1.1 These requirements cover backpressure and other types of check valves and hose couplers for compressed gases other than for liquefied petroleum gas (LP-Gas) in applications covered by NFPA 58, or anhydrous ammonia.
1.2 Check valves and hose couplers covered by these requirements are intended for use with industrial equipment and systems such as, but not limited to, oxygen-fuel gas welding applications covered by the following installation codes:
a) Standard for the Design and Installation of Oxygen-Fuel Gas Systems for Welding, Cutting and Allied Processes, NFPA 51 and
b) Safety in Welding and Cutting and Allied Processes, AWS Z49.1.
1.3 Check valves for use with liquefied petroleum gas in applications covered by NFPA 58 or anhydrous ammonia applications covered by ANSI K61.1 are covered by the requirements in the Standard for Valves for Anhydrous Ammonia and LP-Gas (Other Than Safety Relief), UL 125.
1.4 These requirements do not apply to check valves for compressed gases for use in refrigerated storage systems.
1.5 Except for such observations as are required to ascertain performance characteristics, the assigning of flow capacity ratings are not within the scope of these requirements.