(a) Qualification of welding procedures and welders is required, and must comply with the requirements of Section IX of the ASME BPVC (incorporated by reference; see § 56.01-2) as modified by part 57 of this subchapter.

(b) Each butt-welded joint of Class I of Class I-L piping must be marked with the welder's identification symbol. Dies must not be used to mark the pipe where the pressure exceeds 600 psig or the temperature exceeds 750 °F or in Class I-L systems.