46 C.F.R. § 32.60-35
Tank vessels carrying Grade A liquid cargo—TB/ALL
(a) Grade A liquids having a Reid vapor pressure in excess of 25 pounds per square inch shall be transported in cargo tanks which are independent of the hull.
(b) Barges carrying Grade A liquids having a Reid vapor pressure in excess of 25 pounds per square inch shall be of a Type III barge hull as defined in § 32.63-5(b)(3).