Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services API STANDARD 681 SECOND EDITION, JULY 2021 Special Notes API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed. The use of API publications is voluntary. In some cases, third parties or authorities having jurisdiction may choose to incorporate API standards by reference and may mandate compliance. Neither API nor any of API’s employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. 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Copyright © 2021 American Petroleum Institute ii Foreword Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent. The verbal forms used to express the provisions in this document are as follows. Shall: As used in a standard, “shall” denotes a minimum requirement to conform to the standard. Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required to conform to the standard. May: As used in a standard, “may” denotes a course of action permissible within the limits of a standard. Can: As used in a standard, “can” denotes a statement of possibility or capability. 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Suggested revisions are invited and should be submitted to the Standards Department, API, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001, standards@api.org. iii Contents Page 1 Scope............................................................................................................................................................. 1 2 Normative References................................................................................................................................... 1 3 3.1 3.2 Terms, Definitions, Acronyms, and Abbreviations.......................................................................................... 4 Terms and Definitions.................................................................................................................................... 4 Acronyms and Abbreviations....................................................................................................................... 11 4 4.1 4.2 General........................................................................................................................................................ 11 Unit Responsibility....................................................................................................................................... 11 Nomenclature.............................................................................................................................................. 11 5 5.1 5.2 5.3 Requirements.............................................................................................................................................. 11 Units of Measure.......................................................................................................................................... 11 Statutory Requirements............................................................................................................................... 11 Conflicting Requirements............................................................................................................................. 11 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 Basic Design................................................................................................................................................ 12 General........................................................................................................................................................ 12 Pressure Casings........................................................................................................................................ 15 Casing Connections..................................................................................................................................... 17 Flanges........................................................................................................................................................ 19 External Forces and Moments..................................................................................................................... 20 Rotating Elements....................................................................................................................................... 22 Mechanical Shaft Seals............................................................................................................................... 23 Dynamics..................................................................................................................................................... 25 Bearings, Bearing Housings, and Lubrication.............................................................................................. 27 Materials...................................................................................................................................................... 31 Sealless Design........................................................................................................................................... 36 Nameplates and Rotation Arrows................................................................................................................ 37 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 Accessories................................................................................................................................................. 38 Drivers......................................................................................................................................................... 38 Couplings..................................................................................................................................................... 40 Guards......................................................................................................................................................... 41 Belt Drives................................................................................................................................................... 42 Baseplates................................................................................................................................................... 43 Controls and Instrumentation....................................................................................................................... 46 Ring Liquid System and Auxiliaries.............................................................................................................. 55 Piping........................................................................................................................................................... 58 8 8.1 8.2 8.3 8.4 Inspection, Testing, and Preparation for Shipment...................................................................................... 60 General........................................................................................................................................................ 60 Inspection.................................................................................................................................................... 61 Testing......................................................................................................................................................... 63 Preparation for Shipment............................................................................................................................. 68 9 Vendor’s Data.............................................................................................................................................. 71 Annex A (informative) Data Sheets.......................................................................................................................... 72 v Contents Page Annex B (informative) Contract Documents and Engineering Design Data............................................................. 98 Annex C (informative) Liquid Ring Compressor and Vacuum Pump Nomenclature.............................................. 114 Annex D (normative) Materials and Material Specifications................................................................................... 119 Annex E (informative) Ring Liquid System Schematics......................................................................................... 128 Annex F (informative) System Considerations, Operating Variables, and Test Performance Conversion............. 133 Annex G (informative) Packaging........................................................................................................................... 136 Bibliography............................................................................................................................................................ 139 Figures 1 2 3 4 5 C.1 C.2 C.3 C.4 C.5 C.6 E.1 E.2 E.3 E.4 E.5 Typical Gusset Design................................................................................................................................. 18 Coordinate System for the Forces and Moments in Table 4, Top Suction/Top Discharge LRC/VP Design.21 Coordinate System for the Forces and Moments in Table 4—Top Suction/Side Discharge LRC/VP Design.......................................................................................................................................................... 22 Coordinate System for the Forces and Moments in Table 4—Side Suction/Side Discharge LRC/VP Design.......................................................................................................................................................... 22 Indicative Locations for Taking Vibration on Overhung and Between Bearing LRC/VP.............................. 27 LRC/VP—Two Stage, Between Bearing, Plate Design............................................................................. 114 LRC/VP—Single Stage, Between Bearing, Conical Design, Single Suction............................................. 115 LRC/VP—Single Stage, Between Bearing, Conical Design, Single Suction............................................. 115 LRC/VP—Single Stage, Overhung, Plate Design...................................................................................... 115 Magnetic Drive LRC/VP—Single Stage, Between Bearing, Plate Design, Double Suction....................... 116 LRC/VP Typical Flow Paths....................................................................................................................... 117 LRC/VP Once-through System.................................................................................................................. 128 LRC/VP Partial Recirculation System (NOTE 5)........................................................................................ 129 LRC/VP Total Recirculation System (Vertical Separator)........................................................................... 130 LRC/VP Total Recirculation System (Horizontal Separator)...................................................................... 131 Typical Three-phase Separator.................................................................................................................. 132 Tables 1 2 3 4 5 6 7 8 9 SI and U.S. Standard Conditions................................................................................................................... 9 Conditions for Cooling Water System Design Parameters.......................................................................... 13 Material Casting Factors.............................................................................................................................. 16 Nozzle Loadings.......................................................................................................................................... 20 Power Ratings for Motor Drives................................................................................................................... 39 Minimum Thickness for Control Panels....................................................................................................... 48 Minimum Alarm, Shutdown, and Trip Recommendations............................................................................ 51 Minimum Tubing Wall Thickness................................................................................................................. 59 Materials Inspection Standards................................................................................................................... 62 vi Contents Page 10 11 D.1 D.2 D.3 D.4 Maximum Allowable Free Air Gauss Levels................................................................................................. 63 Performance Tolerances.............................................................................................................................. 67 Material Classes for LRC/VP Parts............................................................................................................ 119 Material Specifications for LRC/VP Parts.................................................................................................. 120 Non-metallic Wear Part Materials.............................................................................................................. 125 Piping Materials......................................................................................................................................... 126 vii Introduction Users of this standard should be aware that further or differing requirements may be needed for individual applications. This standard is not intended to inhibit a vendor from offering, or the purchaser from accepting, alternative equipment or engineering solutions for the individual application. This may be particularly appropriate where there is innovative or developing technology. Where an alternative is offered, the vendor should identify any variations from this standard and provide details. — Annex A contains data sheets which purchasers are encouraged to use. — Annex B contains guidelines for submittal of contract documents and engineering design data including typical forms which may be used to indicate vendor drawing and data requirements. — Annex C contains nomenclature for the various equipment components. — Annex D specifies requirements and gives guidance on materials selection. — Annex E contains schematic drawings of ring liquid systems. — Annex F contains system considerations, operating variables, and test performance guidance. — Annex G contains guidance on packaging. This standard requires the purchaser to specify certain details and features. A bullet [•] in the margin indicates that either a decision by, or further information from, the purchaser is required. Further information should be shown on the data sheets (see example in Annex A) or stated in the quotation request and purchase order. In this standard, U.S. customary units are included in brackets for information. ix Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 1 Scope 1.1 This standard covers the minimum requirements for liquid ring compressor and vacuum pump (LRC/VP) systems for service in the petroleum, chemical, and gas industries. The requirements include basic equipment design, materials, fabrication, inspection, testing, and preparation for shipment. 1.2 This standard requires the purchaser to specify certain details and features. A bullet [•] in the margin indicates that a decision by, or further information from, the purchaser is required. Further information should be stated in the quotation request and purchase order. 1.3 The purchaser and the vendor shall mutually determine the measure that shall be taken to comply with governmental codes, regulations, ordinances, or rules that are applicable to the equipment. 2 Normative References The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any addenda) applies. API Recommended Practice 500, Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2 API Recommended Practice 686, Machinery Installation, and Installation Design API Recommended Practice 691, Risk-based Machinery Management API Standard 520, Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries; Part I— Sizing and Selection API Standard 520, Sizing, Selection, and Installation of Pressure- relieving Devices in Refineries; Part II— Installation API Standard 526, Flanged Steel Pressure Relief Valves API Standard 541, Form-wound Squirrel- cage Induction Motors—500 Horsepower and Larger API Standard 547, General-purpose Form- wound Squirrel-cage Induction Motors—250 Horsepower and Larger API Standard 614, Lubrication, Shaft-sealing, and Control-oil Systems and Auxiliaries API Standard 670: Machinery Protection Systems API Standard 677, General-Purpose Gear Units for Petroleum, Chemical and Gas Industry Services API Standard 682, Pumps—Shaft Sealing Systems for Centrifugal and Rotary Pumps ABMA Standard 7, 1 Shaft, Housing Fits for Metric Radial Ball and Roller Bearings (Except Tapered Roller Bearings) Conforming to Basic Boundary Plans ABMA 19.1, Tapered Roller Bearings—Radial Metric Design 1 American Bearing Manufacturers Association, 2025 M Street, NW, Suite 800, Washington, DC 20036, www.abma-dc.org. 1 2 API Standard 681 ABMA 19.2, Tapered Roller Bearings—Radial Inch Design AGMA 9000, 2 Flexible Couplings—Potential Unbalance Classification AGMA 9002, Bores and Keyways for Flexible Couplings (Inch Series) ASME, 3 Boiler and Pressure Vessel Code (BPVC), Section V—Non-destructive Examination ASMEBPVC, Section VII—Pressure Vessels—Division 1 ASME BPVC, Section IX—Welding and Brazing Qualifications ASME B1.1, Unified Inch Screw Threads (UN and UNR Thread Form) ASME B1.20.1, Pipe Threads, General Purpose (Inch) ASME B16.1, Gray Iron Pipe Flanges and Flanged Fittings (Classes 25, 125 and 250) ASME B16.5, Pipe Flanges and Flanged Fittings NPS 1/2 Through NPS 24 Metric/Inch Standard ASME B16.11, Forged Fittings, Socket Welding and Threaded ASME B16.42, Ductile Iron Pipe Flanges and Flanged Fittings ASME B31.3, Process Piping ASTM A388, Standard Practice for Ultrasonic Examination of Steel Forgings ASTM A578/A578M, Standard Specification for Straight-Beam Ultrasonic Examination of Rolled Steel Plates for Special Applications ASTM A609, Standard Practice for Castings, Carbon, Low-Alloy, and Martensitic Stainless Steel, Ultrasonic Examination Thereof AWS D1.1, 4 Structural Welding Code—Steel ANSI B11/B11.19, 5 Machines—Performance Criteria for Safeguarding EN 1092-1, 6 Flanges and their joints—Circular flanges for pipes, valves, fittings, and accessories, PN designated — Part 1: Steel flanges EN 1092-2, Flanges and their joints—Circular flanges for pipes, valves, fittings, and accessories, PN designated —Part 2: Cast Iron flanges HEI 2854, 7 Performance Standard for Liquid Ring Vacuum Pumps and Compressors IEC 60079, 8 Explosive Atmospheres 2 3 4 5 6 7 8 American Gear Manufacturers Association, 500 Montgomery Street, Suite 350, Alexandria, Virginia 22314, www.agma. org. ASME International, Three Park Avenue, New York, New York 10016-5990, www.asme.org. American Welding Society, 550 NW LeJeune Road, Miami, Florida 33126, www.aws.org. B11 Standards Inc. (Formerly AMT), 7901 Westpark Drive, McLean, VA 22102-4269, www.b11standards.org. European Committee for Standardization, Avenue Marnix 17, B-1000, Brussels, Belgium, www.cen.eu. Heat Exchange Institute, 1300 Sumner Ave., Cleveland, Ohio 44115, www.heatexchange.org. International Electro Technical Commission, 3, rue de Varembé, P.O. Box 131, CH-1211, Geneva 20, Switzerland, www. iec.ch. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 3 IEEE 841, 9 Standard for Petroleum and Chemical Industry—Premium Efficiency, Severe-Duty, Totally Enclosed Fan-cooled (TEFC) Squirrel Cage Induction Motors—Up to and Including 370 kw (500 hp) ISO 7-1, 10 Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances and designation ISO 261, ISO general-purpose metric screw threads — General plan ISO 281, Rolling Bearings — Dynamic load ratings and rating life ISO 21940-11, Mechanical vibration — Rotor balancing — Part 11: Procedures and tolerances for rotors with rigid behaviour ISO 3744, Acoustics — Determination of sound power levels of noise sources using sound pressure — Engineering method in an essentially free field over a reflecting plane ISO 5753, (All Parts), Rolling bearings — Internal Clearance ISO 6708, Pipework components — Definition and selection of DN (nominal size) ISO 8501, (All Parts), Preparation of steel substrates before application of paints and related products—Visual assessment of surface cleanliness ISO 8068, Lubricants, industrial oils, and related products (class L) — Family T (Turbines) — Specification for lubricating oils for turbines ISO 9606-1, Qualification testing of welders — Fusion welding — Part 1: Steels ISO 14120, Safety of Machinery — Guards — General requirement for the design and construction of fixed and movable guards MSS SP-55, 11 Quality Standard for Steel Castings for Valves, Flanges, Fittings and Other Piping Components— Visual Method for Evaluation of Surface Irregularities NACE MR 0103, 12 Petroleum, Petrochemical and Natural Gas Industries — MetallicMaterials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments PNEUROP 6612, 13 Acceptance Specification for Liquid Ring Vacuum Pumps SSPC SP 6, 14 Commercial Blast Cleaning 9 10 11 12 13 14 Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, New Jersey 08854, www.ieee.org. International Organization for Standardization, 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, www.iso.org. Manufacturers Standard Society of the Valve and Fittings Industry, Inc., 127 Park Street, NE, Vienna, Virginia 221804602, www.mss-hq.com. National Association of Corrosion Engineers NACE International, 1440 South Creek Drive, Houston, TX, 77084, www. nace.org. European Association of Manufacturers of Compressors, Vacuum Pumps, Pneumatic Tools and Air & Condensate Treatment Equipment, BluePoint Brussels, 80 Bd Reyers, 1030 Brussels, Belgium, www.pneurop.eu. The Society for Protective Coatings, 800 Trumbell Drive, Pittsburgh, Pennsylvania 15205, www.sspc.org. 4 API Standard 681 3 Terms, Definitions, Acronyms, and Abbreviations 3.1 Terms and Definitions For the purposes of this document, the following terms, definitions, acronyms, and abbreviations apply. 3.1.1 anchor bolt Bolt used to attach the baseplate to the support structure (concrete foundation or steel structure). 3.1.2 baseplate Component on which the drive train and liquid ring compressor or vacuum pump (LRC/VP) are bolted, which is then fastened to the support structure using anchor bolts. 3.1.3 capacity Flow rate of the process fluid through the machine at operating conditions. 3.1.4 casing The composite of all stationary pressure-containing parts of the unit, including all nozzles, seal glands, and other attached parts but excluding the stationary and rotating members of mechanical seals. 3.1.5 certified material test report CMTR Certified report documenting the actual chemical composition and physical properties, of furnished materials. 3.1.6 certified point Point to which the performance tolerances will be applied. NOTE 1 Performance includes the following factors: capacity, power, efficiency, rotational speed, and rated suction and discharge pressures. NOTE 2 This is usually the normal operating point and the vendor will normally require that this point is within the preferred selection range. 3.1.7 containment shell Pressure containing boundary located within the drive end that separates the inner and outer magnet rings of a magnetic drive LRC/VP. 3.1.8 critical speed Shaft rotational speed at which rotor-bearing-support system is in a state of resonance. 3.1.9 design Manufacturer’s calculated parameter. NOTE This is a term used by the equipment manufacturer to describe various parameters such as design power, design pressure, design temperature, or design speed. It is not intended for the purchaser to use this term. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 5 3.1.10 differential pressure The discharge pressure of the process fluid minus the suction pressure of the fluid. 3.1.11 drive train components Equipment used in series to drive the LRC/VP (e.g. motor, gear, fluid drive, clutch). 3.1.12 efficiency Ratio of the LRC/VP net capacity corrected to rated conditions versus brake horsepower. NOTE 1 This ratio would be expressed as CFM/BHP. NOTE 2 This differs from efficiency calculations for pumps in that those efficiencies are typically calculated by dividing power out by power in. 3.1.13 fail safe System or component which will cause the equipment to revert to a permanently safe condition (shutdown or depressurized, or both) in the event of a component failure or failure of the energy supply to the system. 3.1.14 gauge board Bracket or plate used to support and display gauges, switches, and other instruments. NOTE A gauge board is open and not enclosed. 3.1.15 hold-down bolt (mounting bolt) Bolts used to attach the equipment to its mounting surface. 3.1.16 informative information only; cf. normative (3.1.41) NOTE An informative reference or Annex provides advisory or explanatory information. It is intended to assist the understanding or use of the document. 3.1.17 inlet volume flow Flow rate expressed in volume flow units at the conditions of pressure, temperature, compressibility, and gas composition, including moisture content, at the LRC/VP suction flange. 3.1.18 inspection and test plan ITP Single project-specific document used with extended scope for heavy duty LRC/VP in complex packages to consolidate all inspection and test elements, the criteria required to be met, and the roles and responsibilities. 3.1.19 liquid ring compressor or vacuum pump LRC/VP A rotary positive-displacement machine in which gas compression is achieved by the action of a radially bladed impeller mounted in an eccentric or elliptical casing which is partially filled with liquid. 6 API Standard 681 3.1.20 liquid ring compressor Liquid ring compressor is generally designated to apply to all applications where the suction pressure is equal to or above site atmospheric conditions. 3.1.21 liquid ring vacuum pump Liquid ring vacuum pump is generally designated to apply to all applications where the suction pressure is less than site atmospheric conditions regardless of discharge pressure. 3.1.22 liquid ring Liquid ring is the boundary layer of fluid that is created by the interaction of impeller with the fluid contained in the end of the equipment. This ring creates the compression chambers as the impeller rotates. 3.1.23 local Position of devices mounted on or near the equipment or console. 3.1.24 magnetic coupling Attraction of the magnets of the -inner magnet ring and outer magnet ring allowing both to rotate synchronously or asynchronously in the case of a torque ring drive. 3.1.25 magnetic drive liquid ring compressor or vacuum pump Type of sealless LRC/VP which utilizes magnets to drive an internal rotating assembly consisting of an impeller, shaft, and inner drive member (torque ring or inner magnet ring) through a thin, corrosion resistant containment shell (see Annex C). 3.1.26 maximum allowable temperature Maximum continuous temperature for which the manufacturer has designed the equipment (or any part to which the term is referred) when handling the specified fluid at the specified maximum operating pressure. 3.1.27 maximum allowable working pressure MAWP Maximum continuous pressure for which the manufacturer has designed the equipment (or any part to which the term is referred) when handling the specified fluid at the specified maximum allowable temperature. 3.1.28 maximum continuous speed Highest rotational speed (revolutions per minute) at which the machine, as-built and tested, is capable of continuous operation with the specified ring fluid at any of the specified operating conditions. 3.1.29 maximum differential pressure The maximum differential pressure for which the manufacturer has designed the equipment for continuous operation. 3.1.30 maximum discharge pressure Maximum suction pressure plus the maximum differential pressure that the LRC/VP is able to develop when operating at the specified speed, specific gravity, and pumping temperature. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 7 3.1.31 maximum suction pressure Highest suction pressure the LRC/VP will be subject to in service. 3.1.32 minimum continuous speed Lowest rotational speed (revolutions per minute) at which the manufacturer’s design will permit continuous operation with the specified fluid at any of the specified operating conditions. 3.1.33 minimum continuous non-condensable gas flow Lowest non-condensable gas flow at which the LRC/VP equipment can operate. 3.1.34 minimum continuous ring liquid flow Lowest ring liquid flow at which the LRC/VP can operate. 3.1.35 minimum design metal temperature Lowest mean metal temperature (through the thickness) expected in service, including operation upsets, autorefrigeration, and temperature of the surrounding environment, for which the equipment is designed. 3.1.36 nominal pipe size NPS Value approximately equal to a diameter in inches (e.g. NPS 3/4). EXAMPLE NPS 3/4. NOTE 1 Refer to ASME B 31.3. NOTE 2 The letters NPS are followed by a value which is related to an approximate diameter of the bore, in inches, for piping up to and including 12 in. diameter. For piping over 12 in. (NPS 12), the NPS value is the nominal OD. 3.1.37 nominal pressure PN Numerical designation relating to pressure that is a convenient round number for reference purposes (e.g. PN 100). EXAMPLE PN 100 NOTE The permissible working pressure associated with a PN designation depends upon materials, design and working temperature and has to be selected from the pressure/temperature rating tables in corresponding standards. 3.1.38 nondestructive examination NDE Inspection of materials, components, or assemblies typically by means of radiography, liquid penetrant, magnetic particle, or ultrasonic testing. Other methods may be used if agreed to by the purchaser and vendor. 3.1.39 normal operating point Point at which usual operation is expected and optimum efficiency is desired. This point is usually the point at which the vendor certifies that performance is within the tolerances stated in this standard. 8 API Standard 681 3.1.40 normative Information that is required; cf. informative (3.1.16) NOTE A normative reference or Annex enumerates a requirement or mandate of the specification. 3.1.41 observed inspection observed test Inspection or test where the purchaser is notified of the timing of the inspection or test and the inspection or test is performed as scheduled even if the purchaser or their representative is not present. 3.1.42 owner Final recipient of the equipment who may delegate another agent as the purchaser of the equipment. 3.1.43 performance test Running test conducted to verify flow rate, density, differential pressure, torque, and power consumed at specified conditions. 3.1.44 positive material identification PMI Any physical evaluation or test of a material to confirm that the material which has been or will be placed into service is consistent with what is specified by the owner/user. These evaluations or tests can provide either qualitative or quantitative information that is sufficient to verify the composition. 3.1.45 pressure containing part Any part that acts as a barrier between process or motive fluid and the atmosphere. 3.1.46 pressure retaining part Any part whose mechanical failure would allow process or motive fluid to escape to the atmosphere. 3.1.47 purchaser Agency that issues the order and specification to the vendor. NOTE agent. The purchaser can be the owner of the plant in which the equipment is to be installed or the owner’s appointed 3.1.48 radially split Refers to casing joints that are transverse to the shaft centerline. 3.1.49 rated discharge pressure The highest pressure required to meet the conditions specified by the purchaser for the intended service. 3.1.50 rated point Maximum purchaser specified capacity. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 9 3.1.51 rated power Power delivered to the equipment input shaft at rated point. It is also called brake power (brake horsepower, brake kilowatts, etc.). 3.1.52 rated speed 100 % speed Highest rotational speed (revolutions per minute) required to meet any of the specified operating conditions. NOTE Rated speed can be different than the normal operating speed since the normal operating speed is determined by the normal operating point. 3.1.53 remote Control device located away from the equipment or console, typically in a control room. 3.1.54 ring liquid The fluid that is used to form the liquid ring in an LRC/VP. NOTE This is not to be confused with Seal Flush Liquid. 3.1.55 seal flush liquid The fluid that is used to provide lubrication or buffering to a mechanical seal. NOTE This is not to be confused with Ring Liquid. 3.1.56 shutdown Condition as determined by the equipment user that requires action to stop the equipment. 3.1.57 spark resistant material material that is not prone to generate impact sparks under conditions of use. 3.1.58 special tool Tool that is not a commercially available catalog item. 3.1.59 standard volume flow Flow rate expressed in volume flow units at standard conditions. See Table 1. Table 1—SI and U.S. Standard Conditions SI Standard Conditions ISO 13443 Standard Conditions (Natural gas standard reference conditions) Flow Cubic meters per hour (m3/h) Cubic meters per minute (m3/min) Pressure: 101.325 kPa (1.013 bara) Temperature: 15 °C Relative Humidity: Dry 10 API Standard 681 Table 1—SI and U.S. Standard Conditions (Continued) SI Standard Conditions U.S. Standard Conditions Flow Standard cubic feet per minute (scfm) Million standard cubic feet per day (mmscfd) Pressure: 14.7 psia Temperature: 60 °F Relative Humidity: Dry 3.1.60 steady state Condition under which specific metering parameters such as flow rate, differential pressure, speed, suction pressure, discharge pressure, and fluid type are not changing by more than ±10 % over a two-minute period. 3.1.61 suction pressure The pressure of the process fluid measured at the LRC/VP suction flange. 3.1.62 total indicator reading total indicated run-out TIR Difference between the maximum and minimum readings of a dial indicator or similar device, monitoring a face or cylindrical surface for one complete revolution of the monitored surface. NOTE For a cylindrical surface, the indicated run-out implies an eccentricity equal to half the reading. For a flat face, the indicated run-out implies an out-of-squareness equal to the reading. If the diameter in question is not perfectly cylindrical or flat, the interpretation of the meaning of TIR is more complex and can represent ovality or surface irregularities. 3.1.63 trip Automated shutdown to ensure personnel safety (safety critical). 3.1.64 trip speed speed at which the independent emergency overspeed device operates to shut down the driver. 3.1.65 unit responsibility Obligation for coordinating the documentation, delivery, and technical aspects of all the equipment and all auxiliary systems included in the scope of the order. 3.1.66 vendor Manufacturer or manufacturer’s agent that supplies the equipment. 3.1.67 witnessed a classification of inspection or test where the purchaser is notified of the schedule of the inspection or test and a hold is placed until the purchaser or the purchaser’s representative is in attendance or they waive their presence at the inspection or test. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 3.2 11 Acronyms and Abbreviations ASTM ASTM International (formerly American Society for Testing and Materials) EN European Committee for Standardization ISO International Organization for Standardization JIS Japanese Industrial Standards LRC/VP liquid ring compressor or vacuum pump MAWP maximum allowable working pressure PMI positive material identification PWHT post-weld heat treatment 4 General 4.1 Unit Responsibility The vendor who has unit responsibility shall ensure that all sub-vendors comply with the requirements of this standard and all reference documents. These include, as a minimum, such factors as the functionality, power requirements, speed, rotation, general arrangement, couplings, dynamics, noise, lubrication, sealing system, certified material test reports, instrumentation, piping, documentation, conformance to specifications, and testing of components by vendor and any and all sub-vendors. 4.2 Nomenclature A guide to liquid ring compressor and vacuum pump component nomenclature pertaining to different equipment types, flow configurations, and operational characteristics is outlined and listed in Annex C (informative) for reference. 5 Requirements 5.1 Units of Measure Purchaser’s use of a USC data sheet (see Annex A.1) indicates the USC system of measurements shall be used for all data, drawings, and maintenance dimensions. Purchaser’s use of an SI data sheet (see Annex A.2) indicates the SI system of measurements shall be used. NOTE 5.2 Dedicated data sheets for SI units and U.S. customary units are provided in Annex A. Statutory Requirements The purchaser and the vendor shall determine the measures to be taken to comply with any governmental codes, regulations, ordinances, directives, or rules that are applicable to the equipment, its packaging, and any preservatives used. 5.3 Conflicting Requirements [●] The purchaser shall specify the hierarchy of documents. NOTE Typical documents include company and industry specifications, meeting notes, and modifications to these documents. 12 API Standard 681 6 Basic Design 6.1 General 6.1.1 Equipment Reliability [●] 6.1.1.1 Only equipment that is field proven, as defined by the purchaser, is acceptable. NOTE Purchasers can use their engineering judgment in determining what equipment is field proven. API 691 can provide guidance. [●] 6.1.1.2 If specified, the vendor shall provide the documentation to demonstrate that all equipment proposed qualifies as field proven. 6.1.1.3 In the event no such equipment is available, the vendor shall submit an explanation of how their proposed equipment can be considered field proven. NOTE A possible explanation can be that all components comprising the assembled machine satisfy the field proven definition. [●] 6.1.1.4 The purchaser shall specify the period of uninterrupted continuous operation. Shutting down the equipment to perform required maintenance or inspection during the specified uninterrupted operation period is not acceptable. NOTE 1 It is realized that there are some services where this objective is easily attainable and others where it is difficult. NOTE 2 Auxiliary system design and design of the process in which the equipment is installed are very important in meeting this objective. 6.1.1.5 Vendor shall advise in the proposal any component designed for a finite life. NOTE It is recognized that these are design criteria. [●] 6.1.2 The purchaser shall specify the equipment's certified operating point, and all other required operating points. [●] 6.1.3 The purchaser shall specify gas composition(s), including any corrosive agents, and presence of any liquids. 6.1.3.1 The LRC/VP vendor shall use the specified values of flow, the gas composition, and the gas conditions to calculate relative molecular mass, ratio of specific heats (Cp/ Cv)and compressibility factor (Z). 6.1.3.2 The LRC/VP vendor shall provide the calculated values with the proposal and use them to calculate performance data. [●] 6.1.4 The purchaser shall furnish properties of the fluid used for the ring liquid including, but not limited to, the following: — temperature/vapor pressure curve — temperature/viscosity curve, — specific heat, and — specific gravity. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 13 The purchaser shall also furnish information on any gas entrainment or solids present including particle size, percent, and distribution. NOTE Properties of the fluid being used for the ring liquid are critical. 6.1.5 Equipment shall be designed for flammable and hazardous applications. 6.1.6 If non-flammable or non-hazardous service has been specified, the vendor may propose an alternative design. 6.1.7 The equipment shall be capable of operating within the entire performance map at all specified operating conditions, as well as accommodating other conditions, such as trip and startup. [●] 6.1.8 Control of the sound pressure level of all equipment furnished shall be a joint effort of the purchaser and the vendor having unit responsibility. 6.1.8.1 The equipment furnished by the vendor shall conform to the maximum allowable sound pressure level specified. 6.1.8.2 The vendor shall provide expected values for maximum sound pressure level per octave band for the equipment. 6.1.9 Cooling water system or systems shall be designed on the water side for the conditions shown in Table 2. Table 2—Conditions for Cooling Water System Design Parameters Water Velocity overheat exchange surfaces 5 ft/s to 8 ft/s ≥1.5 m/s to 2.5 m/s Maximum allowable working pressure (MAWP) ≥100 psig ≥700 kPag (7 barg) Test pressure (≥1.5 MAWP) ≥150 psig ≥1050 kPag (10.5 barg) Maximum pressure drop 15 psi 100 kPa (1 bar) Maximum inlet temperature 90 °F 30 °C Maximum outlet temperature 120 °F 50 °C Maximum temperature rise 30 °F 20 °C Minimum temperature rise Water side fouling factor Corrosion allowance for carbon steel shells 20 °F 10 °C 0.002 hr-ft2-°F/Btu 0.35 m2K/kW /8 in. 3 mm 1 6.1.9.1 The vendor shall notify the purchaser if the criteria for minimum temperature rise and velocity overheat exchange surfaces result in a conflict. If such a conflict exists. the purchaser shall approve the final selection. NOTE The criterion for velocity overheat exchange surfaces is intended to minimize water-side fouling; the criterion for minimum temperature rise is intended to minimize the use of cooling water. 6.1.9.2 Provision shall be made for complete venting and draining of the system or systems. 6.1.10 Equipment shall be designed to operate simultaneously at the relief valve setting and trip speed without damage regardless of driver power. 6.1.11 LRC/VPs shall be capable of operating at least up to the maximum continuous speed. The maximum continuous speed shall be: a) equal to the speed corresponding to the synchronous speed at frequency for electrical motors, 14 b) API Standard 681 at least 105 % of rated speed for adjustable speed LRC/VPs. 6.1.12 The equipment’s trip speed shall not be less than the following percentages of maximum continuous speed: a) adjustable speed motor—105 %, b) constant speed motor—102 %. 6.1.13 Housings that enclose moving lubricated parts such as bearings, shaft seals, highly polished parts, instruments, and control elements shall be designed to minimize contamination by moisture, dust, and other foreign matter during periods of operation and idleness. 6.1.14 All equipment shall be designed to permit rapid maintenance. Major parts such as casing components and bearing housings shall be designed and manufactured to ensure accurate alignment on reassembly. NOTE This can be accomplished by the use of shouldering, cylindrical dowels, or keys. 6.1.15 The equipment (machine, driver, and auxiliary equipment) shall perform on the test stand(s) and on their permanent foundation within the specified acceptance criteria. After installation, the performance of the combined units shall be the joint responsibility of the purchaser and the vendor who has unit responsibility. [●] 6.1.16 If specified, the vendor shall review and comment on the purchaser’s piping and foundation drawings. NOTE Many factors can adversely affect site performance. These factors include such items as piping loads, alignment at operating conditions, supporting structure, handling during shipment, and handling and assembly at the site. [●] 6.1.17 If specified, the vendor’s representative shall witness: a) A check of the piping alignment performed by unfastening the major flanged connections of the equipment. b) The initial shaft alignment check at ambient conditions. c) Shaft alignment at operating temperature. i.e. hot alignment check. NOTE Refer to API RP 686 for basic guidelines for conducting alignments, shaft hot and cold alignment. [●] 6.1.18 The equipment, including all auxiliaries, shall be suitable for operation under the environmental conditions specified. These conditions shall include whether the installation is indoors (heated or unheated) or outdoors (with or without a roof), maximum and minimum temperatures, unusual humidity, and dusty or corrosive conditions. [●] 6.1.19 The equipment, including all auxiliaries, shall be suitable for operation using the site and utility conditions specified. 6.1.20 All equipment shall be additionally suitable for running on air during commissioning. The vendor shall provide air performance curves, operating guidelines, and any additional features required. NOTE Field run on air is intended to be a confirmation of mechanical integrity, and not a field performance test. 6.1.21 Electrical Classification 6.1.21.1 Locations for installed equipment can be classified as hazardous electrical areas or they can be unclassified. An unclassified area is considered non-hazardous; therefore, motors, electrical instrumentation, equipment, components, and electrical installations for unclassified areas are not governed by hazardous area electrical codes. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 15 [●] 6.1.21.2 If an installation location is classified as hazardous, motors, electrical instrumentation, equipment, components, and electrical installations shall be suitable for the hazardous electrical area classification designation as specified. [●] 6.1.21.3 All applicable electrical codes shall be specified. Local electrical codes that apply shall be provided by the purchaser upon request. 6.1.22 Bolting and Threads 6.1.22.1 Bolting shall be furnished with threads conforming to ASME B1.1 or ISO 261. 6.1.22.2 Fasteners (excluding washers and set-screws) shall have the material grade and manufacturer’s identification symbols applied to the exposed end of studs 3/8 in. (10 mm) in diameter and larger and to the heads of bolts 1/4 in. (6 mm) in diameter and larger. NOTE A set screw is a headless screw with an internal hexagonal opening in one end. 6.1.22.3 If the available area is inadequate, the grade symbol shall be marked on the exposed end of studs and the manufacturer’s identification symbol marked on the other end. 6.1.22.4 Adequate clearance shall be provided at all bolting locations to permit the use of socket or box wrenches. 6.1.22.5 Internal socket-type, slotted-nut, or spanner-type bolting shall not be used unless approved by the purchaser. NOTE For limited space locations, integrally flanged fastener can be required. 6.1.23 Spare and replacement parts for the machine and all furnished auxiliaries shall meet all the criteria of this standard. 6.2 Pressure Casings 6.2.1 The pressure casing shall be designed to: a) Operate without leakage or internal contact between rotating and stationary components while subject simultaneously to the MAWP (and corresponding temperature) and the worst case combination of maximum allowable nozzle loads applied to all nozzles. b) Withstand the hydrostatic test. 6.2.1.1 The tensile stress used in the design of the pressure casing for any material shall not exceed 0.25 times the minimum ultimate tensile strength or 0.67 times the minimum yield strength for that material, whichever is lower, across the full range of specified operating temperatures. NOTE In general deflection is the determining consideration in the design of casings. Ultimate tensile or yield strength is seldom the limiting factor. 6.2.1.2 For cast materials, the allowable tensile stress shall be multiplied by the appropriate casting factor as shown in Table 3. 16 API Standard 681 Table 3—Material Casting Factors Type of NDE Casting Factor Visual, magnetic particle or liquid penetrant 0.8 Spot radiography 0.9 Ultrasonic 0.9 Full radiography 1.0 6.2.1.3 The manufacturer shall state the source of the material properties from those listed in Table D.2 (i.e. ASTM, UNS, ISO, EN, JIS), as well as the casting factors applied, in the proposal. 6.2.1.4 National material standards other than those listed in Annex D, Table D.2, may be used with purchaser approval. 6.2.1.5 Design criteria for application of ceramics/composite containment shells shall be agreed between the vendor and purchaser. 6.2.1.6 Pressure-containing components may be designed with the aid of finite element analysis provided that the value of the stress intensity reflects a requirement to perform a hydrotest at 150 % of MAWP. 6.2.1.7 Rotating equipment pressure casings are outside of the scope of ASME BPVC. ASME BPVC manufacturing data report forms, third party inspections, and stamping are not required. 6.2.2 A corrosion allowance of at least 1/8 in. (3 mm) shall be added to the casing thickness used in 6.2.1.1 or 6.2.1.6. 6.2.2.1 This corrosion allowance shall also be added to all auxiliary connections exposed to the same fluid as the pressure containing casing. 6.2.2.2 The vendor may propose alternative corrosion allowances for consideration if materials of construction with superior corrosion resistance are employed without affecting functionality, safety, and reliability. 6.2.3 The maximum allowable working pressure of the casing shall be at least equal to the specified relief valve set pressure. If a relief valve set pressure is not specified, the maximum allowable working pressure shall be at least 125 % of the maximum discharge pressure as defined in 3.1.30. 6.2.4 Where more than one compression stage is incorporated within a single casing, the whole of that casing shall be designed for the maximum allowable working pressure of the higher pressure stage. 6.2.5 Casings and supports shall be designed to have sufficient strength and rigidity to limit any change in the relative position of the shaft ends at the coupling flange, caused by the worst combination of allowable pressure, torque, and piping forces and moments, to 0.002 in. (50 µm). 6.2.6 Threaded holes in vacuum and pressure parts shall only be provided if approved by the purchaser. 6.2.6.1 To prevent leakage in pressure sections of casings, metal equal to at least ½ in. (12 mm), in addition to the corrosion allowance, shall be left around and below the bottom of drilled and threaded holes. 6.2.6.2 The depth of the threaded holes shall be at least 1.5 times the diameter of the stud, plug, etc. 6.2.7 Studs shall be supplied on the bolted end covers of radially split casings. Studs shall be used instead of cap screws on all other joints except where hexagonal head cap screws are essential for assembly purposes and have been approved by the purchaser. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 17 6.2.8 Jackscrews, guide rods, cylindrical casing-alignment dowels or other appropriate devices, or a combination thereof, shall be provided to facilitate disassembly and reassembly. 6.2.8.1 Guide rods shall be of sufficient length to prevent damage to the internals or casing studs by the casing during disassembly and reassembly. 6.2.8.2 If jackscrews are used as a means of parting contacting faces, one of the faces shall be relieved (counter bored or recessed) to prevent a leaking joint or an improper fit caused by marring of the face. 6.2.9 Mounting surfaces on the LRC/VP shall meet the following criteria: a) They shall be machined to a finish of 250 µin (6.3 µm) Ra (arithmetic average roughness) or better. b) The upper machined or spot-faced surface shall be parallel to the mounting surface. c) Hold-down bolt holes shall be drilled perpendicular to the mounting surface or surfaces. 6.2.9.1 Holes shall be spot faced to a diameter suitable for a washer positioned eccentrically around the bolt. 6.2.9.2 Holes shall not be slotted. 6.3 Casing Connections 6.3.1 Casings with double flow suction or discharge connections shall be furnished with manifolds to a single terminal point connection. The manifolds shall be designed for the same vacuum and maximum allowable working pressure as the casing. 6.3.2 All connections shall be flanged or machined and studded, except where threaded connections are permitted by 6.3.7. 6.3.2.1 All connections shall be suitable for the maximum allowable working pressure of the casing as defined in 3.1.27. 6.3.2.2 Flanged connections may be integral with the casing (or cylinder) or, for casings (cylinders) of weldable material, may be formed by a socket-welded or butt-welded pipe nipple or transition piece, and shall terminate with a welding-neck or socket-weld flange. 6.3.3 All openings or nozzles for piping connections on pressure casings shall be NPS 3/4 (DN 20) or larger. DN connections shall be in accordance with ISO 6708. 6.3.4 Sizes NPS 1-1/4, 2-½, 3-1/2, 5, 7, and 9 (DN 32, DN 65, DN 90, DN 125, DN 175 and DN 225) shall not be used. 6.3.5 Welded auxiliary connections, size NPS 1-1/2 (DN 40) and smaller, shall be reinforced by using forged welding inserts or gussets. 6.3.6 If gussets are provided, the piping shall be gusseted in two orthogonal planes to increase the rigidity of the piped connection in accordance with the following criteria: a) Gussets shall be of a material compatible with the pressure casing and the piping and shall be made of either flat bar with a minimum cross section of 1 in. by 1/8 in. (25 mm by 3 mm) or round bar with a minimum diameter of 3/8 in. (9 mm). b) Gusset design shall be as shown in Figure 1. c) Gussets shall be located at or near the connection end of the piping and fitted to the closest convenient location on the casing to provide maximum rigidity. The long width of gussets made with bar shall be perpendicular to 18 API Standard 681 the pipe and shall be located to avoid interference with the flange bolting or any maintenance areas on the LRC/VP. d) Gusset welding shall meet the fabrication requirements (see 6.10.3), including post-weld heat treatment (PWHT) when required, and the inspection requirements of this International Standard. e) Gussets may also be bolted to the casing if drilling and tapping is done prior to hydrotest. f) Proposals to use clamped or bolted gusset designs shall be submitted to the purchaser for approval. Figure 1—Typical Gusset Design NOTE Typically, these connections are required to support heavy valves which can cause fatigue failure if the connections are not properly reinforced. 6.3.7 For connections other than main process connections, if flanged or machined and studded openings are impractical, threaded connections for pipe sizes not exceeding NPS 1-1/2 (DN 40) may be used with purchaser’s approval as follows: a) On non-weldable materials, such as cast iron; b) Where essential for maintenance (disassembly and assembly). 6.3.8 The first segment of piping screwed or welded to the casing should not be more than 6 in. (150 mm) long and shall be a minimum of Schedule 160 seamless for sizes NPS 1 (DN 25) and smaller and a minimum of Schedule 80 for NPS 1 1/2 (DN 40). 6.3.9 Nipple and flange materials welded to the casing shall meet the requirements of 6.3.10. [●] 6.3.10 Threaded openings for tapered pipe threads shall conform to ASME B 1.20.1 or ISO 7-1 or as specified. If ISO 7-1 has been specified, tapered internal and external threads shall be specified. Bosses for pipe threads shall conform to ASME B16.5. 6.3.11 Threaded connections shall not be seal welded. 6.3.12 Connections welded to the casing shall meet the material requirements of the casing including impact values and temperature pressure rating, rather than the requirements of the connected piping (see 6.10.3.5). 6.3.13 All welding of connections shall be completed before the casing is hydrostatically tested per 8.3.2. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 19 6.3.14 Threaded openings not required to be connected to piping shall be plugged with solid, round-head steel plugs in accordance with ASME B16.11. 6.3.14.1 As a minimum, these plugs shall meet the material requirements of the pressure casing. 6.3.14.2 Plugs that may later require removal shall be of a corrosion-resistant material. Plastic plugs are not permitted. 6.3.15 A process compatible thread sealant/lubricant of proper temperature specification shall be used on all threaded connections. Thread tape shall not be used. 6.3.16 Casings shall be provided with sufficient drains to ensure complete drainage. 6.3.17 A vent connection shall be provided if the LRC/VP is not functionally self-venting by the arrangement of the suction and discharge nozzles. 6.4 Flanges 6.4.1 The CLASS system applies, and all flanges shall conform to ASME B16.1, B16.5, B16.42 as applicable. [●] 6.4.2 If the PN system is specified, all flanges shall conform to EN 1092-1 or EN 1092-2 as applicable, except as specified in 6.4.3 through 6.4.12. NOTE EN 1092-1 flanges are PN 6, 10, 16, 25, 40, 63, 100, 160, 250, 320, and 400. 6.4.3 Steel flanges shall conform to the dimensional requirements of ASME B16.5 or EN 1092-1 as applicable. 6.4.4 Cast, Ductile and Malleable iron flanges shall be flat faced and conform to the dimensional requirements of ASME B16.1, B16.42 or EN 1092–2 as applicable. 6.4.4.1 Class 125 flanges shall have a minimum thickness equal to class 250 for sizes NPS 8 and smaller. 6.4.4.2 PN16 flanges shall have a minimum thickness equal to PN25 for sizes DN 200 and smaller. [●] 6.4.5 The dimensional requirements of flanges in materials other than those covered in 6.4.3 through 6.4.4 shall conform to the dimensional requirements of the flanges specified in 6.4.1 or 6.4.2. 6.4.6 Pressure and temperature ratings shall be considered for materials not covered by referenced flange standards. 6.4.7 Flat face flanges with full raised face thickness are acceptable on casings of all materials. 6.4.8 Flanges in all materials that are thicker or have a larger outside diameter than required by applicable ASME or EN are acceptable. 6.4.8.1 Non-standard (oversized) flanges shall be completely dimensioned on the arrangement drawing. 6.4.8.2 If oversized flanges require studs or bolts of non-standard length, this requirement shall be identified on the arrangement drawing. 6.4.9 Flanges shall be full-faced or spot-faced on the back and shall be designed for through bolting. NOTE It can be impracticable to spot face smaller equipment due to space constraints and accessibility. [●] 6.4.10 Machined and studded connections shall conform to the facing and drilling requirements of ASME B16.1, B16.5, B16.42 or EN 1092-1, EN 1092-2 as specified. 20 API Standard 681 6.4.11 Studs and nuts shall be provided installed, and the first 1.5 threads at both ends of each stud shall be removed. 6.4.12 Machined and studded connections and flanges not in accordance with ASME B16.1, B16.5, B16.42 or EN 1092-1, EN 1092-2 require purchaser's approval. 6.4.13 The vendor shall supply mating flanges, studs, and nuts for all nonstandard connections. 6.4.14 To minimize nozzle loading, and facilitate installation of piping, machine flanges shall be parallel to the plane of the flange as shown on the general arrangement drawing to within 0.5°. 6.4.15 Studs or bolt holes shall straddle centerlines parallel to the main axes of the flange. 6.4.16 All of the purchaser’s connections shall be accessible for disassembly without requiring the machine, or any major part of the machine, to be moved. 6.5 External Forces and Moments 6.5.1 LRC/VP and their baseplates shall be designed for satisfactory performance if subjected to the forces and moments in Table 4 applied simultaneously to both suction and discharge nozzles in the worst case combination for the LRC/VP in question. Two effects of nozzle loads shall be considered: distortion of the casing (6.2.1) and misalignment of the LRC/VP and motor shafts. Table 4—Nozzle Loadings USC Units Nominal Size of Flange (NPS) Forces Each Nozzle F x , Fy and Fz (lbf) Moments Each Nozzle Mx , My and Mz (ft·lbf) ≤2 150 250 3 225 375 4 300 600 6 450 750 8 600 1000 10 750 1250 12 900 1500 14 1050 1750 16 1200 2000 20 1500 2500 24 1800 3000 SI Units Nominal Size of Flange (DN) Forces Each Nozzle F x , Fy and Fz (N) Moments Each Nozzle Mx , My and Mz (N·m) ≤50 650 350 80 1040 560 100 1300 700 150 1950 1050 200 2600 1400 250 3250 1750 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 21 Table 4—Nozzle Loadings (Continued) USC Units Nominal Size of Flange (NPS) Forces Each Nozzle F x , Fy and Fz (lbf) Moments Each Nozzle Mx , My and Mz (ft·lbf) 300 3900 2100 350 4550 2450 400 5200 2800 500 6500 3500 600 7800 4200 6.5.2 The coordinate system(s) shown in Figure 2, Figure 3, and Figure 4 shall be used to apply forces and moments in Table 4. Figure 2—Coordinate System for the Forces and Moments in Table 4, Top Suction/Top Discharge LRC/ VP Design 22 API Standard 681 Figure 3—Coordinate System for the Forces and Moments in Table 4—Top Suction/Side Discharge LRC/VP Design Figure 4—Coordinate System for the Forces and Moments in Table 4—Side Suction/Side Discharge LRC/VP Design 6.6 Rotating Elements 6.6.1 Rotating assemblies shall be designed to be stiff enough to prevent contact between the rotor and the casing when operating at the maximum differential pressure. 6.6.2 Calculated deflection of the shaft at the seals shall not exceed 0.002 in. (50 μm). 6.6.3 The impeller shall be either secured to the shaft by an interference fit or keyed and be capable of transmitting a torque not less than 2.5 times that required for any specified duty and provided with an arrangement for positive axial location. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 23 6.6.4 Solid shaft and single piece impellers are required. 6.6.5 Impellers and similar major rotating components shall be dynamically balanced to ISO 21940-11, grade G2.5. The mass of the arbour used for balancing shall not exceed the mass of the component being balanced. Shafts are not required to be balanced. [●] 6.6.6 If specified, impellers and similar rotating components shall be dynamically balanced to ISO21940-11, grade G1 (equivalent to 6W/n). 6.6.7 Shafts shall be machined from one-piece heat treated steel. 6.6.7.1 Shafts with finished diameters 8 in. (200 mm) and larger shall be forged. 6.6.7.2 Shafts with finished diameters less than 8 in. (200 mm) shall be forged or hot-rolled bar stock purchased to the same quality and heat treatment criteria as shaft forgings. 6.6.8 If not provided as part of the mechanical seal, renewable shaft sleeves (that are removable without machining) shall be provided in the shaft sealing areas. NOTE The sleeve is typically a component of the mechanical seal provided with the machine. 6.6.8.1 Sleeves shall be of wear-, corrosion-, and erosion-resistant material, and shall at a minimum be Stainless Steel. 6.6.8.2 Sleeves shall be ground and polished on their outside surface or finished for the specific seal application. 6.6.8.3 Sleeves shall be positively located on the shaft and shall be not less than 0.125 in. (3 mm) thick. 6.6.8.4 Sleeves shall be sealed at one end and the shaft-sleeve assembly shall extend at least 1/8 in. (3 mm) beyond the outer face of the seal end plate. NOTE faces. Leakage between the shaft and the sleeve thus cannot be confused with leakage through the mechanical seal 6.6.9 Shafts shall be machined and properly finished throughout their length so that there is no more than 0.001 in. (25 μm) total indicated run-out. 6.6.10 Shaft sleeves shall have no more than 0.002 in. (50 μm) total indicated run-out on the outside diameter. 6.7 Mechanical Shaft Seals 6.7.1 Cartridge mechanical shaft seals shall be furnished. 6.7.2 Seal selection shall be suitable for specified variations in suction or discharge conditions, or both, during start-up, operation, or shutdown, including possible upset conditions. [●] 6.7.3 If specified, shaft seals shall be provided in accordance with API Standard 682. 6.7.4 For vendor’s seals not in accordance with API Standard 682, the following items shall be provided in the proposal: a) category; b) type; c) arrangement and geometry; 24 API Standard 681 d) material of construction; e) reference list. NOTE Space or design parameters for some LRC/VP types, sizes, or applications make the use of API Standard 682 seals impractical. 6.7.5 The purchaser shall specify the seal requirements using the selection process and the datasheets in API Standard 682 including any required seal flush plans as defined by API Standard 682. 6.7.6 Seals shall be removable without removing the LRC/VP end housing, suction, or discharge piping, or disturbing the driver. 6.7.7 A spacer coupling, of sufficient length shall be provided by the vendor to enable removal of the bearing housing. 6.7.8 Seals, including component parts, shall withstand the maximum vacuum and maximum allowable working pressure. 6.7.9 Seals shall operate at negligible leakage as required by API Standard 682 at the maximum vacuum and at the maximum allowable working pressure in static and dynamic conditions. 6.7.10 Single seals shall be equipped with a close-fitting throttle bushing on the atmospheric side of the seal to restrict the rate of leakage. If this is not possible due to space limitations, a suitable means of detecting and controlling the leakage shall be provided. [●] 6.7.11 If specified for flammable or toxic fluids, a non-sparking throttle bushing shall be provided to minimize leakage in the event of a complete seal failure. The diametric clearance at the bushing bore shall not be more than 0.025 in. (650 μm). 6.7.12 The seal chamber (process side) shall be provided with an internal or external vent to permit complete venting of the chamber before start-up. 6.7.13 If seal flushing and cooling is provided by the pumped fluid, the LRC/VP vendor shall ensure that sufficient flow reaches the primary seal faces to provide for cooling and maintenance of a stable film at the seal faces. Allowance for cooling flow shall be made when determining the LRC/VP capacity to meet delivered flow requirements. 6.7.14 If an external source of seal flushing is provided by the purchaser, the LRC/VP vendor shall specify the flow, pressure, temperature, and required lubricating properties of the flushing medium. If a restriction orifice is used, it shall not be less than 0.125 in. (3 mm) in diameter. 6.7.15 If a seal gland is used, seal gland component parts shall be satisfactory for the maximum vacuum and maximum seal-chamber design pressure and pumping temperature. It shall have sufficient rigidity to avoid any distortion that would impair seal operation, including distortion that may occur during tightening of the bolts or nuts. 6.7.16 Gland plate connections shall be identified by stamping on the seal end plate labels for the seal fluid inlet and outlet and vent and drain connections. 6.7.17 If required by seal design, direction of rotation shall be shown on each gland plate. 6.7.18 Seal glands and seal chambers shall have provision for only those connections required by the seal flush plan. If other tapped connections are present but not used, they shall be plugged and labeled in accordance with API Standard 682. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 25 6.7.19 The mating joint between the seal gland and the seal chamber face shall incorporate a confined gasket to prevent blowout. 6.7.19.1 The gasket shall be of the controlled compression type with metal to metal gland to seal-chamber contact. 6.7.19.2 If space or design parameters make this requirement impractical, an alternative seal gland design shall be submitted to the purchaser for approval. 6.7.20 In vacuum service, the seal design shall be suitable to seal against atmospheric pressure when the LRC/ VP is not operating. 6.8 Dynamics 6.8.1 Critical Speeds 6.8.1.1 Rotating assemblies shall be designed such that their first dry critical speed is at least 120 % of the maximum continuous or trip speed (whichever is greater). 6.8.1.2 In the design of rotor-bearing systems, consideration shall be given to all potential sources of periodic forcing phenomena (excitation) which shall include, but are not limited to, the following sources: a) unbalance in the rotor system; b) internal rubs; c) blade, vane, and port passing frequencies; d) gear-tooth meshing and side bands; e) coupling misalignment; f) loose rotor-system components; g) ball and race frequencies of rolling element bearings; h) hydraulic effects. NOTE 1 The frequency of a potential source of excitation -can be less than, equal to, or greater than the rotational speed of the rotor. NOTE 2 If the frequency of a periodic forcing phenomenon (excitation) applied to a rotor-bearing support system coincides with a natural frequency of that system, the system will be in a state of resonance. A rotor-bearing support system in resonance can have the magnitude of its normal vibration amplified. The magnitude of amplification and, in the case of critical speeds, the rate of change of the phase-angle with respect to speed, is related to the amount of damping in the system. 6.8.1.3 Resonance of support systems within the vendor’s scope of supply shall not occur within ±20 % of the operating speed of a fixed speed machine, or from 20 % below to 20 % above the operating range of an adjustable speed machine. NOTE Resonances of structural support systems (base, frame, and bearing housings) can adversely affect rotor vibration amplitude. 6.8.1.4 The vendor who has the unit responsibility for the complete drive train shall inform the purchaser of the existence of any undesirable running speeds in the range from zero to trip speed. NOTE 1 Examples of undesirable speeds are those caused by the rotor lateral critical speeds with amplification factors greater than 2.5, train torsionals, and blading modes. 26 API Standard 681 NOTE 2 Normally LRC/VP machines have a rigid shaft and operate below the first lateral critical speed. 6.8.1.4.1 Undesirable speeds shall be illustrated using a Campbell diagram. 6.8.1.4.2 The Campbell Diagram shall be submitted to the purchaser for review and included in the Instruction Manual (see Annex B). [●] 6.8.1.5 If specified, the equipment vendor shall perform a lateral critical speed analysis to determine the critical speeds of the driver and LRC/VP and to assure amplitudes of vibration at any speed from zero to trip speed are within the limits specified in 6.8.2. 6.8.1.6 Excitation of torsional natural frequencies may come from many sources which may or may not be a function of running speed and should be considered in the analysis. These sources may include but are not limited to the following: a) gear characteristics such as unbalance, pitch line runout, and cumulative pitch error; b) cyclic process impulses; c) torsional transients such as start-up of synchronous electric motors and generator phase-to-phase or phaseto-ground faults; d) torsional excitation resulting from electric motors, reciprocating engines, and rotary type positive displacement machines; e) control loop resonance from hydraulic, electronic governors, and adjustable frequency drives; f) one and two times line frequency; g) running speed or speeds; h) harmonic frequencies from adjustable frequency drives. 6.8.1.7 The torsional natural frequencies of the complete train shall be at least 10 % above or 10 % below any applicable excitation frequency within the specified operating speed range (from minimum to maximum continuous speed). 6.8.1.8 When torsional resonances are calculated to fall within the margin specified in 6.8.1.7. a) The purchaser and vendor shall agree that all efforts to remove the critical from within the limiting frequency range have been exhausted. b) A stress analysis shall be performed to demonstrate that the resonances have no adverse effect on the complete train. c) The acceptance criteria for this analysis shall be agreed upon by the purchaser and the vendor. [●] 6.8.1.9 If specified, the vendor shall perform a torsional vibration analysis of the complete coupled train and shall be responsible for directing the modifications necessary to meet the requirements of 6.8.1.6 through 6.8.1.8. 6.8.2 Vibration 6.8.2.1 The overall vibration limits for LRC/VP shall be Vu< 5.1 mm/s RMS (0.20 in./s RMS), where Vuis the unfiltered velocity and RMS is the root mean square, as measured on the bearing housing. The limits shall apply to steady state vibration at any speed and any pressure within the operating range on test or in the field. NOTE See 8.3.3 for vibration requirements related to the Mechanical Running Test. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 27 6.8.2.2 During the performance test, overall vibration measurements over a range specified in 8.3.3.7.2.1 and a Fast Fourier Transform (FFT) spectrum shall be made at each test point except shutoff. 6.8.2.3 The vibration measurements shall be taken on the bearing housing(s) or equivalent location(s). Indicative positions are shown in Figure 5. NOTE Field measurements for noise and vibration can differ from test stand measurements. Figure 5—Indicative Locations for Taking Vibration on Overhung and Between Bearing LRC/VP [●] 6.8.2.4 If specified by the purchaser, the vendor shall demonstrate that the LRC/VP can operate at the quoted maximum and minimum pressure ratios and capacity without exceeding the limits specified in 6.8.2.1. NOTE etc. 6.9 Field performance can deviate significantly from test stand performance due to gas gravities, gas condensabilities, Bearings, Bearing Housings, and Lubrication 6.9.1 Bearings 6.9.1.1 Each shaft shall be supported by two radial bearings. 6.9.1.2 Each shaft shall have one double acting axial (thrust) bearing, which may be combined with one of the radial bearings. , shall be at least 50,000 hours with continuous operation 6.9.1.3 Rolling element bearing’s basic rating life, L10h at rated conditions, and at least 32,000 hours at maximum radial and axial loads and rated speed. life, shall be calculated in accordance with ISO 281 first edition. 6.9.1.4 The basic rating, L10h NOTE 1 The basic rating life, L10h , is the number of hours, at the operating conditions, that 90 percent of a group of identical bearings, will complete or exceed before the evidence of failure. NOTE 2 ISO 281:1990 defines basic rating life L10 in units of millions of revolutions. Industry practice is to convert this to hours and refer to it as L10h , where 28 API Standard 681 L10h is (1,000,000/60N) L10 ; N is Revolutions per minute. 6.9.1.5 Thrust bearings shall be sized for continuous operation through the full operating range including the most adverse specified operating conditions. 6.9.1.6 Calculation of the thrust load shall include but shall not be limited to the following factors within the liquid ring stability range pressures: a) fouling and variation in seal clearances at design and at twice the design internal clearances; b) step thrust from all diameter changes; c) stage reaction and stage maximum differential pressure; d) variations in pressure at all inlet and outlet nozzles; e) external loads from the driving equipment. 6.9.1.7 Thrust forces from metallic flexible element couplings shall be calculated on the basis of the maximum allowable deflection permitted by the coupling manufacturer. 6.9.1.8 Thrust bearings shall be arranged to allow axial positioning of each rotor relative to the casing and setting of the bearings’ clearance or preload. 6.9.1.9 Rolling element bearings shall be located, retained, and mounted in accordance with the following: a) Bearings shall be located on the shaft using shoulders, collars, or other positive locating devices; snap rings and spring-type washers are not acceptable. b) The device used to lock thrust bearings to shafts shall be restricted to a nut with a tab type lock washer. 6.9.1.9.1 For inner race rotation, radial ball and roller bearings shall be retained on the shaft with an interference fit and fitted into the housing with a diametrical clearance, both in accordance with the recommendations of ABMA Standard 7. 6.9.1.9.1.1 Tapered roller bearing fits shall be in accordance with ABMA 19.1 (SI units) and ABMA 19.2 (USC units). 6.9.1.9.1.2 Interference fits and clearances shall consider the complete range of tolerances and operating conditions for each component. NOTE 1 ABMA Standard 7 lists figures and tables which describes the various class fits between the shaft and inner race as well as the various fits and clearances between the outer race and bearing housing. NOTE 2 The actual fits and clearances used in a design depend on many factors such as load, bearing size and type, material properties and other design and performance requirements. NOTE 3 Bearing and shaft material with different coefficients of thermal expansion or parts with the same coefficient of thermal expansion operating at different temperatures could either increase or decrease the interference fit. 6.9.1.9.2 Bearings shall be mounted directly on the shaft Bearing carriers (sleeves)may be acceptable with purchaser’s approval. 6.9.1.10 Single row deep-groove ball bearings shall have a radial internal clearance in accordance with ISO 5753: Group 3 [larger than “N” (Normal) internal clearance]. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services NOTE 1 29 For the purpose of this provision, ABMA 20 Group 3 is equivalent to ISO 5753 Group 3. NOTE 2 The internal clearance of a bearing under operating conditions (effective clearance) is usually smaller than the same bearing’s initial clearance before being installed and operated. This is due to several factors including bearing shrink fit to the shaft or housing, the difference in temperature between the inner and outer rings, etc. NOTE 3 Group 3 clearances are also known as C3 clearances. 6.9.1.11 The selection of the internal clearance Group from ISO 5753 for double row angular contact ball bearings, cylindrical roller bearings, double row self-aligning roller bearings, double row self-aligning ball bearings, and spherical roller bearings shall be determined for the individual application and advised. NOTE 1 For the purpose of this provision, ABMA 20 Groups are equivalent to ISO 5753-Groups. NOTE 2 These clearances apply to non-preloaded bearings and of a design such that they can take purely radial load. NOTE 3 Single row tapered roller bearings and single row angular contact ball bearing mounted back-to-back or face-toface clearance are not covered in ISO 5753 and ABMA 20 since clearances for these bearings are set during assembly in the machine. 6.9.1.12 Double row or single row angular contact ball bearings and two single row ball bearings mounted backto-back, face-to-face, or tandem shall be provided with machined cages. Non-metallic cages shall not be used. 6.9.2 Bearing Housings 6.9.2.1 The bearing housing shall be equipped with replaceable labyrinth-type end seals and deflectors where the shaft passes through the housing. 6.9.2.1.1 Lip-type seals shall not be used. 6.9.2.1.2 The seals and deflectors shall be made of spark resistant materials. 6.9.2.1.3 The design of the seals and deflectors shall effectively retain lubricant in the housing and prevent entry of foreign material into the housing. This shall be achieved without the requirement for external service such as an air purge or grease. 6.9.2.2 Bearing housings for grease lubricated bearings shall be provided with stainless steel pressure type grease fittings for filling while operating and a visible discharge port for observing the displaced grease. 6.9.2.3 For equipment handling flammable or hazardous fluids, bearing housings, load-carrying bearing housing covers and brackets between the machine’s casing and the bearing housings shall be steel. [●] 6.9.2.4 If specified, bearing housings for oil-lubricated non-pressure-fed bearings shall be provided. Bearing housings shall meet the requirements of 6.9.2.4.1 through 6.9.2.4.8 below. 6.9.2.4.1 The housing shall be tapped and plugged with fill and drain openings at least ½-14 NPT (DN 15) in size. 6.9.2.4.2 The housings shall be equipped with constant-level sight-feed oilers at least 4 fluid oz (120 ml) in size, with a positive level positioner (not an external screw), heat-resistant glass containers (not subject to sunlight- or heat-induced opacity or deterioration), and protective wire cages. 6.9.2.4.3 Means shall be provided such as a bulls-eye or an overfill plug, for detecting overfilling of the housings. 6.9.2.4.4 A permanent indication of the proper oil level shall be accurately located and clearly marked on the outside of the bearing housing with permanent metal tags, marks inscribed in the castings, or another durable means. 30 API Standard 681 6.9.2.4.5 A “vented to atmosphere” constant level oiler shall be supplied, and the bearing housing shall be vented to atmosphere. [●] 6.9.2.4.6 If specified, a specific oiler shall be provided. [●] 6.9.2.4.7 If specified, a “vented to bearing housing” constant level oiler shall be provided. [●] 6.9.2.4.8 If specified, an oil sump collection container shall be provided. 6.9.2.4.8.1 This container shall be transparent and shall be located on the bottom of the oil sump to collect bearing housing contaminants such as water. 6.9.2.4.8.2 It shall be fitted with a spring loaded drain petcock. 6.9.2.4.8.3 The collector materials of construction shall be suitable for the lubricant used. [●] 6.9.2.5 If oil mist is specified, the requirements of 6.9.2.5.1 through 6.9.2.5.6 shall apply. 6.9.2.5.1 For pure oil mist lubrication, bearings and bearing housings shall meet the requirements of a) through e) below. a) A threaded 6 mm (1/4 NPT) oil mist inlet connection shall be provided on the housing or end cover for each of the spaces between the rolling element bearing or bearing set and the bearing housing end seal; b) Oil mist fitting connections shall be located so that oil mist will flow through rolling element bearings; c) Oil rings or flingers and constant level oilers shall not be provided, and a mark indicating the oil level is not required; d) Drain-back and any other (feed) oil passages in the bearing housing shall be plugged to prevent the oil mist from bypassing the bearing(s); e) Water cooling systems shall not be provided. NOTE Reclassifiers and oil-mist fittings are normally installed in the field. 6.9.2.5.2 For purge oil-mist lubrication, bearings and bearing housings shall meet the following requirements: a) A threaded NPS ¼ or ½ (6 mm or 12 mm) oil-mist connection shall be located in the top half of the bearing housing to act also as a vent-and-fill connection. b) Constant-level oilers shall be provided, and a mark indicating the oil level is required on the bearing housing. Bearing lubrication is by a conventional oil bath, flinger, or oil ring system. c) Constant-level sight feed oilers shall be equipped with overflow control to allow excess coalesced oil from the mist system to drain from the bearing housing so that oil level in the sump is maintained at proper level. The oil shall be contained to prevent it from draining onto the baseplate. d) Constant-level sight feed oilers shall be piped so that they operate at the internal pressure of the bearing housing, do not vent excess mist at the bearing housing, or allow oil to drip to the baseplate. 6.9.2.5.3 For both pure and purge mist applications, a drain connection shall be located on the bottom of the bearing housing to provide complete oil drainage (see 6.9.2.4). 6.9.2.5.4 Shielded or sealed bearings shall not be used in conjunction with either pure or purge oil-mist systems. 6.9.2.5.5 The oil-mist supply, re-classifier and drain fittings shall be provided by the purchaser. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 31 6.9.2.5.6 Directional re-classifiers, if required, shall be provided by the machine manufacturer. 6.9.2.6 Bearing housings shall have a threaded connection(s) for permanently mounting vibration transducers in accordance with API Standard 670. If metric fasteners are supplied, the threads shall be M8 × 1, 25. 6.9.2.7 A flat surface at least 1 in. (25 mm) in diameter shall be supplied for the location of magnetic-based vibration measuring equipment. 6.9.3 Lubrication 6.9.3.1 Bearings and bearing housings shall be arranged for grease lubrication. 6.9.3.2 Any points that require grease lubrication during operation and which cannot be easily and safely accessed during operation shall be provided with individual austenitic stainless steel extension lines terminating at one common location. [●] 6.9.3.3 If specified, bearings and bearing housings shall be designed for oil lubrication using a mineral oil in accordance with ISO 8068. [●] 6.9.3.4 If specified, provisions shall be made for either pure oil or purge oil-mist lubrication (see 6.9.2.5 for requirements). 6.10 Materials 6.10.1 General 6.10.1.1 Materials of construction shall be selected for the operating and site environmental conditions specified (see 6.10.1.8). NOTE Key materials concerns are mechanical properties and corrosion resistance. 6.10.1.2 Pressure retaining parts of machines shall be steel as a minimum. 6.10.1.3 The material specification of all major components shall be clearly stated in the vendor’s proposal. 6.10.1.4 LRC/VP parts having strength or pressure-integrity requirements are designated as “full compliance” materials in Table D.1 and shall meet all the requirements of the agreed specifications. For any other part (e.g. if corrosion resistance is the primary concern), it is necessary to comply only with the specified chemical composition. 6.10.1.5 Materials shall be identified by reference to applicable international standards, including the material grade (refer to Annex D). a) Where international standards are not available, internationally recognized national standards may be used. b) If no such designation is available, the vendor’s material specification, giving physical properties, chemical composition, and test requirements, shall be included in the proposal. 6.10.1.6 The vendor shall identify the optional tests and inspection procedures that are necessary to ensure that materials are satisfactory for the service. Such tests and inspections shall be listed in the proposal. 6.10.1.7 Minor parts such as nuts, springs, washers, gaskets, and keys shall have corrosion resistance at least equal to that of specified parts in the same environment. [●] 6.10.1.8 The purchaser shall specify any agents (including trace quantities) present in the motive and process fluids and in the site environment, including constituents that can cause corrosion. 32 API Standard 681 6.10.1.9 If austenitic stainless steel parts exposed to conditions that can promote inter-granular corrosion are to be fabricated, hard faced, overlaid, or repaired by welding, they shall be made of low-carbon or stabilized grades. NOTE Overlays or hard surfaces that contain more than 0.10 % carbon can sensitize both low-carbon and stabilized grades of austenitic stainless steel unless a buffer layer that is not sensitive to inter-granular corrosion is applied. 6.10.1.10 Where mating parts such as studs and nuts of austenitic stainless steel or materials with similar galling tendencies are used, they shall be lubricated with an anti-seizure compound suitable for the process temperatures and compatible with the material(s) and specified process fluid(s). NOTE The required torque values to achieve the necessary bolt preload will vary considerably depending if anti-seizure compounds are used on the threads. 6.10.1.11 If the purchaser has specified the presence of hydrogen sulfide in any fluid, materials exposed to that fluid shall be selected and processed in accordance with the requirements of NACE Standard MR 0103. 6.10.1.12 For process gas conditions known to cause Sulfide Stress Cracking as identified by NACE MR0103, ferrous materials not covered by NACE MR 0103 shall not have a yield strength exceeding 90,000 psi (620 N/mm2) nor a hardness exceeding Rockwell C22. 6.10.1.13 Components that are fabricated by welding shall be post-weld heat treated, if required, so that both the welds and the heat-affected zones meet the tensile strength, and ductility, requirements and when required, hardness and impact requirements. 6.10.1.14 The vendor shall select materials to avoid conditions that may result in electrolytic corrosion. Where such conditions cannot be avoided, the purchaser and the vendor shall agree on the material selection and any other precautions necessary. NOTE When dissimilar materials with significantly different electrical potentials are placed in contact in the presence of an electrolytic solution, galvanic couples that can result in serious corrosion of the less noble material can be created. The NACE Corrosion Engineer’s Reference Guide [1] is one resource for selection of suitable materials in these situations. 6.10.1.15 Materials, casting factors, and the quality of any welding shall be equal to those required by Section VIII, Division 1, of the ASME BPVC. The manufacturer’s data report forms, as specified in the code, are not required. NOTE For impact requirements, refer to 6.10.4. 6.10.1.16 Only fully killed, normalized steels made to fine-grain practice are acceptable. Steel made to a coarse austenitic grain size practice (such as ASTM A515) shall not be used. NOTE Low-carbon steels can be notch sensitive and susceptible to brittle fracture at ambient or lower temperatures. [●] 6.10.1.17 If specified, copper or copper alloys shall not be used for parts of machines or auxiliaries in contact with process fluids. Nickel-copper alloy (UNS N04400), bearing babbitt, and precipitation-hardened stainless steels are excluded from this requirement. NOTE Certain corrosive fluids in contact with copper alloys have been known to form explosive compounds. 6.10.1.18 Positive Material Identification (PMI) 6.10.1.18.1 PMI testing shall be in accordance with 6.10.1.18.2 through 6.10.1.18.8. [●] 6.10.1.18.2 If specified, the following alloy steel items shall be subject to PMI testing: a) The pressure casing of rotating equipment b) Shafts Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services c) Impellers d) Blading and shrouds e) Tie bolts f) Shaft sleeves g) Alloy claddings and weld overlays h) Pressure casing joint bolting (studs and nuts) i) Auxiliary equipment (as specified) 33 [●] 6.10.1.18.3 In addition to the components outlined in 6.10.1.18.1 other materials, welds, fabrications, and piping shall be PMI tested as specified. 6.10.1.18.4 If PMI testing has been specified for a fabrication, the components comprising the fabrication, including welds, shall be checked after the fabrication is complete except as permitted in 6.10.1.18.5. Testing may be performed prior to any heat treatment. 6.10.1.18.5 Unique (non-stock) components such as impellers and shafts may be tested after manufacturing and prior to rotor assembly. 6.10.1.18.6 If PMI is specified, techniques providing quantitative results shall be used. NOTE 1 PMI test methods are intended to identify alloy materials and are not intended to establish the exact conformance of a material to an alloy specification. NOTE 2 Additional information on PMI testing can be found in API RP 578 [1]. 6.10.1.18.7 Certified material test reports, visual stamps or markings shall not be considered as substitutes for PMI testing, or vice versa. 6.10.1.18.8 PMI results shall be within the material specification limits, allowing for the measurement uncertainty (inaccuracy) of the PMI device as specified by the device manufacturer. 6.10.2 Castings 6.10.2.1 Castings shall be free from porosity, hot tears, shrink holes, blow holes, cracks, scale, blisters, and similar injurious defects. 6.10.2.2 Surfaces of castings shall be cleaned by sandblasting, shot-blasting, chemical cleaning, or other standard methods. Mold-parting fins and the remains of gates and risers shall be chipped, filed, or ground flush. 6.10.2.3 The use of chaplets in pressure castings shall be held to a minimum. Chaplets shall be clean and corrosion free (plating of chaplets is permitted) and of a composition compatible with the casting. 6.10.2.4 Pressure-containing ferrous castings shall not be repaired except as specified in items a) through c): a) Weldable grades of steel castings shall be repaired by welding, using a qualified welding procedure based on the requirements of Section VIII, Division 1, and Section IX of the ASME BPVC or other internationally recognized standard as approved by the purchaser. b) After major weld repairs and before hydrotest, the complete repaired casting shall be given a post-weld heat treatment to ensure stress relief and continuity of mechanical properties of both weld and parent metal and dimensional stability during subsequent machining operations. 34 c) API Standard 681 All repairs that are not covered by the agreed material specification shall be subject to the purchaser’s approval. 6.10.2.5 Fully enclosed cored voids, which become fully enclosed by methods such as plugging, welding, or assembly, shall not be used. 6.10.3 Welding 6.10.3.1 Welding of piping, pressure-containing parts, rotating parts and other highly stressed parts, weld repairs and any dissimilar-metal welds shall be performed and inspected by operators and procedures qualified in accordance with Section VIII, Division l, and Section IX of the ASME BPVC or another purchaser approved standard such as ISO 9606-1 and ISO 15607 for welding procedures and welder qualification. 6.10.3.2 Other welding, such as welding on baseplates, non-pressure ducting, lagging, and control panels, shall be performed by welders qualified in accordance with AWS D1.1 or Section IX of the ASME BPVC or ISO 107212 or other purchaser approved welding standard. 6.10.3.3 The vendor shall be responsible for the review of all repairs and repair welds to ensure that they are properly heat treated and nondestructively examined for soundness and compliance with the applicable qualified procedures (see 6.10.3.1). a) Repair welds shall be nondestructively tested by the same method used to detect the original flaw; however, the minimum level of inspection after the repair shall be by the magnetic particle method in accordance with 8.2.2.4 for magnetic material and by the liquid penetrant method in accordance with 8.2.2.5 for nonmagnetic material. b) Procedures for major repairs shall be subject to review by the purchaser before any repair is made. 6.10.3.4 Pressure-containing casings made from wrought materials or combinations of wrought and cast materials shall conform to the conditions specified in 6.10.3.4.1 through 6.10.3.4.5. 6.10.3.4.1 Before welding, plate edges shall be examined by the magnetic particle method or liquid penetrant examination to confirm the absence of laminations. 6.10.3.4.2 Accessible surfaces of welds shall be inspected by magnetic particle or liquid penetrant examination after back chipping or gouging and again after post-weld heat treatment. The quality control of welds that will be inaccessible on completion of the fabrication shall be agreed prior to fabrication. 6.10.3.4.3 Pressure-containing welds, including welds of the case to horizontal and vertical joint flanges, shall be full-penetration welds. 6.10.3.4.4 Casings fabricated from materials that, according to Section VIII, Division l, of the ASME BPVC or other internationally recognized standard as approved by the purchaser require post-weld heat treatment, shall be heat treated regardless of thickness. [●] 6.10.3.4.5 If specified, in addition to the requirements of 6.10.3.1, specific welds shall be subjected to 100 % radiography, magnetic particle inspection, or liquid penetrant inspection. 6.10.3.5 Connections welded to pressure casings shall be installed as specified in 6.10.3.5.1 through 6.10.3.5.4. [●] 6.10.3.5.1 If specified, proposed connection designs shall be submitted for approval before fabrication. The drawings shall show weld designs, size, materials, and pre and post-weld heat treatments. 6.10.3.5.2 All welds shall be heat treated in accordance with Section VIII, Division 1, Sections UW-10 and UW40, of the ASME BPVC. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 35 6.10.3.5.3 Post-weld heat treatment, if required, shall be performed after all welds, including piping welds, have been completed. 6.10.3.5.4 Auxiliary piping welded to alloy steel casings shall be of a material with the same nominal properties or shall be of low carbon austenitic stainless steel. Other materials compatible with the casing material and intended service may be used with the purchaser’s approval. NOTE 316L. Low carbon austenitic stainless steel is identified by the letter L after the numerical designation such as 304L or 6.10.4 Low Temperature [●] 6.10.4.1 The purchaser shall specify the minimum design metal temperature and concurrent pressure used to establish impact test and other material requirements. NOTE Normally, this will be the lower of the minimum surrounding ambient temperature or minimum fluid pumping temperature; however, the purchaser can specify a minimum design metal temperature based on properties of the pumped fluid such as auto-refrigeration at reduced pressures. 6.10.4.2 To avoid brittle failures, materials and construction for low temperature service shall be suitable for the minimum design metal temperature. 6.10.4.2.1 The purchaser and the vendor shall agree upon the minimum design metal temperature and any special precautions necessary with regard to conditions that may occur during operation, maintenance, transportation, erection, commissioning, and testing. 6.10.4.2.2 Care shall be taken in the selection of fabrication methods, welding procedures, and materials for vendor furnished steel pressure retaining parts that can be subject to temperatures below the ductile-brittle transition temperature. 6.10.4.2.3 The published design-allowable stresses for materials manufactured in accordance with the ASME BPVC and ANSI standards or other internationally recognized standard as approved by the purchaser are based on minimum tensile properties. Some standards do not differentiate between rimmed, semi killed, fully killed, hotrolled, and normalized material, nor do they take into account whether materials were produced under fine- or course-grain practices all of which can affect material ductility. The vendor shall exercise caution in the selection of materials intended for services between –20 °F (–30 °C) and 100 °F (40 °C). 6.10.4.3 All carbon and low alloy steel pressure containing components including nozzles, flanges, and weldments shall be impact tested in accordance with the requirements of Section VIII, Division 1, Sections UCS65 through 68, of the ASME BPVC or purchaser’s approved equivalent standard. NOTE In general, ferritic steels (such as carbon steel and low alloy steel containing chrome and moly) and martensitic steels (such as 12 % chrome) can have ductile-to-brittle transition temperatures as high as 40 °C (100 °F). The ductile-tobrittle transition temperature is affected by such items as steel manufacturing process heat treatment and minor changes in alloy content. 6.10.4.3.1 High-alloy steels shall be tested in accordance with Section VIII, Division l, Section UHA-51, of the ASME BPVC or purchaser’s approved equivalent standard. [●] 6.10.4.3.2 For materials and thicknesses not covered by Section VIII, Division l of the ASME BPVC or equivalent standards, the purchaser shall specify requirements. 6.10.4.3.3 Impact testing of a material may not be required depending on the minimum design metal temperature, thermal, mechanical, and cyclic loading, and the governing thickness. Refer to requirements of Section VIII, Division l, Section UG-20F of the ASME BPVC. 6.10.4.4 Governing thickness used to determine impact testing requirements shall be the greater of the following: 36 API Standard 681 a) The nominal thickness of the largest butt welded joint. b) The largest nominal section for pressure containment, excluding: c) 1. Structural support sections such as feet or lugs. 2. Sections with increased thickness required for rigidity to mitigate shaft deflection. 3. Structural sections required for attachment or inclusion of mechanical features such as jackets or seal chambers. One fourth of the normal flange thickness. 6.10.4.5 The results of the impact testing shall meet the minimum impact energy requirements of Section VIII, Division l, Section UG-84, of the ASME BPVC or equivalent standard. 6.11 Sealless Design 6.11.1 General 6.11.1.1 LRC/VPs supplied with sealless drives, and all furnished auxiliaries shall, as a minimum, meet all the criteria of this section. NOTE API 685 contains clauses that could be applied to API 681 sealless LRC/VP. 6.11.1.2 The pump design shall ensure that the temperature and pressure in the sealless drive prevent vaporization at all operating conditions. while providing continuous flow for cooling and bearing lubrication. 6.11.1.3 LRC/VPs with sealless drives shall be designed to prevent damage from reverse rotation on starting check-outs. The LRC/VP shall be supplied with the means to detect backward rotation. NOTE One Rotation indicators are available that verify direction of rotation. [●] 6.11.1.4 If vacuum conditions at the LRC/VP suction are specified, the containment shell or stator liner, as applicable, shall be designed for the resulting external pressure. 6.11.2 Secondary Control/Containment [●] 6.11.2.1 Purchaser shall specify if one of the following control/containment options per API Standard 685 for the LRC/VP shall apply: a) Secondary control design; b) Secondary control with primary leakage monitoring device (secondary control system); c) Secondary containment design; d) Secondary containment with primary leakage monitoring device (secondary containment system). [●] 6.11.2.2 If applicable, the hazard-based selection procedure in API Standard 685 2nd Edition, Annex B shall be applied to select the required Control/Containment option. [●] 6.11.2.3 If secondary control system is specified, it shall comply with the requirements of API Standard 685. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 37 6.11.3 Process Cooled/Lubricated Sealless Drive Bearings and Bearing Housings 6.11.3.1 Process cooled/lubricated sealless drive bearings shall be of the precision bored sleeve type. These bearings shall be positively secured in the axial and radial directions to avoid rotation relative to the component on which they are mounted. 6.11.3.2 Sleeve bearings and thrust bearings shall have a surface finish of not more than 16 µin. (0.4 µm) Ra. 6.11.3.3 Bearing materials such as silicon carbide with low coefficients of thermal expansion shall have a radial clearance designed to accommodate relative thermal expansions at the maximum and minimum operating temperature specified on the LRC/VP datasheet. 6.11.3.4 Tolerance rings or similar bearing mounting devices shall be used to allow for relative thermal expansion and provide a resilient mounting surface for the bearings. 6.11.3.5 LRC/VPs with sealless drives using only one radial bearing shall not be used for drive powers above 10 hp (7.5 kW). 6.11.3.6 Thrust bearings shall be designed for thrust in both directions and sized for continuous operation under all conditions within the allowed operating range, including start-up and shutdown conditions as described in the manufacturer’s operating manual. a) All loads shall be determined at minimum design internal clearances and also at maximum design internal clearances. b) Thrust bearings shall provide load capabilities if the normal direction of thrust is momentarily reversed. 6.11.3.7 Lubrication/cooling of the sealless drive bearings shall be by the pumped liquid or by a clean liquid from an external source. The use of an external system requires purchaser’s approval. 6.11.3.8 Bearing housings for LRC/VPs with sealless drive shall include features for vibration measurement as noted in 6.9.2.6 and 6.9.2.7. 6.12 Nameplates and Rotation Arrows 6.12.1 A nameplate shall be securely attached at a readily visible location on the equipment and on any major piece of auxiliary equipment. 6.12.2 Rotation arrows shall be cast-in or attached to each major item of rotating equipment at a readily visible location. 6.12.3 Nameplates and rotation arrows (if attached) shall be of austenitic stainless steel or nickel-copper (UNS N04400) alloy. Attachment pins shall be of the same material as the nameplate. Welding to attach the nameplate to the casing is not permitted. 6.12.4 The following data (where relevant) shall be clearly stamped or engraved on the nameplate, in the specified units: a) vendor’s name; b) serial number; c) size, type, and model; d) design limits and rated data (including suction pressure, suction temperature, discharge pressure, capacity, and speed); 38 API Standard 681 e) purchaser item number or other reference; f) hydrostatic test pressure and test date. 7 Accessories 7.1 Drivers 7.1.1 General [●] 7.1.1.1 The driver shall be of the type specified, shall be sized to meet the maximum specified operating conditions, including external transmission losses (loss for gear, belt, coupling, etc.), and shall be in accordance with applicable specifications, as stated in the inquiry and order. The driver shall operate under the utility and site conditions specified in the inquiry. [●] 7.1.1.2 The driver shall be sized to accept any specified process variations such as changes in the pressure, temperature or properties of the fluids handled, and plant start-up conditions. 7.1.1.3 The driver shall be capable of starting under the conditions specified and the starting method shall be agreed by the purchaser and the vendor. 7.1.1.4 The driver’s starting-torque capabilities shall exceed the speed-torque requirements of the driven equipment. Particular attention shall be given to starting conditions when the machine is used as a vacuum pump and should be required to start with the suction at atmospheric pressure. 7.1.1.5 The supporting feet of drivers with a weight greater than 225 kg (500 lb) shall be provided with vertical jackscrews and shall be drilled with pilot holes that are accessible for use in final doweling. 7.1.2 Motors [●] 7.1.2.1 Electric motor drives shall conform to guidelines of 7.1.2.1.1 through 7.1.2.1.3, or another standard as approved by the purchaser. 7.1.2.1.1 Low voltage induction motors shall be in accordance with IEEE 841 (up to 370 kW [500 HP]). 7.1.2.1.2 General purpose medium voltage induction motors shall be in accordance with API Standard 547 (186 kW [250 HP] and larger). 7.1.2.1.3 Special purpose medium and high voltage induction motors shall be in accordance with API Standard 541 (373 kW [500 HP] and larger). NOTE API Standard 541 and API Standard 547 are applicable to either ANSI/NEMA or IEC, ISO as specified. IEEE 841 at this time is ANSI/NEMA. There is no equivalent IEC or ISO standard to IEEE 841 at this time. 7.1.2.2 Motors shall have nameplate power ratings, excluding the service factor (if any), at least equal to the percentages of power at rated conditions given in Table 5. However, the power at rated conditions shall not exceed the motor nameplate rating. The smallest acceptable motor power rating to be supplied is 5 hp (4 kW). If it appears that this procedure leads to unnecessary oversizing of the motor, an alternative proposal shall be submitted for the purchaser’s approval. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 39 Table 5—Power Ratings for Motor Drives Motor Nameplate Rating Percentage of Rated Power hp kW % <30 <22 125 30 to 75 22 to 55 115 >75 >55 110 7.1.2.2.1 Motors shall not operate above nameplate rating in any operating condition specified. NOTE 1 The margins in Table 5 applies to the design phase of a project. After testing, this margin might not be available due to performance tolerances of the driven equipment. NOTE 2 Starting conditions of both the driver and driven equipment can be different from the normal operating conditions. 7.1.2.2.2 Equipment driven by induction motors shall be rated at the actual motor speed for the rated load condition. [●] 7.1.2.3 The purchaser shall specify the type of motor and its characteristics and accessories, including but not limited to the following: a) electrical characteristics; b) starting conditions (including the expected voltage drop on starting); c) the type of enclosure; d) maximum allowable sound pressure level; e) the area classification, based on API Recommended Practice 500 or equivalent international standard; f) the type of insulation; g) required service factor; h) the ambient temperature and elevation above sea level; i) transmission losses; j) temperature detectors, vibration sensors, and heaters; k) auxiliaries (such as instrumentation); l) vibration acceptance criteria; m) use in adjustable frequency drive applications. 7.1.2.4 The motor’s starting torque shall meet the requirements of the driven equipment, at a reduced voltage of 80 % of the normal voltage, and the motor shall accelerate to full speed within 15 seconds. 7.1.3 Gear Units 7.1.3.1 Gear units shall conform to API Standard 677. 40 API Standard 681 7.1.3.2 Instrumentation and installation shall conform to the requirements of API Standard 614 for lube oil systems and shall include the items indicated for the applicable system in API Standard 677, Third Edition, Appendix C. 7.1.4 Adjustable Frequency Drive (AFD) 7.1.4.1 The manufacturer of the AFD shall confirm that the drive speed range is suitable for startup and all specified operating conditions. 7.1.4.2 The output torque to the connected machinery shall be at least 110 % of the greatest torque required (including any gear and coupling losses) for any of the specified operating conditions. NOTE The machinery manufacturer with overall responsibility is not always the purchaser of an adjustable speed motor or AFD controls. 7.1.4.3 The zero speed torque to the connected machinery shall exceed the static breakaway torque of the entire machinery train. 7.2 Couplings 7.2.1 Non-lubricated flexible element couplings between drivers and driven equipment shall be supplied by the manufacturer of the driven equipment. 7.2.2 Couplings shall be all-metal flexible element; spacer-type couplings manufactured to meet AGMA 9000 Class 9 and shall comply with the following: a) Flexible elements shall be of corrosion-resistant material. b) Couplings shall be designed to retain the spacer if a flexible element ruptures. c) Coupling hubs shall be steel. d) The distance between the driven and driver shaft ends (distance between shaft ends, or DBSE) shall be at least 125 mm (5 in.) and shall permit removal of the coupling, bearings, seal, and rotor, as applicable, without disturbing the driver, driver coupling hub or the suction and discharge piping. This dimension, DBSE, shall always be greater than the minimum total seal length. NOTE The DBSE dimension usually corresponds to the nominal coupling spacer length. e) Provision shall be made for the attachment of alignment equipment without the need to remove the spacer or dismantle the coupling in any way. NOTE One way of achieving this is to provide at least 25 mm (1 in.) of bare shaft between the coupling hub and the bearing housing where alignment brackets can be located. [●] f) g) If specified, couplings shall be balanced to ISO 21940–11 grade G6.3. The maximum shaft thermal growth shall not exceed the allowable disc pack compression to avoid transmitting thrust loads to the LRC/VP and driver bearings. [●] 7.2.3 If specified, couplings shall be balanced to AGMA 9000 Class 10. 7.2.4 Information on shafts, keyway dimensions (if any), and shaft end movements due to end play and thermal effects shall be furnished to the vendor supplying the coupling. NOTE This information is normally furnished by the vendor of the driven equipment or the driver vendor. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 41 7.2.5 The couplings and coupling-to-shaft juncture shall be designed and manufactured to be capable of transmitting power at least equal to the power rating of the driver including service factor. 7.2.6 Flexible couplings shall be keyed to the shaft. Keys and keyways and their tolerances shall conform to AGMA 9002, Commercial class. 7.2.7 Flexible couplings with cylindrical bores shall be mounted with an interference fit. Cylindrical shafts shall comply with (AGMA 9002) and the coupling hubs shall be bored to the following tolerances (ISO 286-2). a) For shafts of 50 mm (2 in.) diameter and smaller—Grade N7 b) For shafts larger than 50 mm (2 in.) diameter—Grade N8 7.2.8 Where maintenance (such as for mechanical seal) requires removal of the coupling hub from the shaft, and the shaft diameter is greater than 65 mm (2.5 in.), the coupling hub shall be a taper fit. Taper for keyed couplings shall be 1/16 slope (0.75 in./ft diametrical). 7.2.9 Coupling hubs shall be furnished with tapped puller holes at least 10 mm (3/8 in.) in size to aid removal. [●] 7.2.10 The coupling surfaces normally used for checking alignment shall be concentric with the axis of coupling hub rotation within the following limits: 0.5 µm total indicated runout per millimeter of shaft diameter (0.0005 in. per in.), with a maximum of 50 µm (0.002 in.) total indicated runout. All other diameters not used for location, registration, or alignment shall be to the coupling manufacturer’s standard, provided balance requirements are met. 7.2.11 If the driver is a horizontal sleeve-bearing motor, limited end-float couplings shall be supplied to prevent the motor rotor from rubbing stationary motor parts. 7.2.12 If the vendor is not required to mount the driver, vendor shall deliver the fully machined half-coupling to the driver manufacturer’s plant or any other designated location, together with the necessary instructions for mounting the half-coupling on the driver shaft. 7.2.13 Couplings shall have un-hindered access from both sides for their removal, alignment and for machine condition monitoring. 7.3 Guards 7.3.1 Guards over couplings between drivers and driven equipment, and shaft guards between bearing housings and seal glands shall be supplied and mounted by the vendor with unit responsibility. 7.3.2 Guards shall enclose the coupling(s) and other rotating components to prevent personnel from contacting moving parts during operation of equipment train. Allowable access dimensions shall comply with specified standards, such as ANSI/B11 B11.19, ISO 14120, or other applicable nationally recognized standard. 7.3.3 Guards shall be constructed with sufficient rigidity to withstand a 900 N (200 lbf) concentric static point load in any direction without the guard contacting moving parts. 7.3.4 Guards shall be fabricated from sheet (solid or perforated), plate or expanded metal. Guards of woven wire shall not be used. 7.3.5 Guard openings shall conform to ISO 14120, EN 953 or B11 Standards, but in no case shall exceed 0.375 in. (10 mm). 7.3.6 Guards shall be constructed of steel, brass, aluminum or nonmetallic (polymer) materials as agreed. [●] 7.3.7 If specified, guards shall be constructed of an agreed spark resistant material. 42 API Standard 681 NOTE 1 Many users consider pure aluminum and aluminum alloys with less than 5 % iron and a maximum content of 2 % magnesium or 0.2 % copper to be spark resistant. However, local regulations, such as EN 13463-1, sometimes prohibit aluminum or non-metallic materials within potentially explosive atmospheres. Nickel-copper alloys (UNSN0440X or UNSN0550X) and copper-based alloys (e.g. brass, bronze, aluminum bronze, beryllium bronze) are generally considered to be spark resistant. Nickel based alloys including alloy 600 (UNSN06600) and alloy 625 (UNSN06625) are considered spark resistant. NOTE 2 titanium. Materials that are not considered “spark resistant” include stainless steels, iron, steel (all alloys), magnesium, and 7.3.8 Guards shall be removable without disturbing the coupled elements. 7.3.9 Seal Gland to Bearing Housing Guards (Shaft Guards) 7.3.9.1 Each shaft guard shall be sufficiently vented to prevent the accumulation of seal emissions, liquid, or vapor. [●] 7.3.9.2 If specified, shaft guards shall have a covered opening of 0.50 in. (12.5 mm) in diameter to provide access for a portable VOC emission probe 0.25 in. (6.4 mm) in diameter) to measure emissions within 0.375 in. (10 mm) distance from the shaft-seal interface location. The location of the opening(s) shall be approved by the purchaser. NOTE Equipment such as pipeline or terminal LRC/VPs can sometimes not require this opening. 7.3.9.3 Shaft guards shall allow visual inspection of the seal without removal of guard. [●] 7.3.9.4 Shaft guards shall be designed to allow for any other specified purchaser requirements, such as: protection from environmental elements (for example rain, sand); provide protection from directional spray in event of significant seal leakage; special venting/draining arrangements. Any of these options (or possible others) shall be explicitly stated by the purchaser. 7.4 Belt Drives 7.4.1 General 7.4.1.1 Belt drives shall only be used for equipment of 150 kW (200 BHP) or less and require purchaser’s approval. 7.4.1.2 Timing type belts and sheaves shall be provided. 7.4.1.3 All belts shall be of the static-conducting type and shall be oil resistant. NOTE Oil resistant belts require a core of Neoprene or an equivalent material. 7.4.1.4 The drive service factor shall not be less than 1.75 based on the driver nameplate power rating. 7.4.2 The vendor shall provide a positive belt-tensioning device. This device shall incorporate a lateral adjustable base with guides and hold-down bolts, two belt-tensioning screws, and locking devices. 7.4.3 All bearing lubrication points shall be accessible. 7.4.4 If a belt drive is to be used, the vendor who has unit responsibility shall inform other manufacturers of the connected equipment. 7.4.4.1 The other manufacturer(s) shall be provided with the radial load resulting from the belt drive. 7.4.4.2 The drive manufacturer shall take into account the radial load and torque variation conditions and shall provide bearings with a life at least equivalent to that specified in 6.9.1. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 43 7.4.5 Belt drives shall meet the requirements of 7.4.5.1 through 7.4.5.7. 7.4.5.1 The distance between the centers of the sheaves shall be at least 1.5 times the diameter of the larger sheave. 7.4.5.2 The belt wrap (contact) angle on the smaller sheave shall be at least 140°. 7.4.5.3 The shaft length on which the sheave hub is fitted shall be at least equal to the width of the sheave hub. 7.4.5.4 The length of a shaft key used to mount a sheave shall be equal to the length of the sheave bore. 7.4.5.5 Each sheave shall be mounted on a tapered adapter bushing. 7.4.5.6 To reduce the moment on shafts due to belt tension, the sheave overhang distance from the adjacent bearing, shall be minimized. 7.4.5.7 Sheaves shall meet the balance requirements of ISO 21940-11, G 6.3. 7.4.6 Removable guards shall be furnished and shall be in accordance with 7.3. 7.5 Baseplates 7.5.1 The vendor shall mount and align the driver and transmission on the baseplate prior to shipment. 7.5.2 All baseplate machinery mounting pads shall meet the following criteria. a) They shall be machined after the baseplate is fabricated. b) They shall be machined to a finish of 6.3 μm (250 μin.) Ra or better. c) They shall have each mounting surface machined within a flatness of 40 μm per linear meter (0.0005 in. per linear foot) of mounting surface. 7.5.3 Mounting pads shall be provided for the LRC/VP and all drive-train components, such as motors and gears. 7.5.3.1 The pads shall be larger than the foot of the mounted equipment, including extra width of shims under drive-train components, to allow levelling of the baseplate without removal of the equipment. 7.5.3.2 The pads shall be fully machined flat and parallel. Corresponding surfaces shall be in the same plane within 150 μm/m (0.002 in./ft) of distance between the pads. [●] 7.5.3.3 If specified, the requirements of 7.5.3.2 shall be demonstrated in the LRC/VP vendor’s shop prior to mounting of the equipment and with the baseplate supported at the foundation bolt holes only. NOTE This demonstration can be performed only when the clamps are released in the milling machine after completion of machining. Installed baseplate flatness can be affected by transportation, handling, and installation procedures beyond the vendor’s scope. 7.5.4 If any piece of rotating equipment has a mass in excess of 250 kg (550 lb), the baseplate shall be supplied with horizontal (axial and lateral) jackscrews, the same size or larger than the vertical jackscrews. 7.5.4.1 The lugs holding these jackscrews shall be attached to the baseplate in such a manner that they do not interfere with the installation of the equipment, jackscrews, spacers, or shims. 7.5.4.2 Jackscrews shall be stainless steel or plated for corrosion resistance. 44 API Standard 681 7.5.4.3 Precautions shall be taken to prevent vertical jackscrews in the equipment feet from marring the shimming surfaces. NOTE Alternative methods of lifting equipment for the removal or insertion of shims or for moving equipment horizontally, such as provision for the use of hydraulic jacks, can be proposed. Such arrangements can be proposed for equipment that is too heavy to be lifted or moved horizontally using jackscrews. 7.5.5 Machinery supports shall be designed to limit the relative displacement of the shaft end caused by the worst combination of pressure, torque, and allowable piping stress to 50 µm (0.002 in.). 7.5.6 Epoxy grout shall be used for machines mounted on concrete foundations. 7.5.6.1 The vendor shall blast-clean in accordance with SSPC SP 6 or ISO 8501 Grade Sa2, all grout contact surfaces of the baseplate and coat those surfaces with a primer compatible with specified epoxy grout. 7.5.6.2 The vendor shall advise the purchaser the actual primer used. 7.5.6.3 The grout manufacturer should be consulted to ensure proper field preparation of the baseplate for satisfactory bonding of the grout to the grout primer. NOTE [●] 7.5.7 Epoxy primers have a limited life after application. The purchaser shall specify the epoxy grout to be used for field installation. 7.5.8 The anchor bolts shall not be used to fasten equipment to the baseplate. 7.5.9 Baseplate shall conform to the following requirements. a) Baseplate shall not be drilled for equipment to be mounted by others. b) Baseplate shall be supplied with leveling screws. A leveling screw shall be provided near each anchor bolt. If the equipment and baseplate are too heavy to be lifted using leveling screws, alternative methods shall be provided by the equipment vendor. The design of the alternative method shall be included in the proposal. c) Outside corners of baseplate which are embedded in the grout shall have 50 mm. (2 in.) minimum radiused outside corners (in the plan view). d) All machinery mounting surfaces shall be treated with a rust preventive immediately after machining. e) Baseplate shall extend at least 25 mm (1 in.) beyond the outer three sides of equipment feet. NOTE 1 Item c): Radiused corners prevent the potential of cracking the grout. NOTE 2 Item e): This requirement allows handling of shims and mounting level or laser type instruments to check alignment. 7.5.10 All pads for drive-train components shall be machined to allow for the installation of shims at least 3 mm (0.125 in.) thick under each component as per requirement of 7.5.10.1 through 7.5.10.6. 7.5.10.1 If the vendor mounts the components, a set of stainless steel shims (shim packs) at least 3 mm (0.12 in.) thick shall be furnished. 7.5.10.2 Shim packs shall not be thicker than 13 mm (0.5 in.) nor contain more than 5 shims. 7.5.10.3 All shim packs shall straddle the hold-down bolts and vertical jackscrews and extend at least 5 mm (1/4 in.) beyond the outer edges of the equipment feet. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 45 7.5.10.4 If the vendor does not mount the components, the pads shall not be drilled, and shims shall not be provided. 7.5.10.5 Shims shall not be used under the LRC/VP. [●] 7.5.10.6 If specified, in addition to shim packs, a stainless steel spacer plate of not less than 5 mm (0.200 in.) thickness, machined on both sides, and of the same length and width as the specific mounting feet, shall be furnished and installed under all equipment feet, including the LRC/VP, driver, and any speed increaser or reducer. 7.5.11 Anchor bolts shall be furnished by the purchaser. 7.5.12 Hold-down bolts (used to attach the equipment to the baseplates) and all jackscrews, shall be supplied by the vendor. 7.5.13 Baseplate shall be designed for installation in accordance with API Recommended Practice 686. 7.5.14 Diametrical clearance between anchor bolts and the anchor bolt holes in the baseplate shall be a minimum of 6 mm (1/4 in.). 7.5.15 Adequate working clearance shall be provided at the hold-down and jackscrew locations to allow the use of standard socket or box wrenches, to achieve the specified torque. [●] 7.5.16 If a baseplate is specified, the purchaser shall indicate the major equipment to be mounted on it. A baseplate shall be a single fabricated steel unit, unless the purchaser and the vendor agree that it may be fabricated in multiple sections. A multiple section baseplate shall have machined and doweled mating surfaces which shall be bolted together to ensure accurate field reassembly. NOTE A baseplate with a nominal length of more than 12 m (40 ft) or a nominal width of more than 4 m (12 ft) are often fabricated in multiple sections because of shipping restrictions. 7.5.17 If a baseplate(s) is provided, it shall extend under the LRC/VP and drive-train components to contain and drain any leakage. [●] 7.5.18 If specified, baseplates or skids shall be provided with leveling pads or targets protected by removable covers. The pads or targets shall be accessible for field leveling after installation, with the equipment mounted and the baseplate on the foundations. 7.5.19 All joints, including deck plate to structural members, shall be continuously seal-welded on both sides to prevent crevice corrosion. Stitch welding, top or bottom, is unacceptable. [●] 7.5.20 If specified, the baseplate shall be designed for column mounting (that is, of sufficient rigidity to be supported at only specified points) without continuous grouting under structural members. The baseplate design shall be agreed upon by the purchaser and the vendor. Design suitability shall be verified by FEA or similar suitable design tool. 7.5.21 Single-piece baseplates shall be furnished with a gutter type drain 3-in. wide and 2-in. deep around the circumference of the base deck. The gutter shall be sloped at least 1 in. 120 toward the driven equipment end, where a tapped drain opening of at least DN 50 (NPS 2) shall be located to effect complete drainage. 7.5.22 The baseplate shall be provided with lifting attachments meeting the requirements of 7.5.22.1 through 7.5.22.7. 7.5.22.1 Attachments shall be provided for at least a four-point lift. 7.5.22.2 Lifting attachments on the baseplate shall be designed using a maximum allowable dynamic stress of one-third of the specified minimum yield strength of the material. 46 API Standard 681 NOTE Design of lifting attachments can be in accordance with standards such as ASME BTH-1 “Design of Below-theHook Lifting Devices”. 7.5.22.3 Lifting the baseplate complete with all equipment mounted shall not permanently distort or otherwise damage the baseplate or the equipment mounted on it. 7.5.22.4 Lugs or trunnions that are attached by welding shall be continuous welds and shall be 100 % NDE tested in accordance with the applicable code. 7.5.22.5 Removable lugs or commercially available specialty products such as pivot type hoisting rings may be provided with purchaser approval. [●] 7.5.22.6 If specified, commercially available lifting attachments shall be furnished with material and load test certifications traceable to an internationally recognized standard and attested by an independently accredited third party agency or organization. 7.5.22.7 The vendor shall advise if a spreader bar is needed, and if equipment shall be uncoupled before lifting. 7.5.23 The bottom of the baseplate between structural members shall be open. 7.5.24 When the baseplate is designed for grouting, it shall be provided with grout and vent holes. 7.5.24.1 At least one grout hole having a clear area of at least 130 cm2 (20 in.2) and no dimension less than 75 mm (3 in.) shall be provided in each bulkhead section. 7.5.24.2 Grout holes shall be located to permit grouting under all load-carrying structural members. 7.5.24.3 Where practical, the grout holes shall be accessible for grouting with the equipment installed. 7.5.24.4 Grout holes shall have 13 mm (½ in.) raised-lip edges, and if located in an area where liquids could impinge on the exposed grout, metallic covers with a minimum thickness of 3 mm (⅛ in.) shall be provided. 7.5.24.5 Vent holes at least 13 mm (½ in.) in size shall be provided at the highest point and located to vent the entire cavity in each bulkhead section of the baseplate. 7.5.25 The underside mounting surfaces of the baseplate shall be in one plane to permit use of a single-level foundation. If multi section baseplates are provided, the mounting pads shall be in one plane after the baseplate sections are doweled and bolted together. 7.5.26 Nonskid surfaces covering all walk and work areas shall be provided on the top of the baseplate. NOTE Nonskid surfaces can be obtained by nonskid coatings or grating. 7.5.27 Two ground clips or pads shall be welded to the baseplate at diagonally opposed corners. These clips or pads shall be of the same material as the baseplate and accommodate a 13 mm (1/2 in. UNC) bolt. 7.6 Controls and Instrumentation 7.6.1 General [●] 7.6.1.1 Controls and instrumentation shall be suitable for outdoor installation. They shall have a minimum ingress protection level of IP66 as detailed in IEC 60529, or a NEMA 4 minimum rating per NEMA Standard Publication 250, as specified. If IP66 protection level is specified, the controls and instrumentation, equipment and wiring shall comply with the construction requirements of IEC 60079 “Electrical apparatus for explosive atmospheres”. NOTE Special consideration can be required for instrumentation working below ̶ 20 °C or above 55 °C. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 47 7.6.1.2 Terminal boxes shall have a minimum ingress protection level of IP 66 as detailed in IEC 60529 or a NEMA 4X minimum rating per NEMA Standard Publication 250, as specified. If IP 66 protection level is applied, the terminal boxes shall comply with the construction requirements of IEC 60079, Electrical apparatus for explosive atmospheres. Terminal boxes shall be 316 SS. NOTE 1 IEC addresses Environment protection and electrical protection separately. Ingress protection is covered by the IP designation in IEC 60529. Electrical protection is covered by IEC 60079. NOTE 2 The IP Code only addresses requirements for protection of people, ingress of solid objects, and ingress of water. There are numerous other requirements covered by the NEMA Type designations that are not addressed by the IEC 60529/ IP Codes. IEC 60529 does not specify the following: a) construction requirements, b) door and cover securement, c) corrosion resistance, d) effects of icing, e) gasket aging and oil resistance, and f) coolant effects. The Type designation of NEMA specifies requirements for these additional performance protections. For this reason, the IEC enclosure IP Code designations cannot be converted to enclosure NEMA Type numbers. (NEMA Publication, A Brief Comparison of NEMA 250 and IEC 60529). NOTE 3 NEMA addresses both environmental and electrical protection (construction features) in one standard NEMA Publication 250. [●] 7.6.1.3 Purchaser shall specify the vendor’s scope of supply for the package control system. 7.6.1.3.1 If the control system is provided by purchaser, the vendor shall provide sufficient performance data for the LRC/VP to enable the purchaser to design a control system for startup and for all specified operating conditions. [●] 7.6.1.3.2 If specified, the vendor shall review the purchaser’s overall control system for compatibility with vendor furnished control equipment. 7.6.1.4 Instrumentation and Controls shall be designed and manufactured for use in the area classification (class, group, and division or zone) specified. 7.6.1.5 All conduit, armored cable and supports shall be designed and installed to be easily removed without damage and shall be located so that it does not hamper removal of bearings, seals, or equipment internals. 7.6.1.6 Where applicable, controls and instrumentation shall conform to API Recommended Practice 551. 7.6.1.7 Instrument in direct contact with the process fluids (gases, oils, etc.) shall have proper sealing to prevent any probable leaks at the most severe operating conditions. 7.6.1.8 Except for instrument air service, bleed valves are required between instruments and their isolation valves. Combination isolation/bleed valves may be used. 48 API Standard 681 7.6.2 Control Systems 7.6.2.1 The purchaser shall specify the method of control, the source of the control signal, its sensitivity and range, and the equipment to be furnished by the vendor. [●] 7.6.2.2 Controlled recycle bypass from discharge to suction is required. If specified, this bypass shall be supplied by the vendor. NOTE Bypass control can be used for suction pressure control, start-up, and LRC/VP protection from cavitation. 7.6.2.3 For an adjustable speed drive, the control signal shall act to adjust the set point of the driver's speedcontrol system. 7.6.2.3.1 The speed of the machine shall vary linearly and directly with the control signal. 7.6.2.3.2 The control range shall be from the maximum continuous speed to the minimum speed required to maintain ring liquid stability (at the specified control parameter conditions). Vendor shall advise the minimum and maximum speed required to maintain ring liquid stability. 7.6.2.4 The full range of the specified control signal shall correspond to the required operating range of the driven equipment. The maximum control signal shall correspond to the maximum continuous speed or the maximum flow. 7.6.2.5 Actuation of the control signal or failure of the signal or actuator shall neither prevent the speed control system from limiting the speed to the maximum continuous speed nor prevent manual regulation. 7.6.2.6 Purchaser shall specify level of automation for the startup and operation of the package, including manual versus automatic operations of valves, main and auxiliary equipment. 7.6.3 Instrument and Control Panels [●] 7.6.3.1 If specified, a panel shall be provided and shall include all panel-mounted instruments for the driven equipment and the driver. Panels shall be designed and fabricated in accordance with the purchaser’s description. The panel is to be freestanding, located on the base of the unit, or in another location, as specified. The instruments on the panel shall be clearly visible to the operator from the driver control point. If the panel contains lamps a lamp test push button shall be provided. The instruments to be mounted on the panel shall be specified. 7.6.3.2 Panels shall be made of steel plate reinforced self-supporting and fully enclosed. The front shall be steel plate at least 3 mm (1/8 in.) thick. Tops and sides shall be a minimum of 12 gauge in accordance with Table 6. All instruments shall be flush mounted on the front of the panel and all fasteners shall be of corrosion-resistant material. All interior and exterior surfaces of carbon steel panels shall be prepared and coated with an industrial grade coating system. Table 6—Minimum Thickness for Control Panels 12 Gauge Steel Material Thickness (in.) Uncoated 0.1046 Galvanized 0.0934 Stainless Steel 0.1094 7.6.3.3 Gauge boards and panels shall be completely assembled, piped, and wired, requiring only connection to the purchaser’s external piping, and wiring circuits. 7.6.3.4 If more than one wiring point is required on a unit for control or instrumentation, the wiring to each electrical control device or instrument shall be provided from common terminal box(es), with terminal posts. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 49 7.6.3.4.1 Separate terminal boxes shall be supplied for segregation of the AC and DC electrical signals. With purchaser’s approval, one terminal box may be provided if it is equipped with an internal barrier that separates the AC and DC wiring. 7.6.3.4.2 Each terminal box shall be mounted on the unit baseplate. 7.6.3.4.3 Wiring shall be installed in metal conduits or enclosures. 7.6.3.5 Racking of the junction boxes requires specific purchaser’s approval. [●] 7.6.3.6 All leads and posts on terminal strips, shutdown devices and instruments shall be tagged for identification. If specified, purchaser’s tagging shall be applied in addition to the vendor’s tagging. 7.6.3.7 Wiring inside panels shall be neatly run in wire ducting. 7.6.3.8 Interconnecting piping, tubing, or wiring for controls and instrumentation, furnished by the vendor, shall be disassembled only to the extent necessary for shipment. [●] 7.6.3.9 If specified, the control panel shall include Programmable Logic Controller (PLC) with the package control logic. The PLC shall be capable of communicating with the purchaser’s distributed control system (DCS). The purchaser shall advise the communication protocol to be used. 7.6.4 Instrumentation 7.6.4.1 Minimum Instrumentation Vendor shall submit recommendations for instrumentation to ensure safe and reliable operation. The following, as a minimum, shall be included (refer to Annex E): a) gas inlet pressure. b) gas inlet temperature. c) ring liquid/gas outlet pressure. d) ring liquid/gas outlet temperature. e) ring liquid supply temperature. f) ring liquid level in separator (not required for once-through or partial recirculation systems), and g) ring liquid supply pressure or flow. 7.6.4.2 Temperature Gauges 7.6.4.2.1 Dial type temperature gauges shall be heavy duty and corrosion resistant. They shall be at least 125 mm (5 in.) diameter, bimetallic or liquid filled types and shall have black marking on a white background. 7.6.4.2.2 The sensing elements of temperature gauges shall be in the flowing fluid. NOTE This is particularly important for lines that run partially full. 7.6.4.2.3 Temperature sensing elements shall be furnished as minimum with austenitic stainless steel, solid bar, and separable thermowells. 50 API Standard 681 7.6.4.2.4 The thermowell shall have a 25 mm (1 in.) process connection. For pressurized lines, this connection shall be flanged. For non-pressurized lines, this connection may be threaded with purchaser approval. The thermowell internal connection shall be 13 mm (1/2 in.). 7.6.4.3 Thermocouples and Resistance Temperature Detectors 7.6.4.3.1 Where practicable, the design and location of thermocouples and resistance temperature detectors shall permit replacement while the unit is operating. 7.6.4.3.2 The lead wires of thermocouples and resistance temperature detectors shall be installed as continuous leads between the thermocouple or detector and the terminal box located on the equipment or the baseplate. 7.6.4.4 Solenoid Valves Direct solenoid-operated valves shall be used only in clean, dry instrument-air service, shall have class F insulation or better, and shall have a continuous service rating. If required for other services, the solenoid shall act as a pilot valve to pneumatic valves. 7.6.4.5 Pressure Gauges 7.6.4.5.1 Pressure gauges (not including built-in instrument air gauges) shall be furnished with AISI Standard Type 316 stainless steel bourdon tubes and stainless steel movements, at least 110 mm (4 1/2 in.) dials, and NPT 1 /2 male alloy steel connections. 7.6.4.5.2 Black printing on a white background is standard for gauges. [●] 7.6.4.5.3 If specified, liquid-filled gauges shall be furnished in locations subject to vibration. 7.6.4.5.4 Gauge ranges shall preferably be selected so that the normal operating pressure is at the middle of the gauge’s range. In no case, however, shall the maximum reading on the dial be less than the applicable relief valve setting plus 10 %. 7.6.4.5.5 Each pressure gauge shall be provided with a device such as a disk inserts or blowout back designed to relieve excess case pressure. 7.6.4.6 Condition Monitoring Devices [●] 7.6.4.6.1 If vibration transducers are specified, they shall be supplied, installed, and calibrated in accordance with API Standard 670. [●] 7.6.4.6.2 If vibration monitors are specified, they shall be supplied and calibrated in accordance with API Standard 670. 7.6.4.7 Pressure Safety (Relief) Valves 7.6.4.7.1 The vendor shall furnish the relief valves that are to be installed on equipment or piping that the vendor is supplying. Other relief valves related to equipment or piping outside the system that the vendor is supplying, shall be furnished by the purchaser. The vendor's quotation shall list all relief valves and shall clearly state that these valves will be furnished by the vendor. 7.6.4.7.2 The sizing, selection and installation of relief valves shall meet the requirements of API Standard 520, Parts 1 and 2. 7.6.4.7.3 Relief valves shall be in accordance with API Standard 526. 7.6.4.7.4 The vendor shall determine the size and set pressure of all relief valves within vendor’s scope of supply and recommend the size and setting of relief valves supplied by others required to protect the vendor’s Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 51 equipment. Relief valve sizes and settings shall take into account all possible modes of equipment failure for the protection of piping systems. 7.6.4.7.5 Relief valves shall have steel bodies. [●] 7.6.4.7.6 If specified, thermal relief valves shall be provided for accessories or cooling jackets that may be blocked-in by isolation valves. 7.6.5 Alarms and Shutdowns 7.6.5.1 An alarm/shutdown system shall be provided which will initiate an alarm if any one of the specified parameters reaches an alarm point and will initiate shutdown of the equipment if any one of the specified parameters reaches the shutdown point. [●] 7.6.5.2 The purchaser shall specify the alarms and shutdown required. Minimum recommendations are listed in Table 7. Table 7—Minimum Alarm, Shutdown, and Trip Recommendations Condition Alarm Shutdown High gas outlet temperature X X High gas outlet pressure X Low gas inlet pressure X High gas inlet pressure X High gas inlet temperature X Low ring liquid flow (for total recirculation systems) X High ring liquid flow X High ring liquid inlet temperature to LRC/VP X Low ring liquid level in separator X High ring liquid level in separator X High hydrocarbon level in separator (applicable to 3-phase separator) X Overspeed (for adjustable speed units only) X Trip X X X 7.6.5.3 The vendor shall advise the purchaser of any additional alarms or shutdowns, or both, considered essential to safeguard the equipment. [●] 7.6.5.4 The purchaser shall specify the extent to which this alarm/shutdown system is to be supplied by the equipment vendor. 7.6.5.5 The alarm/shutdown system shall comply with the requirements of 7.6.5.5.1 through 7.6.5.5.7. 7.6.5.5.1 For every shutdown parameter, an alarm shall be provided with the alarm point set at a lesser deviation from the normal condition than the associated shutdown point. [●] 7.6.5.5.2 Any alarm parameter, reaching the alarm point, shall initiate an audible warning or flashing light or both as specified. It shall be possible to determine which parameter initiated the alarm. 7.6.5.5.3 Any shutdown parameter, reaching the shutdown point, shall cause the equipment to shut down and shall initiate an audible warning or a flashing light or both as specified which shall be distinguishable from those associated with an alarm. It shall be possible to determine which parameter initiated the shutdown. [●] 7.6.5.5.4 If specified, an alarm shall be initiated when any component of the alarm/shutdown system malfunctions and shall be distinguishable from alarms resulting from malfunction of the equipment. 52 API Standard 681 NOTE To accomplish this, redundant sensors are often applied. [●] 7.6.5.5.5 If specified, the equipment shall automatically shut down and an alarm shall be initiated when any malfunction of a component of the shutdown system results in the system being unable to recognize a shutdown condition. This alarm shall be distinguishable from shutdowns resulting from malfunction of the equipment (failsafe system). [●] 7.6.5.5.6 If a non-fail-safe system is specified, a failure that results in the system being unable to recognize a shutdown condition shall also result in all other shutdown and alarms remaining functional. 7.6.5.5.7 If a non-fail safe system is specified, a failure that results in the system being unable to recognize an alarm condition shall also result in all other alarms and shutdowns remaining functional. 7.6.5.6 It shall be possible to test every component of every alarm function while the equipment is in operation. Such testing shall not require the disarming of any shutdown function. 7.6.5.7 With the exception of the final shutdown device (circuit breaker, etc.), it shall be possible to test all components of the shutdown system while the equipment is in operation. The testing of components associated with a shutdown function shall not require disarming of any other shutdown function nor any alarm function. [●] 7.6.5.8 If specified, the alarm/shutdown system shall incorporate a first-out annunciator facility to indicate which parameter first reached the alarm level and which parameter first reached the shutdown level, in the event that multiple alarms or shutdown, or both, result from a single initial event. [●] 7.6.5.9 If specified, the alarm/shutdown system shall incorporate an event recorder to record the order of occurrence of alarms and shutdowns. Time resolution shall be not greater than 100 ms. NOTE rate. The special event recorder normally associated with a DCS sometimes does not have a sufficiently fast scanning 7.6.5.10 The necessary valving or bridging links (jumpers) or other approved protocol shall be provided to enable all instruments and other components, except shutdown sensing devices, to be replaced with the equipment in operation. [●] 7.6.5.11 If specified, shutdown sensing devices shall be provided with valving, bridging links or other approved protocol to allow replacement with the equipment in operation. 7.6.5.12 Isolation valves for shutdown sensing devices shall be provided with means of locking the valves in the open position. 7.6.6 Annunciator 7.6.6.1 If a first-out annunciator feature has been specified in 7.6.5.8, whether as a separate instrument or incorporated into an integrated control and monitoring facility, the sequence of operation shall be as follows. a) The first parameter to reach alarm or shutdown shall cause the flashing of a light and the sounding of an audible device. b) The alarm or shutdown condition shall be acknowledged by operating an alarm silencing button, common to all alarms and shutdowns. c) When the alarm or shutdown is acknowledged, the audible device shall be silenced but the light shall remain steadily lit as long as that alarm or shutdown condition exists. d) If another parameter reaches an alarm or shutdown level the light shall return to the flashing condition and the audible device shall sound, even if the previous alarm/shutdown condition has been acknowledged but still exists. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 53 7.6.6.2 If the first-out annunciator feature is provided by a separate instrument, this shall be mounted on a local panel. 7.6.6.3 There shall be minimum of 20 % spare points and separate connections shall be provided for remote indication if any alarm operates or any shutdown operates. 7.6.7 Alarm and Shutdown Devices 7.6.7.1 General [●] The purchaser should specify whether separate alarm and shutdown devices are required, in accordance with API Standard 614. 7.6.7.2 Locally Mounted Alarm and Shutdown Devices Where alarm or shutdown functions, or both, are initiated by locally mounted transmitters or switches, such devices shall comply with API Standard 614 and 7.6.7.2.1 through 7.6.7.2.7. NOTE API Standard 614 recommends transmitters in lieu of switches for pressure, temperature, level, and vibration measurement, as well as alarm and shutdown. 7.6.7.2.1 Housings for alarm and shutdown devices shall comply with the requirements of the electrical area classification specified. 7.6.7.2.2 The sensing elements of pressure sensing transmitters or switches shall be of Austenitic stainless steel. 7.6.7.2.3 Transmitters or switches shall be equipped with a test connection. [●] 7.6.7.2.4 The transmitter or switch arrangements to be used shall be specified by the purchaser. [●] 7.6.7.2.5 Temperatures shall be measured by thermocouples or resistance temperature detectors as specified in accordance with API 670. [●] 7.6.7.2.6 If specified, vibration monitoring devices shall be provided by instruments complying with the requirements of API Standard 670. 7.6.7.2.7 Level transmitters shall be of the float or displacer type mounted in separate enclosures which can be isolated from the associated vessel in accordance with API Standard 614 and API Standard 682. 7.6.7.2.7.1 Level transmitters shall be capable of testing without shutting down the equipment or removing the vessel or reservoir from service. 7.6.7.2.7.2 Valved test connections shall be provided to enable testing of the transmitter functionality on atmospheric vessels such as oil reservoirs. 7.6.8 Electrical Systems 7.6.8.1 Motors, heaters, and instrumentation shall be suitable for the power supplies specified. A pilot light shall be provided on the incoming side of each supply to indicate that the circuit is energized. The pilot lights shall be installed on the control panel. 7.6.8.2 Electrical equipment located on the unit or on any separate panel shall conform to the electrical area classification specified. 7.6.8.3 Electrical starting and supervisory controls may be either AC or DC. 54 API Standard 681 7.6.8.3.1 DC control voltage should be used. 7.6.8.3.2 AC control voltage may be used, if required by the purchaser or owner. 7.6.8.4 Power and control wiring, located on, adjacent to, or connected to the equipment, shall be resistant to oil, heat, moisture, and abrasion. 7.6.8.4.1 Stranded conductors shall be used if connected to or located on machinery or in other areas subject to vibration. 7.6.8.4.2 Remote control panel wiring may be solid conductor. 7.6.8.4.3 The insulation shall be flame retardant, moisture, and heat resistant thermoplastic, and when necessary, for abrasion resistance shall be provided with an outer covering. 7.6.8.4.4 Wiring shall be suitable for the local temperatures to be encountered. 7.6.8.5 All leads on terminal strips, shutdown devices, and instruments shall be permanently tagged for identification. 7.6.8.6 All terminal boards in junction boxes and control panels shall have at least 20 % spare terminal points. 7.6.8.7 To guard against accidental contact, enclosures shall be provided for all terminal strips, relays, shutdown devices and other energized parts. 7.6.8.8 Electrical power wiring shall be segregated from instrument and control signal wiring both externally and, as far as possible, inside enclosures. Inside enclosures which may be required to be opened with the equipment in operation, for example, for alarm testing or adjustment, shall be provided with secondary shields or covers for all terminal strips and other exposed parts carrying electrical potential in excess of 50 volts. Maintenance access space shall be provided around or adjacent to electrical equipment or in accordance with the National Electrical Code, Article 110 or other internationally recognized standard as approved by the purchaser. 7.6.8.9 Electrical materials including insulation shall be corrosion resistant and non-hygroscopic insofar as is possible. [●] 7.6.8.9.1 If specified, electrical parts (such as coils and windings) shall be protected from fungus attack. [●] 7.6.8.9.2 If specified, unpainted surfaces of electrical parts shall be protected from corrosion by plating or another suitable coating. NOTE Sections 7.6.8.9.1 and 7.6.8.9.2 are often applied for tropical or marine conditions. 7.6.8.10 Control, instrumentation, and power wiring, which is not within a fully enclosed panel or other enclosure, shall be in the form of armored cable or shall be run in metal conduit as specified. 7.6.8.10.1 Cables shall be supported on cable trays supported to prevent damage from pedestrian traffic. 7.6.8.10.2 Conduit shall be properly supported to avoid damage caused by vibration and isolated and shielded to prevent interference between different services. 7.6.8.10.3 Conduits may terminate (in the case of the leads to temperature elements, shall terminate) with a length of flexible metal conduit, long enough to facilitate maintenance without removal of the conduit. In applications where conduit temperatures are above 60 °C (140 °F), the flexible conduit shall be 19 mm bronze hose with four-wall-interlocking construction and joints with packed-on heatproof couplings shall be used. 7.6.8.11 For Division 2 locations, flexible metallic conduits shall have a liquid tight thermosetting or thermoplastic outer jacket and approved fittings. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 7.6.8.12 55 For Division 1 locations, an NFPA-approved connector shall be provided. 7.6.8.13 AC and DC circuits shall be clearly labeled, connected to separate terminal blocks, and isolated from each other. 7.6.8.14 Conduit drains shall be installed in all conduit low points for outdoor installations. [●] 7.6.8.15 If specified for indoor installations, conduit drains shall be installed in all conduit low points. 7.7 Ring Liquid System and Auxiliaries 7.7.1 General 7.7.1.1 A system shall be furnished by the vendor, to supply the ring liquid at a suitable flow, pressure, and temperature to the LRC/VP. The purchaser shall specify the type of system required. NOTE 1 An LRC/VP requires a ring liquid to operate. The extent of the vendor’s scope of supply depends upon how the LRC/VP is integrated into the user’s process. NOTE 2 Typical systems are shown in Annex E. 7.7.1.2 The ring liquid system may include, but need not be limited to, the following components, as specified or required (see 7.7.2 through 7.7.8): a) separator, b) cooler, c) ring liquid strainer, d) ring liquid pump, e) interconnecting piping, f) check valves, and g) ring liquid purge system. 7.7.1.3 Purchaser shall provide initial composition and properties of the ring liquid and makeup liquid. The ring liquid used shall be agreed. 7.7.1.4 Vendor shall design the ring liquid system based on the final composition of the ring liquid and gas in the system at the equilibrium condition. 7.7.1.5 The system shall be designed to supply the required quantity of ring liquid for all specified operating conditions including start-up and “run-in” on air. 7.7.1.6 The system shall be designed and arranged to ensure correct ring liquid level in the LRC/VP during start-up to avoid flooding. 7.7.1.7 The ring liquid level in the compressor shall automatically return to the required start-up level upon shutdown. [●] 7.7.1.8 The purchaser shall specify whether the ring liquid components are to be mounted on the machine base or on a separate skid. 56 API Standard 681 7.7.2 Ring Liquid Separator [●] 7.7.2.1 If a separator is specified, it shall be designed to separate the discharge gas from the ring liquid. Separator(s) shall be supplied as specified in 7.7.2.2 through 7.7.2.8. [●] 7.7.2.2 If specified, the vendor shall state the quantity of the ring liquid which will remain entrained in the gas delivered from the separator at each specified operating condition. The purchaser shall specify any limitations on liquid carryover from the system. NOTE Transient conditions such as start-up and shutdown (or trip) may cause unusual carryover conditions. [●] 7.7.2.3 If liquid-liquid separation is specified, the system shall be designed to separate condensed process vapors from the ring liquid and allow their removal. The purchaser shall advise the separation time. NOTE Liquid-liquid separation can be accomplished in a vessel designed for this purpose or in the same vessel used for liquid-gas separation. 7.7.2.4 Vendor shall advise the actual gas velocity in the separator vapor space. [●] 7.7.2.5 The vendor shall estimate the extent to which the vapor may be expected to condense within the machine. a) The vendor shall account for this in the design of the machine and separator and, if specified, make provision for the removal of condensate. b) The purchaser shall specify the pressure in the system into which the condensate is to be discharged. 7.7.2.6 Separator shall conform to Section VIII, Division 1 of the ASME BPVC and shall be code stamped. 7.7.2.7 As a minimum, separators shall be constructed of carbon steel with a 3 mm (1/8 in.) corrosion allowance. 7.7.2.8 Separators shall be equipped with the following characteristics and appendages: a) capacity to maintain ring liquid level between minimum and maximum operating level during start-up, shutdown, and normal operation; NOTE Retention time is required for sufficient separation to maintain the required ring liquid characteristics. b) [●] c) vessel internals, as necessary to achieve the required gas/liquid/liquid separation performance; if specified, a flanged safety relief valve in accordance with 7.6.4.8; d) flanged opening [150 mm (6 in.) minimum] for servicing and cleaning of the separator internals; e) separate flanged vent, ring liquid-return, ring-liquid-fill and drain connections; f) flanged armored level gauge for the gas-liquid and liquid-liquid interface where applicable; g) vortex breaker upstream of the ring liquid outlet connection and process condensate connection, where provided; [●] h) if specified, separate flanged connections for level transmitter, pressure indicator; [●] j) if specified, separate thermowell connections for a temperature gauge or transmitter. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 57 7.7.3 Ring Liquid Cooler 7.7.3.1 The cooler shall be a water-cooled, shell-and-tube type, with cooling water on the tube side. 7.7.3.2 Coolers shall be constructed and arranged to allow removal of the tube bundles without dismantling piping or machine components. 7.7.3.3 Ring liquid cooler shall be furnished in accordance with Section VIII, Division 1 of the ASME BPVC or other purchaser specified pressure design code. [●] 7.7.3.4 Water-cooled shell-and-tube shall be designed and constructed in accordance with TEMA C or R, as specified. If TEMA class R has been specified, the heat exchanger shall be in accordance with API Standard 660. 7.7.3.5 Tubes shall not have an outside diameter of less than 15 mm (5/8 in.), and the tube wall shall not have a thickness of less than 1.25 mm [18 BWG (0.049 in.)]. 7.7.3.6 U-bend tubes are permitted when approved by the purchaser. NOTE U-bend tubes can be more difficult to clean than straight tube coolers. 7.7.3.7 Coolers shall be equipped with vent and drain connections on their shell and tube sides. 7.7.3.8 If air-cooled heat exchangers are specified, they shall be in accordance with API Standard 661. [●] 7.7.3.9 Materials of construction shall be as specified. 7.7.4 Ring Liquid Strainer [●] If specified, the ring liquid system shall contain as a minimum a Y-type strainer. 7.7.5 Ring Liquid Pump 7.7.5.1 If a ring liquid pump is required, it shall be centrifugal and in accordance with ANSI B73.1 or B73.2. [●] 7.7.5.2 The purchaser may specify a pump in accordance with API Standard 610. 7.7.6 Ring Liquid Piping 7.7.6.1 Ring liquid piping shall be in accordance with the requirements of 7.8. [●] 7.7.6.2 If specified by the purchaser, the vendor shall make provision for manual or automatic makeup and draining of the ring liquid while the equipment is operating. 7.7.7 Check Valves [●] 7.7.7.1 A check valve is required at the suction of the LRC/VP. Pressure drop across the check valve shall be considered in the design of the system. The purchaser will specify if the valve is to be provided by the vendor. 7.7.7.2 Alternative designs, such as a quick acting isolating valve activated on loss of driver power, may be provided as agreed. [●] 7.7.7.3 If specified, the vendor shall provide a discharge check valve. 7.7.8 Ring Liquid Purge System A ring liquid purge system shall be provided, if specified or if required to reduce dissolved solids, gases, or condensed vapors to an acceptable level. Ring liquid purge systems shall be automatic. 58 7.8 API Standard 681 Piping 7.8.1 General 7.8.1.1 Piping design, joint fabrication, examination, and inspection shall be in accordance with ASME B 31.3. 7.8.1.2 Piping systems are defined as follows: a) b) Group I 1) vapor piping, 2) ring liquid (sealing fluid), 3) mechanical seal flushing fluid, 4) recirculation fluid, 5) process-side drains and vents, Group II 1) c) instrument and control air, Group III 1) cooling water, and 2) cooling water drains and vents NOTE Casing connections are discussed in 6.3. 7.8.1.3 Piping systems shall include piping, tubing where permitted, isolating valves, control valves, relief valves, pressure reducers, orifices, temperature gauges and thermowells, pressure gauges, sight flow indicators, and all related vents and drains. 7.8.1.4 Flexible metal hoses shall not be used. 7.8.1.5 The vendor shall furnish all piping systems, including mounted appurtenances, located within the confines of the main unit’s base area, or any auxiliary base area. The piping shall terminate with flanged connections at the edge of the base. 7.8.1.6 Supply of interconnecting piping and piping layout between multiple skids shall be agreed between seller and purchaser. 7.8.1.7 The design of piping systems shall achieve the following: a) proper support and protection to prevent damage from vibration or from shipment, operation, and maintenance; b) proper flexibility and adequate accessibility for operation, maintenance, and thorough cleaning; c) installation in a neat and orderly arrangement adapted to the contours of the equipment without obstructing access areas; d) elimination of air pockets using valved vents or the use of non-accumulating piping arrangements; e) complete drainage through low points without disassembly of piping. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 59 7.8.1.8 The requirements 7.8.1.8.1 through 7.8.1.8.8 shall be considered in piping design: 7.8.1.8.1 The use of flanges and fittings shall be minimized. 7.8.1.8.2 Piping shall preferably be fabricated by bending and welding to minimize the use of flanges and fittings. 7.8.1.8.3 Flanges are permitted only at equipment connections, at the edge of any base and for ease of maintenance. 7.8.1.8.4 The use of flanges at other points is permitted only with the purchaser’s specific approval. 7.8.1.8.5 Other than tees and reducers, welded fittings are permitted only to facilitate pipe layout in congested areas. 7.8.1.8.6 Threaded connections may be used for mechanical seals gland connections. 7.8.1.8.7 Threaded connections shall not be used otherwise, except (with the purchaser’s approval) where essential for space or access reasons. 7.8.1.8.8 Pipe bushings shall not be used. 7.8.1.9 Pipe threads, where permitted, shall be taper threads in accordance with ASME B 1.20.1. 7.8.1.10 Flanges shall be in accordance with ANSI B 16.5. Slip-on flanges are permitted only with the purchaser’s specific approval. 7.8.1.11 For socket-welded construction, a 1.6 mm (1/16-in.) gap shall be left between the pipe end and the bottom of the socket. 7.8.1.12 Connections, piping, valves, and fittings that are sizes NPS 1 ¼, 2 ½ 3 ½, 5, 7, and 9 (DN 32, DN 65, DN 90, DN 125, DN 175 and DN 225) shall not be used. 7.8.1.13 Where space does not permit the use of NPS 1/2 (DN15), 3/4 (DN20), or 1 (DN25) pipe, seamless tubing may be furnished in accordance with Table 8. The make and model of fittings shall be subject to purchaser’s approval. Table 8—Minimum Tubing Wall Thickness Nominal tubing size a mm a b Minimum wall thickness in. mm in. 6 ( /4) b 1.0 0.035 10 (3/8) b 1.0 0.035 1 12 ( /2) 1.5 0.065 20 (3/4) 2.0 0.095 25 (1) 2.6 0.109 1 The tubing size is the outside diameter. The size 6 mm (1/4 in.) and 10 mm (3/8 in.) are permitted for instrument and control air only. 7.8.1.14 The minimum size of any connection shall be NPS ½ (DN15), nominal pipe size. 7.8.1.15 Piping systems furnished by the vendor shall be fabricated, installed in the shop, and properly supported. Bolt holes for flanged connections shall straddle lines parallel to the main horizontal or vertical centerline of the equipment. 60 API Standard 681 7.8.1.16 Welding of piping, pressure-containing parts, rotating parts and other highly stressed parts, weld repairs and any dissimilar-metal welds shall be performed and inspected by operators and procedures qualified in accordance with Section VIII, Division l, and Section IX of the ASME BPVC or another purchaser approved standard for welding procedures and welder qualification. 7.8.1.17 Pipe plugs shall be in accordance with 6.3.14. 7.8.2 Process Piping [●] 7.8.2.1 The extent of and requirements for process piping to be supplied by the vendor will be specified. 7.8.2.2 The requirements of 7.8.1 shall apply to process piping supplied by the vendor. [●] 7.8.2.3 If specified, the vendor shall review the design of all purchaser’s piping, appurtenances, and vessels and supports immediately upstream and downstream of the equipment. The purchaser and the vendor shall agree on the scope of this review. 7.8.2.4 Suction Strainer A temporary strainer shall be supplied by the vendor for use at the suction of the LRC/VP for commissioning and start-up. 7.8.3 Instrument Piping 7.8.3.1 The vendor shall supply all necessary piping, valves, and fittings for instruments and instrument panels. 7.8.3.2 Initial connections for pressure instruments and test points shall comprise a branch and isolation valve to the same standard as the system to which it is connected. Beyond the initial isolation valve, piping or tubing not less than 10 mm outside diameter may be used. 7.8.3.3 Subject to purchaser approval, a common connection may be used for remotely mounted instruments that measure the same pressure. Such common connections shall not be smaller than DN 15 (NPS 1/2) and separate secondary isolation valves shall be provided for each instrument. 7.8.3.4 Where a pressure gauge is to be used for testing pressure alarm or shutdown devices, common connections are required for the pressure gauge and the associated devices. 8 Inspection, Testing, and Preparation for Shipment 8.1 [●] 8.1.1 General The purchaser shall specify the extent of participation in the inspection and testing. [●] 8.1.2 If specified, the purchaser’s representative, the vendor’s representative or both shall indicate compliance in accordance with an inspector’s checklist by initialing, dating, and submitting the completed checklist to the purchaser before shipment. 8.1.3 After advance notification to the vendor, the purchaser’s representative shall have entry to those areas of all vendor and sub-vendor plants where manufacturing, testing or inspection of the equipment is in progress. 8.1.4 The vendor shall notify sub-vendors of the purchaser’s and vendor’s inspection and testing requirements. [●] 8.1.5 If specified, the vendor shall provide their standard inspection and test plan (ITP) to the purchaser for review and acceptance. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 61 [●] 8.1.6 If shop inspection and testing have been specified, the purchaser and the vendor shall coordinate manufacturing hold points and inspectors’ visits. 8.1.7 The expected dates of testing shall be communicated at least 30 days in advance of testing and the actual dates confirmed as agreed. 8.1.8 The vendor shall give at least five working days advanced notification of a witnessed or observed inspection or test. [●] 8.1.9 If specified, witnessed mechanical and performance tests shall require a written notification of a successful preliminary test. The vendor and purchaser shall agree whether or not to maintain the machine test set-up or whether the machine can be removed from the test stand between the preliminary and witnessed tests. NOTE Some purchasers prefer to attend preliminary tests prior to witnessed tests, to understand any difficulties encountered during testing. [●] 8.1.10 If specified, when preliminary unwitnessed mechanical running or performance tests are performed, the data recorded and a description of any modifications to the equipment, instrumentation, or set-up shall be sent to the purchaser prior to the witnessed tests. 8.1.11 Equipment, materials and utilities for the specified inspections and tests shall be provided by the vendor. 8.1.12 The purchaser’s representative shall have access to the vendor’s quality program for review and all major sub-vendors. 8.2 Inspection 8.2.1 General 8.2.1.1 The vendor shall keep the following data available for at least 20 years: a) necessary certification of materials, such as certified material test reports; b) test data to verify that the requirements of the specification have been met; c) fully identified records of all heat treatment whether performed in the normal course of manufacture or as part of a repair procedure; d) results of quality control tests and inspections; e) details of all repairs; f) final assembly maintenance and running clearances; [●] g) other data specified by the purchaser or required by applicable codes and regulations. (Referenced paragraph 5.2.) 8.2.1.2 Pressure-containing parts shall not be painted until the specified inspection of the parts is completed. [●] 8.2.1.3 In addition to the requirements of 6.10 and the ASTM material specifications, the purchaser may identify the following: a) parts that shall be subjected to surface and subsurface examination; b) type of examination required, such as magnetic particle, liquid penetrant, radiographic, and ultrasonic examination. 62 API Standard 681 8.2.2 Material Inspection 8.2.2.1 If radiographic, ultrasonic, magnetic particle or liquid penetrant inspection of welds or materials is required or specified, the standard practices in 8.2.2.2 through 8.2.2.5 shall apply. 8.2.2.1.1 Cast and nodular iron (non-pressure retaining) shall be inspected only in accordance with 8.2.2.4 or 8.2.2.5, or both. 8.2.2.1.2 Welds, cast steel, and wrought material shall be inspected in accordance with 8.2.2.2 through 8.2.2.5. 8.2.2.1.3 Non-Destructive Examination (NDE) shall be performed as required by the material specification. If additional radiographic, ultrasonic, magnetic particle or liquid penetrant examination of the welds or materials is specified by the purchaser, the methods and acceptance criteria shall be in accordance with the standards shown in Table 9. The welding and material inspection datasheet in Annex A may be used for this purpose. Table 9—Materials Inspection Standards Type of Inspection Acceptance Criteria Methods For Fabrications For Castings Visual inspection ASME BPVC Section V, Article 9 Material specification and manufacturer’s standard procedures MSS SP-55 Radiography ASME BPVC Section V, Articles 2 and 22 ASME BPVC Section VIII, Division 1, UW-51 (for 100 % radiography) and UW-52 (for spot radiography) ASME BPVC Section VIII, Division 1, Appendix 7 Ultrasonic inspection ASME BPVC Section V, Articles 5 and 23 ASME BPVC Section VIII, Division 1, Appendix 12 ASME BPVC Section VIII, Division 1, Appendix 7 Magnetic particle inspection ASME BPVC Section V, Articles 7 and 25 ASME BPVC Section VIII, Division 1, Appendix 6 ASME BPVC Section VIII, Division 1, Appendix 7 Liquid penetrant inspection ASME BPVC Section V, Articles 6, and 24 ASME BPVC Section VIII, Division 1, Appendix 8 ASME BPVC Section VIII, Division 1, Appendix 7 8.2.2.1.4 Alternative standards may be proposed by the vendor or specified by the purchaser, and they shall be agreed to by both purchaser and vendor. 8.2.2.1.5 The purchaser shall be notified before making a major repair to a pressure containing part. Major repairs, for the purpose of purchaser notification only, is any defect to be repaired in the vendor’s shop that equals or exceeds any of the three criteria defined below: 1) the depth of the cavity prepared for repair welding exceeds 50 % of the component wall thickness; 2) the length of the cavity prepared for repair welding is longer than 150 mm (6 in.) in any direction; 3) the total area of all repairs to the part under repair exceeds 10 % of the surface area of the part. 8.2.2.1.6 Plate used in fabrications shall be inspected prior to starting fabrication in accordance with the material standard to which the plate was purchased. 8.2.2.2 Radiography Radiography shall be in accordance with ASTM E94. 8.2.2.3 Ultrasonic Inspection 8.2.2.3.1 Ultrasonic inspection shall be in accordance with Section V, Articles 5 and 23 of the ASME BPVC. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 63 8.2.2.3.2 Ultrasonic inspection shall be based upon the procedures ASTM A609 (castings), ASTM A388 (forgings), or ASTM A578 (plate). 8.2.2.4 Magnetic Particle Inspection 8.2.2.4.1 Both wet and dry methods of magnetic particle inspection shall be in accordance with ASTM E 709. 8.2.2.4.2 To prevent buildup of potential voltage in the equipment, all components shall be demagnetized to the free air gauss levels in Table 10 when measured with a calibrated Hall effect probe. NOTE The free air gauss level is measured while suspending the component from a non-conductive strap with no influence from stray magnetic field. Table 10—Maximum Allowable Free Air Gauss Levels Gauss Level Component ±2 Gauss Bearing and seal assemblies including all components ±4 Gauss Casing and all stationary components except bearing and seal assemblies ±2 Gauss Shaft and all rotating Components 8.2.2.5 Liquid Penetrant Inspection Liquid penetrant inspection shall be based upon the procedures of ASTM E 165 and ASTM E 1417. 8.2.3 Mechanical Inspection 8.2.3.1 During assembly of the system and before testing, each component (including cast-in passages of these components) and all piping and appurtenances shall be cleaned chemically or by another appropriate method to remove foreign materials, corrosion products, and mill scale. [●] 8.2.3.2 If specified, the purchaser may inspect for cleanliness the equipment and all piping and appurtenances furnished by or through the vendor before heads are welded to vessels, openings in vessel or exchangers are closed, or piping is finally assembled. [●] 8.2.3.3 If specified, the hardness of parts, welds, and heat-affected zones shall be verified as being within the allowable values by testing of the parts, welds, or heat-affected zones. The method, extent, documentation, and witnessing of the testing shall be agreed upon by the purchaser and the vendor. 8.3 Testing 8.3.1 General 8.3.1.1 Equipment shall be tested in accordance with 8.3.2 and 8.3.3. Other tests that may be specified by the purchaser are described in 8.3.4 and 8.3.5. [●] 8.3.1.2 If specified, at least six weeks before the first scheduled running test, the vendor shall submit to the purchaser, for their review and comment, detailed procedures for the mechanical running test and all specified running optional tests, including acceptance criteria for all monitored parameters. 64 API Standard 681 8.3.2 Hydrostatic Test 8.3.2.1 Pressure-containing parts (including auxiliaries) shall be tested hydrostatically with liquid at a minimum of 1.5 times the maximum allowable working pressure but not less than 150 kPa [1.5 bar (20 psi)]. The test liquid shall be at a higher temperature than the nil-ductility transition temperature of the material being tested. NOTE The nil-ductility temperature is the highest temperature at which a material experiences complete brittle fracture without appreciable plastic deformation. 8.3.2.2 If the part tested is to operate at a temperature at which the strength of a material is below the strength of that material at room temperature, the hydrostatic test pressure shall be multiplied by a factor obtained by dividing the allowable working stress for the material at room temperature by that at operating temperature. 8.3.2.2.1 Allowable stress values used shall conform to those given in ASME B31.3 for piping or in 6.2.1.1 for casings. 8.3.2.2.2 The pressure obtained shall be the minimum pressure at which the hydrostatic test shall be performed. 8.3.2.2.3 Vendor shall advise the actual hydrostatic test pressures used. NOTE Applicability of this requirement to the material being tested should be verified before hydrostatic test, as the properties of many grades of steel do not change appreciably at temperatures up to 200 °C (400 °F). 8.3.2.3 Where applicable, tests shall be in accordance with the code or standard to which the part has been designed. In the event that a discrepancy exists between the code test pressure and the test pressure in this standard, the higher pressure shall govern. 8.3.2.4 The chloride content of liquids used to test austenitic stainless steel materials shall not exceed 50 parts per million. To prevent deposition of chlorides as a result of evaporative drying, all residual liquid shall be removed, and tested parts shall be dried at the conclusion of the test. NOTE Chloride content and its concentration is limited to prevent chloride stress corrosion cracking. 8.3.2.5 Tests shall be maintained for a sufficient period of time to permit complete examination of parts under pressure. 8.3.2.5.1 The hydrostatic test shall be considered satisfactory when neither leaks nor seepage through the pressure containing parts or joints is observed for a minimum of 30 minutes. 8.3.2.5.2 Large, heavy pressure containing parts or complex systems may require a longer testing period to be agreed upon by the purchaser and the vendor. 8.3.2.5.3 Seepage past internal closures required for testing of segmented cases and operation of a test pump to maintain pressure is acceptable. 8.3.2.5.4 Gaskets used during hydrostatic test of an assembled casing shall be of the same design as supplied with the casing. 8.3.2.5.5 Mechanical seals may be installed in the LRC/VP during the hydrostatic test if the mechanical seals are suitable to withstand the hydrostatic test pressure. 8.3.2.6 Where testing of sections of a casing at different pressures is approved, each section shall be tested independently at the appropriate pressure. In addition, a combined test shall be conducted with the appropriate pressures applied simultaneously in each section. NOTE If approved, depending upon LRC/VP type, areas, or regions of the LRC/VP subject to suction pressure can be hydro tested at a lower pressure than regions subject to discharge pressure. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 65 8.3.3 Mechanical Running Test 8.3.3.1 The requirements of 8.3.3.1.1 through 8.3.3.1.4 shall be met before the mechanical running test is performed. 8.3.3.1.1 All oil pressures, viscosities and temperatures shall be within the range of operating values recommended in the vendor’s operating instructions for the specific unit being tested. 8.3.3.1.2 Bearings intended to be lubricated by an oil mist systems shall be pre-lubricated. 8.3.3.1.3 All joints and connections shall be checked for tightness, and any leaks shall be corrected. 8.3.3.1.4 All warning, protective, and control devices used during the test shall be checked and adjusted as required. 8.3.3.2 The contract shaft seals and bearings shall be used in the machine for the mechanical running test. 8.3.3.3 Shop coupling may be used when testing with shop motors. 8.3.3.4 All purchased vibration probes, transducers, and accelerometers shall be in use during the test. If vibration probes are not furnished by the equipment vendor or if the purchased probes are not compatible with shop readout facilities, then shop probes and readouts that meet the accuracy requirements of API Standard 670 shall be used. 8.3.3.4.1 Shop test facilities shall include instrumentation with the capability of continuously monitoring and plotting revolutions per minute, and vibration spectra. 8.3.3.4.2 The vibration characteristics determined by the use of the instrumentation specified in 8.3.3.4 shall serve as the basis for acceptance or rejection of the machine. 8.3.3.4.3 Vibration data shall be recorded in horizontal and vertical directions, at radial planes transverse to each bearing centerline and also in the axial direction as shown in Figure 5. 8.3.3.5 All instrumentation used for the tests shall have valid calibration at the time of the test. 8.3.3.6 The mechanical running test of the equipment shall be conducted as specified in 8.3.3.6.1 through 8.3.3.6.4. 8.3.3.6.1 The mechanical running test shall verify that the operating speed range is free of critical speeds. 8.3.3.6.2 A mechanical run test may be performed either before or following the performance test. 8.3.3.6.3 The mechanical run test shall be one hour or until bearing temperatures have stabilized; that is, when temperature rise relative to ambient temperature is not more than 2 °F (1 °C) over a 10 minute period. Correct operation of the control system shall be demonstrated, when applicable. [●] a) b) If specified, the LRC/VP shall be mechanically run for four hours. This test shall be performed at the rated flow. Mechanical run test shall be conducted with ring liquid present. NOTE The mechanical run test is typically done at either the normal point or rated point for the equipment, as agreed by the vendor and purchaser. 8.3.3.6.4 In the case of adjustable speed units, the test program shall be agreed upon by the purchaser and the vendor, and it shall include a period of operation at maximum continuous speed. 66 API Standard 681 8.3.3.7 The requirements of 8.3.3.7.1 to 8.3.3.7.3 shall be met during the mechanical running test. 8.3.3.7.1 The measured unfiltered vibration shall not exceed the limits of 6.8.2.1 and shall be recorded throughout the operating speed range. NOTE Typically, the instrumentation is verified for proper operation before and after the mechanical running test. 8.3.3.7.2 While the equipment is operating at maximum continuous speed, and at any other speeds or load, or both, that may have been specified in the test agenda, vibration data shall be acquired to determine amplitudes at frequencies other than synchronous. 8.3.3.7.2.1 As a minimum, this data shall cover a frequency range from 10 Hz to 1000 Hz. Equipment operating at shaft speeds from 750 rpm down to 300 rpm should be monitored in a frequency range from 5 Hz to 250 Hz. 8.3.3.7.2.2 If the amplitude of any discrete, nonsynchronous vibration exceeds 20 percent of the allowable vibration as defined in 6.8.2.1 the purchaser and the vendor shall agree on requirements for further investigation which may include additional testing and on the equipment’s acceptability. [●] 8.3.3.7.3 If specified, all real-time vibration data as agreed by the purchaser and vendor shall be recorded and a copy provided to the purchaser. 8.3.3.8 If replacement or modification of bearings or seals or dismantling of the case to replace or modify other parts or assembly is required to correct mechanical or performance deficiencies, the initial test will not be acceptable, and the final shop tests shall be run after these deficiencies are corrected. 8.3.3.9 When spare rotors are ordered, each spare rotor shall be manufactured and balanced, in accordance with the requirements of this standard. [●] 8.3.3.10 If specified, spare rotors shall be given a mechanical run test or performance test, or both. 8.3.3.11 The purchaser shall advise additional testing requirements for spare parts. 8.3.4 Gas Leak Test 8.3.4.1 Each completely assembled LRC/VP casing shall be tested as specified in 8.3.4.2. 8.3.4.2 The casing (with the end seals installed) shall be pressurized to the rated discharge pressure, or in the case of vacuum pumps to 1 bar (15 psi), held at this pressure for a minimum of 30 minutes, and subjected to a soap-bubble test or another approved test to check for gas leaks. 8.3.5 Performance Test 8.3.5.1 LRC/VP shall be tested in accordance with HEI Performance Standards for Liquid Ring Vacuum Pumps. PNEUROP 6612 may be used for a testing standard if agreed. [●] 8.3.5.2 The LRC/VP shall be performance tested together with its ring liquid system. The extent of the test, and the applicable test methods, shall be agreed. 8.3.5.3 The machine shall be tested on air and water. 8.3.5.4 For vacuum pumps, test data shall be recorded at one speed at five suction pressures varying from atmospheric pressures to maximum vacuum. 8.3.5.4.1 For compressors, test data shall be recorded at one speed from minimum discharge pressure to maximum discharge pressure. 8.3.5.4.2 The points are subject to negotiation between purchaser and vendor. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 67 8.3.5.5 The dry air and water performance shall be within the tolerances given in Table 11. Table 11—Performance Tolerances Variable Tolerance (%) Rated inlet volume flow –0 Rated power +4 Ring liquid flow rate ±10 8.3.5.6 Performance at the certified point shall be calculated from test data in accordance with the vendor’s standard procedures, or as otherwise specified. Where the test is to be performed under different conditions or with different fluids from those specified, the method of converting the test results to the specified conditions shall also be agreed upon (see Annex F). 8.3.5.7 If it is necessary to dismantle an LRC/VP for a correction, such as improvement of efficiency, the initial test will not be acceptable, and the final hydrostatic test, gas leak test, and performance test shall be repeated after the correction is made. 8.3.5.8 The performance test shall be conducted using only one contract rotor. 8.3.5.9 The vendor shall maintain a complete, detailed log of all final tests and shall prepare the required number of copies, including test curves and data, certified for correctness. All preliminary tests and mechanical checks shall be completed by the vendor before the purchaser’s witnessed performance test. 8.3.5.10 The requirements of 8.3.5.10.1 through 8.3.5.10.5 shall be met before the performance test is performed. 8.3.5.10.1 The contract shaft seals and bearings shall be used in the machine for the performance test. a) The vendor may propose substitute seals for reasons such as incompatibility of the job seals with the test fluid. b) Use of substitute seals requires purchaser approval. c) The acceptable level of leakage during testing shall be agreed upon by the purchaser and the vendor. 8.3.5.10.2 All lubricating-oil and liquid-sealant pressures, viscosities, and temperatures shall be within the range of operating values recommended in the vendor’s operating instructions for the specified unit being tested. 8.3.5.10.3 Bearings used in oil mist lubrication systems shall be pre-lubricated. 8.3.5.10.4 All joints and connections shall be checked for tightness, and any leaks shall be corrected. 8.3.5.10.5 All warning, protective, and control devices used during the test shall be checked, and adjustments shall be made as required. 8.3.6 Optional Tests If specified, the shop tests described in 8.3.6.1 through 8.3.6.7 shall be performed. Test details shall be agreed upon by the purchaser and the vendor. 8.3.6.1 Complete Unit Test Such components as LRC/VP, couplings, gears, drivers, and auxiliaries that make up a complete unit shall be tested together during the mechanical running test. If agreed by the Purchaser, the complete unit test may be performed in place of separate tests of individual components. 68 API Standard 681 8.3.6.2 Gear Test If an external gearbox is provided in the drive train, it shall be tested with the machine unit during the mechanical running test. 8.3.6.3 Helium Test 8.3.6.3.1 Pressure containing parts, such as casings, shall be tested for gas leakage with helium at the maximum allowable working pressure. 8.3.6.3.2 If the test is conducted with the casing submerged in water, the water shall be at a higher temperature than the nil ductility transition temperature for the material of which the part is made. 8.3.6.3.3 The maximum allowable working pressure shall be maintained for a minimum of 30 minutes, with no bubbles permitted. 8.3.6.3.4 As an alternative, a non-submerged soap-bubble test or other approved method to check for gas leakage may be performed if approved by the purchaser. NOTE A helium test can be appropriate when the molar mass of the gas to be handled is less than 12 or if the gas contains more than 0.1 mole percent hydrogen sulfide. 8.3.6.4 Sound-level Test The sound-level test shall be performed in accordance with ISO 3744 or another agreed standard. NOTE This test usually does not reflect field sound levels due to shop test environment. 8.3.6.5 Ring Stability Test For adjustable speed machines a test agreed to between the purchaser and the vendor shall be conducted to establish the operating limits of liquid ring stability. 8.3.6.6 Auxiliary Equipment Test Auxiliary equipment such as oil systems, gears and control systems shall be tested in the vendor’s shop. Details of the auxiliary equipment tests shall be developed jointly by the purchaser and the vendor. 8.3.6.7 Spare Parts Test Spare parts such as couplings, gears, diaphragms, bearings, and seals shall be tested. 8.4 [●] 8.4.1 Preparation for Shipment Equipment shall be suitably prepared for the type of shipment specified. 8.4.1.1 Blocked rotors shall be identified by means of corrosion-resistant tags attached with stainless steel wire. 8.4.1.2 The preparation shall make the equipment capable of withstanding six months of outdoor storage from the time of shipment, with no disassembly required before operation, except for inspection of bearings and seals. 8.4.1.3 If storage for a longer period is contemplated, the purchaser will consult with the vendor regarding the recommended procedures to be followed. 8.4.2 The equipment shall be prepared for shipment after all testing and inspection have been completed and the equipment has been released by the purchaser. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 69 8.4.3 Except for machined surfaces, all exterior surfaces that may corrode during shipment, storage, or in service, shall be given at least one coat of the manufacturer’s standard paint. The paint shall not contain lead or chromates. NOTE Austenitic stainless steels are typically not painted. 8.4.4 Exposed shafts and shaft couplings shall be wrapped with waterproof, moldable waxed cloth, or vaporphase-inhibitor paper. The seams shall be sealed with oil-proof adhesive tape. 8.4.5 Bearing assemblies shall be fully protected from the entry of moisture and dirt. 8.4.5.1 If vapor-phase-inhibitor crystals in bags are installed in large cavities to absorb moisture, the bags shall be attached in an accessible area for ease of removal. 8.4.5.2 Where applicable, bags shall be installed in wire cages attached to flanged covers, and bag locations shall be indicated by corrosion-resistant tags attached with stainless steel wire. 8.4.6 The interior of the equipment shall be clean; free from scale, welding spatter, and foreign objects; and sprayed or flushed with a suitable rust preventative that is water soluble or can be removed with solvent. The rust preventative shall be applied through all openings while the machine is slow-rolled. 8.4.7 Flanged openings shall be provided with metal closures at least 5 mm (3/16 in.) thick, with elastomer gaskets, and at least four full-diameter bolts. For studded openings, all nuts needed for the intended service shall be used to secure closures. 8.4.8 Threaded openings shall be provided with steel caps or round-head steel plugs. In no case shall nonmetallic (such as plastic) caps or plugs be used. NOTE These are shipping plugs; permanent plugs are covered in 6.3.14. 8.4.9 Openings that have been beveled for welding shall be provided with closures designed to prevent entrance of foreign materials and damage to the bevel. 8.4.10 If a spare rotor is purchased, it shall be prepared for unheated indoor storage for a period of at least three years. 8.4.10.1 The rotor shall be treated with a rust preventative and shall be housed in a vapor-barrier envelope with a slow-release volatile-corrosion inhibitor. [●] 8.4.10.2 The rotor shall be crated for domestic or export shipment, as specified. 8.4.10.3 A purchaser approved resilient material 3.0 mm (1/8 in.) thick [not tetrafluoroethylene (TFE) or polytetrafluoroethylene (PTFE)] shall be used between the rotor and the cradle at the support areas. 8.4.10.4 The rotor shall not be supported at journals. 8.4.11 Internal steel areas of bearing housings and carbon steel oil systems’ auxiliary equipment such as reservoirs, vessels, and piping shall be coated with suitable oil-soluble rust preventive. 8.4.12 Lifting points and lifting lugs shall be clearly identified on the equipment or equipment package. 8.4.12.1 The recommended lifting arrangement shall be as described in the installation manual. 8.4.12.2 The recommended lifting arrangement shall be identified on boxed equipment. 70 API Standard 681 8.4.13 The equipment shall be identified with item and serial numbers. Material shipped separately shall be identified with securely affixed, corrosion-resistant metal tags indicating the item and serial number of the equipment for which it is intended. 8.4.14 The vendor shall provide the purchaser with the instructions necessary to preserve the integrity of the storage preparation after the equipment arrives at the job site and before startup, as described API RP 686, Chapter 3, “Recommended Practices for Machinery Installation and Installation Design”. 8.4.15 Auxiliary piping connections furnished on the purchased equipment shall be impression stamped or permanently tagged to agree with the vendor’s connection table or general arrangement drawing. Service and connection designations shall be indicated. 8.4.16 The fit-up and assembly of machine-mounted piping, intercoolers etc. shall be completed in the vendor’s shop prior to shipment. 8.4.17 Wood used in export shipping shall comply with the requirements of ISPM Publication No.15 [2]. 8.4.18 Composition wood product such as Particleboard, Medium Density Fiberboard (MDF), and Oriented Strand Board (OSB) shall not be used. 8.4.19 Package Markings and Shipping Documentation [●] 8.4.19.1 All markings shall be in English and other specified language. 8.4.19.2 Package markings shall be stenciled on two opposite sides of the shipping unit. A shipping unit may be a box, carton, bundle, crate, drum, loose self-supported piece of equipment etc. 8.4.19.3 Lettering shall be between 76 mm to 125 mm (3 in. to 5 in.) high in weatherproof black ink to ensure visibility. 8.4.19.4 Shipping packages that cannot be stenciled directly shall have attached corrosion resistant metal tags with raised markings. 8.4.19.5 Shipping packages shall be marked with industry standard cautionary symbols indicating center of gravity, sling or lifting points, top heavy packages, fragile and liquid contents, moisture sensitive contents etc. per ASTM D5445-05, Standard Practice for Pictorial Markings for Handling of Goods. 8.4.19.6 Package markings shall include: a) purchaser’s purchase order number and tag number b) shipping unit piece number c) gross weight d) dimensions e) purchaser’s project name 8.4.19.7 Packaged equipment shall be shipped with duplicate packing lists—one inside and the other on the outside of the shipping container. Also, a paper copy of package markings shall be inside each container. 8.4.19.8 One copy of the manufacturer’s installation instructions shall be packed and shipped with the equipment. 8.4.19.9 Equipment or materials that contain or are coated with chemical substances shall be prominently tagged at openings to indicate the nature of contents and precautions for shipping, storage, and handling. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 71 NOTE Some examples include oils, corrosion inhibitors, antifreeze solutions, desiccants, hydrocarbon substances, and unused paint. 8.4.19.9.1 Substances that are supplied with the shipment shall have a Safety Data Sheet (SDS). 8.4.19.9.2 If a substance is exempt from regulation, a statement to that effect shall be included. 8.4.19.9.3 At least two weeks before shipment, SDSs shall be forwarded to the receiving facility, to allow planning for handling of any regulated substances. 8.4.19.9.4 SDSs in protective envelopes shall be affixed to the outside of the shipping package. 9 Vendor’s Data 9.1 The purchaser may specify the content of proposals, meeting frequency and vendor data content/format identified in Annex B. Annex B provides a general outline of information that potentially may be requested by the purchaser. [●] 9.2 If specified, the information specified in Annex B shall be provided. Annex A (informative) Data Sheets 72 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 73 74 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 75 76 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 77 78 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 79 80 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 81 82 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 83 84 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 85 86 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 87 88 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 89 90 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 91 92 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 93 94 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 95 96 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 97 Annex B (informative) Contract Documents and Engineering Design Data B.1 Introduction When specified by the purchaser in 9.2, the contract documents and engineering design data shall be supplied by the vendor, as listed in this annex. B.1.1 The following data shall be identified with the following information on transmittal (cover) letters, title pages, and correspondence: a) purchaser/owner corporate name; b) job/project number; c) equipment item number and service name; d) inquiry or purchase order number; e) any other identification specified in the inquiry or purchase order; f) vendor identifying proposal number, shop order number, serial number, or other reference required to completely identify return correspondence. B.1.2 Each drawing shall have a title block in the lower right-hand corner with the date of certification, identification data specified in B.1.1, revision number and date and title. Similar information shall be provided on all other documents including subvendor items. B.2 B.2.1 Proposals General B.2.1.1 The vendor shall forward the original proposal, with the specified number of copies, to the addressee specified in the inquiry documents. B.2.1.2 The proposal shall include, as a minimum, the data specified in B.2.2 through B.2.5, and a specific statement that the equipment and all its components and auxiliaries are in strict accordance with this standard. B.2.1.3 If the equipment or any of its components or auxiliaries is not in strict accordance, the vendor shall include a list that details and explains each deviation. B.2.1.4 The vendor shall provide sufficient detail to enable the purchaser to evaluate any proposed alternative designs. B.2.1.5 All correspondence shall be clearly identified in accordance with B.1.2. 98 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services B.2.2 99 Drawings B.2.2.1 The drawings indicated on the Vendor Drawing and Data Requirements (VDDR) form in this annex shall be included in the proposal. As a minimum, the following shall be included: a) a general arrangement or outline drawing for each machine train or skid-mounted package, showing overall dimensions, maintenance clearance dimensions, overall weights, erection weights, and the largest maintenance weight for each item. The direction of rotation and the size and location of major purchaser connections shall also be indicated; b) cross-sectional drawings showing the details of the proposed equipment; c) schematics of all auxiliary systems including fuel, lube oil, control, and electrical systems; d) bills of material; e) sketches that show methods of lifting the assembled machine or machines, packages, and major components and auxiliaries. (This information may be included on the drawings specified in item a above.) B.2.2.2 If “typical” drawings, schematic, and bills of material are used, they shall be marked up to show the weight and dimension data to reflect the actual equipment and scope proposed. B.2.3 Technical Data for Proposal B.2.3.1 All technical data shall be given in units of measurement according to the purchase order. If needed, the technical data in alternate units can be included in parentheses. B.2.3.2 The following data shall be included in the proposal. a) purchaser’s data sheets with complete vendor’s information entered thereon and literature to fully describe details of the offering; b) predicted noise data (6.1.8); c) VDDR form (or equivalent listing) indicating the schedule according to which the vendor agrees to transmit all the data specified; d) schedule for shipment of the equipment, in weeks after receipt of an order; e) list of major wearing components, showing any interchangeability with the owner’s existing machines; f) list of spare parts recommended for start-up and normal maintenance purposes; g) list of the special tools furnished for maintenance; h) description of any special weather protection and winterization required for start-up, operation, and periods of idleness, under the site conditions specified on the data sheets. This description shall clearly indicate the protection to be furnished by the purchaser as well as that included in the vendor’s scope of supply; i) complete tabulation of utility requirements, e.g. steam, water, electricity, air, gas, lube oil (including the quantity and supply pressure of the oil required, and the heat load to be removed by the oil), and the nameplate power rating and operating power requirements of auxiliary drivers. Approximate data shall be clearly indicated as such; j) description of any optional or additional tests and inspection procedures for materials as required by 6.10.1.6; 100 API Standard 681 k) description of any special requirements, whether specified in the purchaser’s inquiry or as outlined in this standard; l) a list of machines, similar to the proposed machine(s), that have been installed and operating under conditions analogous to those specified in the inquiry; m) any start-up, shutdown, or operating restrictions required to protect the integrity of the equipment; n) a list of any components that can be construed as being of alternative design, hence requiring purchaser’s acceptance; o) component designed for a finite life (6.1.1.5). B.2.4 Curves The vendor shall provide complete performance curves to encompass the map of operations, with any limitations indicated thereon. Curves shall be based on dry air at 20 °C (68 °F) with water at 15 °C (60 °F) as the ring liquid. B.2.5 Optional Tests The vendor shall furnish an outline of the procedures to be used for each of the special or optional tests that have been specified by the purchaser or proposed by the vendor. B.3 B.3.1 Engineering Design Data General B.3.1.1 Engineering data shall be furnished by the vendor in accordance with the agreed VDDR form. NOTE Typical VDDR form can be modified by the purchaser to match the specific inquiry requirements. B.3.1.2 The purchaser shall review the vendor’s data upon receipt; however, this review shall not constitute permission to deviate from any requirements in the order unless specifically agreed in writing. After the data have been reviewed and accepted, the vendor shall furnish certified copies in the quantities specified. B.3.1.3 A complete list of vendor data shall be included with the first issue of major drawings. This list shall contain titles, drawing numbers, and a schedule for transmittal of each item listed. This list shall cross-reference data with respect to the VDDR form. B.3.2 Drawings and Technical Data The drawings and data furnished by the vendor shall contain sufficient information so that together with the manuals specified in B.3.5, the purchaser can properly install, operate, and maintain the equipment covered by the purchase order. All contract drawings and data shall be clearly legible (8-point minimum font size even if reduced from a larger size drawing), shall cover the scope of the agreed VDDR form, and shall satisfy the applicable detailed descriptions in this annex. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services B.3.3 101 Progress Reports The vendor shall submit progress reports to the purchaser at intervals specified which shall, as a minimum, include the following: a) overall progress summary, b) status of engineering, c) status of document submittals, d) status of major suborders, e) updated production schedule, f) inspection/testing highlights for the month, g) any pending issues. B.3.4 Parts Lists and Recommended Spares B.3.4.1 The vendor shall submit complete parts lists for all equipment and accessories supplied. B.3.4.2 These lists shall include part names, manufacturers’ unique part numbers and materials of construction (identified by applicable international standards). B.3.4.3 Each part shall be completely identified and shown on appropriate cross-sectional, assembly-type cutaway or exploded-view isometric drawings. B.3.4.4 Interchangeable parts shall be identified as such. B.3.4.5 Parts that have been modified from standard dimensions or finish to satisfy specific performance requirements shall be uniquely identified by part number. B.3.4.6 The vendor shall indicate on each of these complete parts lists all those parts that are recommended as start-up or maintenance spares, and the recommended stocking quantities of each. These shall include spare parts recommendations of subvendors that were not available for inclusion in the vendor’s original proposal. B.3.5 B.3.5.1 Installation, Operation, Maintenance, and Technical Data Manuals General The vendor shall provide sufficient written instructions and all necessary drawings to enable the purchaser to install, operate, and maintain all of the equipment covered by the purchase order. This information shall be compiled in a manual or manuals with a cover sheet showing the information listed in B.1.2, an index sheet, and a complete list of the enclosed drawings by title and drawing number. The manual pages and drawings shall be numbered. The manual or manuals shall be prepared specifically for the equipment covered by the purchase order. “Typical” manuals are unacceptable. B.3.5.1.1 A draft manual(s) shall be issued to purchaser 8 weeks prior to mechanical testing for review and comment. 102 API Standard 681 B.3.5.1.2 Refer to the VDDR form for number of copies. Hard copies as well as electronic copies shall be provided as described on the VDDR form. B.3.5.2 Installation Manual B.3.5.2.1 All information required for the proper installation of the equipment shall be compiled in a manual that shall be issued no later than the time of issue of final certified drawings. For this reason, it may be separate from the operating and maintenance instructions. B.3.5.2.2 This manual shall contain information on alignment and grouting procedures, normal and maximum utility requirements, centers of mass, rigging provisions and procedures, and all other installation data. B.3.5.2.3 All drawings and data specified in B.2.2 and B.2.3 that are pertinent to proper installation shall be included as part of this manual. B.3.5.2.4 One extra manual, over and above the specified quantity, shall be included with the first equipment shipped. B.3.5.2.5 All recommended receiving and storage procedures shall be included. NOTE B.3.5.3 Refer to API 686 for data required for installation. Operating and Maintenance Manual A manual containing all required operating and maintenance instructions shall be supplied at shipment. In addition to covering operation at all specified process conditions, this manual shall also contain separate sections covering operation under any specified extreme environmental conditions. Bolt torque values shall be identified as dry or with lubricant. B.3.5.4 Technical Data Manual The vendor shall provide the purchaser with a technical data manual at shipment. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services B.4 VDDR for Liquid Ring Compressors and Vacuum Pumps 103 104 API Standard 681 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 105 106 API Standard 681 B.5 Descriptions B.5.1 1) 2) Liquid Ring Vacuum Pump and Compressor Certified dimensional outline drawing and list of connections, including the following: a) Size, rating, and location of all customer connections; b) Approximate overall handling weights; c) Overall dimensions; d) Shaft centerline height; e) Dimensions of baseplates (if furnished), complete with diameter, number, and locations of bolt holes and thickness of the metal through which the bolts should pass; centers of gravity; and details for foundation design; f) Grouting details; g) Forces and moments for suction and discharge nozzles; h) Center of gravity and lifting points; i) Shaft end separation and alignment data; j) Direction of rotation. Cross-sectional drawings and bill of materials, including the following: Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services a) Journal-bearing shaft and housing fits and tolerances; b) Rolling element bearing shaft and housing fits and tolerances; c) Shaft end details, fits and tolerances. 107 3) Shaft seal drawing and bill of materials. 4) Shaft coupling assembly drawing and bill of materials, including allowable misalignment tolerances and the style of the coupling guard. Coupling alignment diagram, including recommended coupling limits during operation. Note all shaft-end position changes and support growth from a reference ambient temperature of 15 °C (59 °F) or another temperature specified by the purchaser. Include the recommended alignment method and cold setting targets. 5) Ring liquid schematic and bill of material including following: a) ring liquid flowrates, temperatures, and pressures at each use point, b) control, alarm, shutdown, and trip settings (pressure and recommended temperatures), c) utility requirements, including electricity, water, nitrogen, and air, d) pipe, valve, and orifice sizes, e) instrumentation, safety devices, control schemes, and wiring diagrams. 6) Cooling or heating schematic and bill of materials, including cooling or heating media, fluid flows, pressure, pipe and valve sizes, instrumentation, and orifice sizes. 7) Rotor assembly drawings and bill of materials. 8) Ring liquid system component drawing and bill of materials. 9) Primary and auxiliary sealing schematic and bill of materials, including seal fluid, liquid flows, pressure, pipe and valve sizes, instrumentation, and orifice sizes. 10) Electrical and instrumentation schematics, wiring diagrams and bill of materials, including the following: a) Vibration alarm and shutdown limits b) Bearing temperature alarm and shutdown limits, c) Lubricating oil temperature alarm and shutdown limits d) Driver 11) Electrical and instrumentation arrangement drawing and list of connections. 12) Performance curves; including capacity and brake horsepower versus pressure for all operating conditions specified on the data sheets. 13) Breakaway torque (sealless only). 14) Temp-pressure profile (sealless only). 15) Lateral critical speed analysis including unbalanced response analysis: the required number of lateral critical analysis reports, no later than 3 months after the date of order. 108 API Standard 681 16) Torsional critical speed analysis: the required number of torsional critical analysis reports, no later than three months after the date of order (refer to 6.8.1.9). 17) Certified hydrostatic test data. 18) Material Certification 19) Progress Report, including details of progress and cause of any possible delay: the reports shall include engineering, purchasing, manufacturing, and testing schedules for all major components. Planned and actual dates, and the percentage completed, shall be indicated for each milestone in the schedule. 20) Weld procedures for fabrication and repair. 21) Non-destructive test procedure as itemized on the purchase order datasheets or the VDDR form. 22) Performance test data: certified shop logs of the performance test, record of shop test data (which the vendor shall maintain for at least 20 years after the date of shipment); the vendor shall submit certified copies of the test data to the purchaser before shipment. 23) Certified rotor balance data. 24) Data sheets applicable to proposals, purchase, and as-built. 25) Noise data sheets. 26) As-built clearances. 27) Installation, operation, and maintenance manuals, describing installation, operation, and maintenance procedures; each manual shall include the following sections: a) Section One—Installation: i) storage ii) foundation iii) grouting iv) setting equipment v) alignment vi) piping recommendation vii) composite outline drawing for pump/driver train, including anchor-bolt locations viii) dismantling clearances b) Section Two—Operation: i) start-up, including tests and checks before start-up ii) Normal stop and emergency trip iii) routine operational procedures iv) lubricating oil recommendations Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services c) 109 Section Three—Disassembly and assembly: i) rotor in pump casing, ii) journal bearings, iii) thrust bearings (including clearance and preload on rolling element bearings), iv) seals, v) thrust collars, if applicable vi) allowable wear of running clearances vii) fits and clearances for rebuilding viii) routine maintenance procedures and intervals d) Section Four—Performance curves; including capacity and brake horsepower versus pressure for all operating conditions specified on the data sheets e) Section Five—Vibration data: i) vibration analysis data ii) lateral critical speed analysis iii) torsional critical speed analysis f) Section Six—As-built data: i) as-built data sheets ii) as-built clearances iii) rotor balance data for multi-stage pumps iv) noise data sheets v) performance data vi) Hydrotest and Mechanical running test logs g) Section Seven—Drawing and data requirements: i) certified dimensional outline drawing and list of connections ii) cross-sectional drawing and bill of materials iii) rotor assembly and shaft seal drawing and bill of materials iv) lubricating oil arrangement drawing and list of connections v) lubricating oil component drawings and data, and bills of materials vi) electrical and instrumentation schematics, wiring diagrams and bills of materials 110 API Standard 681 vii) electrical and instrumentation arrangement drawing and list of connections viii) coupling assembly drawing and bill of materials ix) primary and auxiliary seal schematic and bill of materials x) primary and auxiliary seal piping, instrumentation, arrangement, and list of connections xi) cooling and heating schematic and bill of materials xii) cooling or heating piping, instrumentation arrangement and list of connections 28) List of recommended spare parts for start-up and normal maintenance including price list; 29) List of maintenance special tools. 30) Safety data sheet. 31) Allowable flange loading, including allowable forces and moments on the process tie-in points as well as the flanges displacements. 32) Relief valve calculation for various relief cases applicable to the relief valve to determine the sizing of the relief device. Calculation of relief valve sizing requires information with regard to pressure drop of the relief lateral (downstream piping). It shall be agreed between the vendor and purchaser to specify which party is responsible for lateral (downstream piping) calculations. 33) Utility list, including complete list of utility consumption including but not limited to required AC/DC electrical consumption, cooling water, nitrogen, instrument air, etc. 34) Shipping List: List of shipped items including weight, dimensions and quantities of all items which are shipped separately including a complete list of ship loose items. 35) Preservation, packaging, and shipping procedures. B.5.2 Driver 36) Certified dimensional outline drawing for motor and all auxiliary equipment, including the following: a) Size and location of main and auxiliary terminal box, conduit, instrumentation, and any piping or ducting; b) ASME rating and facing for any flanged connections; c) Size and location of anchor bolt holes and thicknesses of sections through which bolts should pass; d) Total mass of each item of equipment (motor and auxiliary equipment), heaviest mass, and name of the part; e) Overall dimensions and all horizontal and vertical clearances necessary for dismantling, and the approximate location of lifting lugs; f) Shaft centerline height; g) Shaft end dimensions, plus tolerances for the coupling; h) Direction of rotation. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 111 37) Cross-sectional drawing and bill of materials, including the axial rotor float. 38) Datasheets applicable to proposal, purchase, and as-built. 39) Performance data including the following: 1) 2) For induction motors 150 kW (200 hp) and smaller: i) efficiency and power factor at one-half, three-quarter, and full load, ii) speed-torque curves; For induction motors larger than 150 kW (200 hp) and larger, certified test reports for all test run and performance curves as follows: i) time-current heating curve, ii) speed-torque curves at 70 %, 80 %, 90 % and 100 % of rated voltage, iii) efficiency and power factor curves from 0 to rated service factor, iv) current versus load curves from 0 to rated service factor, v) current versus speed curves from 0 to 100 % of rated speed; 40) Certified drawings of auxiliary systems, including wiring diagrams, for each auxiliary system supplied. The drawings shall clearly indicate the extent of the system to be supplied by the manufacturer and the extent to be supplied by others. 41) Installation, operation, and maintenance manuals describing installation, operating and maintenance procedures. Each manual shall include the following sections: a) Section One—Installation: i) Storage; ii) Setting motor, rigging procedures, component masses and lifting diagram; iii) Piping and conduit recommendations; iv) Composite outline drawing for motor, including locations of anchor-bolt holes; v) b) Dismantling clearances. Section Two—Operation: i) Start-up, including check before start-up; ii) Normal shutdown; iii) Operating limits, including number of successive starts; iv) Lubricating oil recommendations. c) Section Three—Disassembly and assembly instructions: i) Rotor in driver, 112 API Standard 681 ii) Journal bearings, iii) Seals, iv) Routine maintenance procedures and intervals. d) Section Four—Performance data required. e) Section Five—Datasheets: f) i) As-built datasheets, ii) Noise datasheets. Section Six—Drawing and data requirements: i) Certified dimensional outline drawing for motor and all auxiliary equipment, with list of connections; ii) Cross-sectional drawing and bill of materials; iii) Spare parts recommendations and price list; iv) Safety Data Sheets. 42) List of recommended spare parts for commissioning and normal maintenance B.5.3 Gear 43) Gear certified dimensional outline drawing and list of connections, including the following: a) ASME rating and facing for any flanged connections; b) Size and location of anchor bolt holes c) Total mass of gearbox d) Overall dimensions and all horizontal and vertical clearances necessary for dismantling, and the approximate location of lifting lugs; e) Shaft centerline height; f) Shaft end dimensions, plus tolerances for the coupling; g) Direction of rotation. h) Location of junction boxes (if installed on the gearbox) 44) Cross-sectional drawing and bill of materials 45) Gearbox data sheet for proposal, purchase and as-built 46) Mechanical run test data log 47) Gear instruction manuals describing installation, operating and maintenance procedures. Each manual shall include the following sections: Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services a) 113 Section One—Installation and start up: i) Storage; ii) Installation procedures, component masses, lifting diagram, and rigging procedure; iii) outline drawing for gear, including weights, locations of anchor-bolt holes; iv) Dismantling clearances. v) Start-up, including check before start-up; vi) Lubricating oil recommendations. b) Section Two—Disassembly and assembly instructions including routine maintenance procedures and intervals. i) Rotor in gear casing. ii) Journal bearings. iii) Thrust bearings (including clearance and preload on antifriction bearings). iv) Seals. v) Thrust collars, if applicable. vi) Allowable wear of running clearances. vii) Fits and clearances for rebuilding. viii) Routine maintenance procedures and intervals. c) Section Three—Drawing and data requirements: i) Certified dimensional outline drawing with list of connections; ii) Cross-sectional drawing and bill of materials; iii) Instrumentation arrangement and list of connections; iv) As-built data sheets. 48) List of spare parts for commissioning and normal maintenance. Annex C (informative) Liquid Ring Compressor and Vacuum Pump Nomenclature Figures C.1 through Figure C.5 illustrates nomenclature of key parts of a typical LRC/VP. Figure C.6 illustrates the typical operation of an LRC/VP. NOTE This annex does not cover all possible designs. Other designs can be available. Figure C.1—LRC/VP—Two Stage, Between Bearing, Plate Design 114 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services Figure C.2—LRC/VP—Single Stage, Between Bearing, Conical Design, Single Suction Figure C.3—LRC/VP—Single Stage, Between Bearing, Conical Design, Single Suction Figure C.4—LRC/VP—Single Stage, Overhung, Plate Design 115 116 API Standard 681 Figure C.5—Magnetic Drive LRC/VP—Single Stage, Between Bearing, Plate Design, Double Suction Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 117 Figure C.6—LRC/VP Typical Flow Paths C.1 C.1.1 LRC/VP Typical Operation The Liquid Ring Pumping Action A multi-bladed impeller is mounted eccentrically in a circular casing. When the casing is partially filled with liquid and the impeller is set into rotary motion, this causes the liquid ring to be formed as a result of centrifugal force. Due to the eccentricity, the inside contour of the liquid ring contacts the impeller, and the liquid creates a piston action within each set of impeller blades, causing flow into and out of the impeller blade cells. This flow occurs with each revolution of the impeller and results in a volumetric expansion in the section of the outflowing liquid ring, thus causing the medium to be drawn in via the inlet port in the guide plate connected to the suction nozzle. In the area of the inflowing liquid ring, the volume is reduced, thus causing the medium to be compressed. On completion of compression, the medium is discharged via the outlet port in the guide plate which is connected to the discharge nozzle. 118 C.1.2 API Standard 681 Rotor Imbalance As shown in Figure C.6, the liquid ring rotates at the same speed as the rotor but is offset from the axis of the rotor. If, for example, the rotor has 20 chambers, twenty liquid pistons complete an outward suction and an inward discharge stroke for each revolution of the rotor. The frequency of this imbalanced piston would be twenty times the rotational or equal to the vane passing frequency. Because of the large mass and higher frequency of the liquid piston, the rotor mass imbalance becomes a minor factor, and the liquid piston imbalance becomes a major factor in the vibration characteristics of the entire system. Annex D (normative) Materials and Material Specifications D.1 General Table D.1 lists material classes for the purchaser to select (see 6.10.1.4). Table D.2, Table D.3, and Table D.4 may be used for guidance regarding materials specifications. If these tables are used, it shall not be assumed that the material specifications are acceptable without taking full account of the service in which they will be applied. Table D.2 lists corresponding materials that may be considered acceptable. These materials represent family/type and grade only. The final required condition or hardness level (where appropriate) is not specified. These materials might not be interchangeable for all applications. Table D.1—Material Classes for LRC/VP Parts Material Classes and Abbreviations Material Class S-4 S-5 S-6 S-8 a S-9 a C-6 A-7 A-8 Full Compliance Material c STL STL STL STL STL 12 % CR AUS 316 AUS Super Duplex Trim Material STL STL 12 % CR 12 % CR 316 AUS Ni-Cu alloy 12 % CR AUS a 316 AUS Super Duplex Pressure Casing Yes Carbon Steel Carbon Steel Carbon Steel 12 % CR AUS 316 AUS Super Duplex Inner Case Parts No Carbon Steel 12 % CR 316 AUS Ni-Cu Alloy 12 % CR AUS 316 AUS Duplex Super Duplex Impeller Yes Carbon Steel 12 % CR 316 AUS Ni-Cu Alloy 12 % CR AUS 316 AUS Duplex Super Duplex Parts 119 D-1 b D-2 b 120 API Standard 681 Table D.1—Material Classes for LRC/VP Parts (Continued) Material Classes and Abbreviations Material Class S-4 S-5 S-6 S-8 a S-9 a C-6 A-7 A-8 Full Compliance Material c STL STL STL STL STL 12 % CR AUS 316 AUS Super Duplex Trim Material STL STL 12 % CR 12 % CR 316 AUS Ni-Cu alloy 12 % CR AUS a 316 AUS Super Duplex Pressure Casing Yes Carbon Steel Carbon Steel Carbon Steel 12 % CR AUS 316 AUS Super Duplex Shaft Yes Carbon Steel 4140 Alloy Steel 12 % CR 316 AUS Ni-Cu Alloy 12 % CR AUS 316 AUS Duplex Super Duplex Case and Gland Studs Yes 4140 Alloy Steel 4140 Alloy Steel 4140 Alloy Steel 4140 Alloy Steel Ni-Cu Alloy 4140 Alloy Steel 4140 Alloy Steel 4140 Alloy Steel Duplex Super Duplex No AUS spiral wound e or non- AUS, spiralwound Duplex SS spiralwound Parts Case Gasket Wetted Yes Carbon Steel AUS, spiralwound e or non316 AUS f AUS, AUS, spiralspiral- wound e or non316 AUS f 316 AUS f Ni-Cu alloy, spiralwound, PTFE filled e Ni-Cu Alloy Ni-Cu AUS, alloy, spiralspiral316 AUS f 316 AUS f e 316 AUS D-1 b e Duplex D-2 b Duplex SS spiralwound e Super Duplex The vendor shall consider the effects of differential material expansion between casing and rotor and confirm suitability if operating temperatures can exceed 95 °C (200 °F). b Some applications may require alloy grades higher than the Duplex materials given in Table D.2 “Super Duplex” material grades with pitting resistance equivalency (PRE) values greater than 40 can be necessary. PRE ≥40, where the PRE is based on actual chemical analysis. a PRE= wCr + 3, 3w + Mo + 16 wN , where w is the percentage mass fraction of the element indicated by the subscript. Note that alternative materials such as “super austenitic” may also be considered. c See 6.10.1.4. d Austenitic stainless steels include ISO Types 683-13-10/19 (AISI standard types 302, 303, 304, 316, 321, and 347). e If LRC/VPs with axially split casings are furnished, a sheet gasket suitable for the service is acceptable. Spiral-wound gaskets shall contain a filler material suitable for the service. Gaskets other than spiral-wound may be proposed and furnished if proven suitable for service and approved by the purchaser. f For applications where large differences of thermal expansion can result if austenitic stainless steel fasteners are used, alternative fastener materials, such as 12 % or 17 % Cr martensitic steel, with appropriate corrosion resistance, may be used. Table D.2—Material Specifications for LRC/VP Parts USA Material Class Cast Iron General Castings Europe ISO ASTM UNS a 185 Gr 300 A48/A48M Class 25/30/40 F11701/ F12101 Japan EN b Grade Material No. JIS EN 1561 ENGJL-250 ENGJL-300 JL1040 JL1050 G5501 FC 250/300 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 121 Table D.2—Material Specifications for LRC/VP Parts (Continued) USA Material Class Pressure Castings Carbon Steel 4140 Alloy Steel 12 % Chrome Steel Europe Japan ISO ASTM UNS a EN b Grade Material No. — — — — — 1.0619 — — JIS Other Castings/ Internal Parts — — — — — 1.0570 (Cast Steel) GGG40.3 (Nodular Iron) Wrought/ forgings 683-18C25 A266 Class 4 K03506 EN 10222-2 P280 GH 1.0426 G 3202, Cl SFVC 2A Bar Stock: Pressure 683-18C25 A696 Gr B4 G10200 EN 10273 P295 GH 1.0481 G 4051, Cl S25C Bar Stock: General 683-18C45e A576 Gr 1045 G10450 EN 10083-2 C45 1.0503 G 4051, Cl S45C Bolts and Studs 2604-2F31 A193/A193M Gr B7 G41400 EN 10269 42CrMo4 1.7225 G 4107, Class 2, SNB7 Nuts 683-1-C45 A194/A194M Gr 2H K04002 EN 10269 C35 E 1.1181 G 4051, Cl S45C Plate 9328-4, P 355 TN/ PL 355 TN A516/A516M K02403/ EN 10028-3 Gr 65/70 K02700 P355 N P355 NL1 1.0562 1.0566 G 3106, Gr SM400B Pipe 9329-2 PH26 A106/A106M Gr B L245 GA 1.0459 G 3456, Gr. STPT 370/410 K03006 EN 10208-1 — — — G 4051, Cl S25C G 3202, Cl SFVC 2A, SFVC2B EN 10083-1 42CrMo4 1.7225 G 4105, Cl SCM 440 G41400 EN 10269 42CrMo4 1.7225 G 4107, Class 2, SNB7 A194/A194M Gr 2H K04002 EN 10269 C45 E 1.1191 G 4051, Cl S45C — A487/A487M Gr CA6NM J91540 EN 10213 GX4 CrNi 13-4 1.4317 G 5121, C1 SCS 6, SCS 6X — A487/A487M Gr CA6NM J91540 EN 10213 GX 4 CrNi 13-4 1.4317 G 5121, CI SCS 6 SCS 6X Fittings — A105/A105M Bar stock — A434 Class BB A434 Class BC Bolts and Studs 2604-2F31 A193/A193M Gr B7 Nuts 683-1C45 Pressure Castings Impellers and Diffusers K03504 122 API Standard 681 Table D.2—Material Specifications for LRC/VP Parts (Continued) USA Material Class Japan ISO ASTM UNS a EN b Grade Material No. — A487/A487M Gr CA6NM J91540 EN 10213 GX 4 CrNi 13-4 1.4317 G 5121, CI SCS 6 SCS 6X — A743/A743M Gr CA6NM J91540 EN 10283 GX 4 CrNi 13-4 1.4317 G 5121, CI SCS 6, SCS 1X1 683-13-3 A182/A182M Gr F6a Cl 1 A182/A182M Gr F6 NM S41000 S41500 EN 10250-4 EN 10222-5 X12Cr13 X3CrNiMo 13-4-1 1.4006 1.4313 G 3214, Gr. SUS 410-A G 3214, Cl SUS F6 NM Wrought/ Forgings: General 683-13-2 A473 Type 410 S41000 EN 10088 X12Cr13 1.4006 G 3214, Gr. SUS 410-A Bar Stock: Pressure 683-13-3 A479/A479M Type 410 S41000 EN 10272 X12Cr13 1.4006 G 4303 Gr. SUS 410 or 403 Bar Stock: General 683-13-3 A276 Type 410 S41400 EN 10088-3 X12Cr13 1.4006 G 4303 Gr. SUS 410 or 403 Bar Stock: Forgings c 683-13-4 A276 Type 420 A473 Type 416 A582/A582M Type 416 S42000 S41600 S41600 EN 10088-3 X20Cr13 X20CrS1 X20CrS13 1.4021 1.4005 1.4005 G 4303, Gr. SUS 420J1 or 420J2 Bolts and Studs d 3506-1, C4‑70 A193/A193M Gr B6 S41000 EN 10269 X22CrMo V 12-1 1.4923 G 4303 Gr. SUS 410 or 403 Nuts d 3506-2, C4‑70 A194/A194 Gr 6 S41000 EN 10269 X22CrMoV 12-1 1.4923 G 4303 Gr. SUS 410 or 403 Plate 683-13-3 A240/A240M Type 410 S41000 EN 10088-2 X12Cr13 1.4006 G 4304/4305 Gr. SUS 403 or 410 Pipe <500F (260C) (316L) 683-13-10 B444 N06625 A312 Type 316L N06625 S31603 EN10095 NiCr22M09NB 2.4856 G 4902 NCF 625 Fittings <500F (260C) (316L) 9327-5 X2CrNiMo 17-12 B446 N06625 A182 Gr 316L N06625 S31603 EN10088-2 NiCr22M09NB 2.4856 1.4404 G 4902 NCF 625 General Castings General Castings Wrought/ Forgings: Pressure 12 % Chrome Steel Europe JIS Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 123 Table D.2—Material Specifications for LRC/VP Parts (Continued) USA Material Class Japan ISO ASTM UNS a EN b Grade Material No. 683-13-10 A351/A351M Gr CF3 J92500 BSI/BS/ EN 10213-4 GX2CrN 19‑11 1.4309 G 5121, Cl SCS 19A 683-13-19 A351/A351M Gr CF3M J92800 BSI/BS/ EN 10213-4 1.4409 G 5121, Cl SCS 16A SCS 16AX — A743/A743M Gr CF3 J92500 EN 10283 1.4309 1.4404 1.4408 G 5121, Cl SCS 19A — A743/A743M Gr CF3M J92800 EN 10283 1.4409 G 5121, Cl SCS 16A, SCS 16AX 9327-5, XCrNi 1810 A182/A182M Gr F 304L g S30403 EN 10222-5 X2CrNi 19-11 1.4306 G 3214, Gr. SUS F 304 Lg 9327-5, XCrNiMo 17-12 A182/A182M Gr F 316L S31603 EN 10222-5 EN 10250-4 X2CrNiMo 17-12-2 1.4404 G 4304/4305, 9327-5 X2CrNi 18-10 A479/A479M Type 304L g A479/A479M Type 316L A276 Grade 316L S30403 S31603 EN 10088-3 EN 10088-3 X2CrNi 19-11 X2CrNiMo 17-12-2 1.4306 1.4404 G 4303, Gr. SUS 304 L g 4303 Gr. SUS 316 L 9327-5 A479/A479M X2Cr NiMo Type XM19 17-12 S20910 — — — — 9328-5 X2Cr NiMo 17-12-2 A240/A240 Gr 304L g/ 316L S30403 S31603 EN 10028-7 EN 10028-7 X2CrNi 19-11 X2CrNiMo 17-12-2 1.4306 1.4404 G 4304/4305, Gr. SUS 304 L g/316 L Pipe 683-13-10 683-13-19 A312/A312M Type 304L g, 316L S30403 S31603 — — — G 3459 Fittings 9327-5, X2 Cr Ni18-10 9327-5, X2 Cr NiMo 1712 A182/A182M Gr F304L g, Gr 316L S30403 S31603 EN 10222-5 X2CrNi 19-11 X2CrNiMo 17-12-2 1.4306 1.4404 G 3214 Bolts and Studs 3506-1, A4-70 A193/A193M Gr B 8 M S31600 EN 10250-4 X6CrNiMo Ti 17-12-2 1.4571 G 4303, Gr. SUS 316 Nuts 3506-2, A4-70 A194/A194M Gr B 8 M S31600 EN 10250-4 X6CrNiMo Ti 17-12-2 1.4571 G 4303, Gr. SUS 316 Pressure Castings General Castings Wrought/ Forgings Austentic Stainless Steel Europe Bar Stock e Plate GX2CrNi 19‑11 JIS 124 API Standard 681 Table D.2—Material Specifications for LRC/VP Parts (Continued) USA Material Class Pressure Castings Duplex Stainless Steel Wrought/ Forgings Japan ASTM UNS a EN b Grade Material No. A890/A890M Gr. 1B J93372 BSI/BS/ EN 10213-4 GX 1.4517 — A890/890M Gr 3A J93371 — — — G 5121, Gr. SCS 11 A890/890M Gr 4A J9220 BSI/BS/ EN 10213-4 GX2 1.4517 G 5121, Gr. SCS 10 — A995/A995 Gr 1 B A995/A995M Gr 3A A995/A995 Gr 4A J93372 J93371 J9220 — — — — 9327-5, X2CrNiMo N22-5-3 A182/A182 Gr F 51 S31803 EN 10250-4 EN 10222-5 X2CrNiMo N-22-5-3 1.4462 — — A479/A479M S32550 EN 10088-3 1.4507 — S31803 EN 10088-3 X2CrNiMo N-22-5-3 1.4462 B 2312/B 2316 ISO General Castings Europe — JIS Bar Stock 9327-5, X2CrNiMo N22-5-3 Plate — A240/ S31803 EN 10028-7 X2CrNiMo N-22-5-3 1.4462 G 4304/G 4305 Pipe — A790/ S31803 — — — G 3459 Fittings 9327-5, X2CrNiMo N22-5-3 A182/A182 Gr F 51 S31803 EN 10250-4 EN 10222-5 X2CrNiMo N-22-5-3 1.4462 B 2312/B 2316 Gr. SUS329J3L Bolts and Studs — S31803 EN 10088-3 X2CrNiMo N-22-5-3 1.4462 G 4303 Nuts — S31803 EN 10088-3 X2CrNiMo N-22-5-3 1.4462 G 4303 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 125 Table D.2—Material Specifications for LRC/VP Parts (Continued) USA Material Class ISO General Castings Super Duplex Stainless Steel f a b c d e f g — Pressure Castings — Wrought/ Forgings — Europe Grade Japan Material No. JIS 1.4469 — ASTM UNS a EN b A890/A890 Gr 5A J93404 BSI/BS/ EN 10213-4 A890/A890 Gr 6A J93380 — — — — A995/A995M Gr 5A J93404 BSI/BS/ EN 10213-4 GX2CrNiM N 26-7-4 1.4469 — A995/995M Gr 6A J93380 — — — — A182/A182M Gr F55 and F53 S32750 S32760 EN 10250-4 EN 10088-3 1.4501 G 4303, Gr. SUS 329 J4L S32750 S32760 EN 10088-3 1.4501 G 4304/ G 4305, Gr. SUS 329 J4L 1.4501 — — G 3459, Gr. SUS 329 J4LTP Bar Stock — Plate — A240/ S32750 S32760 EN 10028-7 Pipe — A790/ S32750 S32760 — Fittings — A182/A182M Gr F55 and F53 S32750 S32760 EN 10250-4 EN 10088-3 1.4501 B 2312/B 2316 Gr. SUS 329 J4L Bolts and Studs — S32750 S32760 EN 10088-3 1.4501 G 4303 Gr. SUS 329 J4L Nuts — S32750 S32760 EN 10088-3 1.4501 G 4303 Gr. SUS 329 J4L — NS (unified numbering system) designation for chemistry only. Where EN standards do not yet exist, European national standards are available, e.g. AFNOR, BS, DIN, etc. Do not use for shafts in the hardened condition (over 302 HB). Special, normally use 4140 alloy steel. For shafts, standard grades of austenitic stainless steel may be substituted in place of low-carbon (L) grades. Super duplex stainless steel classified with pitting resistance equivalent (PRE) number greater than or equal to 40: P RE = wCr + 3, 3 w Mo + 16 wN , where wis the percentage mass fraction of the element indicated by the subscript “g”. There are many applications that have moderate corrosion properties that do not require the 316/316L and the option of 304/304L is suitable. The option to use 304/304L in for those moderate corrosion applications that do not require the greater corrosion resistance of 316/316L shall be advised by the vendor. Many applications that are moderately corrosive do not require the greater corrosion resistance of 316/316L. The option to use 304/304L for moderate corrosion applications can be proposed by the vendor. Table D.3—Non-metallic Wear Part Materials Material Temperature Limits °F (°C) Application min. max. Polyether ether ketone (PEEK) Chopped-carbon-fiber filled –20(–30) 275 (135) Stationary Parts Polyether ether ketone (PEEK) Continuous-carbon-fiber wound –20 (–30) 450 (230) Stationary or Rotating 126 API Standard 681 Table D.3—Non-metallic Wear Part Materials (Continued) Temperature Limits °F (°C) Material Application min. max. PFA/CF reinforced composite (perfluoroalkoxy carbon-filled polymer) 20 % mass fraction random X-Y oriented carbon-fiber –50 (–46) 450 (230) Stationary Parts Carbon graphite Resin-impregnated –55 (–50) 550 (285) Stationary Parts Babbitt-impregnated –400 (–240) 300 (150) Nickel-impregnated –400 (–240) 750 (400) Copper-impregnated –400 (–240) 750 (400) Non-metallic wear part materials that are proven compatible with the specified process liquid may be proposed within the above limits. Such materials may be selected as wear components for mating against a suitably selected metallic component such as hardened 12 % Cr steel or hard-faced austenitic stainless steel. Materials may be used beyond these limits if proven application experience can be provided, and if approved by the purchaser. Table D.4—Piping Materials Fluid Component Auxiliary Process Liquid All Weldable Materials Steam Cooling Water Gauge Pressure kPa (bar; psi) Nominal Size ≤ 500 (5; 75) > 500 (5; 75) Standard ≤ DN 25 (1 NPS) Optional ≥ DN 40 (1 1/2 NPS) Pipe Seamless a Seamless a Seamless a — Carbon steel, (Galvanized to ISO 10684 or ASTM A153/ A153M) Tubing b Stainless steel (Seamless Type 316) Stainless steel (Seamless Type 316) Stainless steel (Seamless Type 316) Stainless steel (Seamless Type 316) — All Valves Class 800 Class 800 Class 800 Class 200 Bronze Class 200 Bronze Gate and Globe Valve Bolted Bonnet and Gland Bolted Bonnet and Gland Bolted Bonnet and Gland — — Malleable iron (galvanized to ISO 10684 or ASTM A153/ A153M) — Pipe Fittings and Unions Forged Class 3000 Forged Class 3000 Forged Class 3000 Malleable iron (galvanized to ISO 10684 or ASTM A153/ A153M) Tube Fittings Manufacturer’s Standard Manufacturer’s Standard Manufacturer’s Standard Manufacturer’s Standard Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 127 Table D.4—Piping Materials (Continued) Fluid Component Auxiliary Process Liquid Fabricated Joints ≤ DN 25 (1 NPS) Steam Cooling Water Gauge Pressure kPa (bar; psi) Nominal Size All Weldable Materials ≤ 500 (5; 75) > 500 (5; 75) Standard ≤ DN 25 (1 NPS) Optional ≥ DN 40 (1 1/2 NPS) Socket-welded Threaded Socket-welded Threaded — Fabricated Joints ≥ DN 40 (1-1/2 NPS) — — — — — Purchaser to Specify Gaskets — Austenitic Stainless Steel Spiral-wound — Austenitic Stainless Steel Spiral-wound — — Flange Bolting — 4140 Alloy Steel — 4140 Alloy Steel — — Schedule 80 shall be used for pipe sizes from DN 15 to DN 40 (NPS /2 to NPS 1- /2). Schedule 40 shall be used for sizes DN 50 (2 NPS) and larger. b Acceptable tubing sizes (in accordance with ISO 4200) are as follows. 12.7 mm diameter × 1.66 mm wall (1/2 in. diameter × 0.065 in. wall); 19 mm diameter × 2.6 mm wall (3/4 in. diameter × 0.095 in. wall); 25 mm diameter × 2.9 mm wall (1 in. diameter × 0.109 in. wall). a 1 1 Annex E (informative) Ring Liquid System Schematics Figure E.1—LRC/VP Once-through System 128 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services Figure E.2—LRC/VP Partial Recirculation System (NOTE 5) 129 130 API Standard 681 Figure E.3—LRC/VP Total Recirculation System (Vertical Separator) Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services Figure E.4—LRC/VP Total Recirculation System (Horizontal Separator) 131 132 API Standard 681 Figure E.5—Typical Three-phase Separator Annex F (informative) System Considerations, Operating Variables, and Test Performance Conversion F.1 System Consideration—Factors Affecting Performance and Selection of Liquid Ring Compressor and Vacuum Pump Systems Purchaser should provide this information. LRC/VP performance in the user’s process is significantly influenced by process variables. Process variables to be considered during process development, design, and specification can include the following: F.1.1 Gas Inlet to Pumping (or Compressing) Equipment The following process variables should be considered for the gas flowing to the LRC/VP inlet: a) temperature, pressure, mass flows, and molecular weights; b) saturation conditions, and heats of vaporization and condensation; c) solubility of gases in the ring fluid; d) presence of liquid or solid carryover, and particle size if applicable; e) variations with time in process gas specification (that is, batch processes); f) pump-up or pump-down time limitations. NOTE This is the time to achieve stabilized operation. g) reactivity of the gas, or effects of the gas on the ring fluid; NOTE Reactivity is the capability of ring fluid to chemically react with vapor in suction. EXAMPLE F.1.2 Caustic solution might be used as a ring fluid to neutralize acidic vapors in suction stream. Gas Discharged to Process or Vent System The following process variables should be considered for gas flowing to the LRC/VP discharge: a) maximum (allowable) temperatures. b) pressures, including maximum allowable. c) gas mass flows required or desired downstream. d) permitted (or allowable) liquid carryover from the system. e) permitted (or allowable) vapor carryover from the system. 133 134 API Standard 681 F.1.3 Ring Liquid System The following process variables should be considered for the LRC/VP liquid system: a) temperatures and pressures at the inlet to the system. b) temperatures and pressures required (or desired) at the discharge from the system. c) vapor pressure under equilibrium conditions at the LRC/VP suction and discharge within the operating range. d) specific gravity in the operating range. e) viscosity in the operating range. f) reactivity with the gas stream, if applicable. g) miscibility/solubility with inlet liquids or condensed vapors. h) fouling potential of the process fluid in the system heat exchanger. i) specific heat and thermal conductivity within the operating ranges. F.2 Operating Variables—Checklist F.2.1 Inlet mixture can be cooled in LRC/VPs, thus increasing capacity. F.2.2 Inlet mixture can be saturated with condensable vapors. F.2.3 Inlet condensables can be miscible or immiscible with ring liquid. F.2.4 Inlet condensables can be partially condensed in pumps, thus increasing capacity. F.2.5 Cooler ring liquid temperature can increase net capacity and lower effective vapor pressure of service liquid. F.2.6 Lower ring liquid effective vapor pressure can increase capacity. F.2.7 Condensing vapors can increase ring liquid temperature rise and increase heat load to optional heat exchanger. F.2.8 Ring liquid specific heat lower than that of water can increase temperature rise. F.2.9 Ring liquid specific gravity lower than that of water can affect performance. F.2.10 Ring liquid specific viscosity lower than that of water can decrease BHP and, in turn, reduce service liquid temperature rise. F.2.11 Solubility of inlet gas in ring liquid can reduce capacity. F.2.12 Inlet vapors can condense and contaminate the ring fluid modifying its characteristics. Miscible condensables can accumulate in ring liquid and become a dominant factor in determining effective vapor pressure. Immiscible condensables with lower specific gravity than ring liquid can collect at gas/liquid interface and become dominant factors in determining net effective vapor pressure. Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services 135 F.2.13 Performance is generally determined by vapor pressure at effective ring liquid temperature. For two-stage LRC/VPs, the latter is the interstage temperature. F.2.14 Higher ring liquid flow rate can reduce temperature rise and increase net capacity at certified conditions. F.2.15 Ring liquid type can determine effective ring liquid temperature and performance. F.2.15.1 Once-through operation generally provides lowest ring liquid temperature with higher effective ring liquid temperature. F.2.15.2 Full recirculation permits use of separate coolant medium–generally with higher effective ring liquid temperature. F.2.15.3 A minimal ring liquid purge flow should be used to control ring liquid contamination. F.2.16 Back pressures other than standard will affect performance. F.3 Conversion of Standard Test Performance to Specified Operating Conditions F.3.1 Since operating conditions with respect to inlet gases, condensable vapors, ring liquid, and other field conditions often differ from those of the Standard Test, a conversion should be performed. Conversions of this kind should be based upon the manufacturer’s standard method and should be agreed upon before-hand by the parties involved. F.3.2 A check list of operating variables (see F.2) can provide the user with a better understanding of conversions to be made. F.3.3 It should be noted that a rigorous mathematical solution or conversion is generally not practical. The equipment selection procedure is usually a reiteration of a series of approximations. The latter are based upon a combination of user and manufacturer field experience, vendor laboratory tests, and similarity. Annex G (informative) Packaging G.1 General G.1.1 The arrangement of the equipment, including piping and auxiliaries, should be developed jointly by the purchaser and the vendor. The layout should allow appropriate and safe access to all items which can require adjustment during normal operation and obstruction free access for those items that can require removal during normal maintenance, e.g. LRC/VPs and their drivers, strainers, coolers, control valves, instrumentation, root valves etc. G.1.2 All components of the ring liquid compressor package should be completely assembled within the confines of the skid. All connections terminations should be flanged at the skid edge and supported by the structure. Connection locations should be agreed between the purchaser and the vendor. Connection locations should be approved by the purchaser. G.1.3 Cooler tube bundles (if supplied) should be removable without the need of removing any other package item or equipment or structural members or the cooler itself. G.1.4 Space above major equipment and its components, should be free for lifting device approach required for their removal. G.1.5 Maintenance and overhaul, of the equipment should not require steel structure dismantling. G.1.6 Where redundant equipment is supplied, the stand-by equipment should be completely removable without affecting continuous operation of the package. G.1.7 Size and area of the skid platform should be agreed upon to provide safe and easy operation and maintenance access. Also, the skid dimensions should be reviewed between the vendor and purchaser for available plot space, shipping, and transportation requirements, as well as purchaser’s health, safety, and environmental requirements. G.1.8 Lifting points and lugs should be clearly identified on the equipment or equipment package. Lugs and pad eyes should be designed with a clear space around the eye. G.2 Piping and Tubing G.2.1 Piping and tubing should be routed in a safe way, not obstructing required access for installation, operation, and maintenance. G.2.2 All piping and tubing should be arranged so that all maintainable items of equipment are capable of removal with minimum dismantling of piping and tubing. G.2.3 Main or auxiliary piping should not be routed near machine hold-down bolts and anchor bolts. G.2.4 Temporary strainers, blinds etc. if used, should have tags reading “temporary” and protruding out of line/ insulation diameter indicating their presence. 136 Liquid Ring Compressors and Vacuum Pumps in Petroleum, Chemical, and Gas Industry Services G.3 137 Electrical, Control System and Instrumentation G.3.1 API RP 540 and API RP 552 can be used as guidelines for electrical, control and instrumentation installation on the package such as cabling, conduits and cable trays, signal transmission, etc. G.3.2 Electrical and control systems cabinets, terminal boxes and junction boxes door hinges should allow 180° opening-or have easily removable doors. G.3.3 If specified, the local start/stop/hand-off-auto switches for electric motors should be provided and installed at a close and safe distance from the electric motor to allow the operator to observe the operation of the equipment. G.3.4 Push buttons, HMI panels, indicators lights and terminal strips should be easily accessible on the control panel. The minimum and maximum height of installation of components that need frequent access should be agreed. G.3.5 Junction boxes, gauge boards and field instrument panels should be located at the skid edge in a safe place, easily accessible from back and front, away from vibration and heat sources. They should also be fitted with stands/brackets. If specified for outdoor installations sunshade should be provided. G.3.6 Main Terminal box cable entry should be located to provide enough space for routing the power cable into the terminal box without exceeding the cable bend limit. G.3.7 Where cable trays are specified, appropriate drainage should be provided. G.3.8 Extension wires or cables should be run inside a cable tray or metal conduit suitable for the environmental conditions. G.3.9 Local manual shutdown mechanism(s) should be safely and easily accessible. Approach to the local manual shutdown mechanism(s) and the escape route should be jointly reviewed between the vendor and purchaser. G.3.10 Changing individual instrument items should not cause changing or removal of any other mechanical parts. G.3.11 Gauges, sight glasses and other instruments should be installed such that they are not obscured from easy access and observation. G.3.12 Cable trays and rigid conduit should not be routed over the cases of horizontally split rotating machinery. They should not be routed over or in front of removable heads on vessels and exchangers, or where they impair the functionality of inspection openings or panel doors. G.3.13 Where the packaged equipment is required to be disassembled for shipment, mating parts should be match marked to aid the reassembly at the job site. G.4 Walkways, Ladders, and Platforms Access G.4.1 Any special clearance or safe access areas located on the skid (such as proper evacuation route for emergency situation) should be specified by the purchaser. Sufficient head clearance should be available in all walkways and around the equipment. G.4.2 If the walkways and platforms are not in vendor scope of supply, vendor should review the walkways and access platform arrangements to assure adequate access for operation and maintenance upon request. G.4.3 Non-skid surfaces should be provided covering all walk and work areas. 138 NOTE API Standard 681 Non-skid surfaces can be obtained by, non-skid coatings, or grating. G.4.4 Vendor should identify access areas sufficient for removal of major components such as cooler bundle, heater element etc. Maintenance and removal of main components, as well as maintenance and removal of control valve and instruments should be possible without removal or dismantling of adjacent equipment, piping, or structure. G.4.5 Vendor and purchaser should agree on the required platform access to main equipment and auxiliaries, such as valves and instruments. G.4.6 Vendor and purchaser should review safe and appropriate approach for handling the package components as required for installation and maintenance. Bibliography [1] API Recommended Practice 578, Material Verification Program for New and Existing Alloy Piping Systems [2] ISPM, Publication No.15, March 2002, FAO, Rome [3] NACE, Corrosion Engineer’s Reference Guide [4] NEMA, Standard Publication 250 139 200 Massachusetts Avenue, NW Suite 1100 Washington, DC 20001-5571 USA 202-682-8000 Additional copies are available online at www.api.org/pubs Phone Orders: 1-800-854-7179 (Toll-free in the U.S. and Canada) 303-397-7956(Local and International) Fax Orders: 303-397-2740 Information about API publications, programs and services is available on the web at www.api.org. Product No. C68102