the root of the weld shall not be permitted.
NDT operators shall be qualified in accordance with DNV OS-F101 Appendix
D Sec. A.
7.12 Hydrostatic Tests
Contractor shall submit a formal detailed pressure test procedure and provide specifications
of the equipment to be used to satisfactorily hydrotest the welded overlayed pipeline.
Hydrostatic test shall be performed in accordance with Project Specification a written
procedure subject to Client/Company for approval.
All welds shall be left un-insulated for examination during testing.
Test water used shall be clean and free from minerals and suspended matters. Sea water
shall not be used.
The test shall be carried out in presence of Client/Company representative.
7.13 Defects and Repair of Defects
Any welding joint found defective shall be repaired after approval of the weld extent to be
repaired. Defects shall be removed by grinding. Excavation by grinding shall be performed in
order to avoid any contamination of overlaying material and guaranty the non-dilution of
pipeline support in cladding root and hot pass.
The cavity of the repair area shall be checked by PT in order to ensure the complete removal
of the defect.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.
Welding repair in the root and hot pass is not allowed due to the difficulties to prepare the
excavation in the same conditions as for the original bevel and to avoid any dilution between
the base material and the cladding material in root. welds containing a root defect shall be cut
out and rewelded. cutting and rebevelling shall be performed in accordance with section 6.3.
The rebevelling shall be such that all the prior heat affected zones (HAZ zones) are removed.
Repair welding shall be done using qualified welding procedure in accordance to requirements
of DNV OS-F101 Appendix C Sec. E and G and requirements of this specification. The repair
welding procedures shall be individually qualified according to all of the essential variables
listed for WPS qualification in this document.
Completed weld repair shall be examined using the same inspection mean as the
original weld.
Before welding, the weld area shall be preheated as required by the repair procedure.
Only one repair shall be allowed for each defective area.
Arc strikes outside the weld bevel shall not be acceptable. Any arc strikes outside the finished
weld joint shall be carefully removed by grinding until all visible evidence is removed. The area
of the arc strike shall then be etched by welding Contractor with a 10% ammonium persulphate
solution to verify removal. The ground area shall be subject to ultrasonic inspection to
determine the remaining wall thickness. The grinding shall not reduce the wall thickness to
below the specified minimum thickness. The area shall be further inspected with MT or PT to
ensure the absence of cracks.
Cracks of any kind are not permitted. Weld found with cracks (other than crater crack) shall
be cut out.
Defects caused by arc strikes or other reasons shall be rectified by removing a cylinder from
the end of the pipeline. The length of the cylinder removed shall have at least 100mm of sound
material beyond the end of the defect. After new bevel preparation, a new lamination check
by UT and MT or PT shall be performed.
Full record of all repairs shall be maintained by the Contractor. The record shall be made as
each defect is discovered, and shall include the following:
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The weld number
The type and size of defect
The circumferential location (defined to an approved system)
An estimate of the depth (assessed by ultrasonic test where possible)
Where possible, the name of the welder who produced the defect
Repair welding procedure number
Name of repair welder
Copy of the inspection report for the repair
Date of repair
7.14 Flow assurance requirements
Weld overlaying of the pipeline would change the surface profile. Besides the changes
in the roughness, parallel circumferential grooves would be formed. This may change
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the flow assurance studies. Such surface profile may impose some limitations and
makes some uncertainties in the simulations.
7.15 Pipelaying Requirements
Full-scale strain simulations should be considered to validate the proposed design and
installation method for clad or lined pipe. Test programmes should include repeat bend
cycles to simulate dynamic installation conditions.
7.16 Pigging Requirements
Weld overlaying imposes limitations for pigging. Pigging may not be feasible with
certain type of pigs due to the variations in the surface profile. This must be considered
in selection the pig type in operation.
This document is the property of NIOC Any unauthorized attempt to reproduce it, in any form, is strictly prohibited.