The problems between Vestas and Jahnel-Kestermann involve failed gearboxes on NEG Micon 750 kW turbines and the need to replace them (Windpower Monthly, July 2005). Working together with NEG Micon initially, Jahnel-Kestermann made modifications to its gearbox design and produced an upgraded gearbox in which spherical roller bearings were dropped in favour of cylindrical bearings. But, says the company, after its considerable investment Vestas refuses to recommend the use of the gearbox. Meantime, however, Vestas Holland and Vestas Japan are buying the upgraded gearbox, says Jahnel-Kestermann, and this year it expects to sell 300 gearboxes to Vestas India for the Vestas V27 and V47 machines.
The company says it has learned its lesson in the wind industry and will never again be so reliant on a single customer as it was with NEG Micon. It is planning to build around 500 gearboxes a year for the wind sector, but it does not wish its wind business to exceed 40% of company turnover. As well as supplying to Vestas units overseas, it currently also supplies gearboxes for Fuhrländer machines.
Problems with gearboxes in wind turbines have arisen for a variety of reasons, says Jahnel-Kestermann. It blames turbine manufacturers for not providing enough information on loads, inadequate oil lubrication and filtration, and lack of decent turbine maintenance.