Method for performing maintenance on a wind turbine part

Abstract

A method for performing maintenance on an outer surface of at least one wind turbine part, such as a tower (2), a nacelle (3) or a wind turbine blade (5), of an offshore wind turbine (1) is disclosed. An access system (10) is transported to a site of the offshore wind turbine (1), and the access system (10) is transferred to a transition platform (6) at a lower part of the offshore wind turbine (1), while operating the offshore wind turbine (1) in accordance with a normal operating mode. Normal operation of the offshore wind turbine (1) is then stopped, and maintenance is performed on an outer surface of at least one wind turbine part (2, 3, 5) of the offshore wind turbine (1), using the access system (10). When the maintenance has been completed, normal operation of the offshore wind turbine (1) is restarted in accordance with a normal operating mode. Normal operation of the offshore wind turbine (1) is only stopped while the actual maintenance takes place. Thereby the loss in power production is minimised.

Claims

1. A method for performing maintenance on an outer surface of at least one wind turbine part of an offshore wind turbine, the method comprising the steps of: transporting an access system to a site of the offshore wind turbine, transferring the access system to a transition platform at a lower part of the offshore wind turbine, while operating the offshore wind turbine in accordance with a normal operating mode, stopping normal operation of the offshore wind turbine, performing maintenance on an outer surface of at least one wind turbine part of the offshore wind turbine, using the access system, and restarting normal operation of the offshore wind turbine in accordance with a normal operating mode when the maintenance has been completed, wherein the access system comprises two or more detachably assembled modules, wherein the step of transferring the access system to the transition platform comprises transferring the two or more modules to the transition platform, and wherein the method further comprises the step of assembling the access system from the two or more modules at the transition platform.

2. The method according to claim 1, wherein each module of the access system has a weight which is smaller than or equal to 1000 kg.

3. The method according to claim 1, further comprising the steps of disassembling the access system into two or more modules, and transferring the two or more modules from the transition platform, after restarting operation of the offshore wind turbine in accordance with a normal operating mode.

4. The method according to claim 1, wherein the step of performing maintenance comprises hoisting the access system in an upwards direction from the transition platform.

5. The method according to claim 1, wherein the step of transferring the access system to the transition platform is performed by means of a permanent crane arranged at or near the transition platform.

6. The method according to claim 1, wherein the step of performing maintenance on an outer surface of at least one wind turbine part of the offshore wind turbine comprises performing maintenance on at least one wind turbine blade.

7. The method according to claim 1, wherein the step of performing maintenance on an outer surface of at least one wind turbine part of the offshore wind turbine comprises inspecting the outer surface of at least one wind turbine part.

8. The method according to claim 1, wherein the step of performing maintenance on an outer surface of at least one wind turbine part of the offshore wind turbine comprises locking the access system to one of the wind turbine part(s) on which maintenance is performed.

9. The method according to claim 1, further comprising the step of awaiting wind and/or weather conditions fulfilling predefined conditions, the step of awaiting being performed after the access system has been transferred to the transition platform and before stopping normal operation of the offshore wind turbine.

10. The method according to claim 9, wherein the step of awaiting wind and/or weather conditions fulfilling predefined conditions comprises awaiting wind conditions where a wind speed is below 5 m/s.

11. The method according to claim 1, further comprising the steps of: interrupting the step of performing maintenance and returning the access system to the transition platform, restarting operation of the offshore wind turbine in accordance with a normal operating mode, and stopping operation of the offshore wind turbine and completing the step of performing maintenance at a later point in time.

12. The method according to claim 1, wherein the step of stopping normal operation of the offshore wind turbine is performed at least three hours after completion of the step of transferring the access system to the transition platform.

13. The method according to claim 1, further comprising the step of temporarily attaching the access system to the transition platform by means of attachment means provided on the access system and/or on the transition platform.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described in further detail with reference to the accompanying drawings in which

(2) FIG. 1 is a side view of an offshore wind turbine,

(3) FIG. 2 is a cross sectional view of the offshore wind turbine of FIG. 1,

(4) FIG. 3 shows modules of an access system according to an embodiment of the invention, arranged on a sea vessel,

(5) FIG. 4 shows the modules of FIG. 3 in the process of being transferred to a transition platform,

(6) FIGS. 5-8 show an access system according to an embodiment of the invention arranged at a transition platform, and

(7) FIGS. 9-12 illustrate an access system according to an embodiment of the invention performing maintenance on an outer surface of a wind turbine part in accordance with a method according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(8) FIG. 1 is a side view of an offshore wind turbine 1. The offshore wind turbine 1 comprises a tower 2 and a nacelle 3 mounted on top of the tower 2. A rotor 4 carrying three wind turbine blades 5, two of which can be seen, is mounted rotatably on the nacelle 3. A transition platform 6 is mounted on the tower 2 at a lower part thereof. The transition platform 6 may, e.g., be used for transferring equipment and/or personnel between sea vessels and the offshore wind turbine 1. A permanent crane 7 is arranged on the transition platform 6, and may be used for transferring equipment to or from the transition platform 6.

(9) FIG. 2 is a cross sectional view of the offshore wind turbine 1 of FIG. 1, in the direction of the arrows A along the dotted line between the arrow points. The transition platform 6 and the permanent crane 7 arranged thereon can be clearly seen.

(10) FIG. 3 shows a sea vessel 8 carrying three modules 9a, 9b, 9c for an access system according to an embodiment of the invention. The modules 9a, 9b, 9c are transported separately by means of the sea vessel 8, but can be assembled into an access system according to an embodiment of the invention. This will be described in further detail below.

(11) FIG. 4 shows the sea vessel 8 of FIG. 3 arranged adjacent to an offshore wind turbine 1. The offshore wind turbine 1 has a transition platform 6 which is provided with a permanent crane 7, and it could, e.g., be the offshore wind turbine 1 of FIGS. 1 and 2. The permanent crane 7 is in the process of lifting one of the modules 9a onto the transition platform 6. The remaining two modules 9b, 9c are still arranged on the sea vessel 8. Accordingly, the modules 9a, 9b, 9c are lifted, one at a time, onto the transition platform 6 by means of the permanent crane 7. Thereby an access system which is heavier than the lifting capacity of the permanent crane 7 can be lifted onto the transition platform 6 without requiring an additional crane with a larger lifting capacity. The transfer of the modules 9a, 9b, 9c from the sea vessel 8 to the transition platform 6 is performed while the offshore wind turbine 1 operates in accordance with a normal operating mode, i.e. normal power production of the offshore wind turbine 1 is maintained during the transfer.

(12) In FIG. 5 all of the modules 9a, 9b, 9c have been lifted onto the transition platform 6, and the modules 9a, 9b, 9c have been assembled to form an access system 10. The access system 10 can be used for performing maintenance on an outer surface of at least one wind turbine part in a manner which will be described in further detail below. The assembled access system 10 is accommodated at the transition platform 6. The offshore wind turbine 1 is still operated in accordance with a normal operating mode, i.e. no power production loss has yet been introduced.

(13) In FIG. 6 the access system 10 has been connected to the nacelle (not visible) of the offshore wind turbine 1 by a number of cables 11, one of which is shown. This requires that normal operation of the offshore wind turbine 1 is stopped in order to avoid collisions between the wind turbine blades 5 and the cables 11. Thus, the access platform 10 is now ready to be hoisted in an upwards direction by means of the cables 11, in order to perform maintenance on an outer surface of at least one wind turbine part.

(14) In FIG. 7 the sea vessel has left the position adjacent to the offshore wind turbine 1, thereby illustrating that the presence of the sea vessel is not required while the maintenance is performed.

(15) FIG. 8 shows the assembled access system 10 in the process of being hoisted from the transition platform 6 by means of the cables 11, in order to use the access system 10 for performing maintenance on an outer surface of a wind turbine part.

(16) In FIG. 9 the access system 10 has been hoisted clear of the transition platform 6 by means of the cables 11, and is on its way towards a wind turbine blade 5, as indicated by arrows 12.

(17) In FIG. 10 the access system 10 is locked onto a wind turbine blade 5, and is moved along the wind turbine blade 5 in an upwards direction by means of the cables 11, as indicated by arrows 12. Thereby maintenance can be performed on an outer surface of the wind turbine blade 5 by means of the access system 10. For instance, personnel may be present on the access system 10, thereby allowing the personnel to visually inspect the outer surface of the wind turbine blade 5. Alternatively or additionally, the access system 10 may be provided with equipment required for performing relevant kinds of maintenance on the outer surface of the wind turbine blade 5, such as cleaning, painting or coating, replacement, removal or addition of elements, such as sensors, lights, etc. and/or any other suitable kind of maintenance.

(18) Module 9c rests against the tower 2 during the movement of access system 10 along the wind turbine blade 5. This provides guidance for the access system 10 in the horizontal direction during movement of the access system.

(19) In FIG. 11 the access system 10 is in the process of being lowered along the wind turbine blade 5, as indicated by arrows 13. Thus, in FIG. 11 the maintenance on the outer surface of the wind turbine blade 5 has been completed, and the access system 10 is in the process of being returned to the transition platform to allow normal operation of the offshore wind turbine to be restarted.

(20) FIG. 12 also shows an access system 10 according to an embodiment of the invention locked onto a wind turbine blade 5 while performing maintenance on the outer surface of the wind turbine blade 5. In the embodiment illustrated in FIG. 12, an extendable beam 14 extends between the access system 10 and the tower 2. The extendable beam 14 ensures that an appropriate distance is maintained between the access system 10 and the tower 2 as the access system 10 is moved along the wind turbine blade 5. In other words, an extendable beam 14 may replace (or complement) the module 9c (for example seen in FIG. 11) of the access system 10.

(21) A sea vessel 8 is on its way to the offshore wind turbine 1 in order to receive the access platform 10 and transport it away from the site of the offshore wind turbine 1 when it has been returned to the transition platform 6 and normal operation of the offshore wind turbine 1 has been restarted. This may allow the access system 10 to be used for performing maintenance on other offshore wind turbines arranged in the vicinity of the offshore wind turbine 1.