Maintenance method of wind turbine generator

A maintenance method is provided for a wind turbine generator including a tower and a nacelle. The maintenance method includes: attaching a pedestal to the tower; attaching a jack to the pedestal; and lifting the nacelle by using the jack to detach the nacelle from the tower, from a state where the nacelle is rotatably connected to the tower.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a maintenance method of a wind turbine generator, and especially relates to a method for carrying out a maintenance work which involves detaching the nacelle from the tower.

2. Description of the Related Art

Some maintenance works of a wind turbine generator involves detaching the nacelle from the tower. Such maintenance works include replacement of the yaw rotation bearing or a bearing seal, adjustment of a shim attached to the tower-top flange, painting of the outer ring of the yaw rotation bearing, and repair of the lower part of the nacelle cover.

In a case where a maintenance work is carried out after detaching the nacelle from the tower, the nacelle is detached from the tower and is landed on the ground by using a large size crane, and then the intended maintenance work is carried out. However, in the procedure of such maintenance work, there are two problems. Firstly, in order to land the nacelle by using the large size crane, a lot of machinery and much manpower are required, and legal preparation (for example, a road-use permission and so on) is required. This means that the maintenance work requires great costs and a long period for the maintenance. Secondary, a large site is required to place the nacelle and the wind turbine rotor. The area of the site required for the maintenance may reach several dozen meters square. This restricts flexibility of the maintenance. If the maintenance which involves detaching of the nacelle from the tower can be carried out without using a large crane, a large merit would be obtained in reduction of the cost due to simplification of the maintenance and in improvement of the flexibility of the maintenance work.

As a related prior technique, Japanese Patent Application Publication No. 2006-22675A discloses a technique for constructing a tower of a wind turbine generator without using a large size crane. In the technique described in this publication, a mast is inserted into the tower and the nacelle is mounted on the tower and a pushing-up member capable of moving upward and downward relatively to the mast is additionally attached to the mast. In the construction of the tower, the mast is lifted up by applying a reaction force to an already constructed part of the tower via the pushing-up member, and subsequently the pushing-up member is lifted up. After that, the expansion part of the tower is constructed between the already-constructed part of the tower and the pushing-up member. The tower is completed in the same manner, by repeating: the lifting of the mast and the construction of the expansion part of the tower. After the completion of the tower, the mast is removed, and the nacelle is fixed to the tower.

In addition, Japanese Patent Application Publication No. 2002-248560A discloses a technique for replacing a rotation bearing after lifting up a heavy swivel. In this technique, the swivel is lifted up from a pedestal by a lifting jack provided on a placement table placed on a floor surface, and after that, the rotation bearing is replaced. After the replacement of the rotation bearing, the swivel is returned to the pedestal.

SUMMARY OF THE INVENTION

Therefore, an objective of the present invention is to provide a technique to make it possible to perform a maintenance work which involves detaching a nacelle from a tower without using a large size crane.

In one aspect of the present invention, a maintenance method of a wind turbine generator including a tower and a nacelle is provided with steps of: attaching a pedestal to the tower; a step for attaching a jack to the pedestal; and lifting the nacelle by using the jack to detach the nacelle from the tower, from a state where the nacelle is rotatably connected to the tower.

In one embodiment, the maintenance method of the wind turbine generator of this embodiment is applied to replacement of a yaw rotation bearing for rotatably connecting the nacelle to the tower. In this case, the yaw rotation bearing is replaced in a state where the nacelle is lifted by the jack and is detached from the tower.

More specifically, the step of replacing the yaw rotation bearing includes steps of: attaching a pulley to the nacelle; preparing a winch; lifting a container to the vicinity of the nacelle by using a wire connected to the winch and looped on the pulley; putting the yaw rotation bearing attached to the nacelle on the container; and landing the container on which the yaw rotation bearing is put on the ground by using the wire. In addition, in one embodiment, the step for replacing the yaw rotation bearing further includes steps of: lifting the container on which a new yaw rotation bearing is put to the vicinity of the nacelle by using the wire connected to the winch and looped on the pulley; and attaching the new yaw rotation bearing to the nacelle.

In one embodiment, a plurality of jacks may be prepared for lifting the nacelle. In this case, in order to reduce interference with the yaw rotation bearing and/or the container, it is preferable that at least one of the jacks is positioned outside the tower. In this case, the step of attaching the pedestal to the tower may include steps of: boring a manhole through the tower; and inserting the pedestal through the manhole from the inside of the tower to the outside.

In order to improve certainty of the supporting of the nacelle, it is preferable that the maintenance method of the wind turbine generator further includes a step of inserting a stopper between the nacelle and the tower after lifting the nacelle by using the jack to detach the nacelle from the tower.

In one embodiment, the step of attaching the pedestal to the tower includes steps of: forming an internal thread through a tower top flange provided at the upper end of the tower; and connecting the pedestal to the tower by screwing a bolt through the internal thread. In this case, it is preferable that the forming of the internal thread through the tower top flange is achieved by inserting a self-tapping insert into the tower top flange, wherein the self-tapping insert is approximately cylindrical and has threads on the inner and outer surfaces.

The present invention provides a technique for making it possible to perform a maintenance work which involves detaching the nacelle from the tower, without using the large size crane.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a partial cross section view showing the structure of a wind turbine generator to which a maintenance method of one embodiment of the present invention is applied. At first, the overall configuration of a wind turbine generator1will be explained. The wind turbine generator1is provided with: a tower2; a nacelle3mounted on the tower2; and a wind turbine rotor4rotatably attached to the nacelle3. The wind turbine rotor4is provided with a rotor head5and blades6. AlthoughFIG. 1shows only one blade6, a plurality of blades6(typically, three blades6) are actually attached to the rotor head5.

The nacelle3is rotatably coupled to the tower2. As shown inFIG. 2, a yaw rotation bearing7is provided between the nacelle and the tower2. The yaw rotation bearing7includes an inner ring7a, an outer ring7b, and rolling members7c(steel balls in this embodiment) inserted between the rings. The outer ring7aof the yaw rotation bearing7is attached to a nacelle base3aof the nacelle3by using bolts8. On the other hand, the inner ring7bof the yaw rotation bearing7is attached to a tower top flange2aprovided at the top of the tower2by using attachment bolts9. Here, a brake disk11is sandwiched between the inner ring7band the tower top flange2a.Although the outer ring7ais coupled with the nacelle3and the inner ring7bis coupled with the tower top flange2ain this embodiment, the outer ring7amay be coupled to the tower top flange2aand the inner ring7bmay be coupled to the nacelle3.

Referring back toFIG. 1, a yaw rotation mechanism is provided to the lower part of the nacelle3. The yaw rotation mechanism includes a yaw motor12generating a drive force for the yaw rotation, and yaw brake calipers13for braking the rotation of the nacelle3by sandwiching the brake disk11. The yaw brake calipers13are attached to yaw brake pedestals14provided for the nacelle3. An opening is provided to the bottom part of the nacelle3, and a ladder15is attached in the vicinity of the opening. Moreover, cables16connected to apparatuses provided in the nacelle3(a power generator and so on) are withdrawn and suspended from the opening. The cables16include: a power cable attached to the power generator and a control cable attached to the respective apparatuses in the nacelle3.

FIG. 3is an exploded side view showing a method for carrying out the maintenance work which involves detaching the nacelle3from the tower2for the wind turbine generator1having the above-described configuration. In this embodiment, the nacelle3is jacked up by using hydraulic jacks21, and accordingly a clearance20is formed between the nacelle3and the tower2. Various maintenance works are carried out by using the clearance20. Although two hydraulic jacks21are illustrated inFIG. 3, it should be understood that a sufficient number of hydraulic jacks21(for example, eight hydraulic jacks) are actually provided to support the nacelle3.

Specifically, members interrupting a work for detaching the nacelle3from the tower2are first detached. For example, the yaw brake calipers13are detached from the yaw brake pedestals14. If necessary, the cables16suspended from the nacelle3may be also detached.

Moreover, jack-accepting pedestals22are attached to the inner face of the upper end portion of the tower2, and the hydraulic jacks21are attached to the jack-accepting pedestals22. A hydraulic unit23is attached to each of the hydraulic jacks21. The hydraulic unit23supplies operating fluid (operating oil) to the hydraulic jacks21. The hydraulic jacks21are driven by supplying the operating fluid (the operating oil) to the hydraulic jacks21, and thereby the nacelle3is jacked up. It should be noted that the hydraulic unit23is shown as being provided for only one hydraulic jack21inFIG. 3for visibility of the drawing.

FIG. 4is a cross section view showing the structure around the positions at which the hydraulic jacks21and the jack-accepting pedestals22are attached. The jack-accepting pedestals22each include a bottom plate22a, a rib part22b, a reaction force accepter22c, and a flange22d.The bottom plate22ais a member to be attached to a hydraulic jack21. A cylinder21aof a hydraulic jack21is attached to the bottom plate22aby using an attachment bolt24. The rib part22bis a reinforcement member for supporting the load applied in the vertical direction to the bottom plate22a.The reaction force accepter22cis jointed to the bottom plate22a, and is abutted to the inner face of the tower2. The reaction force accepter22cis used for dispersing the force applied from the bottom plate22ato the inner face of the tower2. The flange22dis provided to the upper end part of the rib part22b,and is abutted to the tower top flange2aof the tower2. The flange22dof the jack-accepting pedestal22is coupled to the tower top flange2aby using an attachment bolt25, and thereby the jack-accepting pedestal22is attached to the tower2.

The tip end of the rod21bof the hydraulic jack21is jointed to the nacelle base3aof the nacelle3. In this embodiment, the tip end of the rod21bis coupled to a yaw brake pedestal14by using an attachment bolt26. This prevents the nacelle3from falling down.

When the maintenance method of this embodiment is implemented for the already-constructed wind turbine generator1, no internal thread is provided for attaching the attachment bolt25to the tower top flange2a.In this case, internal threads may be formed in the tower top flange2ain the maintenance work. On this occasion, since through holes are usually formed through the tower top flange2afor coupling the inner ring7bof the yaw rotation bearing7with the tower top flange2aby using the attachment bolts9, the through holes may be used. In this case, as illustrated inFIG. 5, an internal thread can be easily formed through the tower top flange2aby inserting a self-tapping insert28into a through hole by using a self-tapping-insert inserting tool27. As illustrated inFIG. 6, the self-tapping insert28is an approximately-cylindrical member having threads on the inner and outer surfaces, and a cutting blade28ais provided for the self-tapping insert28. Even if no internal thread has been formed through the tower top flange2a, an internal thread can be formed through the tower top flange2aby inserting the self-tapping insert28. After the completion of the maintenance work, the self-tapping insert28is detached.

Maintenance works carried out with the nacelle3jacked up include replacement of the yaw rotation bearing7, replacement of the seal of the yaw rotation bearing7, painting of the outer ring7a, adjustment to obtain flatness of the tower top flange2a(for example, adjustment of a shim), repair of the bottom part of the nacelle cover3bof the nacelle3, for example. Out of them, the replacement of the yaw rotation bearing7is one of the important maintenance works. In the following, a procedure of the replacement of the yaw rotation bearing7will be explained.

At first, after the ladder15and the cables16are detached from the nacelle3, the nacelle3is jacked up in the above-mentioned procedure by the hydraulic jacks21. This results in that a clearance20is provided between the nacelle3and the tower2.

Subsequently, as illustrated inFIG. 7, after the brake disk11is detached and housed inside the nacelle3, the container31used for landing the yaw rotation bearing7on the ground is lifted to the vicinity of the nacelle3. Specifically, a pulley32is attached to a backward frame3cof the nacelle3, a temporal winch33is provided on the ground, and additionally a lifting hole3dfor passing a wire34is provided to the lower part of the nacelle3. One end of the wire34is wound on the temporal winch33, and the other end is attached to the container31with the wire34looped on the pulley32. The container31is lifted up by winding the wire34by the temporal winch33.

FIG. 8is a plan view showing the structure of the container31. The container31includes two guide rails41, frame members42, pulleys43, and drive units44. The container31is configured so that the yaw rotation bearing7put thereon is movable in the longitudinal direction of the guide rail41. Specifically, each of the guide rails41includes an outside rail41aand an inside rail41b, and the inside rails41bare movable in the longitudinal direction with respect to the outer rails41a.As described below, the yaw rotation bearing7is moved in a state in which the yaw rotation bearing7is sandwiched by the inside rails41b.The frame members42are coupled between the outside rails41aof the two guide rails41. The pulleys43and the drive units44form a bearing movement mechanism for applying a force to the yaw rotation bearing7in moving of the yaw rotation bearing7. The pulleys43are attached to both ends of the guide rails41, and the drive units44are attached to the outside rails41aof the guide rails41, each including a capstan44adriven by a motor (not shown in the drawing) as shown inFIGS. 9 and 10. The rotation axes of the capstans44aare vertical to the rotation axes of the pulleys43. As shown inFIG. 9, when the yaw rotation bearing7is moved, wire fixation attachments45are fixed to the yaw rotation bearing7by using bolts, and wires46are attached to the wire fixation attachments45. The yaw rotation bearing7can be moved in the longitudinal direction of the guide rail41by driving the wires46with the pulleys43and the capstans44aof the drive units44, and when the yaw rotation bearing7(or the inside rails41bsandwiching the bearing) is supported, the container31(that is, the outside rails41aof the guide rails41) also can be moved with respect to the yaw rotation bearing7.

Referring back toFIG. 7, after the empty container31is lifted, the lifted container31is inserted into the clearance20between the nacelle3and the tower2, and then one of the frame members42is attached to the tower top flange2aby using bolts. On this occasion, the container31is inserted in the longitudinal direction of the guide rail41.

Moreover, as shown inFIG. 11, the yaw rotation bearing7is detached from the nacelle3and put on the container31, and then the yaw rotation bearing7is moved to a position that is not in a vertically-upward direction of the tower2by the drive units44mounted on the container31. Specifically, the yaw rotation bearing7is put on the container31, and is further sandwiched by the inside rails41b.The wire fixation attachments45are fixed to the yaw rotation bearing7by using bolts, and the wires46are attached to the wire fixation attachments45. The wires46are driven by the pulleys43and the capstans44aof the drive units44to thereby move the yaw rotation bearing7. The yaw rotation bearing7is moved to a position under the pulley32attached to the nacelle3.

After the yaw rotation bearing7is moved to the position under the pulley32, the wire34tied to the temporal winch33is attached to the yaw rotation bearing7, and the yaw rotation bearing7is suspended by the wire34. On this occasion, the wire34is looped on the pulley32. Moreover, the container31is moved by applying a force to the outside rails41awith the bearing movement mechanism, so that the center of the container31is positioned at the center of the yaw rotation bearing7.

Subsequently, as illustrated inFIGS. 12 and 13, the container31is turned by 90° in order to prevent interference between the container31and the tower2. Here, a numeral symbol2binFIG. 13represents the outer rim at the lower end of the tower2. Moreover, the wire34is withdrawn from the temporal winch33in a state in which the yaw rotation bearing7and the container31are suspended by the wire34, and thereby the yaw rotation bearing7and the container31are landed on the ground.

It should be noted that, when a rod21bof a hydraulic jack21interferes with the brake disk11, the container31and/or the yaw rotation bearing7in carrying out the procedure to detach the yaw rotation bearing7, the interfering rod21bis detached from the nacelle3and is pulled down. Preparing a sufficient number of the hydraulic jacks21allows supporting the nacelle3even when the rods21bof some of the hydraulic jacks21are pulled down.

Subsequently, a new yaw rotation bearing7is attached to the nacelle3by implementing the procedure in the reverse order. Specifically, as illustrated inFIG. 14, the yaw rotation bearing7is sandwiched between the inside rails41bof the guide rails41, and the yaw rotation bearing7is attached to the center of the container31. Then, as illustrated inFIG. 15, the wire34is attached to the yaw rotation bearing7, and the yaw rotation bearing7and the container31are pulled up to a position immediately below the nacelle3by using the pulley32attached to the nacelle3and the temporal winch33provided on the ground. On this occasion, in order to prevent the interference between the container31and the tower2, the longitudinal direction of the guide rail41is maintained to be vertical to the radial direction of the tower3.

Next, as shown inFIG. 16, the container is turned by 90°, and thereby the longitudinal direction of the guide rail41is directed to be parallel with the radial direction of the tower3. The drive units44are operated in this state, and thereby the outside rails41aof the guide rails41of the container31are pushed to a position near the center of the tower top flange2aas shown inFIG. 17. Moreover, as illustrated inFIG. 18, one of the frame members42of the container31is fixed to the tower top flange2aby using bolts. Then, the drive units44of the container31are operated, and thereby the yaw rotation bearing7is moved so that the center of the yaw rotation bearing7is positioned around the center of the tower2. After that, the yaw rotation bearing7is attached to the nacelle base3aof the nacelle3. This is followed by pulling down the rods21bof the hydraulic jacks21after the brake disk11is attached, and thereby the nacelle3is pulled down on the tower2. Moreover, the work for restoring the wind turbine generator1is carried out, including the attachment of the attachment bolts8and9of the yaw rotation bearing7, the ladder15and the cables16and so on. This completes the replacement of the yaw rotation bearing7. It should be noted that, when a rod21bof a hydraulic jack21interferes with the brake disk11, the container31and/or the yaw rotation bearing7, the interfering rod21bis detached from the nacelle3and is pulled down, also in the procedure to attach the yaw rotation bearing7.

It should be noted that, although the works for lifting up the container31in the vicinity of the nacelle3and for landing the container31on the ground are carried out in the above-described embodiment by using the pulley32attached to the nacelle3and the temporal winch33provided on the ground, these works may be carried out by using a winch attached to the nacelle3instead. In this case, the container31is lifted up to the vicinity of the nacelle3or is landed on the ground by winding the wire34attached to the container31with the winch or withdrawing the wire from the winch.

Also, although structures for supporting the hydraulic jacks21(that is, the jack-accepting pedestals22) are attached to the tower2so that the hydraulic jacks21are positioned inside the tower2in the above-mentioned procedure of the replacement of the yaw rotation bearing7, the structures for supporting some or all of the hydraulic jacks may be provided outside the tower2.

In one embodiment, as illustrated inFIGS. 19 and 20, manholes51are formed in the vicinity of the upper end of the tower2, and the jack-accepting pedestals52are inserted into the manholes51. A jack-accepting pedestal52is a structure for supporting a hydraulic jack53. It should be noted that, when no manholes51are provided for the tower2as for the already-constructed wind turbine generator1, the manholes51may be newly bored. In a case where the wind turbine generator1is newly constructed, the manholes51may be formed in the construction. AlthoughFIGS. 19 and 20illustrate a state where the jack-accepting pedestal52is not inserted to the manhole51corresponding to a cross section A-A, these drawings are illustrated simply to explain the structure of the manhole51. Actually, the jack-accepting pedestal52is inserted into each of all the manholes51. The rods of the hydraulic jacks53are abutted to the bottom surface of the nacelle base3aof the nacelle3, and thereby the nacelle3is supported. In the configuration ofFIGS. 19 and 20, the nacelle3is supported by the hydraulic jacks53positioned outside the tower2in addition to the hydraulic jacks21positioned inside the tower2. Referring toFIG. 20, in one embodiment, four hydraulic jacks21are provided inside the tower2, and four hydraulic jacks53are provided outside the tower2. In the configuration ofFIG. 20, the hydraulic jacks53are arranged at angle intervals of 90° in the circumferential direction of the tower2.

FIG. 21Ais a diagram showing the structures of manholes51and the jack-accepting pedestals52. As shown inFIG. 21A, the manholes51are provided through the tower2. A flange51ahaving a thickness larger than that of the tower2is provided to a rim of each manhole51. The jack-accepting pedestals52each includes a short pipe52aand a flange52b.FIG. 21Bis a diagram in which a jack-accepting pedestal52is viewed from the short pipe52a.As shown inFIG. 21B, the short pipe52ais schematically in a cylindrical shape, and the flange52bis schematically in a disc shape. The short pipe52ais inserted into the manhole51outward of the tower2, and further the flange51aof the manhole51and the flange52bof the jack-accepting pedestal52are fixed by using bolts to thereby fix the jack-accepting pedestal52to the tower2.FIG. 21Cshows a structure of the short pipe52ain the C-C cross section. A jack insert hole52cis provided for the short pipe52a.A hydraulic jack53is inserted into the jack insert hole52c, and thereby the hydraulic jack53is fixed to the jack-accepting pedestal52.

An advantage of positioning the hydraulic jacks53outside the tower2is that this makes it unlikely for the hydraulic jacks to interfere in replacing the yaw rotation bearing7. When the hydraulic jacks53are positioned outside the tower2, the hydraulic jacks53other than the hydraulic jack(s)53arranged on the path where the container31is moved in and out for replacing the yaw rotation bearing7are able to continuously support the nacelle3constantly without pulling down the rods during the replacement of the yaw rotation bearing7. Referring toFIG. 20, let us consider a case, for example, where the yaw rotation bearing7is replaced by removing the old yaw rotation bearing7to the right side of the tower2by using the container31and a new yaw rotation bearing7is installed from the right side of the tower2. In this case, it is required to pull up and down the rods of the hydraulic jack53positioned on the right side of the tower2, in order to allow the yaw rotation bearing7to go thereby; however, the rods of the other hydraulic jacks53are not required to be pulled up and down. On the other hand, the hydraulic jacks21positioned inside the tower2are required to pull up and down the rods so as not to interfere with the yaw rotation bearing7. As thus discussed, it is preferable that the hydraulic jacks53are positioned outside the tower2for the purpose of the steady supporting of the nacelle3.

As illustrated inFIGS. 22 and 23, it is preferable to support the nacelle3by using stoppers54after jacking up the nacelle3with the hydraulic jacks21(or the hydraulic jacks53) in order to support the nacelle3more steadily. Here, a stopper54is a structural member for supporting the nacelle3by being sandwiched between the tower top flange2aand the nacelle3. The lower ends of the stoppers54are fixed to the tower top flange2aby bolts, and the upper ends of the stoppers54are fixed to the nacelle3by bolts. The use of the stoppers54in addition to the hydraulic jacks21(or the hydraulic jacks53) improves certainty of the supporting of the nacelle3. The stopper(s)54arranged on the path where the container31is moved in and out is detached in replacing the yaw rotation bearing7. When the old yaw rotation bearing7is removed to the right side of the tower2by using the container31and a new yaw rotation bearing7is installed from the right side of the tower2, the stoppers54(stoppers54A) inFIG. 23positioned on the right side of the tower2are detached. Moreover, the rods21bof the hydraulic jacks21interfering with the container31are pulled up and down appropriately, and thus the nacelle3is supported.

As described above, the maintenance method of the wind turbine generator of the present embodiment allows implementing a maintenance work which involves detaching the nacelle from the tower (for example, the replacement of the yaw rotation bearing) without using a large size crane.