World’s largest bearing test rig now operational at Schaeffler
07 March 2012
Schaeffler has successfully completed the design and build of the world’s largest, most powerful test rig for large size bearings. The test rig, officially opened at Schaeffler’s Schweinfurt plant in November, is now fully operational. The ‘Astraios’ test rig enables large size bearings weighing up to 15 tonnes with outside diameters up to 3.5m (particularly those used in wind power applications) to be fully tested in realistic conditions using a comprehensive simulation programme.
At a cost of around 7 million euros, Astraios is a significant investment but will enable Schaeffler to help reduce wind turbine development times for customers, as well as improving the reliability, safety and cost effectiveness of future wind turbine designs.
Astraios will be primarily used to test rotor bearings for multi-Megawatt wind turbines and will help to further improve the understanding of wind turbine systems, the influencing factors and the interrelationship between drive train components. The tests will also provide useful insights into wind turbine operation and maintenance, as well as information on how to optimise the design of any adjacent constructions.
The test rig will perform realistic simulations of static and dynamic loads that act on the rotor bearings and slewing rings. All rotor bearing concepts for wind turbines with an output of up to 6MW can be tested. Functional tests will provide insights into rolling bearing kinematics, temperature and friction behaviour, loads and deformation. The data required for these tests will be provided by more than 300 different sensors mounted on the test rig and in the bearings.
The loading frame is the most important part of the test rig. Four radial and four axial hydraulic cylinders are fixed to this frame, which generate the real loads and moment forces that occur in a wind turbine. The radial cylinders simulate the weight of a rotor hub with rotor blades, while the axial cylinders generate the wind loads.
The rotors and hub on a large wind turbine can weigh in excess of 100 tonnes. This weight acts on the bearing and generates a static radial load and a static ‘nodding’ moment. Accordingly, the four radial cylinders have extremely large dimensions, as each cylinder can generate a maximum of one mega Newton of force, which is equivalent to 100 tonnes of weight. The axial cylinders provide even more – up to 1.5 mega Newton for simulating static axial loads as well as the dynamic nodding and yawing moments. This nodding and yawing is comparable to the lifting, lowering and turning of the wind turbine nacelle.
Different wind speeds are simulated using the test rig’s drive train and planetary gearbox. Typical speeds are 4-20 rpm, although it is also possible to simulate significantly higher speeds.
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