Turbine gearbox bearing eliminates slippage


A new rolling bearing has been developed for wind turbine gearboxes that is  not only resistant to the effects of slippage, but actually prevents slippage  from occurring in the first place.

Rather than using conventional rolling elements, Schaeffler’s FAG tube roller  bearing incorporates three tube rollers. These tube rollers enable the bearing  to rotate without slippage under all load conditions. At the same time, the load  rating and rating life are unaffected.

Slippage is detrimental to rolling bearings; the life and performance of a  rolling bearing will suffer if it is overloaded or under-loaded. This is because  rolling bearings are designed with a minimum load requirement in order to  function optimally. If this minimum load is not met, slippage will occur. This  means that the rolling elements not only rotate, but also slide on the bearing  raceways. Eventually, this can lead to surface damage such as increased wear or  smearing, particularly in critical lubrication conditions.


In wind turbines, rolling bearings have to meet special performance  requirements. The bearings must be designed to withstand extremely low and high  loads that act on the bearing during calm or strong wind conditions. The risk of  damage to a bearing increases significantly when the roller set of a rolling  bearing with high slippage is suddenly subjected to extremely high acceleration  forces. For this reason, Schaeffler has developed the tube roller bearing, which  completely eliminates the problem of slippage.

The FAG tube roller bearing is a conventional cylindrical roller bearing that  incorporates three cylindrical rollers with a slightly increased diameter. These  three rollers have a hollow design and are supported by a roller in the inner  bore. These rollers with a slightly increased diameter generate preload in the  bearing and drive the bearing cage (and therefore the entire roller set) at low  loads.

At higher loads, the bore of the cylindrical rollers ensures sufficient  deflection of the larger rollers so that that they are not overloaded. This  means that the load is evenly distributed to all the rolling elements, similar  to a conventional rolling bearing.

The tube roller and support roller provide increased  fatigue strength to the bearing, which results in a rigid rolling element that  withstands peak load conditions

The support roller in the inner bore of the tube roller has a slight  clearance to ensure that the roller is less rigid (more flexible) at higher  loads. At the same time, this also prevents excessive deflection of the tube  roller. Together, the tube roller and support roller provide increased fatigue  strength to the bearing, which results in a rigid rolling element that  withstands peak load conditions.

The tube roller bearing is not available from Schaeffler’s standard catalogue  but is custom designed for specific customer projects and applications. Initial  prototypes have already been manufactured and tested. Pilot applications in wind  turbine gearboxes are planned for the end of this year.

source: Theengineer