METHOD FOR EXTENDING THE SERVICE LIFE OF A MAIN BEARING ASSEMBLY OF A WIND TURBINE

Abstract

A main bearing assembly of a wind turbine includes at least one main bearing with a rotation axis and at least one bearing row in which a rotor shaft of the wind turbine is mounted. The main bearing assembly has at least one stationary bearing ring, a circulating bearing ring and rolling elements. A method of extending the service life or servicing the main bearing assembly includes rotating the stationary bearing ring about the rotation axis of the main bearing assembly. Alternatively, only a new stationary bearing ring, preferably with at least two bearing ring segments is installed instead of a damaged outer ring, in particular without further important bearing components such as the inner ring being exchanged.

Claims

1. A method for extending a service life of a main bearing assembly of a wind turbine, the method comprising: providing the main bearing assembly with: at least one main bearing having an axis of rotation, at least one bearing row supporting a rotor shaft of the wind turbine in the at least one bearing row, at least one stationary bearing ring, a revolving bearing ring, and rolling elements; and rotating the stationary bearing ring about the axis of rotation of the main bearing assembly.

2. The method according to claim 1, which further comprises rotating the stationary bearing ring by at least 45°.

3. The method according to claim 1, which further comprises rotating the stationary bearing ring by at least 90°.

4. The method according to claim 1, which further comprises rotating the stationary bearing ring within an angular range of from 160° to 200°.

5. The method according to claim 1, which further comprises rotating the stationary bearing ring by 180°.

6. The method according to claim 1, which further comprises using a fixture to retain the rotor shaft during the rotating.

7. The method according to claim 6, which further comprises using the fixture to make the rotor shaft at least partially load-free.

8. The method according to claim 6, which further comprises fastening the fixture to a structural component being at least one of a base frame or a rotor hub.

9. The method according to claim 1, which further comprises providing a multi-row bearing with a plurality of axial bearing rings adjoining one another in a direction of the axis of rotation, and rotating only some of the plurality of axial bearing rings.

10. The method according to claim 1, which further comprises installing the stationary bearing ring and the revolving bearing ring by providing the revolving bearing ring as an outer ring and not rotating the rotor shaft during operation.

11. The method according to claim 1, which further comprises using a condition-monitoring system to carry out condition-monitoring or vibration-monitoring of the main bearing assembly, and establishing a time of implementation of measures for extending the service life as a function of results of the condition-monitoring or vibration-monitoring.

12. The method according to claim 1, which further comprises using housing segments to adjust a bearing clearance.

13. The method according to claim 1, which further comprises rotating the stationary outer ring in a housing.

14. The method according to claim 1, which further comprises using a rotating device for rotating the stationary bearing ring.

15. The method according to claim 1, which further comprises applying heat for rotating the stationary bearing ring.

16. The method according to claim 1, which further comprises providing the main bearing assembly as a three-point bearing or a torque bearing.

17. A method for extending a service life of a main bearing assembly of a wind turbine, the method comprising: providing the main bearing assembly with: at least one main bearing having an axis of rotation, at least one bearing row supporting a rotor shaft of the wind turbine in the at least one bearing row, a fixed housing fastened to a base frame of the wind turbine, at least one stationary outer bearing ring, a revolving bearing ring, and rolling elements; and installing a new stationary bearing ring, with or without at least two bearing-ring segments, in exchange for the at least one stationary outer bearing ring being previously damaged.

18. The method according to claim 17, which further comprises not replacing at least one of: the revolving bearing ring, or a cage, or all or some of the rolling bearings.

19. The method according to claim 17, which further comprises using a fixture to retain the rotor shaft during the exchange.

20. The method according to claim 19, which further comprises using the fixture to make the rotor shaft at least partially load-free.

21. The method according to claim 19, which further comprises fastening the fixture to a structural component being at least one of a base frame or a rotor hub.

22. The method according to claim 17, which further comprises providing a multi-row bearing with a plurality of axial bearing rings adjoining one another in a direction of the axis of rotation, and exchanging only some of the plurality of axial bearing rings.

23. The method according to claim 17, which further comprises replacing the housing with a split housing formed of at least two housing segments.

24. The method according to claim 17, which further comprises installing the stationary bearing ring and the revolving bearing ring by providing the revolving bearing ring as an outer ring and not rotating the rotor shaft during operation.

25. The method according to claim 17, which further comprises using a condition-monitoring system to carry out condition-monitoring or vibration-monitoring of the main bearing assembly, and establishing a time of implementation of measures for extending the service life as a function of results of the condition-monitoring or vibration-monitoring.

26. The method according to claim 17, which further comprises using the bearing-ring segments to adjust a desired bearing clearance.

27. The method according to claim 17, which further comprises using housing segments to adjust a bearing clearance.

28. The method according to claim 17, which further comprises using a rotating device for rotating the stationary bearing ring.

29. The method according to claim 17, which further comprises providing the main bearing assembly as a three-point bearing or a torque bearing.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0041] FIG. 1 is a fragmentary, diagrammatic, perspective view of a main bearing assembly of a wind turbine;

[0042] FIG. 2 is an enlarged, perspective view of a wind turbine in the region of a hub without representation of an enclosure (nacelle) for the main bearing assembly;

[0043] FIGS. 3A and 3B are respective sectional and perspective views of a double-row main bearing; and

[0044] FIGS. 4A and 4B are respective exploded sectional and perspective views of an outer ring as well as an inner ring.

DETAILED DESCRIPTION OF THE INVENTION

[0045] Referring now to the figures of the drawings in detail and first, particularly, to FIGS. 1 and 2 thereof, there is seen a wind turbine 4 having a main bearing assembly 1 taking the form of a 3-point bearing. This main-bearing solution, which is often to be found, utilizes a two-row self-aligning roller bearing as a rotor-side fixed bearing (main bearing 10) and a first gear-stage bearing as a gearbox-side floating bearing. The main bearing 10 has a housing 5 which is fastened to a supporting structure, for example a base frame 6. The entire main bearing assembly 1 is ordinarily disposed in a nacelle, not represented herein in any detail, which is rotatably disposed on a tower, likewise not represented herein in any detail.

[0046] The main bearing 10 has a stationary bearing ring 7 which is fixed by the housing 5 and which constitutes an outer ring of the self-aligning roller bearing. Furthermore, the main bearing 10 has an inner ring which in operation rotates about an axis of rotation 13 together with a rotor shaft 3 and constitutes a revolving bearing ring 8.

[0047] Rolling elements 9 are disposed between the two bearing rings 7, 8. The bearing rings 7, 8, in particular the stationary bearing ring 7, have two rings succeeding one another in the axial direction—that is to say, in the direction of the axis of rotation 13—which are also designated as axial bearing-ring segments. (In the upper half of FIG. 4, a stationary bearing ring 15, divided into two axial bearing-ring segments, is represented in exemplary manner.) A row of rolling elements 9 is disposed in each instance between a respective inner and outer bearing-ring segment, so that two bearing rows 2, namely a hub-side bearing row and a gearbox-side bearing row, have been formed.

[0048] The load zones, due to the wind loads, of this stationary bearing ring 7, or of the stationary axial bearing-ring segments, have been formed in a mirror-image manner between 9 o'clock and 3 o'clock in the case of the hub-side bearing row, and between 3 o'clock and 9 o'clock on the gearbox-side bearing row.

[0049] According to the prior art, the lifespan theory and load-rating calculation are based on the hypothesis of fluctuating shear stress. For that purpose, measurements are taken for estimating the lifespan on the basis of the Hertzian contact stress and empirically ascertained material parameters. According to this theory, the inner ring is, as a rule, the component failing first, since, due to the greater curvature in the rolling direction, as a rule the inner ring undergoes the highest stressing or contact stress.

[0050] However, application-specific experience shows that those assumptions prove to be only partially correct in that case, and other effects overlie that hypothesis. Kinematic and lubrication-related special features in the main bearing arrangement result in a divergent sequence of failures of the individual roller-bearing components. This novel insight is the starting-point for the present novel approach to maintenance. Experience shows that the stationary bearing ring 7 on the gearbox-side bearing row fails first, contrary to the previous fatigue theory of the original bearing construction. The revolving bearing ring 8 likewise already has slight signs of wear at this time; however, it is still fully functional. The same applies to the rolling elements 9 and to a cage in which the rolling elements 9 are retained.

[0051] Consequently it is advantageous to detect the damage to the stationary bearing ring 7 (outer ring) as early as possible with a monitoring system (condition-monitoring, for example vibration-monitoring, axial-clearance-monitoring), in order to avoid larger break-outs of the outer-ring raceway, which, in turn, might damage the revolving bearing ring 8 and the rolling elements 9.

[0052] Rather, experience has shown that early outer-ring damage is mostly localized to the region from 3 o'clock to 9 o'clock. This, in turn, means that the remaining 180° of the outer ring is still almost as good as new.

[0053] Now the invention utilizes this correlation and has developed a method to rotate this stationary bearing ring 7 (outer ring) on the wind turbine by 180° about the axis of rotation 13 when the rotor has been mounted. It is consequently ensured that the undamaged raceway region of the stationary bearing ring 7 can be utilized, and consequently the overall service life of the main bearing assembly 1 is extended, without having to swap the entire main bearing 10.

[0054] In order to rotate this stationary bearing ring 7 (variant 1) or, where appropriate, to replace it with a new bearing ring 7 (variant 2), the bearing ring 7 is firstly removed from its stationary position. In variant 2, the old bearing ring 7 is replaced with new bearing-ring segments 14 (cf. FIG. 4) which constitute the new bearing ring 7.

[0055] Herein lies a further special aspect, since for this purpose in a preferred configuration, the stationary housing 5 is separated from the nacelle structure—that is to say, in particular, from the base frame 6 to which the housing 5 is firmly connected during operation. The housing 5 is offset spatially and temporally to a limited extent, despite the rotor loads and wind loads that are still applied to the rotor shaft 3.

[0056] For this purpose, a fixture, not represented in any detail in the figures, is provided, which fixes the rotor 11, together with the rotor shaft 3 and the remainder of the main bearing 10, during the rotating of the stationary bearing ring 7. In the present document, “rotor 11” is understood to mean the unit formed of the so-called rotor hub 18 with the rotor blades disposed thereon. In the embodiment, the rotor hub 18 is connected in a torsion-resistant manner to the rotor shaft 3 which may also be regarded as part of the rotor. This fixture is connected to one or more of the structural components selected from base frame 6, rotor shaft 3, rotor hub 18 and/or gearbox, and is removed after the adjustment of a bearing clearance or axial clearance of the main bearing assembly 1 and after the renewed fastening of the bearing housing 5 to the base frame 6. For instance, the fixture is supported, on one hand, on the base frame 6 and, on the other hand, on the rotor hub 18 or on the rotor shaft 3, in order to consequently make the main bearing 10 at least partially load-free.

[0057] A further, alternative realization of the repair is represented by the rotating of the stationary bearing ring 7 directly within the bearing housing 5. For this purpose, preferentially merely add-on parts or reconstruction parts—such as, for example, paneling elements or covering elements, seals, etc.—are dismantled, and the rotor shaft 3 is furthermore (partially) relieved, for instance by at least one hydraulic or mechanical supporting element. Subsequently, the stationary outer ring 7 in the housing 5 is rotated about the axis of rotation 13 of the rotor shaft 3 with the aid of a rotating device. Generally, the rotating device is preferentially fastened to the housing 5 and/or to the base frame 6 in all of the rotating variants.

[0058] For the rotation of the stationary bearing ring 7 or of at least one stationary axial bearing-ring segment within the housing, without the latter being dismantled, the procedure in the case of such a three-point bearing arrangement is, for instance, as follows:

[0059] Firstly, the rotor shaft 3 is secured against rotation by a rotor lock, and the rotor weight is raised by hydraulic tools, and consequently the main bearing assembly is partially relieved. Subsequently the reconstruction parts on the existing housing 5 are dismantled, in order to gain access to the stationary bearing ring 7 (outer ring). The rotating device is now fastened to the housing 5 and/or to the base frame 6. This rotating device acts upon the stationary bearing ring 7 in a suitable manner (by force-locking, form-locking, material-locking, or frictional-locking engagement) and rotates the ring relative to the housing 5 about the axis of rotation 13. Rotation may be effected in small portions by appropriate resetting of the rotating device, and may also be effected as a complete rotation by 180°, for instance, insofar as the rotating device makes this possible. Once the stationary bearing ring 7 has been rotated into the desired position, the rotating device is dismantled, and the bearing arrangement is loaded again. Subsequently, the reconstruction parts are mounted again, and the rotor lock is unlocked.

[0060] In the variant of the exchange of the stationary bearing ring, the procedure is, for instance, as follows:

[0061] In a manner similar to that previously described, the bearing is firstly relieved (locking through rotor lock, raise rotor weight . . . ). Subsequently the housing 5 is dismantled; if necessary, the latter is separated in this process (for example, by separation welding or some other destructive separating method). Subsequently, (merely) the stationary bearing ring 7 is removed; for this purpose, the ring is divided up into segments; if necessary, in this case too, a destruction of the bearing ring 7 is effected by separating into the segments (separation welding, blasting). After this, the bearing-ring segments 14 (at least two) of the new stationary bearing ring 7 are mounted. As required, the bearing slackness or bearing clearance is adjusted, for instance by the arrangement of spacer elements (shim plates) between the bearing-ring segments 14. After this, the housing 5 (if necessary, a new one) is re-attached. For this purpose, the housing has typically been subdivided into at least two housing segments. In this case too, the bearing clearance can be adjusted. After this, the fastening of the housing 5 to the base frame or base support takes place. Subsequently, the bearing is loaded again (take fixture away, disengage rotor lock) and can be put back into operation.

[0062] The two variants (rotating/exchanging) previously described may also be combined, insofar as in the first variant—the rotating of the stationary bearing ring—the housing is firstly dismantled, and, after the rotating, is mounted again or replaced with a new one.

[0063] The methods described herein are also suitable, in principle, in the case of a torque bearing which represents a special construction of the main bearing in wind turbines. With this construction, the bearing rings 7, 8 are integrated only in part or not at all within a housing or are secured in the housing 5 or on the rotor shaft 3 by the known interference-fit assembly. Rather, the bearing rings 7, 8 are fastened to the base frame 6, to the rotor hub 18 or to other stationary and rotating structural components by a flange connection using screws. With the aid of the screw coupling and the frictional engagement in the flange connection, the stationary position relative to the base frame 6 or to the rotating rotor hub 18 is consequently ensured. In this way, the rotating or exchanging, according to the invention, of the stationary bearing ring 7 is just as advantageous as in the case of the conventional three-point bearing arrangement.

[0064] For this purpose, a fixture is likewise provided, which fixes the rotating part of the drive train (rotor, inclusive of shaft and generator) to the stationary base frame 6. Subsequently, the flange connection of the stationary bearing ring 7 is disengaged and subsequently rotated about the axis of rotation 13 of the bearing into an advantageous, low-wear position. After the renewed fastening of the flange connection, the fixture can then be removed again, and the rotor can rotate again, or—to be more exact—the wind turbine can be put into operation. Where appropriate, reconstruction parts also have to be dismantled in advance, in order to gain access to the flange connection. Torque bearings are very often employed in directly-driven wind turbines. By a “directly-driven wind turbine,” a plant without gears is generally understood, where the generator rotates at the speed of the rotor. With this construction, the generator can preferentially be utilized for interim fixing and for preventing torsion. In this way, the fixture can consequently be entirely or partially replaced, and the generator structure is utilized, according to a preferred configuration, for the rotating or the exchange of the stationary bearing ring 7.

[0065] To the extent that the term “rotor” is mentioned in the present document, this is generally understood to mean the rotating part of a wind turbine which, in particular, includes the rotor hub 18 with the rotor blades fastened thereto. Typically, the rotor also includes the rotor shaft 3 which is supported by the main bearing assembly 1. The rotor shaft 3 has typically been passed through the main bearing 10 and extends from the hub as far as a gearbox or, in directly-driven wind turbines, as far as the generator.

[0066] To the extent that the term “main bearing assembly” is mentioned in the present document, this is generally understood to mean the bearing arrangement of the rotor shaft 3 of a wind turbine, to the front end of which the rotor hub 18 with the rotor blades has been fastened.

[0067] The term “fixture” is generally understood to mean a retaining device that is fastened temporarily to a structural component such as, for instance, the base frame 6 or some other base support or machine support and that serves, in particular, for temporary support and retention of the rotor shaft 3 during the implementation of the measure described herein.

[0068] A few operational sequences of the method with the individual method steps are presented in the following by way of examples of the rotating or exchanging of the stationary bearing ring:

EXAMPLE 1

[0069] 1.1 Fixing of the rotor shaft 3 to rotor hub 3 and base frame 6 by fixture
1.2 Dismantling of the housing 5 and axial displacement of the housing 5
1.3 Rotating of the stationary bearing ring 7 about axis of rotation 13
1.4 Mounting of the housing 5 on the rotated, stationary bearing ring 7
1.5 Dismantling of the fixture
1.6 Continued operation of the wind turbine (rotating the rotor)

EXAMPLE 2

[0070] 2.1 Fixing of the rotor shaft 3 to rotor hub 18 and base frame 6 by fixture
2.2 Dismantling of the housing 5 and axial displacement of the housing 5
2.3 Removal of the used stationary bearing ring 7
2.4 Mounting of the new bearing-ring segments 14 of the stationary bearing ring 7
2.5 Mounting of the housing 5 on the segmented stationary bearing ring 7
2.6 Dismantling of the fixture
2.7 Continued operation of the wind turbine (rotating the rotor)

EXAMPLE 3

[0071] 3.1 Fixing of the rotor shaft 3 to rotor hub 18 and base frame 6 by fixture
3.2 Removal of the housing 5
3.3 Rotating of the stationary bearing ring 7 about axis of rotation 13, or installation of new bearing-ring segments 14
3.4 Mounting of new housing segments
3.5 Dismantling of the fixture
3.6 Continued operation of the wind turbine (rotating the rotor)

EXAMPLE 4

[0072] 4.1 Fixing of the rotor shaft 3 to rotor hub 18 and base frame 6 by fixture
4.2 Dismantling of the housing 5 and axial displacement of the housing 5
4.3 Removal of the used stationary bearing ring 7
4.4 Mounting of the new bearing-ring segments 14 of the stationary bearing ring 7
4.5 Adjustment of the bearing slackness
4.6 Mounting of the housing 5 on the segmented stationary bearing ring 7
4.7 Dismantling of the fixture
4.8 Continued operation of the wind turbine (rotating of the rotor)

EXAMPLE 5

[0073] 5.1 Fixing of the rotor shaft 3 to rotor hub 18 and base frame 6 by fixture
5.2 Removal of the housing 5
5.3 Rotating of the stationary bearing ring 7 about axis of rotation 13, or installation of new bearing-ring segments 14
5.4 Mounting of new housing segments
5.5 Adjustment of the bearing slackness
5.6 Dismantling of the fixture
5.7 Continued operation of the wind turbine (rotating of the rotor)

EXAMPLE 6

[0074] 6.1 Setting of a rotor lock of the wind turbine and relieving the rotor weight
6.2 Dismantling of add-on parts of the housing 5
6.3 Rotating of the stationary bearing ring 7 about axis of rotation 13 in the housing with the aid of a rotating device
6.4 Mounting of the add-on parts of the housing 5
6.5 Loading with rotor weight, removal of the rotor lock
6.6 Continued operation of the wind turbine (rotating the rotor)

[0075] By virtue of the setting of the rotor lock in step 6.1, a rotation of the rotor is prevented. In principle, this is possible in all of the examples previously described.

[0076] A start-signal for implementing the measures is preferentially given by a condition-monitoring system, especially a vibration-monitoring system.

[0077] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention.

LIST OF REFERENCE SYMBOLS

[0078] 1 main bearing assembly
2 bearing rows
3 rotor shaft
4 wind turbine
5 housing
6 base frame
7 stationary bearing ring
8 revolving bearing ring
9 rolling elements
10 main bearing
11 rotor
13 axis of rotation
14 bearing-ring segments
15 divided stationary bearing ring
17
18 rotor hub