46 C.F.R. § 153.400 General requirements for gauges.
Title 46 - Shipping
(a) Columnar gauge glasses must not be installed on a cargo containment system. (b) Flat sight glasses must meet §38.10–20(h) of this chapter.
Title 46: Shipping
PART 153—SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS
Subpart B—Design and Equipment
Cargo Gauging Systems
§ 153.400 General requirements for gauges.

