46 CFR §151.50-36

1. (a)A cargo tank that contains argon or nitrogen and that has a maximum allowable working pressure of 172 kPa (25 psig) or greater must have one of the following arrangements:
   1. (1)A refrigeration system that keeps the tank pressure below the safety relief valve operating pressure when ambient temperatures are 46 °C (115 °F) air and 32 °C (90 °F) water.
   2. (2)A relief valve or pressure control valve that maintains the tank pressure below the setting of the tank's required safety relief valve in ambient temperatures of 46 °C (115 °F) air and 32 °C (90 °F) water.
2. (b)A cargo tank with a maximum allowable working pressure of less than 172 kPa (25 psig) is approved by the Commandant (CG-ENG) on a case by case basis.
3. (c)Section 151.50-30 also applies to the carriage of argon or nitrogen.