Slewing rings and spherical roller bearings

Jon Lawson

A manufacturer of high performance small wind turbines based in Scotland has specified slewing rings and spherical roller bearings from Schaeffler UK for use on its 133 wind turbine – the quietest wind turbine in its class.

Based in Port Dundas, Glasgow in Scotland, Gaia-Wind is a leading manufacturer of high performance, small wind turbines designed for moderate wind speed sites. The turbines are ideally suited to farms, rural properties, businesses and community projects.

Designed in Denmark and manufactured in Scotland, the Gaia-Wind 133 turbine has an oversized rotor, allowing it to capture significantly more energy than similarly rated machines. With more than 1400 installed worldwide, these turbines are the quietest wind turbines in their class and have a long track record of reliability.

Schaeffler UK has been working with Gaia-Wind for over five years, supplying precision engineered slewing rings and E1 spherical roller bearings for the 133 turbine.

Slewing rings

In order to optimise operating efficiency, wind turbines need to be aligned to wind conditions. In order to achieve this, the slewing rings (yaw bearings) adjust and optimise the position of the nacelle to the direction of the wind. The wind loads and the dynamic inertia forces are transferred via the bearing raceways and screw connections into the head of the tower.

Schaeffler develops and manufactures slewing rings with outside diameters up to 1,250mm. Due to their design, these slewing rings can transmit radial and axial forces, as well as tilting moments. The slewing rings supplied for the 133 turbine are four-point contact bearings, enabling precise angular adjustment at varying loads.

E1 spherical roller bearings

In a wind turbine, the design of the rotor shaft bearing is critical, as this bearing is directly exposed to the loads and forces induced by the wind. Alternating loads with extreme peaks and troughs, as well as fluctuating operating temperatures represent further challenges to the bearing designer.

Suitable for heavy duty, harsh operating environments and where there is a need to compensate for shaft misalignment, E1 spherical roller bearings from Schaeffler support the main shaft of the 133 turbines. These bearings are double-row, self-contained units that comprise solid outer rings with a concave raceway, solid inner rings and barrel rollers with cages. The inner rings have cylindrical bores and are supplied to be fitted into a housed unit to suit the 133 turbine. The bearings are manufactured to Schaeffler’s premium X-life quality standard. The E1 range includes eight bearing series with bore diameters from 20mm up to 1,220mm.