UL 331:2017 pdf download.Strainers for Flammable Fluids and Anhydrous Ammonia.
7.7 A protective coating shall provide resistance against corrosion to a degree not less than that providedby the protective coating specified in 7.8.
7.8 Cadmium plating shall not be less than 0.0o03 inch (0.o08 mm) thick,and zinc plating shall not beless than 0.0005 inch (0.013 mm) thick, except on parts where threads constitute the major portion of thearea, in which case the cadmium or zinc plating shall not be less than 0.00015 inch (0.o038 mm) thick.See 7.2.
7.9 A wire-cloth element, if finer than 60 mesh, shall be resistant to corrosion.A 60-mesh or coarserelement shall be resistant to the fluid it is intended to contact.
8 Bodies and Covers
8.1 An opening threaded for connection of pipe shall be threaded in accordance with the Standard forPipe Threads.ANSIASME B1.20.1.
Exception: Strainers intended for use in installations where pipe fittings incorporate other than NPT typethreads shall be permitted to be provided with pipe threads complying with a national pipe thread standardcompatible with those fittings. The pipe thread type shall be identified in accordance with 20.1.
8.2 A strainer for attachment to pipe larger than 3-inch nominal size shall be provided with flanged pipeconnections. Flanges shall conform to the appropriate American National Standard for pipe flanges andflanged fittings covering the material from which the flange is made, or shall be of a construction found byinvestigation to be equivalent for the specific application.
8.3 Cleanout and drain openings shall be closed by a standard pipe plug, a threaded, shouldered plug.or a wing-nut plug. The specified plugs shall be supplied with a seal to prevent leakage that is compatiblewith the intended fuel(s) as demonstrated by compliance with the performance requirements of thisstandard.A strainer intended for use with gasoline shall have brass plugs or, if of steel, they shall becoated to retard corrosion.
