Method for 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
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Abstract
The invention relates to a method for removing or positioning a structure (103) or a part (107) of a structure which is erected on an underwater bed or anchored to the underwater bed. 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 or a part of a structure which is erected on an underwater bed or anchored to the underwater bed, in which method use is made of:
- 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 such a manner that it can tilt about a horizontal axis, 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;
- and which method comprises the steps of:
- detaching the structure from the underwater bed;
- connecting the structure to the hoisting mechanism;
- hoisting up the structure using the hoisting mechanism;
- attaching the structure to the transport vessel in such a manner that it can tilt about a horizontal axis;
- tilting the structure into a substantially horizontal position.
A method for positioning a structure or a part of the structure on an underwater bed or anchoring it to the underwater bed, in which method use is made of:
- 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 such a manner that it can tilt about a horizontal axis, 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;
- and which method comprises the steps of:
- transporting the structure using the transport vessel;
- tilting the structure from a substantially horizontal transport position into a substantially vertical position, the structure being tiltably attached to the transport vessel;
- connecting the structure to the hoisting mechanism;
- detaching the structure from the transport vessel;
- lowering the structure using the hoisting mechanism;
- detaching the structure from the hoisting mechanism.
Dependencies are inferred from the claim text.