49 C.F.R. § 179.100-17 Closures for openings.
Title 49 - Transportation
(a) Closures shall be of approved design and made of metal not subject to rapid deterioration by the lading. Plugs, if used, shall be solid, with NPT threads, and shall be of a length which will screw at least six threads inside the face of fitting or tank. (b) [Reserved]
Title 49: Transportation
PART 179—SPECIFICATIONS FOR TANK CARS
Subpart C—Specifications for Pressure Tank Car Tanks (Classes DOT-105, 109, 112, 114 and 120)
§ 179.100-17 Closures for openings.
