179.300-13—Venting, loading and unloading valves.
(a)
Valves shall be of approved type, made of metal not subject to rapid deterioration by lading, and shall withstand tank test pressure without leakage. The valves shall be screwed directly into or attached by other approved methods to one tank head. Provision shall be made for closing outlet connections of the valves.
(b)
Threads for openings shall be National Gas Taper Threads (NGT) tapped to gage, clean cut, even and without checks.