46 CFR § 153.432 - Cooling systems.
(a) Each cargo cooling system must have an equivalent standby unit that is installed and that can be placed in operation immediately after failure of the primary cooling system.
(b) Each tankship that has a cargo tank with a required cooling system must have a manual that contains:
(1) A piping diagram for the cooling system; and
(2) Instructions for changing over to the standby system described in paragraph (a) of this section.