Method of removing or positioning a substructure of an offshore platform
AssigneeHeerema Marine Contractors Nederland B. V.
InventorsOnno Ludolf de Waard, Richard Petrus Gerhardus Zoontjes, Jan Molenaar
Life of this patent
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Abstract
The method for removing or positioning a structure (103) which is erected on either an underwater bed or anchored to the underwater bed entails the use of a hoisting mechanism. When the structure (103) is being removed, it is detached from the underwater bed. Then, the structure (103) is connected to a hoisting mechanism which is arranged on a separate hoisting vessel (100). The structure is hoisted up by the hoisting mechanism and is attached to a transport vessel (1) in such a manner that it can tilt about a horizontal axis. Then, the structure is tilted into a substantially horizontal position. The structure is positioned in the reverse order.
Claims16
A method for removing a structure which is attached to an underwater bed, using a hoisting vessel provided with a hoisting mechanism for hoisting up the structure, and a transport vessel for transporting the structure, the transport vessel being provided with attachment means for attaching the structure in a substantially vertical position to the transport vessel and with tilting means for tilting the structure between the substantially vertical position and a substantially horizontal position, wherein the hoisting vessel and the transport vessel are separate vessels, said method comprising the steps of:
- (i) detaching the structure from the underwater bed;
- (ii) connecting the structure to the hoisting mechanism;
- (iii) hoisting up the structure using the hoisting mechanism;
- (iv) attaching the structure to the transport vessel in such a manner that it can tilt about a horizontal axis;
- and
- (v) tilting the structure into a substantially horizontal position.
A method for positioning a structure which is to be attached to an underwater bed, using a hoisting vessel provided with a hoisting mechanism for hoisting up the structure, and a transport vessel for transporting the structure, the transport vessel being provided with attachment means for attaching the structure in a substantially vertical position to the transport vessel and with tilting means for tilting the structure between the substantially vertical position and a substantially horizontal position, wherein the hoisting vessel and the transport vessel are separate vessels, said method comprising the steps of:
- (i) transporting the structure using the transport vessel;
- (ii) tilting the structure from a substantially horizontal transport position into a substantially vertical position, the structure being tiltably attached to the transport vessel;
- (iii) connecting the structure to the hoisting mechanism;
- (iv) detaching the structure from the transport vessel;
- (v) lowering the structure using the hoisting mechanism;
- and
- (vi) detaching the structure from the hoisting mechanism.
Dependencies are inferred from the claim text.