A method of inspecting a wind turbine blade part

Abstract

In a first aspect of the present invention there is provided a method of inspecting a wind turbine blade part comprising a composite shell and a plurality of inserts embedded in the composite shell. The method comprises applying heat to an inspection region of the blade part. The inspection region comprises a plurality of inserts embedded in the composite shell. The method further comprises observing the inspection region using a thermographic camera such that a field of view of the thermographic camera includes a portion of the inspection region comprising a plurality of inserts. The method further comprises assessing a thermogram captured by the thermographic camera to determine the integrity of a bond between each insert and the composite shell.

Description

[0001] A method of inspecting a wind turbine blade part

[0002] Technical field

[0003] The present invention relates generally to wind turbines and more particularly to a method of inspecting a wind turbine blade part comprising a composite shell and a plurality of inserts embedded in the composite shell.

[0004] Background

[0005] Wind turbine blades of modern utility-scale wind turbines are typically very large structures, for example some blades may extend over 70 m in length. Larger wind turbine blades capture more energy from wind incident on the blade such that a wind turbine is therefore able to produce more electrical power. However, increasing the size of wind turbine blades typically also increases the mass of the blade. This introduces challenges in terms of structurally supporting the blade, because of the increased loading experienced by the blade in use.

[0006] Composite materials, such as glass fibre reinforced plastic (GFRP), offer an advantageous balance of strength, e.g. tensile strength, and mass. Accordingly, many wind turbine blades are manufactured from composite materials, and may for example include a composite shell which is substantially hollow. However, whilst composite materials may have good strength and mass characteristics, in some examples such materials can be relatively brittle, and concentrated loads can be detrimental to the longevity of a composite component. Accordingly, attaching composite blade parts to other blade parts, or other wind turbine components, can be challenging.

[0007] Some examples of composite wind turbine blade parts therefore include inserts, such as metal inserts, embedded in the composite shell to provide means for attaching the blade part to other components of the wind turbine. For example, the inserts may be integrated in the composite shell during a moulding process in which the composite shell is formed. However, following manufacture of the blade part, it may be particularly challenging to inspect the embedded inserts without damaging the blade part.

[0008] It is against this background that the present invention has been developed. Summary

[0009] In a first aspect of the present invention there is provided a method of inspecting a wind turbine blade part comprising a composite shell and a plurality of inserts embedded in the composite shell. The method comprises applying heat to an inspection region of the blade part. The inspection region comprises a plurality of inserts embedded in the composite shell. The method further comprises observing the inspection region using a thermographic camera such that a field of view of the thermographic camera includes a portion of the inspection region comprising a plurality of inserts. The method further comprises assessing a thermogram captured by the thermographic camera to determine the integrity of a bond between each insert and the composite shell.

[0010] The thermogram comprises thermographic image data representative of the thermal response of the components in the inspection region observed by the thermographic camera. The thermal response of each component therefore provides a heat signature, i.e. infrared signature, in the thermogram, and such heat signatures can be assessed to determine the integrity of the bond between each insert and the composite shell.

[0011] For example, the heat signatures of the inserts embedded in the composite shell represent the heat transferred to and from the inserts. If an insert is thoroughly bonded in the composite shell, heat applied to the inspection region will be conducted effectively between the composite shell and the respective insert. Conversely, if an insert is not thoroughly bonded in the composite shell, for example if the insert is loose or has become at least partially disbonded from the composite shell, then an air gap may be present between the insert and the composite shell. Such an air gap may provide a thermal break, i.e. insulation, affecting the transfer of heat between the insert and the composite shell. Accordingly, a heat signature of a loose or disbonded insert is visually different to a heat signature of a thoroughly bonded insert when assessing the thermogram. Such differences can be identified when assessing the thermogram to thereby determine the integrity of the bond between each insert and the composite shell.

[0012] Observing the inspection region using a thermographic camera and assessing a thermogram captured by the thermographic camera enables non-destructive inspection of the inserts and composite shell without requiring visibility of the inserts in the composite shell. In particular, the method may facilitate non-destructive inspection of the inserts and composite shell when the blade part is attached to a wind turbine, i.e. when the blade part is in-situ, without requiring removal of the blade part from the turbine Applying heat to the blade part, i.e. actively heating the blade part, is advantageous for the inspection method. Actively applying heat to the blade part provides a high degree of control and repeatability for the inspection method, because the blade part, and in particular the composite shell, can be reliably heated to a target temperature in each application of the method. This means that the thermograms produced in each application of the method are consistent and therefore simple to analyse. Active heat application also helps to quickly and reliably heat the blade part to the temperature required for the inserts to produce an identifiable heat signature in the thermogram.

[0013] The inserts in the blade part are typically configured for facilitating attachment of the blade part to another component or supporting apparatus. For example, as described later in more detail, the inserts may be located in a root portion of a wind turbine blade to facilitate connecting the blade to a wind turbine hub, or hub components, via the inserts. It follows that the inserts are load-bearing components which, in normal use, may be expected to transfer significant loads into and out of the blade part. As such, the inserts are typically embedded in a portion of the composite shell having a relatively high shell thickness, compared to other portions of the composite shell, because the composite shell surrounding the inserts is configured to supply and receive loads from the inserts. Active application of heat is therefore particularly beneficial in this specific method, to ensure that the thick composite shell surrounding the inserts is sufficiently heated to transfer heat to the inserts such that heat signatures of these can be assessed in the resultant thermogram.

[0014] The plurality of inserts embedded in the composite shell may be integrated with the composite material of the shell during manufacture of the blade part. As such, the inserts may be referred to as “integrated inserts”, i.e. integrated in the composite shell.

[0015] The blade part may define at least part of a root portion of a wind turbine blade. In some examples, the plurality of inserts may therefore be located in the root portion of a blade. In such examples, the plurality of inserts may be distributed circumferentially around the root portion, i.e. spaced evenly around the circumference of the root portion. The inserts may be configured to mate with corresponding fasteners to attach the root portion of the wind turbine blade to a hub or a hub-side component of a wind turbine, such as a pitch bearing or a stiffening plate.

[0016] In some examples, the blade part may be a blade shell of a wind turbine blade. For example, the composite shell of the blade part may form substantially the entire blade shell of a wind turbine blade. Accordingly, an inboard end of the blade part may define a root end of the blade, and an outboard end of the blade part may define a tip end of the blade.

[0017] In some other examples, the blade part may be a blade module of a modular wind turbine blade. Accordingly, the blade part may be configured for connection to another blade module to form the modular wind turbine blade. The plurality of inserts embedded in the composite shell may therefore be configured to facilitate connecting the blade part to another blade module of the modular wind turbine blade. It will be appreciated that in such examples, the plurality of inserts may be located at either an inboard end or an outboard end of a blade part, i.e. blade module.

[0018] In some examples, the plurality of inserts may each be formed of a different material compared to the composite shell. Composite materials, such as glass fibre reinforced plastic (GFRP), can provide relative high load bearing capacity at a relative low component weight, whilst also facilitating strict control of load paths and weight distribution. Accordingly, the shell of the wind turbine blade part may be an advantageous application for composite materials. However, composite materials such as GFRP can be relatively brittle and concentrated loads can be detrimental to the longevity of a composite component. It follows that whilst composite materials may be advantageous for forming the shell of the blade part, such materials also present challenges for attaching the blade part to other components and supporting apparatus. The plurality of inserts are configured specifically for attaching the blade part to other components or supporting apparatus. Accordingly, the inserts may be formed of a material, such as steel, having a higher stiffness and / or strength compared to the composite shell in which the inserts are embedded.

[0019] In some examples, a plurality of the inserts may each comprise a threaded bore configured for receiving a threaded fastener, such as a bolt, for attaching the blade part to another wind turbine component, such as a hub or hub-side components, or another blade module, for example. In some examples, a plurality of the inserts may each comprise a threaded fastener configured to extend from the composite shell to mate with a nut or other component comprising a threaded bore to thereby attach the blade part to another wind turbine component.

[0020] The method described herein is particularly advantageous for inspecting examples of blade parts including inserts formed of a different material to the composite material of the shell, because the different materials will typically have different thermal properties, such as heat capacity and heat conductivity. Such differences in the thermal properties of the inserts and the composite shell mean that the thermal response of the inserts and the composite shell to the application of heat is substantially different and therefore provides clearly distinguishable heat signatures in the thermogram.

[0021] In some examples, the plurality of inserts may each be formed of a material having a higher thermal conductivity than the material of the composite shell. Thermal conductivity is a heat transfer characteristic of a material, and is a measure of the ability of a material to transfer heat through the material by the heat transfer mechanism of conduction. Thermal conductivity is measured in watts per meter kelvin (W / mK). In examples where the inserts are formed of a material having a higher thermal conductivity than the composite shell material, it follows that applying heat to the inspection region may cause portions of the composite shell surrounding a thoroughly bonded insert to heat up more quickly than portions of the composite shell surrounding a loose or disbonded insert, or no insert. These differences can be identified when assessing the thermogram to thereby determine whether the inserts are thoroughly bonded.

[0022] In some examples, assessing the thermogram may comprise comparing a heat signature representing one or more inserts in the inspection region to a heat signature representing one or more other inserts in the inspection region. Such a comparison can facilitate fast and simple identification of any potentially problematic inserts which are not thoroughly bonded in the composite shell. When thoroughly bonded to the composite shell, the heat signature of each insert should be substantially the same when assessing the thermogram. Through a visual comparison of the heat signatures representing different inserts in the inspection region, any anomalous heat signatures indicating a disbonded or loose insert can be identified quickly and easily.

[0023] If follows that in some preferred examples, the heat signature of a respective insert may be the image of the insert represented in the thermogram. As such, the heat signature may define a profile outline representing the respective insert. In examples wherein the respective insert is thoroughly bonded in the composite shell, the heat signature, i.e. the profile outline in the thermogram, may be expected to approximate an outer profile of the insert. Conversely, in an example wherein a respective insert is loose, or disbonded, the heat signature, i.e. the profile outline in the thermogram may not match or approximate an outer profile of the insert, and may instead show a substantially different profile. Accordingly, analysis of the heat signature, such as the profile outline, in the thermogram may facilitate a non-destructive assessment of the integrity of the bond between the insert and the composite shell.

[0024] Additionally or alternatively, in some examples a heat signature, such as the heat signature representing an insert, may be a temperature value, such as an average temperature value, which may be obtained by assessing the thermogram. Accordingly, in some examples assessing the thermogram may comprise analysing a heat signature representing an average temperature of an insert. An average temperature value may be obtained by averaging values represented by a plurality of pixels in the thermogram. A heat signature representing an insert and indicating an anomalous average temperature of the insert, compared to other inserts represented in the thermogram, may indicate that the insert having an anomalous average temperature is loose or disbonded.

[0025] In some examples, assessing the thermogram may comprise comparing a heat signature representing one or more inserts in the inspection region to a heat signature representing a portion of the composite shell in the inspection region. For example, the heat signature of the portion of the composite shell may provide a baseline or reference temperature to which the heat signature representing an insert can be compared. Additionally or alternatively, the method may comprise analysing the heat signature representing a portion of the composite shell to thereby measure the temperature of the portion of the composite shell. This may be helpful for determining when the correct amount of heat has been applied to the inspection region, i.e. for determining whether the inspection region has been heated to a target temperature.

[0026] In some examples, the method may comprise measuring an initial temperature of the inspection region of the blade part before the step of applying heat to the inspection region. For example, measuring the initial temperature of the inspection region may comprise observing the inspection region using the thermographic camera, before heat is applied. The thermographic camera may provide an indication of the initial temperature of the inspection region, in particular of the composite shell, of the blade part. Additionally or alternatively, measuring the initial temperature of the inspection region may comprise capturing an initial thermogram of the inspection region, using the thermographic camera, before heat is applied. The initial thermogram may then be assessed to thereby determine the initial temperature of the inspection region, in particular of the composite shell, of the blade part. Measuring the initial temperature of the inspection region means that the initial temperature can be taken into account when assessing a thermogram captured by the thermographic camera to determine the integrity of a bond between each insert and the composite shell. For example, one side of the blade part may be warmer, or colder, than the other side, for example due to exposure to sunlight, or wind, respectively. Measuring the initial temperature therefore provides a baseline measurement from which changes in temperature, due to the application of heat to the inspection region, can be measured when assessing the thermogram.

[0027] In some examples, assessing the thermogram may comprise evaluating thermographic image data in the thermogram to determine the heat transferred between each insert represented in the thermogram and the composite shell. For example, the thermographic camera may be directed to a surface of the composite shell such that observing the inspection region comprises observing a surface of the composite shell. A thermogram captured by the thermographic camera may therefore illustrate the heat transferred from the inserts to the composite shell, and namely to the surface of the composite shell observed by the thermographic camera. The method therefore facilitates inspection of the inserts without requiring any damage or modification of the composite shell.

[0028] In some examples, applying heat to the inspection region may comprise applying heat to a first side of the composite shell. Further, observing the inspection region may comprise observing a second side of the composite shell opposite to the first side. For example, the first side may define an interior surface of the blade part and the second side may define an exterior surface. In some other examples, the first side may define an exterior surface and the second side may define an interior surface.

[0029] In some examples the thermographic image data in the thermogram may therefore represent the heat transferred through the entire thickness of the composite shell in the inspection region. In portions of the blade part comprising an insert embedded in the composite shell, the thermogram may therefore represent the heat transferred through a first thickness portion of the composite shell to the respective inserts, through the insert, and from the insert to a second thickness portion of the composite shell. As previously described, a portion of the blade part comprising a loose or disbonded insert may comprise an air gap between the insert and the composite shell. In such an example, heat transfer between the first thickness portion of the composite shell and the insert, or between the insert and the second thickness portion of the composite shell, may be interrupted or retarded by the air gap such that a heat signature of the respective loose or disbonded insert is visually different compared to a heat signature of a thoroughly bonded insert. The method may therefore comprise assessing a thermogram representing the heat transferred through the entire thickness of the composite shell in the inspection region to determine the integrity of the bond between each insert and the composite shell.

[0030] Applying heat to the first side of the composite shell, and observing the opposing second side of the composite shell may be particularly advantageous for assessing the integrity of the bond between each insert and the composite shell. This is because any air gap resulting from a loose or disbonded insert will produce a visually identifiably different heat signature in the thermogram in relation to a respective insert. For example, irrespective of whether an air gap is present around the entire insert, between the first thickness portion of the composite shell and the insert, or between the insert and the second thickness portion of the composite shell, any such air gap will impede the transfer of heat from the first side of the composite shell to the second side, and will therefore affect the resultant heat signature in the thermogram such that a loose or disbonded insert can be easily detected.

[0031] In some examples, observing the inspection region may comprise observing an interior surface of the composite shell. Observing an interior surface of the composite shell using the thermographic camera may be advantageous for providing consistent and reliable thermographic image data. For example, the method may be performed on a blade part in situ, such as a blade part attached to a wind turbine. An interior surface of the composite shell may therefore be less susceptible to variations in the external environment, such as temperature, sunlight, wind and weather conditions. Accordingly, the interior surface of the composite shell may remain at a substantially constant temperature such that different thermograms captured in different applications of the method may each record relatively consistent background composite shell temperatures such that any anomalous heat signatures relating to loose or disbonded inserts are easily identifiable. Observing an interior surface of the composite shell may also help to protect the thermographic camera and inspection personnel from external weather conditions, thereby making it easier to perform the inspection method.

[0032] In some examples, applying heat to the inspection region may comprise applying heat to an exterior surface of the composite shell. Applying heat to an exterior surface of the composite shell may facilitate a simplified method compared to applying heat to an interior surface of the composite shell. In some examples, applying heat may include blowing or directing heated fluid, such as air or water, towards the inspection region of the blade part. Alternatively, in some more preferred examples, applying heat to the inspection region may comprise arranging a heating blanket on the exterior surface of the composite shell and operating the heating blanket to apply heat to the exterior surface of the composite shell in the inspection region. Use of a heating blanket for actively applying heat to the inspection region of the blade part may facilitate a substantially uniform application of heat throughout or across the inspection region. This may advantageously ensure that heat is evenly applied to each portion of the composite shell in which a respective one of the plurality of inserts is embedded. As such, each portion of the composite shell, and each insert may therefore be subject to the same heating conditions, and any anomalies in the heat signatures representing the inserts can be easily identified.

[0033] In some examples, the heating blanket may be an electric heating blanket. For example, the heating blanket may be powered by single phase AC electrical power. Such a configuration may be advantageous for examples wherein the method is performed on a blade part in situ, i.e. attached to a wind turbine, because such a single-phase AC powered heating blanket could be powered by the wind turbine power supply. This may therefore simplify the apparatus required for the inspection method.

[0034] In some examples, the heating blanket may comprise one or more straps configured to extend around a periphery of the blade part including the exterior surface. Accordingly, arranging the heating blanket in such an example may comprise arranging the strap(s) around the periphery of the blade part and tightening the strap(s) to fasten the heating blanket to the composite shell. Strapping the heating blanket to the composite shell may advantageously distribute pressure on the heating blanket such that the force holding the heating blanket to the surface of the composite shell is evenly distributed across the heating blanket. This in turn may help to ensure that substantially all of the heating blanket is held against the surface of the composite shell, thereby ensuring even distribution of heat throughout the inspection region.

[0035] Further, strapping the heating blanket to the composite shell may help to fix and maintain the heating blanket in position whilst applying heat to the inspection region, irrespective of the position or orientation of the blade part. As such, strapping the heating blanket to the composite shell may be particularly advantageous in examples wherein the inspection method is performed in situ, with the wind turbine blade part attached to a wind turbine.

[0036] In some preferred examples, the heating blanket may be arranged such that heating elements of the heating blanket are arranged between the exterior surface of the blade part and the strap(s) of the heating blanket. Accordingly, the heating elements may be sandwiched between the strap(s) and the exterior surface such that tightening the straps further clamps the heating elements to the composite shell.

[0037] Fastening the heating blanket to the composite shell may preferably comprise removably fastening the heating blanket to the composite shell such that the heating blanket can be removed easily following the inspection method.

[0038] In some examples, the exterior surface of the blade part may be a convex surface throughout the inspection region. The heating blanket may be configured to extend across or around the entire periphery of the blade part in the inspection region. For example, the exterior surface of the composite shell may define the entire periphery of the blade part in the inspection region. Accordingly, applying heat to the exterior surface of the composite shell may comprise wrapping the heating blanket around the periphery of the blade part, on the exterior surface of the composite shell in the inspection region.

[0039] As previously described, in some examples the blade part may define the root portion of a wind turbine blade. The root portion of a wind turbine blade is typically substantially cylindrical, and the exterior surface of the root portion is therefore typically a convex surface. It follows that in some examples, the heating blanket may be configured to extend around the entire periphery of the root portion of a wind turbine blade, i.e. may be configured to extend circumferentially around the entire root portion of a blade.

[0040] In some examples, the method may alternatively comprise arranging a plurality of heating blankets on the exterior surface of the composite shell to thereby extend, in combination, across or around the entire periphery of the blade part in the inspection region.

[0041] Wrapping the heating blanket, or heating blankets, around the entire periphery of the blade part in the inspection region helps to evenly distribute heat throughout the entire inspection area at the same time. As such, all of the thermograms required for assessing each of the inserts in the inspection region can all be taken within a short time period, i.e. at substantially the same time, without needing to reposition the heating blanket to heat different portions of the inspection region. Accordingly, this facilitates a particularly fast and efficient inspection method.

[0042] In some examples, the step of observing the inspection region using a thermographic camera may be performed whilst heat is applied to the inspection region. Accordingly, the step of observing the inspection region may commence prior to the end of the step of applying heat to the inspection region. Observing the inspection region using the thermographic camera during application of heat to the inspection region may be advantageous for reducing inspection times and thereby increasing efficiency.

[0043] For example, as previously described, the composite shell may be relatively thick in the portions in which the inserts are embedded. As such, the thick composite shell may have a relatively high heat capacity such that heating and cooling the composite shell can take a long time. However, specifically observing an inspection region of the blade part which is already known to comprise a plurality of inserts means that anomalous inserts, such as loose or disbonded inserts, are immediately recognisable compared to other inserts observed using the thermographic camera and represented in a respective thermogram, without needing to wait for a full heating and cooling of the respective portion of the composite shell to facilitate identification of such anomalies.

[0044] In some examples, the method may further comprise capturing a series of thermograms of the same portion of the inspection region over a time period during which heat is applied to the inspection region. Accordingly, the method may comprise capturing a plurality of thermograms of the same portion of the inspection region, with each thermogram taken at a different time after starting a respective period of applying heat to the inspection region. Such a method may therefore be advantageous for tracking, via assessment of the resultant series of thermograms, the thermal response of the composite shell and embedded inserts to the application of heat over time. In particular, such a method may facilitate the capture of thermograms comprising clearer and more defined heat signatures. This is because by taking a series of thermograms, there is a higher probability that at least one of the thermograms will be taken around the “sweet spot” of heat application. The sweet spot of heat application is where sufficient heat has been applied to the inspection area for the plurality of inserts to each produce a defined and identifiable heat signature, but before too much heat has been applied such that the heat of the inserts and the surrounding composite shell is substantially equalized or uniform, which would mean that individual heat signatures of the inserts cannot be identified for assessment.

[0045] In some examples, the method may comprise capturing a series of thermograms of the same portion of the inspection region over a time period after cessation of heat application to the inspection region, i.e. during a cooling down period after the end of the step of applying heat to the inspection region. Such a method may also increase the probability that at least one of the thermograms will be taken around a “sweet spot” where the inspection area is at a sufficient temperature for the plurality of inserts to each produce a defined and identifiable heat signature, without the inspection area being too hot such that the heat of the inserts and the surrounding composite shell is substantially equalized or uniform, which would mean that individual heat signatures of the inserts cannot be identified for assessment.

[0046] In some examples, the method may comprise capturing a plurality of thermograms of a plurality of different portions of the inspection region, where each thermogram represents a different portion of the inspection region. For example, a first thermogram captured by the thermographic camera may include a first portion of the inspection region, a second thermogram may include a second portion of the inspection region, and a third thermogram may include a third portion of the inspection region, for example. Each thermogram may be a still thermogram, or alternatively, one or more of the thermograms may be still frames taken from a video recorded by the thermographic camera.

[0047] In some examples, capturing a plurality of thermograms of a plurality of different portions of the inspection region may comprise rearranging, repositioning or reorienting the thermographic camera to capture each thermogram. For example, the method may comprise arranging the thermographic camera in a first orientation such that a field of view of the thermographic camera includes a first portion of the inspection region comprising a plurality of inserts. After capturing a thermogram representing the first portion of the inspection region, the method may comprise rearranging, repositioning or reorienting the thermographic camera into a second orientation such that the field of view of the thermographic camera includes a second portion of the inspection region comprising a plurality of inserts. The method may further comprise capturing a thermogram representing the second portion of the inspection region. Such method steps may be repeated such that a plurality of thermograms are captured, with each thermogram representing a different portion of the inspection region, such that the entire inspection region, an in particular each of the inserts in the composite shell in the inspection region, can be assessed by assessing the plurality of thermograms.

[0048] In some preferred examples, the first portion of the inspection region may comprise at least one insert, preferably at least two inserts, which are also in the second portion of the inspection region. Accordingly, the first and second portions of the inspection region preferably overlap, such that at least one, preferably at least two inserts are common to both the first and second portions. This may also apply to further portions of the inspection region such that any pair of neighbouring portions of the inspection region preferably comprise at least one insert, more preferably at least two inserts, that are common between the neighbouring portions. This may help with alignment of the thermographic camera for capturing each portion, and also helps to ensure that all of the inspection region is imaged thoroughly, and no portions are missed, such the integrity of the bond between each insert and the composite shell can be assessed.

[0049] In some examples, the method may comprise assessing a plurality of thermograms and comparing a heat signature representing one or more inserts in the first portion of the inspection region to a heat signature representing one or more inserts in a different portion of the inspection region, such as the second or third portions of the inspection region for example.

[0050] In some preferred examples, the thermographic camera may comprise a wide-angle lens such that a thermogram captured by the thermographic camera illustrates the heat signatures of as many inserts as possible. Such a configuration may be advantageous because a greater number of inserts can be analysed on each individual thermogram, thereby requiring fewer thermograms to be taken in order to assess all of the inserts of a respective blade part. For example, the blade part may define the root portion of a blade, and the inserts may be spaced around the circumference of the root portion. In some advantageous examples the thermographic camera may be configured and positioned to capture at least 25%, preferably at least 30%, and more preferably at least 35% of the circumference of the root portion in the field of view of the thermographic camera. Such a configuration and / or arrangement may advantageously reduce the time required for a full inspection of all of the inserts in the root portion.

[0051] In some examples, the thermogram may be a still frame selected from a plurality of frames in a video captured by the thermographic camera. For example, the method may comprise using the thermographic camera to record a video in which the field of view sweeps across the inspection region of the blade part. Sweeping the field of view across the inspection region may be achieved by effecting relative motion between the thermographic camera and the inspection region. For example, the thermographic camera may be moved across, or around, the inspection region of a stationary blade part. Alternatively, the blade part, and thereby the inspection area of the blade part, may be moved past, or around, a stationary thermographic camera. For example, if the blade part defines the root portion of a wind turbine blade attached to a wind turbine hub, the thermographic camera may be positioned in the hub, and the blade may be pitched, i.e. rotated, relative to the hub such that the inspection region is thereby swept through the field of view of the thermographic camera. Recording a video using the thermographic camera may enable a fast and efficient method for capturing a plurality of thermograms for assessing all of the inserts in the inspection region.

[0052] In some examples of the method, the thermographic camera may be located on fixture or bracket. For example, the thermographic camera may be fastened to a bracket or other fixture in the hub of a wind turbine and directed towards an attached blade such that the field of view of the thermographic camera includes a root portion of the blade. Locating the thermographic camera on a bracket, stand, or other fixture may increase accuracy and consistency when capturing thermograms to assess the inspection region. Such fixtures may help to ensure that the thermogram is consistently captured from the same location such that the field of view of the thermogram consistently captures the same components of the blade part for assessment.

[0053] In some examples, the method may further comprise capturing a photograph of the same field of view as that observed by the thermographic camera to facilitate a comparison between the thermograph and the photograph. Such a method may be advantageous for interpreting heat signatures in the thermogram. For example, components such as cable trays, wiring, or ducting on a surface of the blade part may interfere with the infrared radiation observed by the thermographic camera. Such components may therefore affect the heat signatures represented in the thermogram. Accordingly, capturing a visual light photograph for comparison with the thermogram may help to interpret the thermographic data represented in the thermogram.

[0054] In some examples, the composite shell may not have a uniform thickness throughout the inspection region, and one or more portions of the composite shell may have an increased thickness. For example, the blade part may be formed of two half shells attached together, particularly in examples in which the blade part defines the root portion of a wind turbine bade. The composite shell may therefore have an increased thickness in portions of the inspection region where the half shell are attached together, to provide additional strength and rigidity at the join between the half shells. As previously described, thick portions of the composite shell may conduct heat to, and from, the inserts more slowly. A direct comparison of respective heat signatures of inserts in thick and thin portions of the composite shell, following application of the same amount of heat for the same length of time, may incorrectly indicate that the insert in the thick portion of the composite shell may be loose or disbonded. This may be because less heat has been transferred to and from the insert in the given time period due to the thickness of the composite shell. In some examples, the method may therefore comprise identifying portions of the composite shell in the inspection region having an increased thickness relative to an average thickness of the composite shell in the inspection area. In some preferred examples, such portions may be identified prior to the step of assessing the thermogram captured by the thermographic camera to determine the integrity of the bond between each insert and the composite shell. The thermogram may then be assessed in context, with knowledge of the thicker portions of the composite shell that could lead to false identification of a loose or disbonded insert. Accordingly, such a method step may improve accuracy of the assessment of the thermogram to more reliably determine the integrity of the bond between each insert and the composite shell.

[0055] Brief description of the drawings

[0056] Examples of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

[0057] Figure 1 is a schematic perspective view of a wind turbine;

[0058] Figure 2 is a schematic perspective view of a wind turbine blade part;

[0059] Figure 3 is a schematic perspective view of a heating blanket and a thermographic camera arranged with the blade part in a thermographic inspection method; and

[0060] Figure 4 is an example of a thermogram captured by the thermographic camera.

[0061] Detailed description

[0062] Figure 1 shows a schematic perspective view of a wind turbine 10. For example, the wind turbine 10 may be an on-shore wind turbine or an off-shore wind turbine. The wind turbine 10 includes a rotor 12 that is rotatably coupled to a nacelle 14. The rotor 12 includes a central hub 16 and a plurality of wind turbine blades 18 extending from the hub 16. Each blade 18 extends between a root end 20 and a tip end 22. As shown in Figure 1 , in some examples the root end 20 of each wind turbine blade 18 may be attached to the hub 16. For example, the root end 20 of a blade 18 may be attached to the hub 16 via a pitch bearing (not shown) such that the blade 18 is rotatable relative to the hub 16.

[0063] Figure 2 shows a schematic perspective view of a blade part 24 of a wind turbine blade 18. In the examples shown in the accompanying figures, the blade part 24 is a blade shell which extends between the root end 20 and the tip end 22 of the respective blade 18, i.e. along a full length of the wind turbine blade 18. In some other examples (not shown), the wind turbine blade 18 may be a modular wind turbine blade, and the blade part 24 may therefore be a blade module. In each example, the blade part 24 comprises a composite shell 26. As described by way of background, composite materials, such as glass fibre reinforced plastic (GFRP), may be advantageous for forming the shell of the blade part 24 because of the strength and mass characteristics of such composite materials.

[0064] The blade part 24 is configured for attachment to another wind turbine component, such as the hub 16, a pitch bearing (not shown) or another blade module (not shown). For ease of reference, the invention will be described primarily with reference to the example in the figures, in which the blade part 24 is a blade shell, i.e. a full length blade shell, of a wind turbine blade 18. Accordingly, in some examples the blade part 24 may define the root end 20 of the wind turbine blade 18, and the root end 20 may be configured for attachment to the hub 16 or pitch bearing of the wind turbine 10.

[0065] T o facilitate attachment of the blade part 24 to another wind turbine component, the blade part 24 includes a plurality of inserts 28 embedded in the composite shell 26. For example, the inserts 28 may each include a threaded bore configured to receive a bolt or other fastener to thereby form a mechanical fastening to attach the blade part 24 to another turbine component. It follows that in some examples, the inserts 28 may each be formed of a different material compared to the composite shell 26. For example, the inserts 28 may be formed of a metal, such as steel. The inserts 28 may be embedded, i.e. integrated, in the composite shell 26 during manufacture of the blade part 24.

[0066] For example, as described by way of background, the inserts 28 may be integrated in the composite shell 26 during a forming or moulding method, such as vacuum assisted resin transfer moulding (VARTM), used to manufacture the composite shell 26. Inspection of the inserts 28 following manufacture of the blade part 24, for example to inspect a bond between the inserts 28 and composite shell 26, may therefore be challenging.

[0067] Examples of a non-destructive method of inspecting the blade part 24 will be described with reference to the remaining figures. The method involves inspecting an inspection region 30 of the blade part 24, indicated by the dashed-dot line in Figure 2. The inspection region 30 comprises a plurality of inserts 28 embedded in the composite shell 26 of the blade part 24. As will now be described with reference primarily to Figures 3 and 4, the inspection method involves a thermographic assessment of the inspection region 30. Referring initially to Figure 3, the method includes applying heat to the inspection region 30. For example, as shown in Figure 3, heat may be applied to an exterior surface 32 of the composite shell 26. Heat may be applied to the inspection region 30 by means of a heating blanket 34. As such, the method may involve arranging a heating blanket 34 on the exterior surface 32 of the composite shell 26 and operating the heating blanket 34 to thereby apply heat to the inspection region 30.

[0068] In some examples the heating blanket 34 may be strapped to the blade part 24. For example, as shown in Figure 3, the heating blanket 34 may comprise a strap 36 configured to extend around a periphery of the blade part 24 which includes the exterior surface 32. Accordingly, the method may include arranging the strap 36 around the periphery of the blade part 24 and tightening the strap 36 to thereby fasten the heating blanket 34 to the composite shell 26.

[0069] Strapping the heating blanket 34 to the blade part 24 may be particularly advantageous in examples where the exterior surface 32 of the blade part 24 is a convex surface throughout the inspection region 30. For example, as shown in Figure 3, in examples where the blade part 24 defines a root portion 38 of the wind turbine blade 18, the exterior surface 32 of the blade part 24 may be convex throughout the inspection region 30. Strapping the heating blanket 34 to a convex surface may help to ensure that substantially all of the heating blanket 34 is held against the surface 32, thereby improving the application of heat to the inspection region 30. In some examples, the heating blanket 34 may be configured to extend across or around the entire periphery of the blade part 24 in the inspection region 30. This may help to ensure that the entirety of the inspection region 30 of the blade part 24 is evenly heated.

[0070] As referred to previously, the inspection method involves a thermographic assessment of the inspection region 30. Accordingly, the method involves observing the inspection region 30 using a thermographic camera 40. The thermographic camera 40 is arranged such that a field of view 42 of the thermographic camera 40 includes a portion of the inspection region 30 comprising a plurality of inserts 28. In some examples, as shown in Figure 3, the thermographic camera 40 may observe an interior surface 44 of the composite shell 26.

[0071] It follows that in some examples, the inspection method may involve applying heat to a first side of the composite shell 26 and observing a second side of the composite shell 26 that is opposite to the first side. It should be appreciated that the first side of the composite shell 26 may define one of the interior or exterior surface 44, 32 of the composite shell 26, and the second side may define the other of the interior or exterior surface 44, 32 of the composite shell 26.

[0072] The thermographic camera 40 may capture a thermogram to thereby facilitate assessment of the integrity of a bond between each insert 28 and the composite shell 26. In some examples, the thermographic camera 40 may be configured to capture individual still thermographic images, i.e. thermograms. Alternatively, in some other examples the thermographic camera 40 may be configured to record a thermographic video. Accordingly, assessment of a thermogram may comprise assessing a still frame selected from a plurality of frames in a thermographic video.

[0073] Figure 4 shows an example of a thermogram 46 captured by the thermographic camera 40. The integrity of the bond between each insert 28 and the composite shell 26 can be assessed by analysing the thermogram 46. For example, the thermal response of each component in the field of view 42 of the thermographic camera 40 may be represented by a respective heat signature, i.e. infrared signature, in the thermogram 46. In particular, the thermogram 46 therefore comprises thermographic image data representing the response, i.e. the thermal response, of a portion of the composite shell 26 and the plurality of embedded inserts 28 to the application of heat. Notably, analysis of the thermogram 46 can facilitate an assessment of the integrity of the bond between each insert 28 and the composite shell 26, because the thermal response of a thoroughly bonded insert 28 is different to the thermal response of a loose or disbonded insert 28.

[0074] For example, with heat applied to the inspection region 30 of the blade part 24, for example to an external surface 32 of the composite shell 26, the heat may be conducted through the shell 26 to the inserts 28. If an insert 28 is loose, or not thoroughly bonded to the composite shell 26, less heat will be conducted to the insert 28. Similarly, for a loose or disbonded insert 28, less heat will be conducted from the insert 28 to the composite shell 26. Accordingly, the method may involve evaluating thermographic image data in the thermogram 46 to determine the heat transferred between each insert 28 represented in the thermogram 46 and the composite shell 26. Such an evaluation may indicate that an insert 28 is loose or disbonded if a heat signature 48 representing the insert 28 is different to an expected heat signature 48, or different compared to heat signatures 48 representing other inserts 28.

[0075] With reference to Figure 4 for example, heat signatures 48 in the thermogram 46 may define respective profile outlines 50 representing the respective inserts 28 in the portion of the inspection region 30 observed by the thermographic camera 40. From a visual analysis of the thermogram 46 it may be evident that one of the heat signatures 50i representing an insert 28i comprises an anomalous profile outline 50i, i.e. a profile outline 50i which is different to the profile outlines 50 representing the other inserts 28. This may indicate that the insert 28i represented by the anomalous heat signature 50i is loose or disbonded, because less heat has been transferred to and / or from the insert 28i, thereby resulting in the insert 28i being represented by an anomalous profile outline 50i in the thermogram 46. The same analysis may be applicable in examples where the heat signatures 48 in the thermogram 46 are representative of an average temperature of the respective inserts 28, and where an anomalous average temperature indicated by a heat signature 48 in the thermogram 46 indicates a loose or disbonded insert 28. Accordingly, the inspection method may include comparing a heat signature 48 representing one or more inserts 28 in the inspection region 30 to a heat signature 48 representing one or more other inserts 28 in the inspection region 30.

[0076] In some examples, the inspection region 30 may be observed with the thermographic camera 40 whilst heat is applied. For example the method may include capturing a series of thermograms 46 of the same portion of the inspection region 30 over a time period during which heat is applied to the inspection region 30. This may increase the probability of capturing a thermogram 46 in a sweet spot where sufficient heat has been supplied to the inspection region 30 for the inserts 28 to produce clear heat signatures 48 in the thermogram 46 for assessment, but before the entire inspection region 30 equalises to substantially the same temperature.

[0077] As previously described, in some examples the inserts 28 may be formed of a different material to the composite shell 26. As such, the inserts 28 may be formed of a material having a higher thermal conductivity than the material of the composite shell 26. Accordingly, portions of the composite shell 26 in which thoroughly bonded inserts 28 are embedded may heat up more quickly than those portions of the composite shell 26 not including inserts 28, or portions of the shell 26 including a loose or disbonded insert 28. Capturing a series of thermograms 46 during heating of the inspection region 30 may therefore be advantageous in such an example because the difference in thermal conductivity may facilitate quick and simple identification of loose or disbonded inserts 28.

[0078] Whilst not shown in the accompanying figures, in some examples, the apparatus may include a photographic camera (not shown). For example, during the inspection method, the photographic camera may capture a photograph of the same field of view 42 as that observed by the thermographic camera 40. Accordingly, the thermogram 46 in such an example may be compared to the photograph to provide context to the thermographic data represented in the thermogram 46.

[0079] It should be appreciated that whilst the method has been described with reference to observing a portion of the inspection region 30 comprising a plurality of inserts 28, the method may include observing a plurality of portions of the inspection region 30 each comprising a plurality of inserts 28. For example, the thermographic camera 40 may be arranged in a first orientation to observe a first portion of the inspection region 30, and after capturing a first thermogram 46 representing the first portion, the thermographic camera 40 may be moved or reoriented to a second orientation to observe a second portion of the inspection region 30. A second thermogram 46 representing the second portion of the inspection region 30 may then be captured. Alternatively, the thermographic camera 40 may remain stationary, for example in the hub 16 of the wind turbine 10, and the blade part 24 may be moved relative to the thermographic camera 40 such that different portions of the inspection region 30 are moved into and out of the field of view 42 of the camera 40, such that a plurality of thermograms 46, i.e. at least a first and second thermogram 46, can be captured to represent a plurality of different portions of the inspection region 30. In some examples, the method may include comparing heat signatures 48 in the first thermogram 46 to heat signatures 48 in the second thermogram 46.

[0080] Notably, in each example described herein, the method facilitates non-destructive inspection of the bond between inserts 28 and the composite shell 26 by assessing a thermogram 46 captured by a thermographic camera 40. Accordingly, the blade part 24 can be inspected without damaging the composite shell 26. In some examples the method may therefore be performed on a blade part 24 attached to a wind turbine 10.

[0081] The description provided herein serves to demonstrate a plurality of possible examples of the present invention. Features described in relation to any of the examples above may be readily combined with any other features described with reference to different examples without departing from the scope of the invention as defined in the appended claims.

Claims

Claims1. A method of inspecting a wind turbine blade part (24) comprising a composite shell (26) and a plurality of inserts (28) embedded in the composite shell, the method comprising: applying heat to an inspection region (30) of the blade part, the inspection region comprising a plurality of inserts embedded in the composite shell; observing the inspection region using a thermographic camera (40) such that a field of view (42) of the thermographic camera includes a portion of the inspection region comprising a plurality of inserts; and assessing a thermogram (46) captured by the thermographic camera to determine the integrity of a bond between each insert and the composite shell.

2. The method of claim 1 , wherein the plurality of inserts (28) are each formed of a different material compared to the composite shell (26).

3. The method of claim 2, wherein the plurality of inserts (28) are each formed of a material having a higher thermal conductivity than the material of the composite shell (26).

4. The method of any preceding claim, wherein assessing the thermogram (46) comprises comparing a heat signature (48) representing one or more inserts (28) in the inspection region (30) to a heat signature representing one or more other inserts in the inspection region.

5. The method of any preceding claim, wherein assessing the thermogram (46) comprises evaluating thermographic image data in the thermogram to determine the heat transferred between each insert (28) represented in the thermogram and the composite shell (26).

6. The method of any preceding claim, wherein applying heat to the inspection region (30) comprises applying heat to a first side of the composite shell (26), and wherein observing the inspection region comprises observing a second side of the composite shell opposite to the first side.

7. The method of any preceding claim, wherein observing the inspection region (30) comprises observing an interior surface (44) of the composite shell (26).

8. The method of any preceding claim, wherein applying heat to the inspection region (30) comprises applying heat to an exterior surface (32) of the composite shell (26).

9. The method of claim 8, wherein applying heat to the inspection region (30) comprises arranging a heating blanket (34) on the exterior surface (32) of the composite shell and operating the heating blanket to apply heat to the exterior surface of the composite shell in the inspection region.

10. The method of claim 9, wherein the heating blanket (34) comprises one or more straps (36) configured to extend around a periphery of the blade part (24) including the exterior surface (32), and wherein arranging the heating blanket comprises arranging the strap(s) around the periphery of the blade part and tightening the strap(s) to fasten the heating blanket to the composite shell (26).

11. The method of claim 9 or claim 10, wherein the exterior surface (32) of the blade part is a convex surface throughout the inspection region (30), and wherein the heating blanket (34) is configured to extend across or around the entire periphery of the blade part (24) in the inspection region.

12. The method of any preceding claim, wherein the step of observing the inspection region (30) using a thermographic camera (40) is performed whilst heat is applied to the inspection region (30).

13. The method of claim 12, further comprising capturing a series of thermograms (46) of the same portion of the inspection region (30) over a time period during which heat is applied to the inspection region.

14. The method of any preceding claim, wherein the thermogram (46) is a still frame selected from a plurality of frames in a video captured by the thermographic camera (40).

15. The method of any preceding claim, further comprising capturing a photograph of the same field of view (42) as that observed by the thermographic camera (40) to facilitate a comparison between the thermograph (46) and the photograph.

Images