46 CFR §154.660

1. (a)Pipe welding must meet part 57 of this chapter.
2. (b)Longitudinal butt welds, in piping that does not meet a standard or specification under § 56.60-1 of this chapter, and girth butt welds must meet the following:
   1. (1)Butt welds of pipes made from carbon, carbon manganese, or low alloy steels must meet § 56.50-105 of this chapter, including the requirements for post-weld heat treatment.
   2. (2)Except for piping inside an independent cargo tank type A, B, or C, butt welds must be 100% radiographically tested if the design temperature is lower than −10 °C (14 °F), and:
      1. (i)The wall thickness is greater than 10 mm (0.394 in.); or
      2. (ii)The nominal pipe diameter is greater than 100 mm (nominal 4 in.).
   3. (3)If Table 4 references this section, butt welds for deck cargo piping exceeding 75 mm (3 in.) in diameter must be 100% radiographically tested.
   4. (4)Butt welds of pipes not meeting paragraph (b)(2) or (b)(3) of this section must meet the non-destructive testing requirements under Subpart 56.95 of this chapter.