49 CFR 178.338-4 - Joints.
(a) All joints in the tank, and in the jacket if evacuated, must be as prescribed in Section VIII of the ASME Code (IBR, see § 171.7 of this subchapter), except that a butt weld with one plate edge offset is not authorized.
(b) Welding procedure and welder performance tests must be made in accordance with Section IX of the ASME Code. Records of the qualification must be retained by the tank manufacturer for at least five years and must be made available, upon request, to any duly identified representative of the Department, or the owner of the cargo tank.
(d) Substructures must be properly fitted before attachment and the welding sequence must minimize stresses due to shrinkage of welds.
(e) Filler material containing more than 0.05 percent vanadium may not be used with quenched and tempered steel.