Renewable Energy
the angle of light incidence changes as well as the illuminated point on the receiving element. During a measurement, the diffusely scattered light of the laser line is detected by a highly sensitive CMOS chip, which produces a precise image of the surface profile. Each change of the profile changes the displayed line, resulting in an altered image on the chip. Each line can be considered as a series of points. If the scanner traverses over the weld seam, a 3D image of the object is produced by apposing the individual line profiles. A so-called ‘point cloud’ is formed because the image is composed of thousands of individual measurement points. Using this method, a faultless weld seam is guaranteed for wind turbines.
“The
unnoticeable yet extremely important task of supporting the gondola and resisting all types of weather conditions requires a high degree of quality and reliability.”
Profile scanners After several years in use, components are dismantled and routinely inspected for wear or damage. For this, scanCONTROL profile scanners are also used in order to produce a 3D image of the gear wheel. Several laser triangulation sensors that establish a
movement of the gear wheel under load are used for testing the stiffness of gear wheels for pitch control. Tese sensors measure the distance to the gear wheel with one laser spot; in doing so, each movement is registered. ●
Fig. 2. Rotor blade MB5000 from Multibrid mounted in the test rig. This blade has a length of 56.5m.
Source: Fraunhofer Institut IWES, Bremerhaven
Inspected weld seam Te tower of a wind turbine is usually considered as the least noticeable part. However, with a height of 130m and a weight of several hundred tonnes, the tower is the largest and heaviest part of a wind turbine. Te unnoticeable yet extremely important task of supporting the gondola and resisting all types of weather conditions requires a high degree of quality and reliability. Tubular steel towers are a very frequent structure to use and usually consist of two to five segments, each one up to 30m in length. A segment of a tower is rolled from steel sheet 20mm to 40mm thick and then welded. Te individual segments are bolted or welded together, whereby a flange has to be welded onto the segment for the bolted variant. In doing so, each weld seam must withstand the very high loads on the tower in the finished condition. For safety reasons, a quality inspection of the weld seams is therefore a critical step. Laser scanners from Micro-Epsilon are already being used in many other industry sectors for the automatic, precision inspection of weld seams. Te weld seam inspection of pipelines provides a suitable comparison. A laser projects a spot or a line onto an object. Te
diffuse reflected light there is recorded using the light- sensitive receiving unit (CMOS). If the object departs,
Fig. 3. The rotor blade under load. Heavy-duty draw-wires bend the rotor blade to maximum load. Draw-wire sensors measure the displacement. Source: Fraunhofer Institut IWES, Bremerhaven.
Erich Winkler is product manager, optical sensors, MICRO-EPSILON MESSTECHNIK GmbH & Co KG, Ortenburg, Germany.
www.micro-epsilon.com
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