Lifting system for lifting a monopile, cradle, vessel, and method for storing a monopile on a vessel

Abstract

A lifting system for lifting a monopile, the system comprising a pair of coupling members for connection to the monopile at a longitudinally spaced interval, each of the pair of coupling members having a support for connection to a hoisting device, e.g., a crane, a sling at least partially surrounding the monopile, the sling hanging from the support to form a loop, and a tightening device for changing the length of the sling.

Description

[Technical Field]

[0001] The present invention relates to a lifting system for lifting a monopile.

[0002] Offshore wind turbines may be installed on monopiles driven into the seabed. Typically, the monopiles are manufactured on land and loaded onto a vessel at a quay. The monopile is transferred from the quay to the vessel by a crane and stored horizontally on the vessel's deck. The crane has hoisting cables from which a spreader beam is suspended. Before hoisting the monopile, two slings are connected around the monopile and attached to the spreader beam. After the monopile is installed on the deck, the slings are disconnected from the monopile and connected to another monopile, which will be transferred from the quay to the vessel. After installing the monopile on the deck, the vessel sails to the offshore site where the monopile will be installed into the seabed. At the offshore site, a crane on the vessel can lift the stored monopile after connecting the same spreader beam or another spreader beam including two slings or another sling to the monopile and transfer it to an upending device used to rotate the monopile vertically. Subsequently, the monopile is transported to a location on the vessel, where it can be lowered to the seabed and driven into the seabed by a pile driver. A disadvantage of the above-mentioned operation is that it takes a lot of time to operate at the offshore site. Summary of the Invention [Problem to be solved by the invention]

[0003] It is an object of the present invention to provide a lifting system that minimizes operation time at an offshore site. [Means for solving the problem]

[0004] This object is achieved by a lifting system for lifting a monopile according to the invention, comprising a pair of coupling members for connection to the monopile at a distance from each other in the longitudinal direction of the monopile, each of the pair of coupling members having a support for connection to a hoisting device, for example a crane, a sling for at least partially surrounding the monopile, the sling hanging from the support to form a loop, and a tightening device for changing the length of the loop.

[0005] An advantage of the lifting system according to the present invention is that the pair of connecting members has a relatively simple mechanical structure, which can be connected to the monopile before it is loaded onto a ship, for example, at a quay, and can be held on the monopile until it is loaded onto the ship's upending device. The support can be used to temporarily secure the monopile to a ship, for example, while transporting the monopile to an offshore site, so that the monopile is suspended from the support by a sling. The tightening device provides an opportunity to fasten the sling around the monopile by shortening the length of the loop. This means that the pair of connecting members can function as an offshore tightening tool. At the offshore site, the monopile can be easily lifted by connecting a hoisting member to the support, thus eliminating the time-consuming task of fastening the sling to each of the monopiles. The support and the sling of the connecting members can be adapted so that the monopile fastens to the support when the loop is shortened.

[0006] The pair of coupling members may be separate units.

[0007] The sling may be attached or releasably attachable to the support at its first and second positions, the first and second positions being spaced apart from each other, which means that when shortening the loop of the sling, the monopile may be fastened between the sling and the support at each of the pair of connecting members.

[0008] The sling comprises an endless element wound around the support at the first position and at the second position, in which case the loop of the sling, i.e. the part of the endless element capable of supporting the monopile, is formed by two parts of the sling.

[0009] In certain embodiments, in the second position, the sling is wrapped around two fixed sling guides spaced apart from one another in a plane, and the tightening device includes a dynamic sling guide that guides the sling between the two fixed sling guides, the dynamic sling guide being movable transversely relative to the two fixed sling guides in the plane. The dynamic sling guide can be operated by an actuator. The two fixed sling guides can be pins.

[0010] At the second position, the sling may be wrapped around two fixed sling guides spaced apart from one another, and the two fixed sling guides at the second position may be pins.

[0011] The support may be rigid.

[0012] The support may be an elongated element, for example a steel beam.

[0013] The lifting system comprises a hoisting member for connection to a hoisting device, the hoisting member being releasably attachable to the supports. When the pair of coupling members are separate units, they are preferably applied to the monopile at a fixed distance from each other, since the hoisting member may have fixed dimensions.

[0014] The hoisting member may comprise a rectangular frame having two opposing sides that is releasably attachable to each of the supports.

[0015] The present invention also relates to a cradle for receiving a monopile equipped with the lifting system described herein above, wherein a plurality of said supports fit into cooperating receivers of the cradle, which is advantageous because the monopile can be easily placed in the cradle and lifted from the cradle without detaching the pair of connecting members from the monopile.

[0016] In a preferred embodiment, the two fixed sling guides in the first and second positions may fit into the receiver since in this case the two fixed sling guides have two functions: a function for the sling and a function for being received by the receiver of the cradle.

[0017] The present invention also relates to a watercraft comprising a deck and a cradle, the cradle being movable across the deck.

[0018] The cradle may be movable longitudinally and laterally on the deck, longitudinally, for example to store the monopile away from a crane on the vessel, and laterally, to allow the position of the centre of gravity of the monopile to be changed transversely of the vessel.

[0019] The present invention also relates to a method for storing a monopile on a vessel equipped with a cradle as described hereinabove by using the lifting system as described hereinabove, wherein a plurality of the slings are fitted around the monopile and attached to individual supports spaced apart along the monopile to form individual loops of the slings around the monopile, the individual tightening devices are operated to shorten the loops of the slings until a desired distance is reached between the supports and the monopile, a hoisting member is connected to the supports, thereafter the supports and the monopile equipped with the slings are lifted and transferred to the cradle, the supports are placed in the receiver, and the hoisting member is disconnected from the supports. In the resulting stored state of the monopile, the cradle supports the supports and the support supports support the monopile through the individual slings. When a vessel navigates to an offshore site to install the stored monopile, the support can be simply connected to, for example, a hoisting member and hoisted to transfer the monopile to an upending device where the pair of coupling members can be disconnected from the monopile by operating the clamping device and removing the support and the sling from the monopile.

[0020] The invention will be explained hereinafter with reference to schematic drawings which show, by way of example, one embodiment of the invention. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of one embodiment of a lifting system according to the present invention, showing a monopile being lifted by the lifting system and positioned above a cradle. [Figure 2] FIG. 2 is a view similar to FIG. 1 showing the monopile received by the cradle. [Figure 3] FIG. 3 is a view similar to FIG. 2, showing another state. [Figure 4] Figure 4 is a view similar to Figure 3, showing two monopiles received in the cradle. [Figure 5] FIG. 5 is a front view of the coupling member of the lifting system shown in FIG. [Figure 6] 6 is a side view of the coupling member taken along the line VI in FIG. [Figure 7] FIG. 7 is a view similar to FIG. 6, showing the coupling member in the VII direction in FIG. [Figure 8] FIG. 8 is a view similar to FIG. 7, but showing a different state of the coupling member. [Figure 9] FIG. 9 is a view similar to FIG. 5, but showing a different state of the coupling member. [Figure 10] FIG. 10 is a top view of one embodiment of a watercraft in accordance with the present invention. [Figure 11] FIG. 11 is a view similar to FIG. 10 but showing the vessel in a different state. [Figure 12] FIG. 12 is a view similar to FIG. 10 showing the vessel in yet another state. DETAILED DESCRIPTION OF THE INVENTION

[0022] Figure 1 shows one embodiment of a lifting system according to the present invention. The lifting system 1 comprises a pair of coupling members 2 connected to a monopile 3 at a distance from each other in the longitudinal direction of the monopile 3. In the state shown in Figure 1, the pair of coupling members 2 are attached to a hoisting member 4, which is suspended from a crane (not shown). Figure 1 shows the monopile 3 positioned above a cradle 5.

[0023] Figure 2 shows the monopile 3 being lowered and received in a cradle 5, in which the pair of connecting members 2 are supported by the cradle 5. The cradle 5 is shown as two separate U-shaped frames, but they may also be attached to each other. Figure 3 shows that, after placing the monopile 3 in the cradle 5, the hoisting member 4 is detached from the pair of connecting members 2, for example by a pin release mechanism, and is lifted relative to the monopile 3 and the cradle 5. Figure 4 shows that another monopile 6 has been received in the cradle 5 and placed above the monopile 3, so that the cradle 5 now comprises a stack of two monopiles 3, 6.

[0024] Figure 5 shows one of the pair of connecting members 2. One connecting member 2 has a rigid support 7 and a sling 8 that hangs from the support 7 and partially surrounds the monopile 3. The sling 8 forms a loop that surrounds the monopile 3. The support 7 is an elongated element in the shape of a beam, for example a steel beam. The sling 8 comprises a flexible endless element, for example a rope or cable, that has loops at a first position 9 and a second position 10 of the support 7. The first position 9 and the second position 10 are located at opposite ends of the support 7. Figure 6 shows that at the first position 9, the sling 8 is wrapped around two pins 11 of the support 7.

[0025] Figure 7 shows that in the second position 10, the sling 8 is wound around two fixed sling guides 12 in the form of pins, which are spaced apart from each other in a horizontal plane. Between the two fixed sling guides 12, the sling 8 is guided by a dynamic sling guide 13 in the form of a freely rotatable wheel. The dynamic sling guide 13 is movable relative to the two fixed sling guides 12 perpendicular to the horizontal plane by an actuator (not shown) in order to change the length of the loop of the sling 8 around the monopile 3. In this way, a clamping device 14 is created for connecting the sling 8 around the monopile 3 and the support 7. The latter state is shown in Figures 5 to 7, while Figures 8 and 9 show the state in which the clamping device 14 is released so that the sling 8 is slack. As a result, the support 7 and the sling 8 are not fastened around the monopile 3 and this state can be used to connect or disconnect the connecting member 2 to the monopile 3.

[0026] 1 to 4, the hoisting member 4 is releasably attachable to and detachable from the support 7. In the embodiment shown, the hoisting member 4 has a rigid rectangular frame with release mechanisms at each corner to allow the frame to engage with the support 7.

[0027] In practice, the monopile 3 may be provided with an indicator, such as a line 15, as shown in Figure 1, where the pair of coupling members 2 should be positioned so that the hoisting member 4 can correctly engage with the multiple supports 7.

[0028] 1 to 4 show that the cradle 5 is provided with upwardly facing hooks 16 that define receivers for receiving the pins 11 of the supports 7 and the fixed sling guides 12. Moreover, the cradle 5 is further provided with a retaining member 17 that engages with the monopile 3 in its final position within the cradle 5 so as to lock the monopile 3 horizontally relative to the cradle 5.

[0029] Figure 10 illustrates the cradle 5 carrying the monopiles 3, 6 shown in Figure 4 installed on a vessel 18 for transport to an offshore site where the monopiles will be installed on the seabed, for example for mounting a wind turbine on the monopile. The monopile is transported horizontally and then upended at the offshore site by an upending device. The cradle 5 is movable across the deck 20 of the vessel 18 to move the monopiles to be upended close to a crane 21 also installed on the deck 20. The cradle 5 can be moved longitudinally of the vessel 18 to use the space on the deck 20 away from the crane 21 for storing the monopiles 3, 6, and can be moved laterally to move the center of gravity of the cradle 5 carrying the monopiles 3, 6 to or near the longitudinal center plane of the vessel 18. For this reason, a rail 22 for guiding the cradle 5 is provided on the deck 20 (see FIG. 11).

[0030] Figure 10 shows that the monopiles 3, 6 are loaded onto the cradle 5 from a quay (not shown) when the cradle 5 is located on the starboard side or is moving to the starboard side, and Figure 11 shows that the cradle 5 with the monopiles 3, 6 is then moved to the port side. Prior to departure to the offshore site, multiple cradles 5 can be loaded with multiple monopiles and stored on the deck 20. Figure 12 illustrates that another cradle 5' is loaded with a monopile 3' while the loaded cradle 5 is moved to a position away from the crane 21.

[0031] At the offshore site, each of the cradles 5, 5' is moved towards the crane 21 so that it can lift the stored monopiles 3, 6 after each of the cradles 5, 5' has connected its hoisting members 4 to a respective pair of supports 7 attached to an individual monopile.

[0032] From the above, it is clear that the presence of the pair of connecting members minimizes the operation time at the offshore site, since it is not necessary to connect a sling to each of the plurality of monopiles.

[0033] The present invention is not limited to the embodiments shown in the drawings and described herein above, which may be varied in different ways within the scope of the claims and their technical equivalents. For example, in alternative embodiments, the sling may have a different shape, such as a single rope with loops at its opposite ends. Moreover, the tightening device and the manner of attachment of the sling to the support may be different in alternative embodiments. It is also conceivable that the lifting system comprises supports fixed to and spaced apart from each other, instead of having connecting members as separate units.

Claims

1. A lifting system (1) for lifting monopiles (3, 6), the system (1) comprising a pair of coupling members (2) for connection to the monopiles (3, 6) at a distance from each other in the longitudinal direction of the monopiles (3, 6), wherein each of the pair of coupling members (2) comprises a support (7) for connection to a hoisting device, for example a crane (21), a sling (8) for at least partially surrounding the monopiles (3, 6), the sling (8) hanging from the support (7) to form a loop, and a tightening device (14) for changing the length of the loop (8).

2. 2. The lifting system (1) according to claim 1, wherein the pair of coupling members (2) are separate units.

3. 3. A lifting system (1) according to claim 1 or 2, wherein the sling (8) is attached or releasably attachable to the support (7) at a first position (9) and a second position (10) thereof, the first position and the second position (9, 10) being spaced apart from each other.

4. 4. A lifting system (1) according to claim 3, wherein the sling (8) comprises an endless element wound around the support (7) at the first position (9) and at the second position (10).

5. 5. A lifting system (1) according to claim 3 or 4, wherein in the second position (10), the sling (8) is wound around two fixed sling guides (12) spaced apart from each other in a plane, and wherein the tightening device (14) comprises a dynamic sling guide (13) that guides the sling (8) between the two fixed sling guides (12), and the dynamic sling guide (13) is movable in a transverse direction of the plane relative to the two fixed sling guides (12).

6. 6. A lifting system (1) according to claim 5, wherein in the first position (9), the sling (8) is wound around two fixed sling guides (11) spaced apart from each other.

7. A lifting system (1) according to any one of claims 1 to 6, wherein the support (7) is rigid.

8. A lifting system (1) according to any one of the preceding claims, wherein the support (7) is an elongated element.

9. 9. The lifting system (1) according to any one of claims 1 to 8, wherein the lifting system (1) comprises a hoisting member (4) for connection to a lifting device (21), the hoisting member (4) being releasably attachable to and detachable from the plurality of supports (7).

10. 10. A lifting system (1) according to claim 9, wherein the hoisting member (4) comprises a rectangular frame having two opposite sides which are releasably attachable to each of the supports (7).

11. A cradle (5) for receiving a monopile (3, 6) equipped with a lifting system (1) according to any one of claims 1 to 10, wherein a plurality of said supports (7) fit into cooperating receivers (16) of said cradle (5).

12. A cradle (5) according to claim 11 when dependent on claims 5 and 6, wherein the two fixed sling guides (11, 12) in the first and second positions (9, 10) fit into the receiver (16).

13. A vessel (18) comprising a deck (20) and a cradle (5) according to claim 11 or 12, the cradle (5) being movable across the deck (20).

14. 14. A vessel (18) according to claim 13, wherein the cradle (5) is movable longitudinally and laterally across the deck (20).

15. A method for storing a monopile (3) on a vessel (18) equipped with a cradle (5) according to claim 11 or 12 by using a lifting system (1) according to any one of claims 1 to 10, wherein a plurality of the slings (8) are attached around the monopile (3) and attached to individual supports (7) at intervals along the monopile (3) to form individual loops of the slings (8) around the monopile (3), and the individual tightening devices (14) the loops of the slings (8) are shortened until the distance between the supports (7) and the monopile (3) reaches a desired distance, a hoisting member (4) is connected to the supports (7), then the supports (7) with the slings (8) and the monopile (3) are lifted and transferred to the cradle (5), the supports (7) are placed in the receiver (16), and the hoisting member (4) is disconnected from the supports (7).

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