Mitigating vibration in upright support structures

Abstract

A method of installing a damper (22) onto an upright tower (14) of a wind turbine (10), the method comprising: lifting the damper (22) to an elevated position beside the tower (14); inserting a guide member (56) through a mounting opening (42) of the tower (14), 5 from inside the tower (14); and engaging the guide member (56) with the damper (22) while in the elevated position.

Description

[0001] Mitigating vibration in upright support structures

[0002] Technical Field

[0003] This invention relates to mitigating vibration in an upright support structure, particularly a wind turbine tower whose nacelle has been removed.

[0004] Background

[0005] A typical wind turbine generator (WTG), or ‘wind turbine’, includes a rotor supported by a nacelle that is mounted at the top of an upright, and typically relatively slender, tower that acts as a support structure. When the tower is subjected to wind, wind-induced vibration (WIV) may arise due to vortex shedding as air flows circumferentially around the surface of the tower.

[0006] In this respect, as air flows around the tower exterior, low-pressure vortices may be created on the downstream side of the tower. These vortices detach intermittently from either side of the tower, giving rise to an alternating force that acts on the tower to induce side-to-side movement, such that the tower oscillates. The frequency of the alternating force and the corresponding oscillation of the tower depends on the diameter and height of the tower, and the wind speed. It follows that at a certain wind speed, referred to as the critical wind speed, the frequency of the alternating force coincides with the natural frequency of the structure, leading to resonance.

[0007] The overall structure formed when the nacelle and rotor are installed onto the tower may be tuned to have a natural frequency that avoids resonance. However, the natural frequency of the tower in isolation is different to that of the overall structure, and so the tower may be more vulnerable to resonance when standing in isolation.

[0008] One scenario in which a tower may stand in isolation is during installation, before the nacelle has been installed. To address WIV that may arise in this scenario, one or more tower installation dampers (TIDs) may be fitted to the tower before it is erected, to remain in place while the tower is erected and until the nacelle has been mounted, to damp vibration of the tower during installation. Once the nacelle has been mounted, the TID is removed and mounting holes used to secure the TID to the tower during installation may be covered, for example using tape, to minimise disruption to the smooth exterior of the tower. An example of this approach is disclosed in the Applicant’s earlier application, WO 2020 / 001720.

[0009] However, after commissioning of a wind turbine there may be occasions when a nacelle is removed from its supporting tower, at which point the tower, now isolated and devoid of TIDs, is once again vulnerable to resonance due to WIV. This situation may arise during decommissioning of the wind turbine, for example, or during a repowering procedure, in which the nacelle of a wind turbine is replaced. In this respect, when a nacelle reaches the end of its operating life there may be a significant cost benefit associated with re-using the tower, and so the nacelle may be removed from the tower and replaced with a new model. As there is no TID attached to the tower, mounting of the new nacelle may rely on a suitable weather window. However, mounting a new nacelle is a lengthy procedure and wind turbines are often installed at sites that are prone to rapid changes in wind conditions. There is therefore a risk that a tower may start to resonate during a repowering procedure if wind conditions change suddenly.

[0010] In one known approach to mitigate this, a mechanical damper may be fitted to an upright tower with the use of guide ropes. The guide ropes are attached to the damper and fed through mounting openings in the tower, and can be pulled to guide the damper into position for fixing to the tower. Once installed, the damper resists WIV of the tower while the nacelle is replaced. However, this method is time-consuming, and the guide ropes are inherently very long and so cumbersome and prone to being caught by wind, making them difficult to handle and creating a risk of tangling in nearby trees or structures.

[0011] It is against this background that the invention has been devised.

[0012] Summary of the Invention

[0013] An aspect of the invention provides a method of installing a damper onto an upright tower of a wind turbine. The damper may be a tower installation damper, for example, and may be configured to mitigate vibration of the tower, for example due to wind, and particularly when the tower stands in isolation without a nacelle mounted at the top. The method comprises: lifting the damper to an elevated position beside the tower; inserting a rigid guide member through a mounting opening of the tower, from inside the tower; and engaging the guide member with the damper while in the elevated position. The mounting opening may be a mounting hole, for example. The mounting opening may already be present on the tower from a previous installation of a damper, for example during initial commissioning on the wind turbine. The tower may have multiple mounting openings.

[0014] The use of a rigid guide member to engage the damper from inside the tower, for example by personnel inside the tower, provides a controlled and reliable way to catch the damper while it is beside the tower, for example suspended on a lifting line. The guide member may engage a mounting foot of the damper, for example.

[0015] The method may comprise pulling the damper towards the tower using the guide member. The method may comprise operating a retraction mechanism to retract the guide member through the mounting opening to pull the damper towards the tower. The guide member may include or define part of the retraction mechanism. For example, the guide member may include a thread that cooperates with a rider element such as a nut to form the retraction mechanism. The guide member may form part of a guide tool, which tool may also include the retraction mechanism. The use of a retraction mechanism may enhance control over drawing of the damper towards the tower.

[0016] The method may comprise manoeuvring the damper using the guide member. The method may comprise operating the guide member as a lever to manoeuvre the damper.

[0017] The guide member is rigid, for example in the form of a rigid bar.

[0018] The guide member may comprise a threaded portion. The threaded portion may extend fully or partially along the length of the guide member, for example. The method may comprise rotating the guide member to engage the threaded portion of the guide member with a threaded hole of the damper. The method may comprise subsequently removing the guide member and engaging a fixing such as a bolt with the threaded hole. The threaded hole may be a mounting hole of the damper, and may be located on a mounting foot of the damper. The method may comprise effecting relative rotation between the guide member and a rider element carried on the threaded portion of the guide member to pull the damper towards the tower. The guide member and the rider element may cooperate to form a retraction mechanism configured to retract the guide member through the mounting opening. The rider element could be a nut, for example. The method may comprise rotating the rider element to retract the guide member through the mounting opening. The guide member may be held against rotation while rotating the rider element, for example by holding a handle attached to the guide member.

[0019] The method may comprise positioning at least part of a protective element within the mounting opening, between the mounting opening and the guide member. The protective element could be a washer, or a portion of a washer, for example.

[0020] The method may comprise engaging a fixing with the damper through another mounting opening of the tower, while the guide member is engaged with the damper. This may be followed by removing the guide member and engaging another fixing with the damper through the mounting opening from which the guide member has been removed. Alternatively, the method may comprise securing the damper to the mounting opening using the guide member.

[0021] The method may comprise inserting multiple guide members through respective mounting openings of the tower to engage the damper. The method may comprise engaging each guide member with a respective receptacle of the damper, such as a fixing hole or a mounting foot of the damper.

[0022] The damper may be level with the mounting opening when in the elevated position. For example, the damper may be at a height such that the mounting opening is level with a corresponding fixing hole of the damper.

[0023] The method may comprise securing a line used to lift the damper inside the tower, once the damper is installed on the tower.

[0024] The damper may be lifted using a crane, for example.

[0025] Another aspect of the invention provides a system, or kit, for mitigating vibration in an upright tower of awind turbine. The system may be used when a nacelle of the wind turbine is to be removed, for example, to mitigate vibration of the tower while it stands in isolation. The system comprises: a damper for installing onto the tower; and at least one rigid guide member configured for insertion through a mounting opening of the tower, from inside the tower, to engage the damper while the tower is upright and the damper is in an elevated position beside the tower, for example suspended beside the tower on a lifting line. The system may comprise at least one fixing, such as a bolt, for securing the damper to the tower. It may also be possible for the guide member to serve as a fixing.

[0026] The system may comprise a guide tool that comprises the guide member, the guide tool further comprising a retraction mechanism that is operable to retract the guide member through the mounting opening while engaged with the damper. The retraction mechanism may comprise a rider element such as a nut carried on the guide member, for example. The system may comprise a threaded interface between the guide member and the rider element.

[0027] The system may comprise a stopper configured to prevent the guide member passing entirely through the mounting opening. For example, the stopper may be fixed relative to the guide member and may be wider than the mounting opening. Alternatively, the stopper could be narrower than the opening but may cooperate with another component such as a washer that is wider than the opening. The stopper may be part of the retraction mechanism, if present, for example. The guide tool may have a handle, in which case the handle may act as a stopper.

[0028] It will be appreciated that preferred and / or optional features of each aspect of the invention may be incorporated alone or in appropriate combination in the other aspects of the invention also.

[0029] Brief Description of the Drawings

[0030] So that it may be more fully understood, the invention will now be described, by way of example only, with reference to the following drawings, in which like features are assigned like reference numerals, and in which:

[0031] Figure 1 is a front view of a wind turbine, with a tower damper installed;

[0032] Figure 2 is a rear view of a tower damper in isolation, suspended on a lifting line;

[0033] Figure 3 is an end view of the tower damper of Figure 2;

[0034] Figure 4 shows the tower damper of Figure 2 being lifted towards an elevated position beside a tower of the wind turbine of Figure 1 ; Figures 5 and 6 show the tower damper in top and side views respectively with lines attached;

[0035] Figure 7 shows the tower damper positioned level with mounting holes of the tower;

[0036] Figure 8 shows a portion of the tower in radial section;

[0037] Figures 9a to 9d show stages of engaging and manoeuvring the tower damper with a guide tool;

[0038] Figure 10 shows a guide tool in perspective view;

[0039] Figures 11a to 11c show stages of engaging and manoeuvring the tower damper with the guide tool of Figure 10;

[0040] Figures 12a to 12c show stages of securing the tower damper to the tower; and

[0041] Figure 13 shows stowing of a lifting line following installation of the tower damper.

[0042] Detailed Description

[0043] In general terms, embodiments of the invention enable a damper for a wind turbine tower, such as a TID, to be installed onto the tower of a wind turbine when erect and upright, thereby facilitating operations that involve removing a nacelle from a tower, for example a repowering procedure. In embodiments to be described, guide tools are used to engage and capture the TID while suspended in an elevated, above-ground or above-water position beside the tower, and to manoeuvre the Tl D into position for securing to the tower. Each guide tool may include a rigid guide member that can be inserted through a mounting opening of the tower, from inside the tower, to engage the TID and thereby assist with positioning the TID correctly for securing to the tower.

[0044] To provide context for the invention, Figure 1 shows a horizontal-axis WTG, referred to below as a wind turbine 10, to which embodiments of the invention may be applied. It is emphasised, however, that the wind turbine 10 shown in Figure 1 is merely an example, and embodiments of the invention may be implemented in support structures for a range of wind turbine configurations.

[0045] In the example shown in Figure 1, the wind turbine 10 includes a nacelle 12 mounted at the top of a tower 14, the tower 14 being generally columnar and so tall and slender, and with a gentle upward taper such that the tower 14 is slightly conic in shape. The nacelle 12 supports a front facing rotor 16 comprising a plurality of blades 18 that extend generally radially from a central hub 20. The nacelle 12 houses components that convert rotation of the rotor 16 due to wind into electrical power.

[0046] Figure 1 also shows a damper in the form of a TID 22 secured to the side of the tower 14, at a position near the top of the tower 14 and a short distance below the nacelle 12. In this example, the nacelle 12 is about to be removed and replaced in a repowering procedure, and so the TID 22 has been installed to protect the tower 14 against WIV while it stands in isolation, after the nacelle 12 has been removed.

[0047] Figures 2 and 3 show the TID 22 in more detail and are now referred to collectively. It is noted, however, that the configuration of the TID 22 is not the subject of this disclosure and embodiments of the invention are applicable to other dampers having various configurations.

[0048] The TID 22 shown in Figures 2 and 3 has a generally cylindrical main housing 24, which in this example contains a pendulum structure supported by a suspension arrangement that allows the pendulum structure to displace to absorb and therefore damp vibration in the tower 14, when installed. The main housing 24 is, in turn, received in an outer frame having a generally flat rear wall 26 extending between an upper end section 28 and a lower end section 30, the TID 22 being shown with the rear wall 26 upright in Figure 2 and laid flat in Figure 3. The rear wall 26 and end sections 28, 30 of the frame collectively receive and support the main housing 24.

[0049] As shown most clearly in Figure 2, the rear wall 26 of the frame includes a set of four mounting feet 32 that extend outwardly from the rear wall 26 to embrace and secure to the generally cylindrical external surface of the tower 14. Each foot 32 is secured to the rear wall 26 by a suitable bracket arrangement 34. Each mounting foot 32 has an outwardly-facing surface defining a mounting face 36 that engages the surface of the tower 14, when installed. The mounting face 36 may be defined by a mounting pad of compressible material that can conform to the surface of the tower 14, for example.

[0050] The mounting feet 32 are arranged in two pairs, one on each side of the rear wall 26, and collectively assume a generally rectangular formation. In this example, each pair of feet 32 are spaced with their respective centres 600mm apart, while the horizontal distance between feet 32 at the same vertical level is approximately 1000mm. These dimensions may vary, however.

[0051] The pairs of feet 32 are turned slightly inwardly toward one another so that each pair is oriented to face towards a central axis of the tower 14 when engaged, so that the feet 32 conform to the outer profile of the tower 14. Similarly, the feet 32 may be oriented or otherwise have flexibility to conform to the conic profile of the tower 14. Optionally, shim plates may be fitted to adjust the orientation of each foot 32 to adapt to the profile of the tower 14.

[0052] The mounting face 36 of each mounting foot 32 includes a pair of fixing holes 40 that are spaced vertically, in the orientation shown in Figure 2. This spacing is 150mm in this example, but this may vary. The fixing holes 40 are threaded and configured to receive bolts (shown in Figures 12a to 12c) to secure the foot 32 to the tower 14. In this respect, as Figure 7 shows, the tower 14 includes a set of mounting holes 42 that penetrate a wall of the tower 14, through which bolts can be inserted to engage their respective fixing holes 40 of the TID 22. The cross-sectional view of Figure 8 reveals that the mounting holes 42 extend radially through the wall of the tower 14.

[0053] The fixing holes 40 of the TID 22 are configured to align with the mounting holes 42, each fixing hole 40 aligning with a respective mounting hole 42 and being coaxial with its respective mounting hole 42, once aligned, due to the angling of the feet 32. Once the fixing and mounting holes 42 are aligned, a bolt can be inserted through the tower mounting hole 42, from inside the tower 14, to screw into the associated fixing hole 40 of the TID 22 and thereby secure the associated foot 32 and, in turn, the TID 22, to the tower 14. The fixing holes 40 therefore act as receptacles of the TID 22 that are configured to receive fixings in the form of bolts.

[0054] It is noted that the TID 22, or a similar TID, may have been used when the wind turbine 10 was first commissioned, in which case the TID 22 may have been installed onto the tower 14 when the tower 14 was lying horizontally, prior to erection. In this situation, the TID 22 can be positioned on top of the horizontally-oriented tower 14 and bolts can be fitted from underneath by personnel inside the tower 14, for example. Aligning the fixing holes 40 with the tower mounting holes 42 to secure the TID 22 to the tower 14 when upright presents a different challenge, but can be achieved using the approach described below. It follows that this embodiment of the invention advantageously allows the existing TID 22 to be retrofitted to the tower 14 without significant modification.

[0055] In this respect, one modification that is made to the TID 22 in this example is to add an additional padeye for a lifting line, as the TID 22 is to be lifted in a different way relative to when used during initial commissioning of the wind turbine 10. The additional padeye is at the bottom of the frame on the lower end section 30, on the opposite side to the rear wall 26, and so defines a lower padeye 44. The lower padeye 44 is shown most clearly in Figure 3. The TID 22 further includes an upper padeye 46 on an upper surface of the upper end section 28 of the frame, and a side padeye on 48 one side of the lower end section 30 of the frame.

[0056] If appropriate, the TID 22 may also be modified to remove features that could pose a risk of colliding with the tower 14 when the TID 22 is hoisted beside the tower 14, to ensure that the feet 32 of the TID 22 engage the tower 14 before any other part of the TID 22.

[0057] As Figure 2 shows, when lifting the TID 22 for installation onto the upright tower 14, a lifting line 50 is secured to the upper padeye 46, for example using a shackle, the upper padeye 46 therefore acting as the primary padeye for the lifting operation through which the main load of the TID 22 is transferred while suspended.

[0058] Figure 4 shows the TID 22 being raised towards an elevated position beside the tower 14 during a lifting operation, to draw level with the mounting holes 42 for installation onto the tower 14. This shows the TID 22 suspended from the lifting line 50, which is supported by a crane (not shown). Tag lines 52 attached to the lower and side padeyes 44, 48 extend downwardly and outwardly from the TID 22, to stabilise and resist rotation of the TID 22 during its ascent. Figures 5 and 6 provide, schematically, top and front views respectively of the configuration of the lifting line 50 and tag lines 52 during the lifting operation. The number and positions of the tag lines may vary in practice. Figure 7 shows the TID 22 having reached an elevated position beside the tower 14. In this elevated position, the height of the TID 22 is such that the fixing holes 40 of the feet 32 are substantially level with the corresponding mounting holes 42 of the tower 14. At this stage, guide tools are employed to capture and manoeuvre the TID 22 into position to align the fixing holes 40 with the mounting holes 42, and to hold the TID 22 in position while the bolts are fitted to secure the TID 22 to the tower 14.

[0059] Figures 9a to 9d show, in simplified and schematic form, a series of stages of a process to capture and manoeuvre the TID 22 using a guide tool 54 that is operated by a person inside the tower 14. These figures show the process for a single guide tool 54 to illustrate the principle, but it should be understood that a similar process may be performed with separate guide tools for multiple mounting points defined by the mounting holes 42.

[0060] In this simplified example, the guide tool 54 takes the form of a simple, rigid guide member 56 defined by a threaded rod, the thread of the rod corresponding to that of the fixing holes 40 of the TID 22. The guide member 56 may be of a material such as steel, for example, although this may vary. As described later, the guide tool 54 may have other features to facilitate installation of the TID 22.

[0061] Figure 9a shows the guide member 56 being inserted through one of the mounting holes 42 in the wall of the tower 14, from inside the tower 14, to engage the TID 22 and, more specifically, to engage the fixing hole 40 of the foot 32 of the TID 22 that is to be aligned with the mounting hole 42 that the guide member 56 is inserted through. The operator has visibility of the guide member 56 and the TID 22 through another of the mounting holes 42, allowing the operator to aim the guide member 56 appropriately. In this respect, the mounting holes 42 may be, for example, 40mm in diameter. The guide member 56 is 24mm in diameter in this example. These dimensions may vary in other examples.

[0062] As Figure 9b shows, once the guide member 56 reaches the target fixing hole 40, it can be inserted into the hole and rotated to engage the respective threads of the guide member 56 and the hole by screwing action, thereby engaging the guide member 56 with the fixing hole 40. This may be regarded as capturing the TID 22, to the extent that the guide member 56, which the operator has hold of, is now connected to the TID 22. Once the guide member 56 is engaged with the fixing hole 40, as Figure 9c shows the guide member 56 can be manipulated to manoeuvre the foot 32 of the TID 22 that it is engaged with. In this example, this involves levering the guide member 56 against the edge of the mounting hole 42, enabling the TID 22 to be reoriented such that the mounting face 36 of the foot 32 is parallel to the surface of the tower 14. Then, as Figure 9d shows, the guide member 56 can be retracted through the mounting hole 42 to pull the foot 32 of the TID 22 into engagement with the exterior of the tower 14, with the fixing hole 40 in alignment with the tower mounting hole 42. In this example, the guide member 56 is retracted by pulling it manually, but in other examples the guide tool includes additional features to assist retraction.

[0063] In this respect, Figure 10 shows an enhanced guide tool 154 for use in capturing and guiding a TID 22 during installation. The guide tool 154 includes an elongate, threaded rod defining a guide member 56, which may be substantially the same as that of the simplified example of Figures 9a to 9d.

[0064] The guide tool 154 further includes a nut 58 and a washer 60 carried on the guide member 56 at a position slightly offset from a midpoint of the guide member 56 in the configuration shown, and a handle 62 attached at a rear end of the guide tool 154.

[0065] The nut 58 has a thread corresponding to that of the guide member 56 and so forms a threaded interface with the guide member 56. The nut 58 acts as a rider element that can ride back and forth along a central axis 64 of the guide member 56 when rotated relative to the guide member 56. As shall become clear, this allows the nut 58 to assist with retracting the guide member 56 from the mounting hole 42 during operation, and so the nut 58 also defines a retraction element or adjustment element, and more generally defines an operating member of the guide tool 154 and so is referred to as the operating nut 58. Correspondingly, the nut 58 and the thread of the guide member 56 cooperate to define a retraction mechanism for retracting the guide member 56 through the mounting hole 42.

[0066] A knob 66 is attached to the operating nut 58 to facilitate rotation of the operating nut 58 by hand, the knob 66 being generally disc-like and having an outer surface with an undulating profile to aid gripping by the operator. The washer 60 has a central opening 68 that is sized to receive the guide member 56 in a relatively close fit, and a disc-like main portion 70 that has a wider diameter than the mounting holes 42 of the tower 14. The washer 60 further includes an axial protrusion of reduced diameter that defines a lip 72. The lip 72 is generally annular and is configured for insertion into the mounting hole 42 to occupy a correspondingly annular space between the surface of the mounting hole 42 and the guide member 56, and thereby act as a protective element that protects the thread of the guide member 56. The lip 72 may also act as a spacer that centralises the guide member 56 in the mounting hole 42.

[0067] The handle 62 has a generally C-shaped frame 74 that is attached to the guide member 56 by further nuts 76, one on each side of a straight central portion of the frame 74, and a bar 78 that is fixed to the frame 74 that can be held by the user. The bar 78 extends parallel to the central portion of the frame 74 and so orthogonally to the axis 64 of the guide member 56. The nuts 76 are tightened to prevent rotation of the handle 62 relative to the guide member 56. The handle 62 can be used to manipulate the guide member 56 and to hold the guide member 56 against rotation when the operating nut 58 is turned.

[0068] Figures 11a to 11c show, in schematic and simplified form, use of the guide tool 154 of Figure 10 in a first part of a process for installing the TID 22 onto the tower 14 of the wind turbine 10, and more specifically a sub-process in which the guide tool 154 is used to catch a foot 32 of the TID 22, to draw it into engagement with the tower 14 and to align the fixing hole 40 of the TID 22 that it catches with the associated mounting hole 42 of the tower 14.

[0069] Figure 11a corresponds to the stage of the first example shown in Figure 9b, in which the guide member 56 of the guide tool 154 has been engaged with the corresponding fixing hole 40 of the TID 22 by screwing the guide member 56 into the fixing hole 40. The handle 62 of the guide tool 154 facilitates this engagement in this example. At this stage, the operating nut 58 and washer 60 are in a retracted position at the rear end of the guide member 56, adjacent to the handle 62, to enable the guide member 56 to be fully inserted through the mounting hole 42 and therefore maximise the reach of the guide tool 154.

[0070] It is noted that the operating nut 58 also serves as a stopper in this situation, in that it prevents the guide member 56 from being pushed or pulled fully through the mounting hole 42 and out of the tower 14, for example if pulled by the TID 22 as the TID 22 sways due to wind. The handle 62 may be regarded as providing a second stopper and so further reduces the risk of the TID 22 pulling the guide member 56 away from the tower 14.

[0071] Figure 11b corresponds to the stage of the first example shown in Figure 9c, in that the guide tool 154 has been manipulated to manoeuvre the engaged foot 32 of the TID 22 so that its mounting face 36 is parallel to the surface of the tower 14. The lip 72 of the washer 60, positioned in the mounting hole 42 between the guide member 56 and the surface of the hole, protects the thread of the guide member 56 while the guide member 56 is levered against the edge of the mounting hole 42, by acting as the contact point with the mounting hole 42.

[0072] Then, the operating nut 58 is turned via the knob 66 while the handle 62 is held to prevent rotation of the guide member 56, effecting relative rotation between the operating nut 58 and the guide member 56. Stopping rotation of the guide member 56 also avoids the guide member 56 unscrewing from and therefore disengaging the fixing hole 40. The relative rotation between the operating nut 58 and the guide member 56 acts to move the operating nut 58 to the right and the guide member 56 to the left, in the view shown in Figure 11b. Since axial movement of the operating nut 58 is constrained by its engagement with the washer 60, which in turn is engaged with the wall of the tower 14, the rotation of the operating nut 58 acts to retract the guide member 56 through the mounting hole 42, bringing the engaged mounting foot 32 of the TID 22 with it. With continued turning of the operating nut 58, the guide member 56 is retracted to the extent that the mounting face 36 of the foot 32 of the TID 22 comes into engagement with the tower 14, as shown in Figure 11c. In this way, the operating nut 58 provides for controlled retraction of the guide member 56 and correspondingly controlled guiding of the TID 22.

[0073] The operation shown in Figures 11a to 11c is repeated with at least one further guide tool 154 for an associated pair of fixing and mounting holes 40, 42, to fix the orientation of the TID 22 relative to the tower 14 and so align the mounting holes 42 with the fixing holes. In this example, the process is repeated three times so that each foot 32 of the TID 22 is engaged by, and temporarily held in engagement with the tower 14 by, a respective guide tool 154. The process may optionally be repeated for all eight fixing holes 40. In principle, it would be possible to leave the guide tools 154 in place to serve also as fixings that secure the TID 22 to the tower 14. However, over time the operating nuts 58 of the guide tools 154 could loosen as the TID 22 pulls away from the tower 14 under its own weight. Accordingly, in this example the guide tools 154 are replaced with bolts to provide a more robust attachment of the TID 22 to the tower 14.

[0074] In this respect, Figures 12a to 12c show stages of a sub-process to replace guide tools 154 with bolts 80 to serve as longer term fixings for the TID 22. Figure 12a shows the starting point for this stage of the procedure, in which each mounting foot 32 of the TID 22 is engaged by a single guide tool 154, the mounting face 36 of the foot 32 being in contact with the surface of the tower 14. As multiple guide tools 154 are engaged with the TID 22, the fixing holes 40 of the TID 22 are aligned with the mounting holes 42 of the tower 14.

[0075] Figure 12a shows two of the feet 32 of the TID 22, corresponding to one of the pairs. It should be appreciated that the other pair of feet 32 on the other side of the TID 22 may be configured and processed similarly. It is noted that the order in which the feet 32 are secured may vary, and in this example the second foot 32 to be secured is the one that is diagonally opposite to the first foot 32 secured. For example, referring to the orientations shown in Figure 2, if the upper left foot 32 is secured first then the next foot 32 to be secured is the lower right foot 32.

[0076] In the configuration shown in Figure 12a, one of the fixing holes 40 of each foot 32 remains open, and so can receive a bolt 80. Before the first bolt 80 is fitted, the handle 62 and associated nuts 76, the operating nut 58 and the washer 60 are removed from the upper guide member 56 shown in Figure 12a, and a bushing plate 82 is fitted over the guide member 56, the bushing plate 82 including holes 84 that align with the fixing holes 40 of the uppermost TID foot 32. Meanwhile, the lower guide tool 154 visible in Figure 12a, and the guide tools 154 attached to the other feet 32, hold the TID 22 in position and so prevent the TID 22 from swaying away from the tower 14 once the operating nut 58 and handle 62 are removed from the upper guide member 56.

[0077] Then, as Figure 12b shows, the first bolt 80 is installed, such that a head 86 of the bolt 80 engages the bushing plate 82 and a shank 88 of the bolt 80 extends through the bushing plate 82 and the tower mounting hole 42 to screw into and thus engage the fixing hole 40 of the TID 22. Once tightened, the bolt 80 secures the TID foot 32 to the external surface of the tower 14, and the bushing plate 82 spreads the load over a wider area of the tower wall.

[0078] Next, as Figure 12c shows, the guide member 56 that remains engaged with the other fixing hole 40 of the same foot 32 can be removed and replaced with a bolt 80. The upper foot 32 is then fully secured to, and firmly engaged with, the tower 14. This process is repeated for the remaining feet 32 of the TID 22, until bolts 80 are installed in all eight fixing holes 40, at which point installation of the TID 22 onto the tower 14 is complete.

[0079] The lifting line 50 that was used to lift the TID 22 into position beside the tower 14 may remain attached to the TID 22 for use in its subsequent removal. As Figure 13 shows, the loose end of the lifting line 50, once detached from the crane, can be stowed and secured inside the tower 14 by looping the line over the upper open end of the tower 14, once the nacelle 12 has been removed.

[0080] To summarise, the guide tools of the above examples provide an improved way to install a damper to a wind turbine tower while upright, by using a rigid guide member to catch the damper while suspended beside the tower. This approach enables the damper to be captured reliably and safely, and to be positioned onto the tower in a controlled manner.

[0081] The skilled person will appreciate that modifications may be made to the specific embodiments described above without departing from the inventive concept as defined by the claims.

[0082] For example, a guide member may engage a Tl D or other damper in alternative ways other than by screwing as in the above examples. Complementary interlocking formations forming a docking arrangement may be employed on the damper and the guide member, for example. The guide member could also engage the damper magnetically.

[0083] As noted above, in principle the guide tools could be used to secure the damper to the tower and thereby dispense with the need for separate fixings. To facilitate this, the guide tool could be adapted to lock the operating nut in position and thereby secure the TID, for example using a locking element such as a pin. Alternatively, clamps could be used to clamp the guide members and, in turn, the damper, in position. Although the operating nut and the washer are separate parts in the above example, in other variants an integrated rider element may be provided that has both a threaded hole for engaging the thread of the guide member and a washer portion, including a lip, to fulfil the functions of both the operating nut and the washer.

[0084] Various other forms of retraction mechanism are possible. For example, a lever arrangement could be used instead of a nut and threaded interface. It is also possible for retraction of a guide member to be motorised. As another alternative, a guide tool may not have a retraction mechanism but may instead have only a handle to assist with catching and manoeuvring the damper.

Claims

Claims1. A method of installing a damper (22) onto an upright tower (14) of a wind turbine (10), the method comprising: lifting the damper (22) to an elevated position beside the tower (14); inserting a rigid guide member (56) through a mounting opening (42) of the tower (14), from inside the tower (14); and engaging the guide member (56) with the damper (22) while in the elevated position.

2. The method of claim 1, comprising pulling the damper (22) towards the tower (14) using the guide member (56).

3. The method of claim 2, comprising operating a retraction mechanism (58, 56) to retract the guide member (56) through the mounting opening (42) to pull the damper (22) towards the tower (14).

4. The method of any preceding claim, comprising manoeuvring the damper (22) using the guide member (56).

5. The method of claim 4, comprising operating the guide member (56) as a lever to manoeuvre the damper (22).

6. The method of any preceding claim, wherein the guide member (56) comprises a threaded portion.

7. The method of claim 6, comprising rotating the guide member (56) to engage the threaded portion of the guide member (56) with a threaded hole (40) of the damper (22).

8. The method of claim 7, comprising subsequently removing the guide member (56) and engaging a fixing (80) with the threaded hole (40).

9. The method of any of claims 6 to 8, comprising effecting relative rotation between the guide member (56) and a rider element (58) carried on the threaded portion of the guide member (56) to pull the damper (22) towards the tower (14).

10. The method of claim 9, comprising rotating the rider element (58) to retract the guide member (56) through the mounting opening (42).

11. The method of claim 10, comprising holding the guide member (56) against rotation while rotating the rider element (58).

12. The method of any preceding claim, comprising positioning at least part of a protective element (72) within the mounting opening (42), between the mounting opening (42) and the guide member (56).

13. The method of any preceding claim, comprising engaging a fixing (80) with the damper (22) through another mounting opening (42) of the tower (14), while the guide member (56) is engaged with the damper (22).

14. The method of claim 13, followed by removing the guide member (56) and engaging another fixing (80) with the damper (22) through the mounting opening (42) from which the guide member (56) has been removed.

15. The method of any of claims 1 to 13, comprising securing the damper (22) to the mounting opening (42) using the guide member (56).

16. The method of any preceding claim, comprising inserting multiple guide members (56) through respective mounting openings (42) of the tower (14) to engage the damper (22).

17. The method of claim 16, comprising engaging each guide member (56) with a respective receptacle (40) of the damper (22).

18. The method of any preceding claim, wherein the damper (22) is level with the mounting opening (42) when in the elevated position.

19. A system for mitigating vibration in an upright tower (14) of a wind turbine (10), the system comprising: a damper (22) for installing onto the tower (14); and at least one rigid guide member (56) configured for insertion through a mounting opening (42) of the tower (14), from inside the tower (14), to engage the damper (22) while the tower (14) is upright and the damper (22) is in an elevated position beside the tower (14).

20. The system of claim 19, comprising at least one fixing (80) for securing the damper (22) to the tower (14).

21. The system of claim 19 or claim 20, comprising a guide tool (154) that comprises the guide member (56), the guide tool (154) further comprising a retraction mechanism (58, 56) that is operable to retract the guide member (56) through the mounting opening (42) while engaged with the damper (22).

22. The system of claim 21 , wherein the retraction mechanism comprises a rider element (58) carried on the guide member (56).

23. The system of claim 22, comprising a threaded interface between the guide member (56) and the rider element (58).

24. The system of any of claims 19 to 23, comprising a stopper (58, 62) configured to prevent the guide member (56) passing entirely through the mounting opening (42).

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