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UL 51 – Standard for Power-Operated Pumps and Bypass Valves for Anhydrous Ammonia, LP-Gas, and Propylene

Please note: All interim revisions for this edition available at time of your purchase will be included.

Power-Operated Pumps and Bypass Valves for Anhydrous Ammonia, LP-Gas, and Propylene
UL 51

1 Scope
1.1 These requirements cover power-operated pumps and bypass valves for use in liquid transfer operations in non-refrigerated systems in installations for:

Anhydrous ammonia systems installed in accordance with the Safety Requirements for the Storage and Handling of Anhydrous Ammonia, CGA/GAS G-2.1 (ANSI K61.1);
Liquefied petroleum gas (LP-Gas) systems installed in accordance with the Liquefied Petroleum Gas Code, NFPA No. 58; and
Propylene systems.

1.2 These requirements do not cover:

Pumps or compressors intended for handling anhydrous ammonia or LP-Gas or propylene in the gaseous phase and
Pumps, compressors or bypass valves for anhydrous ammonia, LP-Gas, or propylene for use in chemical, petro-chemical, petroleum, or utility power plants; nor pipeline or marine terminals; nor related storage facilities at such plants or terminals.

1.3 Equipment covered by these requirements is for use with LP-Gas, propylene, or anhydrous ammonia as covered by the Standards and Codes in 1.1 and shall have a minimum service pressure rating in accordance with Table 1.1.

A pump without an integral bypass valve with a higher differential pressure obtained in the Differential Pressure Test, Section 17, is permitted to have a lower minimum service pressure rating if it is marked in accordance with 25.2.

Table 1.1 Minimum service pressure for rating pumps and bypass valves.

Maximum differential pressure produced when subjected to the Differential Pressure Test, Section 17	Anhydrous ammonia and LP-Gas equipment minimum service pressure rating	Propylene equipment minimum service pressure rating
psig (kPa)	psig (kPa)	psig (kPa)
£ 100 (689) Propylene equipment only	Not applicable	350 (2415)
£ 125 (862)	350 (2415)	375 (2585)
>125 (863) # 150 (1034)	375 (2586)	400 (2758)
>150 (1034) # 200 (1379)	400 (2758)	425 (2930)
200 (1379)	200 + differential pressure produced (1379 + differential pressure produced)	225 + differential pressure produced (1551 + differential pressure produced)