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Subpart A—Introduction, Approvals and Reports8

Subpart B—General Design Requirements11

Subpart C—Specifications for Pressure Tank Car Tanks (Classes DOT-105, 109, 112, 114 and 120)31

Subpart D—Specifications for Non-Pressure Tank Car Tanks (Classes DOT-111AW, 115AW, and 117AW)69

Subpart E—Specifications for Multi-Unit Tank Car Tanks (Classes DOT-106A and 110AW)20

Subpart F—Specification for Cryogenic Liquid Tank Car Tanks and Seamless Steel Tanks (Classes DOT-113 and 107A)44

Regulationcurrent

49 CFR 179.200-21

-21 Closures for openings.

Current as of 2026-08-18 Government source

eCFR editorial compilationAuthoritative but unofficial

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(a)All plugs shall be solid, with NPT threads, and shall be of a length which will screw at least 6 threads inside the face of fitting or tank. Plugs, when inserted from the outside of tank heads, shall have the letter “S” at least 3/8 inch in size stamped with steel stamp or cast on the outside surface to indicate the plug is solid.#

(b)[Reserved]#