(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]
source: 29 FR 18995, Dec. 29, 1964, unless otherwise noted. Redesignated at 32 FR 5606, Apr. 5, 1967.
cite as: 49 CFR 179.200-21