UL 51:2013 free download

UL 51:2013 free download Power-Operated Pumps and Bypass Valves for Anhydrous Ammonia, LP-Gas, and Propylene
2 Components
2.1 Except as indicated in 2.2, a component of a product covered by this standard shall comply with therequirements for that component.See Appendix A for a list of standards covering components generallyused in the products covered by this standard.
2.2 A component is not required to comply with a specific requirement that:
a) Involves a feature or characteristic not required in the application of the component in theproduct covered by this standard, or
b) ls superseded by a requirement in this standard.
2.3 A component shall be used in accordance with its rating established for the intended conditions ofuse.
2.4 Specific components are incomplete in construction features or restricted in performance capabilities.Such components are intended for use only under limited conditions,such as certain temperatures notexceeding specified limits, and shall be used only under those specific conditions.
2.5 Electrical components，including motors and wiring,when incorporated by a manufacturer in theassembly of a pump for LP-Gas or propylene, and the means provided in the pump assembly for electricalconnections,shall comply with the requirements for equipment for use in hazardous locations, Class l,Group D, in the National Electrical Code,NFPA 70,Articles 500 and 501.
2.6 Electrical components，including motors and wiring and connections shall comply with therequirements for equipment for use in hazardous locations, Class l, Group D, in the National ElectricalCode,NFPA 70,Articles 5o0 and 501.
Exception: When incorporated by a manufacturer in the assembly of a pump for anhydrous ammonia,the above described electrical components need only to comply with the requirements for ordinary(nonhazardous) locations or for outdoor use locations，if the assembly is appropriately marked todesignate the limitations in location and use involved with the electrical features.
3 Units of Measurement
3.1 Values stated without parentheses are the requirement. Values in parentheses are explanatory orapproximate information.
4 Undated References
4.1 Any undated reference to a code or standard appearing in the requirements of this standard shall be interpreted as referring to the latest edition of that code or standard.
5 Glossary
5.1 For the purpose of this standard the following definitions apply.
5.2 BYPASS VALVE – A valve used on the discharge side of a pump which opens automatically at a predetermined differential pressure so as to direct part or all of the pump discharge back to
the supply tank. It is either provided as part of a pump assembly (integral bypass valve), or it is a separate valve which is piped into the pump discharge system at the time of installation.
5.3 LIQUEFIED PETROLEUM GAS (LP-GAS OR LPG) – Any material having a vapor pressure not exceeding that allowed for commercial propane, as defined in Standard Specification for Liquefied Petroleum (LP) Gases, ASTM D1 835, that is composed predominantly of the following hydrocarbons, either by themselves (excluding propylene) or as mixtures: propane, propylene, butane (normal butane or isobutane) and butylenes.
5.4 RELIEF VALVE – A recirculating valve which opens at a predetermined differential pressure to direct the pump discharge back to the intake side of the pump. When provided, it is included as part of the pump assembly.