Farther than the eye can see
Normal functioning of wind turbines induces damage to the rotor blades that decreases their service lifetime, increases operating costs and threatens safety. Currently, most manufacturers of rotor blades perform a final check via a visual and acoustic inspection by a technical expert, clearly leaving plenty of room for human error. A small number employ passive thermography to make conclusions about parts adhesion, but this can only be done while the parts are still warm after manufacturing. The ‘Development of a methodology for preventive maintenance of wind turbines trough the use of thermography’ (Prewind) project was designed to apply passive and active thermography technology for early detection of damage to rotor blades. The proposed non-destructive testing (NDT) methods using active thermography can be carried out at any stage in the life-cycle of a rotor blade and is relevant to manufacturing, on-site assembly and maintenance as well as for use by insurance inspectors. The researchers first carried out an assessment of typical failures, quality control methods, quality standards and manufacturing requirements. They concluded that the most critical factors affecting wind turbine operation are the electrical connections, the electrical systems and the rotor blades, in order of importance. The investigators then developed Prewind methodologies for passive thermography in evaluation of electrical and mechanical parts and active thermography for inspection of rotor blades, including selection of camera and heat source, among others. To supplement the accurate detection of damage with an evaluation of its seriousness, the researchers catalogued typical defects via an extension of field testing to gather as much information as possible. Finally, they developed an e-learning tool for wind turbine inspection technicians including modules on thermography as a science, thermography as applied to wind turbine inspection and the Prewind methodology itself. In summary, the Prewind project significantly enhanced the state of wind turbine inspection technology and methodology that until now relied primarily on visual inspection of parts. The results should decrease costs while increasing efficiency and safety, a boon for manufacturers, operators and the European economy.
