Liquid Ring Compressors and Vacuum
Pumps in Petroleum, Chemical, and Gas
Industry Services
API STANDARD 681
SECOND EDITION, JULY 2021
Special Notes
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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.
This document was produced under API standardization procedures that ensure appropriate notification and participation
in the developmental process and is designated as an API standard. Questions concerning the interpretation of the
content of this publication or comments and questions concerning the procedures under which this publication was
developed should be directed in writing to the Director of Standards, American Petroleum Institute, 200 Massachusetts
Avenue, NW, Suite 1100, Washington, DC 20001. Requests for permission to reproduce or translate all or any part of
the material published herein should also be addressed to the director.
Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-time
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the API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published
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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
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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 ​Vu​​is 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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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
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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.
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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
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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.
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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
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[●] 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.
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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
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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.
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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.
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B.2.2
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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;
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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.
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B.3.3
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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.
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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.
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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.
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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.
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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 ​w​is 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
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Product No. C68102