A stabilisation system and assembly for use in deep water offshore

Abstract

A stabilisation assembly for use in deep water. The assembly comprises a telescopic spar for securement within a moon pool of a floating support vessel. The securement mechanism includes a gimbal joint secured within the moon pool through which the spar is suspended to allow movement of the vessel with respect to the spar during use.

Description

[0001] A STABILISATION SYSTEM AND ASSEMBLY FOR USE IN DEEP WATER OFFSHORE

[0002] Field of invention

[0003] The present invention relates to a stabilisation system and assembly for use in deep water offshore. More especially the invention relates to a stabilisation system and assembly for a crane, platform, wind turbine or the like in deep water offshore.

[0004] Backaround to the Invention

[0005] The demand for heavy lifting operations in deep water offshore has never been greater, with increasing decommissioning of oil and gas installations in favour of a rapid expansion of the offshore wind industry to combat climate change.

[0006] Within the wind industry there is a drive for larger, more economic machines sited offshore in deep water to take advantage of the higher, more constant and cleaner air flows. Future generations of wind turbines are likely to rival prominent tall landmarks for size. 15MW turbines for example are approaching 265m in height.

[0007] Heavy lifting in deep waters offshore has always been a challenge. It requires specialist machinery at huge expense. Historically, operations have required calm weather windows to operate efficiently often leading to drawn-out, overrun projects caused by unsettled weather conditions.

[0008] Nevertheless, the rise of offshore wind energy over recent years has made offshore lifting operations a regular occurrence and current solutions are struggling to cope.

[0009] Current heave compensated cranes have limitations on size. Traditional large cranes have limitations on sea and weather conditions. Current Jack-up cranes are limited to sea depth. Current semi-submersible cranes are limited by expense (typically around $1 B per vessel).

[0010] The present invention seeks to provide a crane stabilisation system and assembly for use in deep water offshore which does not have the limitations discussed above.

[0011] Specifically, the invention seeks to utilise a more versatile spar platform suitable for transportation to, and use in, deep water lifting operations.

[0012] Spar platforms are recognised for providing high stability in any sea condition. Due to the deep draft however, they can only be fully deployed at a deep water site. As such, where spars are used, they have to be floated on their side to the deployment site before being up righted. Their considerable length makes the transportability and deployment challenging.

[0013] The invention seeks to provide an improved spar assembly that is telescopic to increase versatility and transportability utilising a conventional vessel or sea going barge.

[0014] Further, the invention seeks to provide a more versatile stabilisation mechanism which is not limited, and is largely unaffected by, sea conditions.

[0015] Specially, the invention seeks to provide an improved deep sea stabilisation assembly allowing pivotal movement between the support vessel and the spar during use such that the industrial equipment supported by the spar is largely unaffected by changes in sea conditions.

[0016] The industrial equipment could be, for example without limitation, a platform (to allow maintenance of offshore equipment for example), a crane, or a wind turbine.

[0017] Statements of the Invention

[0018] According to one aspect of the invention, there is provided a stabilisation assembly for use in deep water, the assembly comprising a telescopic spar for securement within a moon pool of a floating support vessel, the securement mechanism including a gimbal joint secured within the moon pool through which the spar is suspended to allow movement of the vessel with respect to the spar during use.

[0019] Preferably, the spar supports a crane.

[0020] Alternatively, or additionally, the spar supports a wind turbine.

[0021] Alternatively, or additionally, the spar supports a platform.

[0022] Preferably, the spar is constructed to have at least two tubular sleeve sections, one slidable within the other to telescopically extend or retract the spar.

[0023] Preferably, the spar is constructed of three tubular sections.

[0024] Preferably, each section includes helical strakes on the outer surface.

[0025] Preferably, the spar includes a collapsible bladder in a top section to enable adjustment of the buoyancy of the spar.

[0026] Preferably, a bottom section includes a ballast secured thereto. Preferably, the spar includes internal access ladders and platforms that self-deploy during extension of the spar.

[0027] Preferably, the gimbal joint comprises inner and outer concentric rings with pivot points at 90 degrees to each other.

[0028] Preferably, the inner ring is connected to the spar via two opposing pivot points at 180 degrees to each other and is connected to the outer ring via another two opposing pivot points at 90 degrees to the spar connections.

[0029] Preferably, the outer ring is split longitudinally into two halves which are pivotally connected at each end, and which share a common pinion to the inner ring.

[0030] Preferably, the end of each half ring distal to the pivotal connection has a counterweight secured thereto.

[0031] Preferably, each counterweight is secured to the outer ring via an arm supported on a perpendicularly orientated shaft and bearing point fixed to an inner wall of the moon pool to create a fulcrum.

[0032] Preferably, the counterweights are housed within recesses built into the deck and hull of the vessel.

[0033] Preferably, the assembly further comprising means to lock the gimbal rings and counterweights in position.

[0034] According to a second aspect of the invention, there is provided a floating vessel having at least two moon pools, each including a stabilisation assembly according to the first aspect.

[0035] According to a third aspect of the invention, there is provided a construction for location in deep water offshore, the construction having secured thereto a telescopic spar to provide stability to the construction when extended.

[0036] By construction it is meant an industrial installation to be located in deep water offshore. For example, a wind turbine or platform. The platform could be a service platform for maintenance of a wind turbine by authorised personnel.

[0037] According to a fourth aspect of the invention, there is provided, a floating vessel for transportation of the construction of the fourth aspect to a location in deep water offshore, the floating vessel including a gimbal joint of any previous aspect secured within framework on the vessel, the gimbal joint having means to receive and suspend the telescopic spar whilst the spar is fully retracted, during transportation. According to a fifth aspect of the invention, there is provided method of stabilising a wind turbine in a deep water location offshore, the wind turbine having a stabilisation assembly of any previous aspect and the method comprises the steps of retracting the spar such that the ballast is flush with the bottom if a hull of the floating vessel; locking the gimbal joint and counterweights in position within the moon pool of the floating vessel; transporting the wind turbine to the deep water offshore location; unlocking the gimbal joint and counterweights to allow pivotal movement; and fully extending the spar downwardly to stabilise the wind turbine.

[0038] According to a sixth aspect of the invention, there is provided method of stabilising a wind turbine in a deep water location offshore, the wind turbine having a stabilisation assembly of any previous aspect and method of stabilising a wind turbine in a deep water location offshore using the floating vessel of the fifth aspect, the wind turbine having a stabilisation assembly of any previous aspect, and the method comprising the steps of parting the gimbal joint to receive the wind turbine spar when the spar is fully retracted; clamping the gimbal joint around the spar; locking the gimbal joint and counterweights in position to prevent any pivotal movement, transporting the wind turbine to the deep water offshore location; unlocking the gimbal joint and counterweights to allow pivotal movement; fully extending the spar downwardly to stabilise the wind turbine; and parting the gimbal joint to release the wind turbine spar.

[0039] Brief description of drawings

[0040] At least one embodiment of the invention will now be described with reference to the accompanying figures, in which:

[0041] Figure 1 illustrates a crane stabilisation assembly constructed in accordance with a first embodiment of the invention;

[0042] Figure 2 illustrates the assembly of figure 1 , with the spar deployed;

[0043] Figure 3 illustrates the deployment of the spar;

[0044] Figure 4 is plan cross-sectional view of the assembly;

[0045] Figure 5 is a side schematic cross-sectional view of the assembly;

[0046] Figure 6 illustrates a crane stabilisation assembly constructed in accordance with a second embodiment of the invention;

[0047] Figure 7 illustrates the assembly of figure 6, with the spars deployed;

[0048] Figure 8 illustrates a crane stabilisation assembly constructed in accordance with a third embodiment of the invention; Figure 9 illustrates a crane stabilisation assembly constructed in accordance with a fourth embodiment of the invention;

[0049] Figure 10 illustrates a crane stabilisation assembly constructed in accordance with a fifth embodiment of the invention;

[0050] Figure 11 is a plan view of the assembly of figure 10; and

[0051] Figure 12 illustrates a wind turbine deployed offshore.

[0052] Detailed description of the invention

[0053] A crane stabilisation assembly for use in deep water offshore is shown in general schematic form in figure 1 . The assembly comprises a floating industrial support vessel 2, such as a seagoing barge.

[0054] The vessel 2 is constructed with a moon pool 4. A moon pool is a common feature of industrial deep water vessels such as marine drilling platforms, diving support vessels and the like and is an opening in the floor or base of the hull usually to provide access to the water, allowing technicians to lower tools or instruments into the sea.

[0055] The vessel 2 carries a spar 6. Spars are commonly used for providing a stable foundation for offshore equipment, being large diameter vertical buoyant cylinders ballasted with a deep draft which makes the structure less responsive to wind, waves and currents.

[0056] The spar 6 is suspended and held within the confines of the vessel within and through the moon pool 4. Industrial operating equipment, for example a crane 8 structure is secured at or near to the top of the spar 6. As will be described later, the industrial equipment could be a platform or wind turbine for example.

[0057] The spar 6 is telescopic so to allow it to be deployed to a downwardly extended state to increase its draft, and thereby to provide a stabilised platform independent of the vessel 2 once it is at the deep water site.

[0058] Figure 2 shows the spar 6 in its extended, deployed state.

[0059] By virtue of the fact that the spar 6 is telescopic, the vessel 2 can travel through shallower water carrying the spar 6 in its retracted state, until the vessel reaches deep water at which point the spar 6 can be deployed.

[0060] Figure 3 shows the telescopic mechanism of the spar 6. The crane is not shown for ease of description. The spar 6 is constructed in three tubular sleeve sections 10 having progressively decreasing diameters to allow the third end section 10C to slide within the second middle section 10B and for the second section to slide within the first top section 10A. Any number of sections 10 may be used to vary the possible draft size of the spar 6.

[0061] The sections 10 may include helical strakes to increase hydrodynamic stabilisation.

[0062] Alternatively, the spar could be made up of at least one tube section and one truss section with heave plates.

[0063] Air could be pumped into a collapsible bladder located the top section of the spar 6 to adjust the ballast / buoyancy to compensate for the crane lift weight load.

[0064] A permanent ballast 12 is secured to the distal end of the third sleeve 10C to stabilise the spar 6 at its tip, the deepest point in the water.

[0065] Internal access ladders 14 and platforms 16 may be pre-installed to self-deploy as the spar 6 extends, as shown best in figure 3B.

[0066] Figure 4 is a plan cross-section view of the securement mechanism that suspends the spar 6 within the moon pool 4 of the vessel 2. The mechanism secures the spar 6 in such a way that the vessel 2 can pivot about the spar 6 as weather conditions change and the mechanism is deployed.

[0067] The suspension mechanism consists of a double axes gimbal / universal joint arrangement consisting of inner and outer concentric rings 18, 20 with pivot points at 90° angles to each other.

[0068] The inner ring 18 is connected to the spar 6 via two opposing pivot points at 180° to each other and is connected to the outer ring 20 via another two opposing pivot points at 90° to the spar connections.

[0069] As can be seen in figure 5, the outer ring 20 is split longitudinally into two halves 22 which are pivotally connected at each end and share a common pinion 24 to the inner ring 18.

[0070] The end of each half ring 22 distal to the pivotal connection 26 has a counterweight 28 secured thereto via an arm 30 supported on a perpendicularly orientated shaft and bearing point 32 fixed to the inner wall of the moon pool 4 to create a fulcrum.

[0071] The counterweights 28 extend into, to be housed within recesses 34 built into the deck and hull of the vessel 2.

[0072] The gimbal mechanism and counterweights compensate for heave, pitch and roll experienced by the vessel 2 when the spar 6 is deployed in deep water offshore. The gimbal rings 18, 20 and counterweights 28 are locked in position during transportation. At this time, the gimbal joint and counterweights 28 are locked with locking pins and the spar 6 is telescopically retracted into the crane tower to a point where the top of the ballast 12 is flush with the bottom of the hull of the vessel 2.

[0073] Further compensation could be added to the crane, if necessary, by adding an extending counterweight opposing the jib, a heave compensating winch, or above hook spring heave compensators.

[0074] Once in position, pins locking the gimbal joint are remove spar 6 is deployed before the crane jib is lifted. Once the spar 6 is fully extended, the vessel 2 is able to move independently from the spar 6. The counterweights 28 are generally selected to have equal weight to the entire of the crane structure, excluding the crane lifting weight load.

[0075] Surge, sway and yaw movements are controlled by actuating thrusters on the vessel 2.

[0076] Figures 6 and 7 illustrate a further embodiment of the invention, providing a vessel 36 with a large deck area and two moon pools 38. The deck areas is divided into two platform sections 40, each with motion compensating mechanisms as described.

[0077] Figure 6 shows the vessel 36 harbourside in shallow water. It can be seen that the spars, which on this example support each platform 40, are fully retracted. The gimbal joints 42 and counterweights 44 are locked in position. The vessel 36 can now be driven out to sea.

[0078] Figure 7 shows the vessel 36 at its deployment location in deep water. In this case, both platform spars 46 are deployed to stabilise the platform decks independent of movement of the vessel 36.

[0079] Figure 8 illustrates a further embodiment of invention, providing a vessel 36 which includes a crane spar 6 as previously described on one part of the deck area and a platform 40 on the other. In the figure, both the crane spar 6 and the platform spar 46 are deployed for stabilisation of the crane 8 and platform 40 respectively.

[0080] Figure 9 shows a further embodiment of the invention, providing a vessel 2 with a single moon pool 4 and a crane spar 6 that also supports platform 40.

[0081] Figures 10 and 11 illustrate a vessel 48 capable of carrying wind turbines 50 for transportation to a deepwater site offshore. The wind turbines have a telescopic spar 6 as previously described to provide stabilisation of the wind turbine 50 at the deepwater site. The spar 6 is retracted when the vessel 48 is in the harbour for loading. In this case, the gimbal mechanism which supports the spar 6 is mounted within framework 52 secured to and extending from the side of the vessel 48. A further gimbal mechanism and framework 52 is provided on another side of the vessel 2 to allow loading and transportation of two wind turbines 50 at the same time. Any number of wind turbines 50 may be loaded onto the vessel 48 for transportation at the same time, depending on the size of the vessel 48.

[0082] The spars 6 of each wind turbine are lifted and lowered into the gimbal mechanism using a harbourside crane 54.

[0083] As can be seen in figure 11 , each gimbal joint can be separable at one point to accept the retracted spars 6. Once in place, the gimbal joint is closed and secured with a gimbal clamp and the gimbal mechanism and counterweights are locked in place for transportation.

[0084] Once at the deepwater site, each gimbal joint is unlocked in turn and the spars 6 deployed. Weight transfer is simultaneously compensated by using ballast tanks on the vessel 48. Once the spars 6 are fully deployed and each wind turbine 50 is supported, with anchors secured, the gimbal clamp is released and the vessel 48 is able to move away using side boosters.

[0085] Figure 12 illustrates a fully supported wind turbine 50 with its spar 6 deployed.

Claims

CLAIMS1 . A stabilisation assembly for use in deep water, the assembly comprising a telescopic spar for securement within a moon pool of a floating support vessel, the securement mechanism including a gimbal joint secured within the moon pool through which the spar is suspended to allow movement of the vessel with respect to the spar during use.

2. A stabilisation assembly according to claim 1 , wherein the spar supports a crane.

3. A stabilisation assembly according to claim 1 , wherein the spar supports a wind turbine.

4. A stabilisation assembly according to claim 1 , wherein the spar supports a platform.

5. A stabilisation assembly according to any preceding claim, wherein the spar is constructed to have at least two tubular sleeve sections, one slidable within the other to telescopically extend or retract the spar.

6. A stabilisation assembly according to claim 5, wherein the spar is constructed of three tubular sections.

7. A stabilisation assembly according to claim 5 or claim 6, wherein each section includes helical strakes on the outer surface.

8. A stabilisation assembly according to any one of claims 5 to 7, wherein the spar includes a collapsible bladder in a top section to enable adjustment of the buoyancy of the spar.

9. A stabilisation assembly according to any one of claims 5 to 8, wherein a bottom section includes a ballast secured thereto.

10. A stabilisation assembly according to any one of claims 5 to 9, wherein the spar includes internal access ladders and platforms that self-deploy during extension of the spar.1 1. A stabilisation assembly according to any preceding claim, wherein the gimbal joint comprises inner and outer concentric rings with pivot points at 90 degrees to each other.

12. A stabilisation assembly according to claim 1 1 , wherein the inner ring is connected to the spar via two opposing pivot points at 180 degrees to each other and is connected to the outer ring via another two opposing pivot points at 90 degrees to the spar connections.

13. A stabilisation assembly according to claim 12, wherein the outer ring is split longitudinally into two halves which are pivotally connected at each end, and which share a common pinion to the inner ring.

14. A stabilisation assembly according to claim 13, wherein the end of each half ring distal to the pivotal connection has a counterweight secured thereto.

15. A stabilisation assembly according to claim 14, wherein each counterweight is secured to the outer ring via an arm supported on a perpendicularly orientated shaft and bearing point fixed to an inner wall of the moon pool to create a fulcrum.

16. A stabilisation assembly according to claim 15, wherein the counterweights are housed within recesses built into the deck and hull of the vessel.

17. A stabilisation assembly according to any of claims 14 to 16, further comprising means to lock the gimbal rings and counterweights in position.

18. A floating vessel having at least two moon pools, each including a stabilisation assembly according to any preceding claim.

19. A construction for location in deep water offshore, the construction having secured thereto a telescopic spar to provide stability to the construction when extended.

20. A floating vessel for transportation of the construction of claim 19 to a location in deep water offshore, the floating vessel including a gimbal joint of any preceding claim secured within framework on the vessel, the gimbal joint having means to receive and suspend the telescopic spar whilst the spar is fully retracted, during transportation.

21. A method of stabilising a wind turbine in a deep water location offshore, the wind turbine having a stabilisation assembly of any one of claims 14 to 17, the method comprising the steps of: retracting the spar such that the ballast is flush with the bottom if a hull of the floating vessel;locking the gimbal joint and counterweights in position within the moon pool of the floating vessel; transporting the wind turbine to the deep water offshore location; unlocking the gimbal joint and counterweights to allow pivotal movement; and fully extending the spar downwardly to stabilise the wind turbine.

22. A method of stabilising a wind turbine in a deep water location offshore using the floating vessel of claim 20, the wind turbine having a stabilisation assembly of any one of claims 14 to 17, the method comprising the steps of: parting the gimbal joint to receive the wind turbine spar when the spar is fully retracted; clamping the gimbal joint around the spar; locking the gimbal joint and counterweights in position to prevent any pivotal movement, transporting the wind turbine to the deep water offshore location; unlocking the gimbal joint and counterweights to allow pivotal movement; fully extending the spar downwardly to stabilise the wind turbine; and parting the gimbal joint to release the wind turbine spar.

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