NFPA 54 "National Fuel Gas Code - 2006

Section:5.6.2.2 - Steel and Wrought Iron. Steel and wrought iron pipe shall be at least of standard weight (schedule 40) and shall comply with one of the following standards:

(1) ANSI/ASTM: B36.10 welded and seamless wrought steel pipe.
(2) ASTM A53, Standard specifications for pipe, steel, black, and hot-dipped, zinc coated welded and seamless.
(3) ASTM A106, Standard specification for Seamless carbon steel pipe for high-temperature service.