46 C.F.R. § 151.03-49 Sounding tube.
Title 46 - Shipping
This is an unperforated tube fitted to an ullage hole, secured so as to be vapor tight to the underside of the tank top open at the bottom, and extending to within 18 inches or less of the bottom of the tank.
Title 46: Shipping
PART 151—BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES
Subpart 151.03—Definitions
§ 151.03-49 Sounding tube.
