This article is part of the 2017 Renewable Energy Handbook. A complete digital version of the handbook is here: https://goo.gl/Sg4mHO
A wide range of bearings perform different functions throughout a wind turbine. For instance:
The slewing ring bearing from Kaydon is available without gears, or gears on inside or outside.
Slewing ring bearings are typically found in the pitch and yaw locations of a turbine and help ensure that the blades rotate smoothly. As long as proper maintenance procedures are observed, they do not usually experience many problems besides normal wear and tear over time.
Spherical roller bearings are often used in the main shaft of the turbine. It is also common to find a tapered roller bearings (TRB) used in combination with a cylindrical roller bearing (CRB) at this location, said Stephen Curtis, director of Renewable Energy Business. There are a number of different bearing designs that can be found in the gearbox of a wind turbine, but most often, various combinations of CRBs, TRBs and ball bearings are used.
Bearing manufacturers are constantly developing new solutions to improve the lives of the components. An example of this, Curtis said, is new sealing solutions designed to improve retention of lubrication.
The spherical roller bearing for a main shaft is manufactured by Timken.
Incorporating new designs into gearbox bearings has been a recent trend in new bearing developments. Along with the CRBs and TRBs commonly used in gearboxes, integrated planet bearings have also been added to reduce the total number of components in the assembly by directly machining bearing races into the surrounding components of the gearbox, said Richard Brooks, manager – Wind Energy Aftermarket at Timken Co. The semi-integrated design is most commonly used because of its ability to create greater gearbox density, reduce total gearbox mass and eliminate any fretting in the integrated component. Brooks said that this design also has the potential to improve load sharing among the planet gears.
“These advances are driving improved gearbox reliability in the wind industry and are being introduced as upgraded retrofits for some older gearbox models,” Brooks said.
It is difficult to make general recommendations as far as installation and maintenance of bearings.
“Bearing applications in a turbine are developed specifically for each customer and their components,” Curtis said. “Bearing manufacturers make recommendations about how to install and maintain the chosen bearing for each application.”
Is there a reason why Babbitted bearings are not used in wind turbines? They typically stand up to high loads, have long service life, and do not exhibit catastrophic failure.