C.F.R.
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Title 49
» CHAPTER I—PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION › SUBCHAPTER C—HAZARDOUS MATERIALS REGULATIONS › PART 179—SPECIFICATIONS FOR TANK CARS › Subpart D—Specifications for Non-Pressure Tank Car Tanks (Classes DOT-111AW, 115AW, and 117AW)
(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]