MOORING SYSTEM

Abstract

A mooring system for mooring a floating platform having a plurality of stabilizing arms with floats, the mooring system including an anchoring system containing a plurality of anchors and anchoring cables for anchoring the mooring system in deep sea. The center part of the mooring system includes a mooring unit containing a plurality of mooring elements and positioning wires, where each mooring element is connected to an adjacent mooring element with a positioning wire and to an anchor.

Claims

1. Mooring system for mooring a floating platform having a plurality of stabilizing arms with floats, the mooring system comprising an anchoring system containing a plurality of anchors and anchoring cables for anchoring the mooring system in deep sea, wherein the centre part of the mooring system comprises a mooring unit containing a plurality of mooring elements and positioning wires, where each mooring element is connected to an adjacent mooring element with a positioning wire and to an anchor.

2. The mooring system according to claim 1, wherein each mooring element comprises an elongated floating container having a common cavity for air and ballast water.

3. The mooring system according to claim 1, wherein each mooring element comprises a mid part with a cylindrical cross-section.

4. The mooring system according to claim 1, wherein each mooring element comprises a funnel shaped upper part and a cylindric bottom part.

5. The mooring system according to claim 1, wherein the mooring system comprises three mooring elements and the anchor system comprises three anchors.

6. The mooring system according to claim 1, wherein a first mooring element is positioned by three anchors, a second mooring element is positioned by an anchor cable and a positioning wire, and wherein a third mooring element is positioned by an anchoring cable and a positioning wire.

7. The mooring system according to claim 1, wherein three mooring elements form a triangular pattern with a mooring element in each corner, each mooring element being positioned by a positioning wire to the adjacent mooring elements and to an anchor.

8. Mooring facility comprising a vast number of mooring systems according to claim 1, wherein all mooring systems comprising three anchoring cables are anchored adjacently in a hexagonal pattern of anchors, using adjacent anchors in common, whereby the limit of necessary anchors tends to one anchor per two platforms.

9. Method for providing a mooring system for a floating wind power platform comprising a plurality of buoys anchored by anchoring cables in deep sea, the method comprising: providing a mooring unit containing three mooring elements, anchoring each mooring unit with an anchor, positioning the three mooring elements in a triangular pattern by keeping them separated by a positioning wire.

10. Method of docking a floating platform having a plurality of floats with a mooring system according to claim 1, the method comprising: transporting the platform in a float position to the mooring site, immersing each of the mooring element of the mooring system to a receiving position by filling ballast water into a buoyancy compartment of the mooring element, positioning the floats of the floating platform face to face with the mooring elements, raising the mooring elements and lowering the floats to make the docking means to interlock by regulating the amount of ballast water in the float and in the mooring element respectively.

11. The mooring system according to claim 2, wherein each mooring element comprises a mid part with a cylindrical cross-section.

12. The mooring system according to claim 2, wherein each mooring element comprises a funnel shaped upper part and a cylindric bottom part.

13. The mooring system according to claim 3, wherein each mooring element comprises a funnel shaped upper part and a cylindric bottom part.

14. The mooring system according to claim 2, wherein the mooring system comprises three mooring elements and the anchor system comprises three anchors.

15. The mooring system according to claim 3, wherein the mooring system comprises three mooring elements and the anchor system comprises three anchors.

16. The mooring system according to claim 4, wherein the mooring system comprises three mooring elements and the anchor system comprises three anchors.

17. The mooring system according to claim 5, wherein the mooring system comprises three mooring elements and the anchor system comprises three anchors.

18. The mooring system according to claim 2, wherein a first mooring element is positioned by three anchors, a second mooring element is positioned by an anchor cable and a positioning wire, and wherein a third mooring element is positioned by an anchoring cable and a positioning wire.

19. The mooring system according to claim 3, wherein a first mooring element is positioned by three anchors, a second mooring element is positioned by an anchor cable and a positioning wire, and wherein a third mooring element is positioned by an anchoring cable and a positioning wire.

20. The mooring system according to claim 4, wherein a first mooring element is positioned by three anchors, a second mooring element is positioned by an anchor cable and a positioning wire, and wherein a third mooring element is positioned by an anchoring cable and a positioning wire.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features and advantages of the present invention will become more apparent to a person skilled in the art from the following detailed description in conjunction with the appended drawings in which:

[0029] FIG. 1. is plan view of a mooring system according to the invention and a floating platform to be moored,

[0030] FIG. 2. is a plan view of mooring facility comprising a plurality of mooring systems,

[0031] FIG. 3. Is a plan view of a method to moor a floating platform,

[0032] FIG. 4. is a section view of a part of a floating platform ready to dock with a mooring element, and

[0033] FIG. 5. Is a three-dimensional sketch of the docking of a float and a mooring element.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] A mooring system 17 comprising an anchoring system 16 and a mooring unit 18 is shown in FIG. 1. The mooring unit is permanently anchored by the anchoring system. The mooring unit 18 comprises in the embodiment shown three mooring elements 19 as corners in a triangular pattern. The mooring elements are connected with each other with a positioning wire 26 to be kept at a desired separation from each other. Each mooring element is thus secured by two adjacent mooring elements with a positioning wire and by an anchor 27 (not shown) with an anchoring cable 25. Thus the mooring unit forms a mooring triangle with a mooring element in each corner. The mooring element 19 comprises a floating vertically elongated container suitable to be filled with a mixture of water and air. By controlling the content of that mixture the buoyancy effect and the height position of the mooring element may be controlled.

[0035] A floating platform 13 to be received by the mooring unit 18 is also shown in FIG. 1. In the embodiment shown the floating platform comprises a tower 1 stabilized by three arms 6. The outer end of each arm includes a float 11 comprising a floating elongated container. The elongated container is vertically aligned. All of the floats are connected with each other with a connecting wire 12 to make the arms equally spread around the tower. The float may be filled with a mixture of water and air to receive a desired buoyancy effect ant to define its height level in the sea.

[0036] When mooring the floating platform it is first transported into the mooring unit 18 by for instance a tug boat. Upon arrival of the platform the mooring element 19 are lowered in the sea by filling water into their inside compartments. Thereby the platform in its transport height will be capable of passing into the mooring unit triangle over the positioning wires. When the floating platform is positioned inside the mooring triangle each float 11 of the floating platform is facing a mooring element 19. Thus each float may be moored to the facing mooring element. In an embodiment the mooring is achieved by a rope, cable or the like. In an embodiment the float and the mooring element is equipped with docking means by which the two entities dock to form a single unit.

[0037] A facility of a great number of mooring systems 17 anchored by anchoring cables 25 to anchors 27 is shown in FIG. 2. As can be seen by the embodiment shown a single mooring system must use three anchors. But the more mooring systems included in the mooring facility the fewer anchors are needed. For a vast number of mooring systems the limit tends to be one anchor for every two mooring system. According to the invention a second set of mooring systems B may be added to the first set of mooring systems A. The second set of mooring systems are slightly rotated to the first set but may use already existing anchors. By the use of a first and second set of mooring systems A+B the limit number of anchors tends to one anchor for every three anchoring systems.

[0038] In an embodiment shown in FIG. 3 the mooring unit 18 comprises three mooring elements positioned in a V-shaped pattern. The method of mooring starts with a first float 11a being moored at the first mooring element 19a in position A. The floating platforming is then rotated clockwise to position B whereby the second float 11b may be moored to the second mooring element 19b. While the second float 11b is moored to the second mooring element 19b the floating platform is rotated anticlockwise as shown in position C until the third float 11c reaches the third mooring element 19c in position D where the third float is moored. By this method the floating platform may be moored with one float at the time. The final shape of the mooring system resembles a triangular pattern where all anchor forces are transferred directly to the floating platform in the direction of the arms.

[0039] According to the invention the stationary mooring system is equipped with docking means as shown in FIG. 4. The embodiment shown depict part of a floating platform 13 with a float 11 and a mooring element 19 of a mooring system. The floating platform comprises a tower 1 with a main float 5, a first elongated element 8, a second elongated element 7 and a float 11. In the embodiment shown the first elongated element 8 comprises a catenary element and the second elongated element 7 comprises a strut element. The float comprises a funnel shaped body 21, a centre part 22 and a lower body 23 forming together a common cavity. The floating platform is raised to a transport level by emptying water 20 from inner cavity of the float 11 and the main float 5.

[0040] In the embodiment shown the float comprises docking means 31 in the form of hooks. The mooring system comprises a plurality of mooring element 19 having a slim cylindric mid section 29 and a bigger cylindric lower body 30. The mooring element is held in position by an anchoring cable 25 and two positioning wires 26. Both the wires and the cables are attached to the mooring element by a span 24. For stabilizing purpose both the float and the mooring element may comprise a ballast weight 36 in the bottom. As shown in FIG. 4 the mooring element may also comprise contact means to connect an external electric cable 33 with an internal electric cable 34.

[0041] In the embodiment shown the positioning wire 26 and the anchor cables 25 are cut to indicate that they comprise considerably longer lines at an actual site. The anchor cables may comprise hundreds of meters depending on the sea bed condition and the dept. Preferably suction anchors are used. The positioning wire may be in the range of 100 to 200 meters. Each of the mooring elements comprises three cavities which are structurally connected to form a common compartment. By pumping air or water in or out of the compartment the mooring element the height may be adjusted in the sea to keep a predetermined float position.

[0042] By the lightweight construction of the floating wind power platform the construction can be made very big. Accordingly the diameter of the rotor may be 200 m. The total height above the sea level of the tower including the first float may be 130-150 m. The length of the arm may be in the range of 90-120 m. Hence the ratio between the arm and the tower would almost one. The length of the mooring means may be in the range of 25-35 m and the cross section of the mid part 2-5 m. According to the invention the transport position of the platform is about 30 m higher that the submerged position. The draught of the platform under transport may be less than 9 meters.

[0043] Although favourable the scope of the invention must not be limited by the embodiments presented but contain also embodiments obvious to a person skilled in the art. The anchor lines may comprise any kind of material with good tensile properties. The mooring element may comprise stationary or temporary means for pre-stressing the anchor lines.