46 CFR § 153.964 - Discharge by gas pressurization.
(a) The tank to be offloaded has an SR or PV venting system;
(c) The pressurizing line has:
(1) A pressure reducing valve whose setting does not exceed 90% of the tank's relief valve setting and a manual control valve between the pressure reducing valve and the tank; or
(2) For an inert gas medium:
(ii) A manual control valve between the safety relief valve and the tank; and
(iii) A check valve between the manual control valve and the tank.