Patent ID: 7077071

Claim:
A vessel converted from a single outer hull construction with a spanning, single elevation, pre-located, topside deck into a double hull construction without alteration of the single outer hull and maintaining the topside deck at a single elevation, said single hull vessel having a central cargo tank flanked on either side by port and starboard wing tanks, said central cargo tank being defined by pre-located port and pre-located starboard sidewalls and pre-located fore and aft transverse bulkheads, and an added elevated floor in said central cargo tank, said elevated floor spanning said pre-located sidewalls and said pre-located bulkheads to define within said outer hull a sealed compartment separating the central cargo tank from the outer hull, said spanning elevated floor being of substantially a single elevation and substantially parallel to said spanning topside deck and substantially the same width as a width of the central cargo tank; and at least one hatch opening formed in said pre-located topside deck of said vessel to provide access to said central cargo tank, said hatch opening having peripheral edge spaced away from and inboard of the pre-located port and starboard sidewalls of said central cargo tank so that said hatch opening and said topside deck remain substantially at a single elevation with minimal degradation of structural integrity of said topside deck.