Robot diving in the ocean checking welds for wind turbines safety

Offshore wind power plants are exposed to enormous pressure: wind, waves and salt water rock towers and attacking the weld of the foundations. Periodically examines these welds of divers elaborate on defects. Now robots will take over and will be even faster and more reliable.

Wind power plants are exposed to enormous forces on the high seas. The waves whips against the Poles, the wind is shaking the rotors. It’s especially important that the foundation of heavily loaded systems that shows no weaknesses. Especially as the foundation in the aggressive salt water reacting and corrode fast.

Welding in the concrete-steel foundations are construction weak spots.

The weld of the foundations are particularly at risk, where cracks can form. Therefore dive regularly trained divers in the depth and examine these foundations.

offshore wind energy
For the foundations of offshore installations, three welded steel tubes to a tripod are put together and anchored on the sea floor. It is the actual wind turbine. One of the steel tubes of tripods in the sea will be sunk in the image. These tubes are conventionally welded and subject to the stress of salt water under water. Photo: Foundation of offshore wind energy

This is enormously cost. First, the divers must free the weld to be examined by algae and mussels. Then they create an electromagnetic field and iron filings on it. A possible crack reveals itself in this process immediately because the iron filings there accumulate.

Because at this point the applied electromagnetic field accelerate process significantly.

Testing can take a whole day

This procedure is not only exhausting, it is also time consuming. Such a test ever takes a whole day. Researchers of the Fraunhofer Institute for ceramic technologies and systems IKTS in Dresden have developed a robot in cooperation with various industry partners who can take over this work in the future. The new mate’s ROV, which is an abbreviation for remote operating vehicle.

“The heart is a sensor cuff, which is placed to the weld and about the plant life there remains”, explains Andreas beak IKTS project manager. This collar has sensor elements, which are lined up at intervals of about five centimeters like on a string of pearls. You can thus determine extent and depth of a crack in the welding seam. That was impossible with the iron filings. In addition: with the ROV is one weld after completed only ten minutes.

UV waves are reflected at imperfections

For a measurement, still a diver down into the deep sea and via an interface must connect a handhold device on the cuff. In future, the ROV to do this independently. About batteries, this handset also provides the necessary energy for a measurement.

Round Robin one of the sensor elements in the cuff sends ultrasonic waves in the weld into one. These UV waves are reflected at imperfections. The other sensors to detect these reflections. There is an image, similarly a computer tomography. The examiner of the offshore facility receives a picture of weld at the existing defects are color-coded according to relevance.

IKTS presentation at the Hanover Expo 2016

A first practical test in the offshore wind farm Baltic 1 is now successful. The researchers of the IKTS added a jagged metal pipe to crack a 0.9 mm wide, 45 mm long and 7 mm deep and brought on the seabed of the Baltic Sea at a 18m depth. The ROV worked perfectly realized this rift.

Robot diving ocean to check welds for wind turbine safetyIn five years, the automatic test system should be certified and ready for use by robots. At the Hannover Fair from 25 to 29 April, the scientists present their ROV in Hall 2 at stand C16/C22.

You are interested in the foundations of offshore installations? Then the report on foundations is particularly exciting, turned off just on the sea floor. Such foundations are used in the English Channel off the coast of Normandy.