Method and apparatus for the offshore installation of multi-ton packages such as deck packages, jackets, and sunken vessels

A method for the offshore lifting of a multi-ton package such as a deck package, sunken vessel or jacket, comprising the steps of:

• a) transporting a lifting assembly to a desired site of the package;
• b) attaching a lifting assembly to the package at multiple positions including positions that are at least on generally opposite sides of the package, the lifting assembly including at least three chords, including a horizontal chord normally in tension during the lifting process which has a variable length and a diagonally extending chord normally in compression during the lifting process;
• c) wherein in step "a" the lifting assembly includes two opposed lifting booms connected by at least one compression frame member that spans between upper end portions of the booms, a plurality of slings with end portions that respectively attach to the combination of booms and compression frame member;
• d) structurally supporting the lifting assembly with one or more lift barges;
• e) supporting the package with the slings;
• and
• f) lifting the package by changing the length of the horizontal chord of the lifting assembly.

A method for the offshore lifting a multi-ton package such as a deck package, jacket or submerged vessel, comprising the steps of:

• a) transporting a lifting assembly to a desired site having the package;
• b) attaching the lifting assembly to the package at multiple elevational positions on the package, including upper and lower positions that are at least on generally opposite sides of the package;
• c) wherein the lifting assembly includes opposed floating barges having diagonally extending lifting booms thereon connected at their upper ends by a compression member and horizonal chords that can be varied in length and in step "b" vertical slings are used to attach the upper end portion of each of the diagonally extending lifting booms at the compression member to the package;
• d) structurally supporting each of the lifting booms at the lower end portion thereof with one of the barges, each boom being pivotally attached to its barge;
• e) wherein the package is supported by the slings depending from the upper end of the booms and the slings attaching to the package;
• and
• f) elevating the package by changing the length of the horizontal chord of each lifting assembly.