Schaeffler has optimized its spherical roller bearings for rotor main bearing supports with the objective of increasing the reliability, availability, and efficiency of wind turbines. The development of an asymmetrical spherical roller bearing represents yet another step towards more robustness.
Schaeffler’s optimized spherical roller bearings were subjected to testing as part of the company’s “X-life” seal of approval. The necessary validation steps have been certified by Germanischer Lloyd.
The bearing supports of the rotor shaft are of central significance in wind turbines. The locating bearing is subject to especially high axial loads. With this in mind, Schaeffler has optimized its tried and tested standard spherical roller bearings to meet the challenging requirements for use in turbines. The company has also developed an asymmetrical bearing design.
Robust design for reduced wear With regard to microgeometry, developers have improved the surfaces to reduce friction, and therefore the application of energy and wear. In addition, they have adjusted osculation to transmit rolling element normal forces across a large surface, reducing contact pressure.
The rolling elements have also been specially profiled. Adjustments in macrogeometry primarily comprise two aspects. First, the engineers have reduced the internal bearing clearance, which has improved the operating clearance. This has also reduced the rolling bearing forces and the axial sliding of the drive train. Second, they used a firm center rib for the locating bearing supports of the wind turbine rotor and increased axial rigidity, which reduced the axial displacement of the drivetrain.
The firm center rib helps distribute the contact pressure along the roller. With these two measures, they have been able to increase the bearings’ robustness against wear, which is mainly caused by axial displacement.
As part of validation, the bearings were subjected to comprehensive testing to be granted Schaeffler’s “X-life” seal of approval. The necessary validation steps have been certified by Germanischer Lloyd (certificate GL-CER-002-2015).
Better load distribution with asymmetry The asymmetrical bearing represents yet another advancement in design. It significantly increases the axial-load carrying capacity and service life of the main bearings in wind turbines. It allows a greater contact angle on the row of bearings supporting the axial load, and a flatter contact angle on the row of bearings that mainly support radial loads.
This design results in a better load distribution, reduced contact pressure, and a significant reduction of the axial sliding distance.