46 C.F.R. § 153.406 Standards for containment systems having required restricted gauges.
Title 46 - Shipping
When Table 1 requires a cargo's containment system to have a restricted gauge, the containment system must have: (a) A closed gauging system; or (b) A system that has: (1) A restricted gauge (e.g., a sounding tube) with an orifice diameter not exceeding 20 cm (approx. 7.8 in.); (2) A permanently attached gauge cover that is vapor tight when in place; and (3) A venting system that has either: (i) Lock open PV valves; or (ii) Valved bypasses around the PV valves.
Title 46: Shipping
PART 153—SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS
Subpart B—Design and Equipment
Cargo Gauging Systems
§ 153.406 Standards for containment systems having required restricted gauges.
