Section 157.400 - Purpose and applicability(a) The purpose of this subpart is to establish mandatory safety and operational requirements to reduce environmental damage resulting from petroleum oil spills.(b) This subpart applies to each tank vessel specified in § 157.01 of this part that- (1) Is 5,000 gross tons or more;(2) Carries petroleum oil in bulk as cargo or oil cargo residue; and(3) Is not equipped with a double hull meeting § 157.10d of this part, or an equivalent to the requirements of § 157.10d , but required to be equipped with a double hull at a date set forth in 46 U.S.C. 3703a (b)(3) and (c)(3) .CGD 91-045, 61 FR 39788, July 30, 1996, as amended by USCG-2000-7641, 66 FR 55573, Nov. 2, 2001