Jack-up platform comprising a mooring system and method for mooring a floating vessel

Abstract

A jack-up platform is described having a horizontal working deck that may be jacked up out of the water by moving its legs to a position wherein they take support on an underwater bottom. The jack-up platform further comprises a mooring system for mooring a floating vessel at a mooring side of the jack-up platform. The mooring system comprises an elongated support means for supporting a hull part of the floating vessel, and guiding means connected to the hull of the jack-up platform at the mooring side. The guiding means are able to rigidly hold the elongated support means in a support position, in which the elongated support means is within reach of the hull part of the floating vessel to be supported when the hull is jacked out of the water and the jack-up platform rests on its legs. A method for mooring a floating vessel using the jack-up platform is also described.

Claims

1. A jack-up platform comprising a hull, a horizontal working deck and a number of vertical legs that connect to the working deck through jacking systems, each jacking system being configured to move a leg between a lower position, in which the leg takes support on an underwater bottom and the hull is jacked out of the water, and a higher position, in which the leg is free from the underwater bottom and the hull is floating on the water, wherein the jack-up platform further comprises a lifting device configured for lifting objects from a floating vessel, and a mooring system configured to moor the floating vessel at a mooring side of the jack-up platform, the mooring system comprising at least two elongated support means for supporting a hull part of the floating vessel, and for connecting the floating vessel to the jack-up platform, and guiding means connected to the hull of the jack-up platform at the mooring side, and configured to rigidly hold the elongated support means in a support position, in which the elongated support means are within reach of the hull part of the floating vessel to be supported when the hull is jacked out of the water and the jack-up platform rests on its legs, wherein the mooring system is configured to stabilize the floating vessel in at least a horizontal plane relative to the jack-up platform and the lifting device by limiting horizontal movements.

2. Jack-up platform according to claim 1, wherein the lifting device is configured to lift the elongated support means from a resting position on the working deck and provide the elongated support means to the guiding means and into its support position.

3. Jack-up platform according to claim 1, wherein the guiding means are hingedly connected to the hull of the jack-up platform, and the lifting device is configured to up-end the elongated support means from a resting position on the working deck around the guiding means and into its support position.

4. Jack-up platform according to claim 1, wherein the guiding means hold the elongated support means.

5. Jack-up platform according to claim 1, wherein the guiding means are configured to hold the elongated support means and move the same between different vertical positions.

6. Jack-up platform according to claim 1, wherein elongated support means, in the support position, takes support on or in the underwater bottom.

7. Jack-up platform according to claim 1, wherein a vertical leg of the jack-up platform comprises a transversely enlarged foot support and an elongated support means, in the support position, takes support on or in the transversely enlarged foot support.

8. Jack-up platform according to claim 1 wherein the guiding means comprise at least one vertical leg of the jack-up platform located at the mooring side.

9. Jack-up platform according to claim 1, further comprising a connecting structure configured to connect an elongated support means with a vertical leg of the jack-up platform, while allowing the elongated support means to be moved between different vertical positions.

10. Jack-up platform according to claim 1, wherein the elongated support means extends vertically in the support position.

11. Jack-up platform according to claim 1, wherein the number of elongated support means is at least three.

12. Assembly of a jack-up platform in accordance with claim 1 and a floating vessel, moored against it with the mooring system.

13. Assembly according to claim 12, wherein the mooring system, the jack-up platform and/or the floating vessel comprises auxiliary equipment selected from among winches, mooring lines and fenders.

14. Assembly according to claim 12, wherein the floating vessel comprises a dynamic positioning (DP) system.

15. Method for lifting an object from a floating vessel provided at a mooring side of a jack-up platform in accordance with claim 1, the method comprising the steps of: moving the legs of the jack-up platform from a higher position, in which the legs are free from an underwater bottom and the hull is floating on the water, to a lower position, in which the legs take support on the underwater bottom and the hull is jacked out of the water; providing elongated support means, configured for supporting a hull part of the floating vessel and connecting the floating vessel to the jack-up platform, in a support position of the elongated support means within reach of the hull part of the floating vessel to be supported by guiding means connected to the hull of the jack-up platform at the mooring side; rigidly holding the elongated support means in the support position by the guiding means; mooring the floating vessel against the elongated support means, and stabilizing the floating vessel in at least a horizontal plane relative to the jack-up platform and the lifting device by limiting horizontal movements; and lifting an object from a deck of the moored floating vessel and providing the object on the working deck of the jack-up platform or other substrate.

16. Method according to claim 15, wherein the object comprises a foundation element of a wind turbine.

17. Method according to claim 15, further comprising lowering the object onto and into the underwater bottom.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will now be elucidated with reference to the following figures, without however being limited thereto. In the figures:

(2) FIG. 1 represents a schematic perspective view of a jack-up platform against which a floating vessel is moored in accordance with an embodiment of the invention;

(3) FIG. 2 represents a schematic side view of the jack-up platform shown in the embodiment of FIG. 1;

(4) FIG. 3A shows a schematic top view of the jack-up platform shown in the embodiment of FIG. 1;

(5) FIG. 3B shows a schematic top view of the jack-up platform shown in the embodiment of FIG. 1 against which a floating vessel is moored;

(6) FIG. 4 represents a schematic perspective view of a jack-up platform against which a floating vessel is moored in accordance with yet another embodiment of the invention;

(7) FIG. 5 represents a schematic side view of the jack-up platform shown in the embodiment of FIG. 4;

(8) FIG. 6 represents a schematic perspective view of a jack-up platform against which a floating vessel is moored in accordance with yet another embodiment of the invention;

(9) FIG. 7 represents a schematic side view of the jack-up platform shown in the embodiment of FIG. 6;

(10) FIG. 8A to 8E schematically show a top view of method steps that include lifting the elongated support means with a lifting device from a resting position on the working deck of the jack-up platform and providing the elongated support means to the guiding means and into its support position in accordance with an embodiment of the invention;

(11) FIG. 9A to 9E schematically show a side view of the method steps shown in FIGS. 8A to 8E respectively;

(12) FIG. 10 represents a schematic perspective view of a jack-up platform against which a floating vessel is moored in accordance with yet another embodiment of the invention; and finally

(13) FIG. 11 represents a schematic perspective view of a jack-up platform against which a floating vessel is moored in accordance with yet another embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

(14) With reference to FIGS. 1 and 2, a jack-up vessel or platform 1 in accordance with an embodiment of the invention, comprises a hull 10, a horizontal working deck 11 and a number of vertically extending legs 12 that connect to the working deck 11 through a jacking system 13, provided on corners of the hull 10. Each jacking system 13 is configured to move a leg 12 between a higher position, in which the leg 12 is free from an underwater bottom 2 and the hull 10 is floating on the water 3, and a lower position, shown in FIGS. 1 and 2. In the lower position of the legs 12, each leg 12 takes support on or in the underwater bottom 2 and the hull 10 is jacked out of the water over some distance 14 between a bottom of the hull 10 and the water surface 30. The legs 12 shown are of lattice type and at a bottom side provided with shoes or spud cans 120. The legs 12 may be embodied differently however, and may for instance comprise solid legs, optionally without shoes 120.

(15) The jack-up platform 1 further comprises a mooring system 4. The mooring system 4 is configured to moor a floating vessel 5 at a mooring side 15 of the jack-up platform 1. In the shown embodiment, the mooring system 4 comprises three elongated support means in the form of lattice or other leader legs of triangular or other cross-section shape 40, and guiding means, which could come in the form of a jacking system 41, rigidly connected to the hull 10 of the jack-up platform 1 along a line extending parallel to the mooring side 15 of the hull 10. The connection may be welded, or may be embodied by any other suitable way of connection. Each guiding means 41 in operation holds an elongated leader leg 40 and is able to move the leader leg 40 up and down between different vertical positions, as schematically shown by the arrows 43 in FIG. 1. Each guiding means 41 is configured to rigidly hold an elongated leader leg 40 in a support position, shown in FIGS. 1 and 2, in which each elongated leader leg 40 (or at least some of these legs 40) is within reach of a hull part 50 of the floating vessel 5 to be supported when the hull 10 is jacked out of the water 3 over the distance 14 and the jack-up platform 1 rests on its legs 12. In the support position, each leader leg 40 is jacked down sufficiently to be able to support said hull part 50 of the floating vessel 5, moored against the jack-up platform 1. In the support position, each leader leg 40 thereto extends into the water 3 over a distance 42 (see FIG. 2) that reaches sufficiently deep to enable supporting the hull part 50 of the floating vessel 5 in mooring position. An outer end of each leader leg 40 is hanging freely in the water 3.

(16) In the mooring position of the floating vessel 5, the connection between the floating vessel or barge 5 and the leader legs 40 may be accomplished by using conventional mooring lines 51 and winches 52, provided on the floating vessel 5. The winches could also be provided on the jack-up vessel 1, or be integrated in one or more of the leader legs 40. The winches 52 are configured to take in a length of mooring line 51, thereby bringing the vessel 5 closer to the leader legs 40 in the direction of the arrow 53 of FIG. 3B, until the hull part 50 contacts the leader legs 40. Paying out a length of mooring line 51 may remove the floating vessel 5 from the mooring side 15 of the jack-up platform. To prevent peak loads on the leader legs 40 from occurring, shock dampers may be incorporated in between each leader leg 40 and the hull part 50 of the floating vessel 5, such as the fenders 54.

(17) The jack-up platform 1 further comprises a lifting device 6, a boom 60 of which is pivotably provided around a lifting device base 61, supported on the working deck 11 of the jack-up platform 1. The lifting device 6 is further provided with hoisting cables 62 and, at a free outer end thereof, with a hoisting block 63 with hook, from which an object (not shown) may be suspended. In an embodiment, the lifting device 6 may also be used for lifting a number of leader legs 40 from a resting position on the working deck 11 and providing each leader leg 40 into its corresponding guiding means 41, and for lowering each leader leg 40 into its support position. Alternatively, the leader legs 40 and the guiding means 41 are pre-assembled and configured to be able to be up-ended overboard together, whereby the guiding means 41 are provided with a hinge point on the side of the hull 10. This embodiment is shown in FIGS. 8A to 8E, and 9A to 9E. As shown in FIGS. 8A and 8B, three leader legs 40 are provided in a rest position on the working deck 11 of the jack-up platform 1. This may also be the position of the leader legs 40 during transport to the offshore site of interest. In their rest position, the leader legs 40 may for instance be provided horizontally (as shown) in appropriate storage means. As shown in FIGS. 8B and 9B, the lifting device 6 is luffed up and a hoisting frame 64 connected to the hoisting block 63 is brought to the leader legs 40 which are then attached to three cables 65 of the hoisting frame 64 at a port side of the jack-up platform 1. Please note that the hoisting frame 64 and the mooring system may also be provided at starboard side of the jack-up platform 1. Referring to FIGS. 8C and 9C, the lifting device 6 up-ends the three leader legs 40 suspended from the frame 64 and brings them to the starboard side of the jack-up platform, which starboard side, in the embodiment shown, corresponds with the mooring side 15 of the jack-up platform 1. The leader legs 40 are up-ended together with their respective guiding means 41, and lowered further into their support positions, as shown in FIGS. 8D and 9D. Each leader leg 40 is clamped by its corresponding guiding means 41, and firmly held in this support position. As shown in FIGS. 8E and 9E, a floating vessel 5 may then be moored against the elongated leader legs 40 with appropriate auxiliary equipment such as winches, mooring lines and fenders, as already described above. As shown in FIG. 8E, the floating vessel 5 may be provided with objects to be lifted, which in the embodiment shown comprise wind turbine blades 7 and a nacelle 8, carried on deck 55 of the vessel 5.

(18) In another embodiment, the guiding means 41 are provided with an optional hinge point on the side of the hull 10, and the leader legs 40 positioned on deck separately from the guiding means 41. The leader legs 40 may then be taken up by the lifting device 6 and inserted in the guiding means 41, and brought overboard.

(19) FIGS. 4 and 5 show yet another embodiment of the invention. Here, a jack-up platform is provided having the same features as the embodiment shown in FIGS. 1 and 2, but having the three leader legs 40, in the support position, extend into the underwater bottom 2 over some distance 44 to take support in the underwater bottom 2. In this embodiment, forces exerted by the moored vessel 5 on the leader legs 40 are not only absorbed by the guiding means 41 and led into the hull 10 of the jack-up platform 1, but are also absorbed by their fixation into the underwater bottom 2. In order to facilitate penetration of the leader legs 40 into the underwater bottom 2, the leader legs 40 may at a bottom side thereof be provided with pointed end parts 45.

(20) Yet another embodiment of the invention is shown in FIGS. 6 and 7. Here, a jack-up platform is provided having the same features as the embodiment shown in FIGS. 1 and 2, but having the three leader legs 40, in the support position, extend into an enlarged foot section or shoe 120 of each vertical leg 12 of the jack-up vessel or platform 1. In the support position of the leader legs 40, each leader leg 40 at the mooring side 15 of the jack-up vessel or platform 1 then takes support in its corresponding spud leg shoe 120, provided on the mooring side 15. In this embodiment, forces exerted by the moored vessel 5 on the leader legs 40 are not only absorbed by the guiding means 41 and led into the hull 10 of the jack-up platform 1, but are also absorbed by their fixation into the shoes 120. The connection between a lower part of the leader legs 4 and the shoes 120 may be permanent, for instance by welding, or may be detachable, for instance by providing the shoes 120 with holes into which a lower part of each leader leg 40 may be received and, optionally, secured. This embodiment has the additional advantage of not having to rely on the, sometimes uncertain or variable, properties and cohesion of the underwater bottom 2.

(21) FIG. 10 yet shows another embodiment of the jack-up platform 1 and mooring system 4. In the embodiment shown, the jack-up platform 1 further comprises a connecting structure 9, comprising a steel brace or beam 90, that is configured to connect the leader legs 40 with a vertical spud leg 12 of the jack-up platform 1. The connecting structure 9 connects with each spud leg 12 through guides 91 that are provided on each end of the brace or beam 90. The guides 91 allow the leader legs 40 to be moved between different vertical positions, relative to the spud legs 12 of the jack-up platform 1. In this embodiment, forces exerted by the moored vessel 5 on the

(22) leader legs 40 are not only absorbed by the guiding means 41 and led into the hull 10 of the jack-up platform 1, but are also absorbed by the spud legs 12 on the mooring side 15, or alternatively, on spud legs provided on another side than the mooring side 15. The forces are transmitted to said spud legs 12 through the connecting structure 9. The connecting structure 9 shown had one brace 90 but may also comprise a plurality of braces, provided on different heights (vertical levels).

(23) As shown in FIG. 11, another embodiment comprises a jack-up platform 1 wherein the guiding means actually comprise the vertical spud legs 12 provided at the mooring side 15 of the jack-up platform 1, and its corresponding jacking system 13. The elongated leader legs 40 in this embodiment extend vertically along the mooring side spud legs 12 in the support position. They are attached to the mooring side spud legs 12 through leader leg guides 47 that are fixedly provided on each end of each leader leg 40. An upper and a lower leader leg gliding guide 47 of a leader leg 40 are provided around a spud leg 12 such that they allow the leader leg 40 to be moved between different vertical positions, relative to the spud leg 12 of the jack-up platform 1. At least an upper or a lower leader leg guide 47 (or both) may be fixed onto the leg 12 in the support position of the leader leg 40. In this embodiment, forces exerted by the moored vessel 5 on the leader legs 40 are not absorbed by the guiding means 41 and led into the hull 10 of the jack-up platform 1. Instead, they are absorbed by the jacking system 13 of the spud legs 12 at the mooring side 15. This may be a practical solution, as long as the expected mooring forces do not increase to levels such that the integrity of the spud legs 12 system may be compromised.

(24) The invented jack-up platform 1 may be used advantageously for mooring a floating vessel 5 against it. An assembly of the invented jack-up platform 1 and such a floating vessel 5 is for instance shown in FIGS. 1, 3B, 4, 6, 8E, 9E, 10 and 11, and represents a relatively stable assembly, due to the stabilizing effect of the spud legs 12 and the mooring system 4 on the assembly (1, 5). The floating vessel 5 may comprise a dynamic positioning (DP) system 56, as schematically shown in FIG. 8E.

(25) The assembly (1, 5) of a floating vessel 5 moored against a jack-up platform 1 under the intervention of the mooring system 4, allows to safely lifting an object, such as a wind turbine blade 7 or a nacelle 8, from the deck 55 of the moored floating vessel 5. Other systems may in addition be used to safely lift-off an object. Another benefit of the invented mooring system is that the floating vessel is kept positioned in the horizontal direction as close as possible to the jack-up platform 1 and its lifting device to maximize the lifting device's efficiency. Having the invented mooring system on the lifting device vessel means it can be used with all different kinds of floating vessels without being forced to adapt the latter. The lifted object may be provided on the working deck 11 of the jack-up platform 1 or on another substrate, such as a foundation element of a wind turbine (not shown) provided in the underwater bottom 2. It is without saying that other objects may be lifted such as a monopile, a transition piece, wind turbine components and other objects that are used in installing wind turbines offshore.

(26) The invention is not limited to the above described embodiments and also comprises modifications thereof, to the extent that these fall within the scope of the claims appended below.