API 681 standard liquid ring vacuum pump

API 681 liquid ring vacuum pumps for petroleum, chemical and gas industries

1.  Range
1. 1 This standard includes the design of vacuum pumps and compressors and the design of their systems.More applications.
1.2 The key to system design lies in the correct operation of vacuum pump and compressor. Energy should not only be spent on the design of the system, but also on how to meet the requirements of the users.
1.3 Although this standard covers the minimum requirements for petroleum refining systems, the Buyer may wish to consider pumps that do not fully meet the requirements of this standard, depending on the specific requirements of the medium being non-flammable, non-toxic, etc.
Note: the (●) symbol before each paragraph indicates that the factor is at buyer’s discretion. These decisions should be reflected in the data sheet (Appendix A); Otherwise, it should be included in the inquiry or order.

2. Alternative design
The seller may propose alternative designs. Comparable metric sizes, fasteners, and flanges may be used instead, subject to mutual consent.
3. Request conflicting measures
In the event of a conflict between this standard and an inquiry or order, the content of the order shall prevail.
4. Definition of terms
Terms used in this International Standard are defined in clauses 1.4.1-1.4.26.
4.1 Alarm point: refers to a preset point and a parameter used for alarm.
4.2 Rated pressure point:
4.3 Hydraulic bearings: bearings designed on the principle of liquid lubrication. Their surfaces are oriented to facilitate the formation of oil wedges in relative motion to withstand loads.
4.4 Inspiratory capacity (inch3 / min) (ICFM) : refers to the air intake at the inlet flange of the compressor at a certain pressure, temperature, compression coefficient, including humidity. Actual air intake (ACFM)
4.5 Liquid ring vacuum pump or compressor: refers to a rotating machine, through the radial blade impeller in the eccentric or elliptic shell rotation, the shell is punched with liquid, to achieve the purpose of gas compression or the formation of a vacuum.
4.6 Maximum allowable pressure difference: refers to the maximum allowable pressure difference designed by the producer during continuous operation.
4.7 Maximum permissible speed: (RPM) : the maximum speed of continuous operation allowed by the manufacturer’s design.
4.8 Max allowable temperature: the maximum continuous temperature specified by the manufacturer for the equipment (or any part of the term referred to) to deliver a liquid at specified pressures.
4.9. Maximum allowable vacuum: the maximum vacuum designed by the manufacturer for the equipment (minimum suction pressure),
The vaporization pressure of the seal fluid under operating pressure.
4.10 Maximum allowable working pressure: The maximum continuous pressure specified by the manufacturer when transferring a liquid to the equipment (or any part of the term) at a specified temperature.
Maximum continuous speed :(RPM) at least 105% of the rated speed. For the normal speed drive machine the maximum continuous speed should be equal to its speed.
4.12 Maximum differential pressure: refers to the value obtained by subtracting the minimum inlet pressure from the maximum outlet pressure of the pump at the specified speed, specified specific gravity and specified temperature.
4.13 Maximum outlet pressure: the sum of the maximum suction pressure plus the maximum differential pressure generated when the pump operates at specified speed, specific gravity and temperature.
4.14 Maximum sealing pressure: The maximum pressure at the sealing place during any specified static or operating conditions or downtime.
4.15 Minimum allowable temperature: the minimum continuous temperature specified by the manufacturer for the equipment (or any part of the term referred to).
4.16 Normal operating point: refers to the expected operating point of normal operation.
4.17 Housing: A combination of all stationary and internal-pressure bearing parts, including all inlet and outlet, shaft seals, and other parts mounted on the housing, but excluding the stationary elements and rotating elements of the mechanical seal.
4.18 Radial division: refers to the connection surface of the shell perpendicular to the center line of the pump shaft.
4.19 Rated discharge pressure: the maximum pressure under the conditions specified by the Seller.
4.20 Rated operating point: refers to the operating point where the Seller guarantees the performance within the tolerance range stated in this Standard. Performance includes a range of parameters: flow, power, efficiency, speed and rated inlet and outlet pressure.
4.21 Dead point: refers to a parameter set in advance, which can be automatically or manually shut down if necessary.
4.22 Standard flow: it is expressed in the rated flow category. Rated flow in ISO standard is m3/h or m3/min at standard atmospheric pressure (1.013bar) and 0℃. The usual units are cubic inches per minute (SCFM) or hundred million cubic inches per day (MMSCFD) at absolute pressure of 14.7 LBS/inch 2 and 60°F.
4.23 Total indication (runout) reading (TIR) : the total pointer reading refers to the diameter runout or end runout measured by the dial indicator. The pointer reading reveals that the nonperpendicularity is equal to the reading or the eccentricity is equal to half the reading.
Tripping speed: the speed at which the safety device acts to cause the driver to stop in an emergency due to independent accident overspeed.
4.25 Unit responsibility: shall mean the responsibility for coordinating and resolving technical problems with the equipment and all auxiliary systems included in the order. These include factors such as power requirements, speed, steering, overall layout, couplings, dynamics, noise, lubrication, sealing systems, mechanical test reports, equipment, piping and component tests, etc.
Wet critical speed: the natural vibration frequency of the rotor calculated after taking into account the additional supporting and damping effects of pumped liquid in various running clearances of the rotor under working conditions, and taking into account the flexibility and damping effects in the bearing.

5. Relevance standards
5.1 The Standard is related to the United States standard, other international standards or national standards, which are to be followed by the buyer and the seller through mutual consultation and reflected in these standards or outside the United States standard.
5.2 As of the date of publication of this International Standard, references to any of the following specifications in the valid edition of this International Standard shall form part of this International Standard. The applicability of such standards, codes and technical specifications shall be determined by the buyer and the seller through consultation.
AFBMA Bearing Manufacturers Association of America
Fit seats for shafts and bearing boxes for standard 7 metric radial ball and roller bearings.
Nominal 9 ball bearing load rating and fatigue life.
Inch design for standard 19 tapered roller bearings
Metric design for standard 19.1 tapered roller bearings
Standard 20 Metric ball and roller bearings conforming to the basic boundary plan (including boundary dimensions, tolerances and markings) (excluding tapered roller bearings)
AGMA American Gear Manufacturers Association
9000- just (990) flexible couplings – classification of potential unevenness
Holes and keyways for flexible couplings (Inch system)
AISC Steel Structure Manual
American Institute of Engineers, ANSI
B1.1 inch thread
B1.20.1 General purpose (Inch) pipe thread
B1.20.3 Thread of dry seal pipe (Inch)
B16.1 cast iron pipe flanges and flange fittings, pressure classes 25,125,250 and 800
B16.5 Steel tube flanges and flange fittings, nickel alloys and other alloys
B16.11 Insert forged steel fittings for welded and threaded connections
B16.42 Ductile iron pipe flanges and flange fittings
B73.1 Technical specification for end suction centrifugal pumps for chemical industry
B73.2 Technical specification for vertical pipeline pumps for chemical industry
S2.19 Mechanical vibration – equilibrium quantity of rigid rotors – Part 1, allowable residual unbalance
API American Petroleum Institute
Spec 5L long pipe technical Specification
Classification of electrical installations in RP 500A Petroleum Facility area
RP 520 Size, selection and installation of pressure relief equipment in facility area
Flanges of standard 526 steel safety valve
Standard 550 Extraction Instrumentation and Control Systems By Installment Manual (OOP)
Centrifugal pumps for standard 610 general refineries
General purpose steam turbines for a standard 611 refinery
Standard 615 Sound control for mechanical equipment used in refinery
Standard 660 tubular heat exchangers for general refinery use
Standard 670 vibration, axial displacement and bearing temperature monitoring system
General purpose gear plant for standard 677 refinery
Manual of Standards for Petroleum Measurement, Chapter 15, “Manual for the Use of Iso units in petroleum and Related Industries”
ASME American Society of Mechanical Engineers
B1.20.1 Pipe Thread for General Purpose (Inch)
B16.47 large diameter steel flange: NPS26-NPS60
B31.3 Boilers and pressure vessels in chemical plants and petroleum refineries,
The first part Ⅴ “NDT”,
The first part Ⅷ “pressure vessel”
The first Ⅸ part “welding and brazing quality qualification conditions”
ASTM American Society for Testing materials
A 105 Carbon steel forgings for piping parts
A 106 seamless carbon steel tubes for high temperature equipment
A 120 Non-galvanized and hot-dipped galvanized (electrogalvanized) welded and seamless steel tubes for general use
A 153 Galvanization (hot dip) of iron and steel members
A 181 Carbon steel forgings for general purpose piping
A 193 Bolted alloy steel and stainless steel for high temperature use
A 194 Carbon steel and alloy steel nuts for high temperature and pressure
A 197 Cupola malleable iron
A 247 Calculation method for graphite structure in cast iron processes
A 269 Austenitic stainless steel and welded steel tubes for general use
A 278 Grey cast iron castings for internal pressure bearing parts up to 650°F (345 ° C)
A 338 Railway \ ships \ and other heavy duty malleable iron flanges \ pipe fittings and valve parts for temperatures below 650°F (345 ° C)
A 395 Malleable iron shall be used for pressure retaining shell in case of temperature increase
A 515 medium and high temperature carbon steel container plates
A 524 seamless carbon steel pipe at room temperature and lower temperature
A 536 ductile iron
E 94 X – ray inspection (examination) guidelines
Standard photograph of magnetic particle traces on ferrous metal castings
E 142 methods for controlling the quality of X-ray flaw detection
Operation method of E 709 magnetic particle flaw detection
AWS American Welding Society
D1.1 Specification for welding of steel structures
EEMUA
Liquid ring vacuum pump and compressor
HEI Heat Exchange Society
Performance standard for liquid ring vacuum pumps
NACE National Anticorrosive Engineers Association
Metal material that is resistant to stress corrosion cracking of sulphide for MR 01-75 oil field equipment
NEMA National Electrical Manufacturers Association
SM 23 steam turbines for mechanical transmission
NFPA National Fire Protection Association
National Electrical Code, Chapters 500 to 501
Cleaning and pressurization of electrical equipment housing
OSHA Occupational Safety and health Standards
29 Federal Regulations, Chapter 1910
PNEUROP 6612 compressors, vacuum pumps and pneumatic tools manufactured in the European Community
Acceptable performance tests and specifications for liquid ring vacuum pumps
SSPC Steel Structure Coatings Association
SP6 industrial shot peening cleaning
TEMA Pipe heat exchanger Manufacturing Association
Tubular Heat Exchanger Production Association standard
5.3 The buyer and the seller shall jointly decide on a number of measures to ensure that the equipment is applicable to governmental regulations, regulatory regulations, or rules.
5.4 The seller shall have the responsibility to ask the agent at the next higher level for the specific usage of the equipment.

6. Unit change
It is mentioned in Chapter 15 that SI units are used in API petroleum measurement standards, and the results are rounded to the nearest SI units.