Schaeffler has developed a new, compact bearing unit for moment bearing concepts in wind turbine rotor bearing supports. The flange-mounted tapered roller bearing unit allows all forces and moments in a bearing to be safely supported due to the large pressure angle and tight axial guidance of the rotor. The double row tapered roller bearing unit in an ‘O’ arrangement, with grease lubrication and seals, is supplied pre-assembled. The inner rings are flange-mounted to the rotor, while the outer ring is flange-mounted to the nacelle of the wind turbine. The bearing clearance is preset, which significantly reduces logistics and mounting costs.
In order to improve reliability, availability and therefore the cost effectiveness of wind turbines, Schaeffler has optimised its spherical roller bearings for main rotor bearing supports. This bearing design is used exclusively on the shaft bearing support – the most common bearing support concept. In order to optimise the bearing, both its micro- and macro-geometry were addressed. The result is conclusive: it was possible to reduce friction and pressures in the bearing, to improve the distribution of forces, and to increase the axial rigidity. These optimised spherical roller bearings therefore have greater resistance to wear, which specifically occurs as a result of axial displacement. These bearings successfully completed a comprehensive range of tests as part of their validation for Schaeffler’s “X-life” premium quality seal of approval. The validation steps required for this have been certified by Germanischer Lloyd (GL certificate GL-CER-002-2015).
This asymmetrical design represents a significant step forward. It substantially increases the axial load carrying capacity and therefore the operating life of main bearings in wind turbines. It allows a larger contact angle to be used on the bearing row subject to axial loads and a smaller contact angle on the bearing row subject primarily to radial loads. This has resulted in improved load distribution, lower contact pressures and a significant reduction in the axial displacement.
