Patent ID: 7281483

Claim:
A semi-submersible drilling or production vessel comprising: a plurality of stabilizing columns each having a top and bottom; a deck disposed between the tops of the plurality of stabilizing columns forming a vessel with a waterline; at least one void tank in at least one stabilizing column; at least one active variable ballast compartment disposed below the at least one void tank in the at least one stabilizing column containing the at least one void tank; at least one emergency water ballast compartment disposed at the bottom of the at least one stabilizing column below the at least one active variable ballast compartment and below the at least one void tank, wherein the at least one emergency water ballast compartment is a pressure equalized tank and is flooded during normal operating conditions; a pressurized air source disposed above the waterline near the tops of the plurality of stabilizing columns, wherein the pressurized air source is adapted for expelling water from the emergency ballast compartment; at least one control valve connected to the pressurized air source for rapidly passing air into the emergency water ballast compartment; and at least one port in the emergency water ballast compartment for expelling water from the emergency water ballast compartment.