Code of Federal Regulations Title 46. Shipping § 46.154.524 Piping joints:  Welded and screwed couplings

(a) A butt welded joint with complete penetration at the weld root except that for design temperatures colder than –10° C (14° F) the butt weld must be double welded or must be welded using:

(b) A slip-on welded joint with sleeves and attachment welds is allowed for an open ended pipe with an external diameter of 50 mm (2 in.) or less and a design temperature of –55° C (–67° F), or warmer.

(c) A socket weld fitting with attachment welds is allowed for pipe with an external diameter of 50 mm (2 in.) or less and a design temperature of –55° C (–67° F) or warmer.

(d) Screwed couplings are allowed for instrumentation and control piping that meets § 56.30–20 and § 56.50–105 (a)(4) and (b)(4) of this chapter.

(e) A method or fitting specially approved by the Commandant (CG–ENG).