46 C.F.R. § 154.411
Cargo tank thermal loads
For the calculations required under § 154.406(a)(4), the following determined loads must be specially approved by the Commandant (CG-ENG):
(a) Transient thermal loads for the cooling down periods of cargo tanks for design temperatures lower than −55 °C (−67 °F).
(b) Stationary thermal loads for cargo tanks for design temperatures lower than −55 °C (−67 °F) that cause high thermal stress.