MechChem Africa July-August 2022

Steel and heat treatment raises performance in wind turbines

A new steel and heat treatment process has been developed for SKF high durability wind turbine gearboxes to raise the torque density, reduce bearing and gear size by up to 25%, and improve the rated life while at the same time avoiding premature failures. S KF has developed a new roller bearing for wind turbine gearboxes that offers bearing rating life at the forefront of the industryandenables

crostructure, residual stress and hardness.” This tailored steel and heat treatment process has several benefits: it increases bearing rating life and enables downsizing while increasing the new bearings capacity to resists typical failuremodes in gearboxes, such as premature failures related toWhite Etching Cracks (WECs), micro-pitting and wear. Internal tests and calculations show up to a fivefold increase in bearing life compared to current industry standard. Moreover, an up to 10-times higher ro bustness against stress induced premature failures with WECs have been proven on inhouse test rigs. The improved performance of SKF high durability gearbox bearings means the bear ings can be downsized, helping to increase torque density of the gearbox. This is critical in the latest generation of multi-megawatt

turbines. In a typical planetary stage of a 6.0 MWwind turbine gearbox, a size reduction of the planet wheel bearing of up to 25%, and consequently of the planet gear as well, is achievable by using SKF high durability gearbox bearings while keeping the same life rating as the industry standard bearing. Similar size reductions can be achieved on different positions in the gearbox. In a parallel gear stage, thebearing size reductionwill also reduce the risk of slip-related damage. Resistance to typical failure modes could help gearbox manufacturers, turbine owners and service providers to increase reliability and have less unplanned turbine standstill and repair cost. These new features help to reduce the Levelised Cost of Energy (LCoE) for wind and support thewind industry journey to become a cornerstone in the future energy mix. www.skf.com

reduction of downtime and maintenance. The SKF high durability gearbox bearing for wind relies on a tailored combination of steel and heat treatment process that is developed to raise fatigue resistance and robustness. A thermochemical heat treatment process improves its surface and subsurface properties. “The heat treatment process enriches the surface layer of the bearing components and improves the material strength both at and below the surface, covering the high stressed material volume during bearing operation,” says David Vaes, manager of the Wind Gearbox Competence Centre at SKF. “Rolling bearing performance depends very much on material parameters such as mi

18 ¦ MechChem Africa • July-August 2022