49 CFR 179.200-21 - Closures for openings.
(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.
Title 49 published on 2014-10-01
no entries appear in the Federal Register after this date.