Mounting Of Offshore Structures
Offshore structures such as wind turbines, wave machines and tidal stream turbines are mounted in a previously located foundation including a socket. The foundation includes an upper body with a conical inner surface which acts as a guide for inserting a leading end of the structure into the socket. The conical surface also provides a reaction surface for setting the vertical alignment of the structure when inserted in the socket. Clamps are provided supported by an A frame for controlled lowering of the structure into the socket.
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This application is a continuation of U.S. Ser. No. 10/531,857, filed 19 Apr. 2005 (now U.S. Pat. No. 7,877,933), which application is a US National Stage of International Application No. PCT/GB03/004529 filed 20 Oct. 2003, which claims the benefit of GB 0224656.9, filed 23 Oct. 2002.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to the mounting of structures offshore and more especially to the mounting of structures such as wind turbines, wave machines and tidal stream turbines.
2. Description of Related Art
Conventionally, wind turbines or the like are mounted offshore in a suitable foundation. The wind turbines are transported to the installation site, either in a complete state or for assembly on site, by means of a jack up barge. However, jack up barges are expensive and can be difficult to use in certain locations where difficult seabed conditions or strong currents occur.
The present invention therefore seeks to provide method and apparatus for installation and alignment of offshore structures such as wind turbines which permits the use of towed or self-propelled barges or other suitable vessels to support the structure and further enables alignment of the structure at a desired angle (normally vertical) even where the foundation is installed at an angle.
BRIEF SUMMARY OF THE INVENTIONAccording to a first aspect of the present invention there is provided a foundation for mounting an offshore structure, the foundation comprising a socket for receiving and retaining an end part of the structure, the socket having a base surface preferably of conical shape, an intermediate supporting part and an upper body having an internal guiding surface for guiding said end part into the intermediate supporting part, said guiding surface also forming a reaction surface operatively co-operating with alignment means of the structure for alignment of the structure when inserted in the foundation.
Preferably said guiding surface is frusto-conical.
Further preferably said intermediate supporting part has a substantially cylindrical inner surface sized to conform with a corresponding outer surface of said end part.
According to a second aspect of the invention there is provided a structure for mounting in the foundation of the first aspect of the invention, said structure comprising an end part for insertion into the socket of the foundation, said end part preferably having a leading end portion preferably of substantially conical shape corresponding to said conical base surface, and alignment means mounted on said end part operative to co-operate with said guiding surface when said end part is in the socket to align the structure into a desired alignment.
In a preferred embodiment of this aspect the invention, the alignment means are removable.
Preferably, the outer surface of the end part is substantially cylindrical.
Preferably also, a curved, substantially spherical or part spherical element is disposed on the tip of the leading end portion whereby the (preferably) conical leading end portion is prevented from fully abutting the conical base surface of the socket.
According to a third aspect of the invention there is provided the combination of a foundation for mounting an offshore structure and a structure mountable in the foundation, wherein the structure comprises an end part preferably having a leading end portion preferably of substantially conical shape and alignment means located on the leading end part, the foundation comprising a socket comprising a base surface preferably of substantially conical shape sized substantially to conform with the substantially conical end portion, an intermediate supporting part and an upper body having an internal guiding surface wherein the socket operatively receives the leading end part such that the base surface and the end portion are in juxtaposition and the internal guiding surface operatively provides a reaction surface against which the alignment means operatively act for adjustment of the structure into a desired alignment.
Preferably in this third aspect of the invention the alignment means are removeable.
Preferably also the internal guiding surface is frusto-conical.
In a much preferred embodiment, the inner surface of the intermediate supporting part and the outer surface of the end part of the structure are cylindrical.
In another preferred embodiment of this aspect of the invention said inner and outer surfaces are spaced apart in use. This allows the joint between the structure and the socket to be filled with grout to secure the structure in the socket in the desired alignment.
In another preferred embodiment a curved, substantially spherical or part spherical element is disposed on the tip of the leading end portion whereby the (conical) leading end portion is prevented from fully abutting the (conical) base surface of the socket. This feature assists in ensuring that a space between the structure and the socket is provided (for the insertion of grout) and also allows the structure to be aligned (with respect to the vertical) and also rotated as necessary before it is fixed in position.
A fourth aspect of the invention provides apparatus for mounting a structure as according to the second aspect of the invention in a foundation according to the first aspect of the invention, the apparatus comprising a transporting barge, means for retaining the structure on the barge during transportation in a reclined position, means for moving the structure from the reclined position to an upright position and for lowering the structure in said upright position over the side of the barge, and a guide wire attachable to the end of the structure for guiding the leading end of the structure into the socket.
Preferably the means for moving the structure from the reclined position to an upright position comprises a winched cable-stayed “A” frame.
Preferably the structure is retained while in its upright position, and lowered, by means of one or more clamps engaging the structure, the clamping arrangement allowing controlled axial movement of the structure relative to the means for supporting the structure.
Preferably the apparatus further comprises means for supplying grout to the joint between the end part of the structure and the socket.
Preferably also the means comprise supply hoses which are operatively disconnectable from the supply of grout and are sealable, and the apparatus further comprises a buoy to which the supply hoses may be attached after disconnection from the supply of grout.
Preferably the apparatus further comprises means for recovering the alignment means after the structure has been mounted in the foundation.
According to a fifth aspect of the invention there is provided method of mounting an offshore structure in a sub-surface foundation, the method comprising:
i) providing a sub-surface foundation according to the first aspect of the invention;
ii) providing a structure according to the second aspect of the invention and supporting the structure in a reclined position on a barge;
iii) providing a winched cable stayed A frame on the barge and moving the structure from the reclined position to an upright position by means of the A frame;
iv) supporting the structure in its upright position by means of clamps attached to the A frame;
v) attaching a guide wire to an end part of the structure and guiding the end part of the structure into the socket of the foundation by means of the guide wire;
vi) lowering the alignment means down the end part of the structure until the alignment means engage the internal guiding surface of the upper body of the socket and adjusting the alignment of the structure by means of the alignment means acting on the internal guiding surface until a desired alignment is achieved; and
vii) releasing the clamps supporting the structure.
A preferred embodiment of this aspect of the invention further comprises the steps of:
viii) providing grout injection hoses and injecting grout into the joint between the structure and the socket;
ix) sealing the grout injection hoses; and
x) attaching the sealed clamp hoses to a surface buoy.
Preferably the method of this embodiment comprises the further step of recovering the grout injection hoses and/or the alignment means when the grout in the joint has set.
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the following drawings in which:
To facilitate an understanding of the principles and features of the various embodiments of the invention, various illustrative embodiments are explained below. Although preferred embodiments of the invention are explained in detail, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the invention is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiments, specific terminology will be resorted to for the sake of clarity.
It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural references unless the context clearly dictates otherwise. For example, reference to a component is intended also to include composition of a plurality of components. References to a composition containing “a” constituent is intended to include other constituents in addition to the one named.
Also, in describing the preferred embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.
Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, other exemplary embodiments include from the one particular value and/or to the other particular value.
By “comprising” or “containing” or “including” is meant that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.
It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a composition does not preclude the presence of additional components than those expressly identified.
Referring now to the drawings,
In the upright position, the structure 4 is supported by a number of clamps 20. In the clamping arrangement illustrated in
In a less preferred variation, separate means such as a crane are provided to support the weight of the structure and the clamps are used only for alignment of the structure 4.
In the clamping arrangement shown in
In erecting the structure 4, a combination of hydraulic cylinders and/or cables can be used to ensure that as the weight of the structure 4 passes over centre the motion of the A frame is controlled. Alternatively, the pivots on which the A frame is mounted can be located to ensure that the weight always remains on the barge side of the pivot, so that the need to over centre is avoided.
When the structure 4 is in its upright position a guide or pull wire is attached to the end part 10 of the structure 4. The guide wire is used to guide the end part 10 of the structure into a pre-positioned foundation 30. The foundation 30 includes a socket 32 having a base surface 34 having an internally conical shape and a generally cylindrical intermediate part 36. Mounted at an upper part of the intermediate part 36 is an upper body 38. The upper body 38 includes an internal surface 40 which is frusto-conical. As the structure 4 is lowered from the barge by use of the clamps 20 the inner surface 40 assists in guiding the end part 10 of the structure 4 into the socket 32, in combination with the conical leading end portion 12 and the guide wire. Once the structure 4 is accommodated in the socket 32, the structure provides a temporary means of locating the barge which permits movement of the barge in the swell of the water and rotationally around the structure 4 but prevents translational movement of the barge away from the structure.
An “interface ball” 13 in the form of a curved, spherical or part spherical element is disposed on the apex of leading end portion 12 (
When the structure 4 has been located in the socket 32, alignment of the structure 4 is undertaken. For this purpose, alignment means 14 are lowered down the end part 10 until they contact the inner surface 40. The alignment means preferably comprise a plurality of hydraulic cylinders and typically four such cylinders are provided. Once the alignment means are in place, the clamps 20 can be released. The alignment means 14 are then used to set the structure 4 in its desired alignment. The inner surface 40 acts at this stage as a reaction surface against which the alignment means 14 (hydraulic cylinders) act to provide the required movement of the structure to adjust its position and, when that position is achieved, to retain the structure in that position. Once the desired alignment is achieved, the alignment means can be locked in position.
In one preferred arrangement of the invention where the installation of the structure is essentially permanent, grout is injected into the void between the walls of the socket 32 and the end part 10 of the structure through suitable hoses. When the joint is full of grout, the hoses can be sealed off and attached to a buoy. The barge 2 can then move away and be engaged in other work. When the grout is fully set a barge 2 may return to retrieve the alignment means 14.
In an alternative arrangement, the alignment means 14 may be left in place when locked in position and no grout is then required. This facilitates later removal of the structure 4, for example for maintenance on land. In this case, the alignment means 14 which may be shove cylinders, screw jacks or the like can be built as a fixed part of the structure 4 so that for removal of the structure 4 it is not necessary to pick up cables, hoses and the like to initiate release of the alignment means 14, these being provided integrally with the structure.
In a variation of the invention illustrated in
Therefore, while embodiments of the invention are described with reference to exemplary embodiments, those skilled in the art will understand that variations and modifications can be effected within the scope of the invention as defined in the appended claims. Accordingly, the scope of the various embodiments of the present invention should not be limited to the above discussed embodiments, and should only be defined by the following claims and all equivalents.
Claims
1. A structure comprising an end part adapted for insertion into a foundation, the foundation comprising a socket having a base surface, an intermediate supporting part and an upper body having an internal guiding surface adapted to guide said end part into the intermediate supporting part, said structure further comprising an active adjustable alignment means disposed on said end part positionable, when said end part has been accommodated in the socket, to act on said internal guiding surface, the alignment means being configured such that adjustment thereof moves the structure relative to the socket to align the structure into a desired alignment, the alignment means detachable from the end part with the end part remaining in the foundation.
2. The structure as claimed in claim 1, wherein the outer surface of the end part is substantially cylindrical.
3. The structure as claimed in claim 1, wherein the end part further includes a leading end portion of substantially conical shape.
4. The structure as claimed in claim 1, wherein the alignment means are a plurality of hydraulic cylinders.
5. The structure as claimed in claim 1, further comprising a means for recovering the alignment means from the end part after the end part is inserted into the foundation and the alignment means is detached from the end part.
6. The structure as claimed in claim 1, the alignment means moveable along the length of end part.
7. The structure as claimed in claim 3, wherein a curved, substantially spherical or part spherical element is disposed on the tip of the leading end portion whereby the conical leading end portion is prevented from fully abutting the base surface of the socket.
8. The structure as claimed in claim 6, the alignment means reattachable to the end part.
9. An offshore structure mountable in a foundation, wherein the structure comprises an end part having a leading end portion of substantially conical shape and controllable alignment means located on the leading end part, the foundation comprising a socket comprising a base surface of substantially conical shape sized substantially to conform with the substantially conical end portion, an intermediate supporting part and an upper body having an internal guiding surface that is frusto-conical, wherein the socket operatively receives the leading end part such that the conical base surface and the conical end portion are in juxtaposition and the internal guiding surface operatively provides a reaction surface against which the adjustable alignment means operatively act for adjustment of the structure into a desired alignment when the end part has been accommodated in the socket, the alignment means detachable from the end part after the end part is inserted in the foundation, and wherein the inner surface of the intermediate supporting part and the outer surface of the end part of the structure are cylindrical.
10. The structure as claimed in claim 9, wherein said inner and outer surfaces are spaced apart in use.
11. The structure as claimed in claim 9, wherein a curved, substantially spherical or part spherical element is disposed on the tip of the leading end portion whereby the conical leading end portion is prevented from fully abutting the conical base surface of the socket.
12. The structure as claimed in claim 9, wherein the alignment means are a plurality of hydraulic cylinders.
13. The structure as claimed in claim 9, further comprising a means for recovering the alignment means from the end part after the end part is inserted into the foundation and the alignment means is detached from the end part.
14. The structure as claimed in claim 9, the alignment means moveable along the length of the end part.
15. The structure as claimed in claim 9, the alignment means reattachable to the end part.
Type: Application
Filed: Feb 1, 2011
Publication Date: May 26, 2011
Applicant: IHC Engineering Business Limited (Riding Mill)
Inventor: Michael John Watchorn (Stocksfield)
Application Number: 13/018,694
International Classification: E02D 27/52 (20060101); E02D 27/42 (20060101);