Method and system for assembling a structure for offshore use

Abstract

A method, system and support apparatus 130, 145 (160 in other figures) for assembling a structure 200, e.g. a tripod lifting structure with three legs, for use in offshore assembly of a further struct

Claims

1. A method of assembling a structure for use in offshore assembly of a further structure, the method comprising:coupling a first leg of the structure to a support apparatus disposed in a first assembly orientation;rotating the support apparatus to a second assembly orientation; and coupling a second leg of the structure to the support apparatus.

2. The method of claim 1, comprising rotating the support apparatus to a further assembly orientation different from the first and second assembly orientations and coupling a further leg of the structure to the support apparatus.

3. The method of claim 1 or 2, comprising coupling a total of three or more legs of the structure to the support apparatus.

4. The method claim 3, comprising assembling a tripod structure having three legs, for use in offshore assembly of the further structure.

5. The method of claim 4, comprising the steps of:coupling the first leg to the support apparatus in the first assembly orientation;rotating the support apparatus approximately 120 degrees to the second assembly orientation;coupling the second leg of the offshore assembly to the support apparatus;rotating the support apparatus approximately a further 120 degrees to a third assembly orientation;coupling a third leg of the offshore assembly to the support apparatus.

6. The method of any preceding claim, wherein the support structure comprises a top-assembly, and wherein coupling each leg of the structure to the support apparatus comprises coupling each leg of the structure to the top-assembly.

7. The method of claim 6, wherein the top-assembly forms an apex of the structure for use in offshore assembly of the further structure.

8. The method of any preceding claim, wherein the support apparatus is provided on or coupled to one or more rails or guides, and wherein the method comprises moving the support apparatus along the one or more rails or guides to an assembly location for coupling the / each leg to the support apparatus.

9. The method of claim 8 wherein, after coupling each leg to the support structure: the support apparatus is transitioned away from the assembly location along the one or more rails or guides;then, the support apparatus is rotated to a / the further assembly orientation; and thenthe support apparatus is transitioned back to the assembly area along the one or more rails or guides to receive a / the further leg.

10. The method of any of claim 8 or 9, wherein a crane having at least one supporting member is provided at the assembly location, said crane being configured to lift the / each leg, and wherein the method comprises:moving the support apparatus a sufficient distance along from the one or more rails or guides away from the assembly location such that the support apparatus is rotated between different assembly orientations without the / each leg coupled to the support apparatus interfering with the at least one supporting member.

11. The method of any of claims 8 to 10, wherein the one or more rails or guides extend from the assembly location to a vessel, and wherein the method comprises transitioning the (assembled) structure for use in offshore assembly of the further structure from the assembly location to the vessel.

12. A system for assembling a structure for use in offshore assembly of a further structure, the system comprising a moveable and rotatable support apparatus configured to receive a first leg of the structure.

13. The system of claim 12, wherein the support apparatus is configured to receive a plurality of legs.

14. The system of claim 12 or 13, wherein the support apparatus is configured to receive three legs to form a tripod structure for use in offshore assembly of the further structure.

15. The system of any of claims 12 to 14, wherein the support structure comprises a top-assembly, and wherein coupling the / each leg of the structure to the support apparatus comprises coupling the / each leg of the structure to the topassembly.

16. The system of any of claims 12 to 15 comprising a crane, wherein the crane comprises at least one supporting member provided at the assembly location, said crane being configured to lift the / each leg.

17. The system of claim 16, wherein the crane comprises a gantry crane having a lifting member extending from a gantry portion disposed over the assembly location and configured to lift the / each leg.

18. The system of any of claims 12 to 17, wherein the support apparatus is provided on or coupled to one or more rails or guides for moving the support apparatus to an assembly location for coupling the / each leg to the support apparatus.

19. The system of claim 18, wherein the one or more rails or guides extends away from the assembly location a sufficient distance to enable the support apparatus to move along from the one or more rails or guides away from the assembly location such that the support apparatus is rotated between different assembly orientations without the / each leg coupled to the support apparatus interfering with the at least one supporting member.

20. The system of claim 18 or 19, wherein the one or more rails or guides extend from the assembly location to a vessel.

21. A support apparatus for use in assembly of a structure for use in offshore assembly of a further structure, the support apparatus comprising:a tower structure; anda plurality of arms extending from the tower structure;5 wherein each arm and an upper portion of the tower structure isconfigured to support each leg of the structure for use in offshore assembly.

22. The support apparatus of claim 21, wherein the upper portion of the tower structure comprises a top-assembly for coupling to each leg of the structure for10 use in offshore assembly.

23. The support apparatus of claim 22, wherein:the top-assembly forms an apex of the structure for use in offshore assembly of the further structure; and15 the top-assembly is detachably coupled to a main portion of the towerstructure.s

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