Fraunhofer IWES has reached an important milestone in the development of a test rig for wind turbine slewing bearings measuring up to 6.5 m in diameter: the cylinders and mechanics for the application of real wind loads of up to 50 MNm have been installed and are now operational. As such, the researchers are well within the schedule, which envisages commissioning of the entire test rig by the end of the year. It will then be possible to validate a rolling bearing fully and in a reproducible manner in the laboratory without the need for field measurement campaigns. This is supposed to lead to noticeable savings in the time required up to market launch for new constructions for manufacturers and will also enhance the reliability of these products.
The slewing bearings in wind turbines are subjected to significantly different loads than in other industrial applications: continuous load changes, varying speeds, and interfaces with complex rigidity profiles result in frequent damage or, indeed, malfunctioning. Researchers at Fraunhofer want to improve the design methods further and reduce the risk of failure in the interests of more cost-effective turbine operation. Tests into wear, fatigue, and functionality on the new test rig BEAT6.1 (Bearing Endurance and Acceptance Test rig) at the Hamburg site will lay the foundations for this work.
The first test objects have already been installed: Two two-row four-point rolling bearings measuring 5 meters in diameter and weighing 10 tons are clamped horizontally into position and run through commissioning and functionality tests within the scope of the HAPT (highly accelerated pitch bearing test) research project.
“The six load application cylinders have been successfully commissioned and have set the 150 t load platform in motion. As such, we are now even closer to complete commissioning of the test rig,” explained Head of Department Dipl.-Ing. Christian Broer.
The next step involves the fine-tuning of the cylinders and the dynamic loads in six degrees of freedom. Each cylinder can generate a force of 3.4 MN (approx. 340 tons). It is expected that this will be completed by the end of October. The project’s general commissioner is IDOM, which has already handled load application for the nacelle test rig for Fraunhofer IWES in Bremerhaven.
“The tests performed as part of the HAPT project enable us to put our research work from the past five years into practice and, for the first time, subject blade bearings to a genuine, accelerated endurance run. It is therefore possible to test them for their entire service life prior to installation on a wind turbine,” explained Senior Engineer Matthias Stammler.
The BEAT6.1 bearing test rig will initially be operated with test jobs within the scope of the public HAPT project. However, following this, it will be available to all interested parties. Initial inquiries from the industry confirm the demand for this type of testing. For the durability testing of the rolling bearings of wind turbines up to 10 MW, time series, which simulate various damage mechanisms, are created by means of complex data analyses. This test rig expands Fraunhofer IWES’ portfolio of validation services, which, in turn, support turbine and component manufacturers to safeguard further and new developments prior to their market launch.