| 摘要 |
Upon loading of oil cargo the ullage space of a tank of an oil tanker is sealed substantially gas tight with the gaseous contents of the ullage space both (i) initially inerted so as to be incapable of supporting combustion of any oil within the tank, and (ii) at an initial pressure less than atmosphere. The tank is preferably continued closed, preferably optionally with closed loop recirculation for purposes of gas mixing, for the entire voyage of the tanker save that (1) ullage space gas pressure uncommonly exceeds limits because of any of (i) leakage of atmospheric gases into the tank, and/or (ii) outgassing of gases within the oil contents of the tank, (iii) evaporation of the oil or portions thereof, and/or (iv) expansion of the ullage space gases upon thermal heating, and/or (2) free oxygen within the ullage space gases exceeds limits because of any leakage of atmospheric gases into the tank, at which time the tank is re-inerted, preferably with flue gases, or again de-pressurized, as and when required. Normally ullage space gas pressure remains, nonetheless to potentially becoming more positive, suitably negative throughout the entire voyage of the tanker, continuously preventing that hydrostatic pressure within the tank should equalize with a surrounding ocean upon any occasion of incipient rupture of the tank below the water line and thus continuously precluding at least some outflow of oil as would otherwise occur upon the occasion of the rupture. Normally free oxygen within the ullage space gases remains, nonetheless to potentially increasing, suitably low throughout the entire voyage of the tanker so as to prevent that combustion should occur.
|
