A METHOD FOR CONTROLLING TRANSFER OF A SUSPENDED LOAD BETWEEN AN OFFSHORE WIND TURBINE AND A FLOATING VESSEL

Abstract

A method and a system (1) for controlling transfer of a suspended load (2) between an offshore wind turbine (3) and a floating vessel (4) are disclosed. Movements, relative to the floating vessel (4), of a load (2) suspended in a hoisting mechanism (6, 15) and/or of a hooking part (9) of the hoisting mechanism (6, 15), are detected. A position and/or inclination of a landing platform (8) arranged on the floating vessel (4) is adjusted, based on the detected movements, in order to compensate for relative movements between the floating vessel (4) and the suspended load (2) and/or the hooking part (9), thereby synchronizing movements of the landing platform (4) to movements of the suspended load (2) and/or the hooking part (9), while moving the suspended load (2) and/or the hooking part (9) towards the adjustable landing platform (8).

Claims

1. A method for controlling transfer of a suspended load between an offshore wind turbine and a floating vessel, where a hoisting mechanism is connected to the offshore wind turbine, and the floating vessel comprises an adjustable landing platform, the method comprising the steps of: detecting movements, relative to the floating vessel, of a load suspended in the hoisting mechanism and/or of a hooking part of the hoisting mechanism, the hooking part being adapted for connecting a load to the hoisting mechanism, adjusting a position and/or inclination of the landing platform, based on the detected movements, in order to compensate for relative movements between the floating vessel and the suspended load and/or the hooking part, thereby synchronizing movements of the landing platform to movements of the suspended load and/or the hooking part, and moving the suspended load and/or the hooking part towards the adjustable landing platform.

2. A method according to claim 1, wherein the load is suspended in the hoisting mechanism, via the hooking part, and wherein the method further comprises the steps of: moving the suspended load towards the adjustable landing platform, positioning the suspended load on the adjustable landing platform, and releasing the load from the hooking part.

3. A method according to claim 2, further comprising the steps of attaching the load to the hooking part, at an uptower position of the offshore wind turbine, and moving the load towards the adjustable landing platform by means of the hoisting mechanism.

4. A method according to claim 1, wherein the load is positioned on the adjustable landing platform, and wherein the method further comprises the steps of: moving the hooking part towards the load positioned on the adjustable landing platform, attaching the load to the hooking part, and hoisting the load away from the adjustable landing platform towards an uptower position of the offshore wind turbine by means of the hoisting mechanism.

5. A method according to claim 4, further comprising the step of releasing the load from the hooking part at the uptower position of the offshore wind turbine.

6. A method according to claim 1, further comprising the step of guiding the suspended load and/or the hooking part by means of one or more taglines.

7. A method according to claim 1, wherein the step of detecting movements of a load suspended in the hoisting mechanism and/or of a hooking part of the hoisting mechanism comprises detecting the movements by means of one or more sensors arranged on the suspended load and/or the hooking part, and wherein the method further comprises the step of communicating sensor readings from the one or more sensors to a control unit for controlling the adjustable landing platform.

8. A method according to claim 1, wherein the offshore wind turbine is mounted on a floating foundation.

9. A method according to claim 1, further comprising the step of transferring the suspended load from the hoisting mechanism to a floating hoisting mechanism arranged on the floating vessel and/or from the floating hoisting mechanism to the hoisting mechanism.

10. A method according to claim 9, wherein the floating hoisting mechanism is arranged on the adjustable landing platform.

11. A system for transferring a suspended load, the system comprising: an offshore wind turbine, a hoisting mechanism being connected to the offshore wind turbine, the hoisting mechanism comprising a hooking part being adapted for connecting a load to the hoisting mechanism, a floating vessel comprising an adjustable landing platform, means for detecting movements, relative to the floating vessel, of a load suspended in the hoisting mechanism and/or of the hooking part of the hoisting mechanism, means for adjusting a position and/or inclination of the landing platform, based on the detected movements in order to compensate for relative movements between the floating vessel and the suspended load and/or the hooking part.

12. A system according to claim 11, wherein the hoisting mechanism forms part of the offshore wind turbine.

13. A system according to claim 11, further comprising one or more taglines for guiding the suspended load.

14. A system according to claim 11, wherein the offshore wind turbine is mounted on a floating foundation.

15. A system according to any claim 11, further comprising a floating hoisting mechanism arranged on the floating vessel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The invention will now be described in further detail with reference to the accompanying drawings in which

[0069] FIGS. 1-5 illustrate systems for transferring a suspended load according to five different embodiments of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0070] FIG. 1 is a schematic view of a system 1 for transferring a suspended load 2 according to a first embodiment of the invention. The system 1 comprises an offshore wind turbine 3 and a floating vessel 4 positioned adjacent to the offshore wind turbine 3. The offshore wind turbine 3 is mounted on a monopile 5, i.e. it is fixed to the seabed. The load 2 may, e.g., be a component for the offshore wind turbine 3, such as a gearbox, a shaft, a bearing, a generator, etc., which is to be installed in the offshore wind turbine 3 or removed therefrom. A hoisting mechanism 6, in the form of a crane, is mounted on a nacelle 7 of the offshore wind turbine 3. An adjustable landing platform 8 is arranged on the floating vessel 4.

[0071] The load 2 is attached to the hoisting mechanism 6 via a hooking part 9, and it is in the process of being hoisted from the landing platform 8 towards the nacelle 7 of the offshore wind turbine 3, or being lowered from the nacelle 7 of the offshore wind turbine 3 towards the landing platform 8. The load 2 is further connected to a winch 10 arranged on the landing platform 8, via a tagline 11.

[0072] The system 1 of FIG. 1 may be operated in the following manner. In the case that the load 2 is being removed from the offshore wind turbine 3, it is initially detached from the position where it was installed and attached to the hooking part 9 of the hoisting mechanism 6 at or near the nacelle 7. Furthermore, the tagline 11 is connected to the load 2.

[0073] The load 2 is then lowered towards the landing platform 8 by means of the hoisting mechanism 6. During this, the winch 10 ensures that the tagline 11 is kept tight in order to guide the load 2.

[0074] During the entire movement of the load 2 towards the landing platform 8, or at least when the load 2 approaches the landing platform 8, movements of the suspended load 2 and/or the hooking part 9, relative to the floating vessel 4, are detected. This could be performed by means of suitable sensors mounted directly on the load 2 and/or the hooking part 9, such as accelerometer, gyroscopes, compasses, and/or any other suitable kind of sensor being able to detect movement, position, orientation, inclination, etc. of the suspended load 2 and/or the hooking part 9. Alternatively, remote monitoring, e.g. optical monitoring, of specific parts and/or markers on the suspended load 2 and/or the hooking part 9 may be applied.

[0075] Based on the measured relative movements, a position and/or inclination of the landing platform 8 is/are adjusted. This is done by appropriately adjusting pistons 12 which interconnect the landing platform 8 and the floating vessel 4.

[0076] Accordingly, the landing platform 8 is moved in such a manner that it compensates for the relative movements between the suspended load 2 and the floating vessel 4. Thereby the movements of the landing platform 8 are synchronized to the movements of the suspended load 2, which is approaching the landing platform 8. This allows the suspended load 2 to be moved the last part of the way to the landing platform 8 and positioned thereon with no, or only very small, relative movements between the suspended load 2 and the landing platform 8. Thereby the risk of collisions between the load 2 and the landing platform 8 during this part of the process is significantly reduced.

[0077] Once the load 2 has been safely positioned on the landing platform 8, it may be released from the hooking part 9, and the hooking part 9 may be hoisted away from the landing platform 8 by means of the hoisting mechanism 6.

[0078] In the case that the load 2 is being installed in the offshore wind turbine 3, the load 2 is initially positioned on the landing platform 8. The hooking part 9 of the hoisting mechanism 6 is lowered towards the landing platform 8 and the load 2 positioned thereon.

[0079] During this, the movements of the hooking part 9, relative to the floating vessel 4 are detected, and the position and/or inclination of the landing platform 8 is/are adjusted based thereon, and in the manner described above. Thereby the hooking part 9 can be moved close to the load 2 without risking collisions between the hooking part 9 and the load 2.

[0080] When the hooking part 9 has been moved sufficiently close to the load 2, the load 2 is attached to the hooking part 9 and to the tagline 11. The load 2 is then hoisted from the landing platform 8 towards the nacelle 7 of the offshore wind turbine 3, by means of the hoisting mechanism 6 and while guiding the load 2 by means of the tagline 11.

[0081] When the load 2 has reached the nacelle 7, it is disconnected from the hooking part 9 and installed in an appropriate position at the offshore wind turbine 3.

[0082] FIG. 2 is a schematic view of a system 1 for transferring a suspended load 2 according to a second embodiment of the invention. The system 1 of FIG. 2 is very similar to the system 1 of FIG. 1, and it will therefore not be described in detail here.

[0083] In the system 1 of FIG. 2, the offshore wind turbine 3 is mounted on a floating foundation 13. Thereby the offshore wind turbine 3 also follows movements of the waves, similar to the floating vessel 4. This is likely to cause larger relative movements between the offshore wind turbine 3 and the floating vessel 4, and thereby also between the load 2 suspended from the hoisting mechanism 6 on the offshore wind turbine 3 and the floating vessel 4. Therefore, the method according to the invention described above with reference to FIG. 1 is particularly suitable in the system 1 of FIG. 2.

[0084] FIG. 3 is a schematic view of a system 1 for transferring a suspended load 2 according to a third embodiment of the invention. The system 1 of FIG. 3 is very similar to the system 1 of FIG. 2, and it will therefore not be described in detail here.

[0085] The system 1 of FIG. 3 further comprises a floating hoisting mechanism 14 arranged on the landing platform 8. The floating hoisting mechanism 14 handles the movements of the load 2 during the part of the transfer process where the load 2 is closest to the landing platform 8.

[0086] In the case that the load 2 is being transferred from the nacelle 7 of the offshore wind turbine 3 to the landing platform 8, the load 2 is initially transferred by means of the hoisting mechanism 6, essentially in the manner described above with reference to FIG. 1. At some point, the load 2 is transferred from the hoisting mechanism 6 to the floating hoisting mechanism 14. In order to ensure a smooth transfer, relative movements between the load 2 and the floating hoisting mechanism 14 must be minimised. This is done by detecting movements of the suspended load 2 and/or the hooking part 9, relative to the floating vessel 4, and adjusting the position and/or inclination of the landing platform 8 based thereon, essentially as described above with reference to FIG. 1.

[0087] Once the load 2 has been transferred to the floating hoisting mechanism 14, the load 2 is lowered further and positioned on the landing platform 8 by means of the floating hoisting mechanism 14.

[0088] In the case that the load 2 is being transferred from the landing platform 8 to the nacelle 7 of the offshore wind turbine 3, the load 2 is initially connected to the floating hoisting mechanism 14, and the load 2 is hoisted away from the landing platform 8 by means of the floating hoisting mechanism 14. At some point the load 2 is transferred from the floating hoisting mechanism 14 to the hoisting mechanism 6, while the relative movements between the load 2, connected to the floating hoisting mechanism 14, and the hooking part 9 of the hoisting mechanism 6 are minimised by appropriately adjusting the position and/or inclination of the landing platform 8, essentially as described above.

[0089] Once the load 2 has been transferred to the hoisting mechanism 6, the load 2 is hoisted to the nacelle 7 by means of the hoisting mechanism 6.

[0090] FIG. 4 is a schematic view of a system 1 for transferring a suspended load 2 according to a fourth embodiment of the invention. The system 1 of FIG. 4 is very similar to the system 1 of FIG. 1, and it will therefore not be described in detail here.

[0091] However, in the system 1 of FIG. 4, the hoisting mechanism 6 further comprises wires 15 interconnecting the nacelle 7 of the offshore wind turbine 3 and the landing platform 8.

[0092] The load 2 is guided along a diagonal direction, i.e. along a direction having a horizontal component as well as a vertical component, between the nacelle 7 and the floating vessel 14, by means of the wires 15. This is obtained by connecting the load 2 to the wires 15 in a manner which allows the load 2 to move along and be guided by the wires 15. For instance, the load 2 may be connected to the wires 15 via a set of wheels running along the wires 15.

[0093] FIG. 5 is a schematic view of a system 1 for transferring a suspended load 2 according to a fifth embodiment of the invention. The system 1 of FIG. 5 is similar to the system 1 of FIG. 2, in the sense that the offshore wind turbine 1 is mounted on a floating foundation 13, and to the system 1 of FIG. 4, in the sense that the hosting mechanism 6 comprises wires 15 interconnecting the nacelle 7 of the offshore wind turbine 3 and the landing platform 8. The system 1 of FIG. 5 will therefore not be described in detail here.