Nose in the Wind
If wind turbines keep their noses in the wind all year round, it’s on their bones. In the EU project “Shearios”, DEKRA subsidiary Visatec and its partners are developing a robotic vehicle that uses shearography technology.
The service technicians work on the hub and rotors at heights of up to 170 metres. Photo: REpower Systems AG
A really cool robot should have a name like R2-D2 or C-3PO. In the science fiction universe of Star Wars, a robotic system like the VT 610 ICMCL with this name wouldn’t make a career. The vehicle developed by the DEKRA subsidiary Visatec, with its approximately 60 centimeters long and equally wide chassis, shows promising characteristics for the future. The VT 610 ICMCL is a real climbing natural that literally sucks itself onto non-magnetic surfaces with the help of a vacuum motor. The vacuum chamber is enclosed in an airtight, bulbous jacket made of special rubber, while a filigree chain drive ensures that the 13.6 kilogram trolley proceeds unperturbed into dangerous expanses. The remote-controlled inspection system feels particularly at home in industrial plants with tanks, containers and chimneys. In the near future, wind power plants could also become a workplace for the small robot.
Rain, frost and lightning strikes put lots of stress on wind turbines
In the EU research project “Shearios”, the VT 610 ICMCL crawler already plays a major role. The robotics company Visatec, which has been part of DEKRA since 2014 and is based in the Allgäu region of Germany, is part of a consortium of seven partners from the energy sector that is committed to the mobile mechanized inspection of rotors using the Shearography measurement method. The VT 610 ICMCL is to act as the carrier for the inspection system. In fact, the need for inspections is huge. In Germany alone, around 30,000 wind turbines with a total output of over 56,000 megawatts keep their noses in the wind to generate electricity. Over the typical service life of a turbine of 20 years, rain, frost and lightning strikes put lots of stress on the rotor blades. The consequences are cracks in the blade shell, erosion damage at the leading edge or lightning damage at the blade tip. In the worst case, a deficiency can cause a blade to break off. It is therefore obvious that wind turbines must be regularly inspected and maintained.
Plant operators increasingly rely on technological systems for inspection
Climbers with rope access technology inspect the rotor blade using visual and knock tests. Photo: juwi Holding AG
In practice, this is often a job for industrial climbers who take a close look at the systems at dizzying heights of up to 170 meters. To do this, the climbing professionals have to rope down the rotor blade from the hub and inspect the surface piece by piece. In the case of large systems, the inspection can take a whole day. It is logical that no electricity is produced during this time. The plant operators therefore have a great interest in ensuring that the inspections are carried out quickly. This is why high-resolution cameras on the ground and drones equipped with cameras are now also being used. Here and there, the technology is used to obtain an inventory of the condition of the rotor blades. This is also the aim of the EU project “Shearios”. Shearography is an optical full-surface inspection method that is suitable for defect detection in composite materials. The laser-based system works with a special camera and looks, so to speak, under the surface of the material. With its measuring technology, it detects deformations and irregularities. From the high-resolution image transmitted by the camera for evaluation, the inspector can draw conclusions about the defect.
The operator of the vehicle always has a safe floor under his feet
A typical scenario for using the system is for the operator to manoeuvre the carriage with the installed measurement system using joysticks. The connection between the crawler and the control unit and between the camera and laptop is made using special cables that are pulled behind the vehicle them in a bundle. When the operator gives the VT 610 ICMCL the spurs, the little trolley searches the rotor blades from top to bottom at four meters per minute. A tangible advantage: the operator, inspectors and service technicians have safe ground under their feet during the entire inspection, while the robot high up on the rotor blades replaces the human eyes. Current status of “Shearios”: The system is in the design phase.
The versatile VT 610 ICMCL trolley is the perfect carrier for a shear system. Photo: ICM
The engineers are still working on how the measuring technology can be optimally attached to the chassis. It also needs to be clarified how the VT 610 ICMCL can most efficiently reach its starting position on the rotor blade. In four or five months, the first practical tests will take place on the wind turbines installed onshore and offshore by the British project partner EDF Energy. The results of the “Shearios” project should be available by the end of 2020.
