StacksVerified U.S. regulatory reference

46 CFR §154.524

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Pipe lengths without flanges must be joined by one of the following:
  1. (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:
    1. (1)A backing ring that for design pressures greater than 979 kPa gauge (142 psig) must be removed after the weld is completed;
    2. (2)A consumable insert; or
    3. (3)An inert gas back-up on the first weld pass.
  2. (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.
  3. (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.
  4. (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.
  5. (e)A method or fitting specially approved by the Commandant (CG-ENG).