46 CFR § 128.450
Liquid-mud systems
April 15, 2021
(a) Liquid-mud piping systems may use resiliently seated valves of Category A to comply with §§56.20-15 and 56.50-60 of this chapter.
(b) Tanks for oil-based liquid mud must be fitted with tank vents equipped with flame screens. Vents must not discharge to the interior of the vessel.