(a) Tanks carrying liquids or liquefied gases at ambient temperatures regulated by this subchapter shall be limited in the amount of cargo loaded to that which will avoid the tank being liquid full at 105 °F if insulated, or 115 °F if uninsulated. If specific filling densities are designated in Subpart 151.50 of this part, they shall take precedence over that noted above.
(b) Refrigerated and semirefrigerated tanks shall be filled so that there is an outage of at least 2 percent of the volume of the tank at the temperature corresponding to the vapor pressure of the cargo at the safety relief valve setting. A reduction in the required outage may be permitted by the Commandant when warranted by special design considerations. Normally, then, the maximum volume to which a tank may be loaded is:
VL = 0.98drV ÷ dL
where:
VL = Maximum volume to which tank may be loaded.
V = Volume of tank.
dr = Density of cargo at the temperature required for a cargo vapor pressure equal to the relief valve setting.
dL = Density of cargo at the loading temperature and pressure.