Specialist bearings developed for wind turbine applications

With renewable energy very much a hot topic, RA Rodriguez is well placed to meet demand for critical drive components. It is the UK factory representative for Kaydon, an American bearings specialist whose largest ever order was recently received from an OEM in this application sector.

Kaydon has been involved in wind energy for more than 20 years and has developed a range of bearings for pitch, yaw and gearbox applications in land-based or offshore wind turbines rated form from 200kW to 5MW and beyond.

Typical requirements are for a large slewing ring in diameters ranging from 2-5m. To combine the function of a bearing and gear, teeth can be cut into the inner or outer race. The use of a single larger diameter bearing enables wiring and other services to pass through the bore with ease. This simplifies the overall system design, improves outward appearance and protects components.

Four-point contact

Selecting the right bearing design depends on load, stiffness, speed, size and the smoothness of rotation required. One that has proven to be particularly popular for wind turbines, however, is the four-point contact ball bearing that uses a Gothic arch form on the inner and outer races. This bearing accepts combinations of radial, thrust and moment loads.

To satisfy requirements for maximum load capacity within a given envelope, especially in larger sized bearings, Kaydon has also developed an eight-point contact bearing that is also widely used in wind turbines. This is an annular bearing with two rows of balls whose innovative feature is its use of the Gothic arch internal geometry in both rows. Tests have confirmed that this additional row increases load capacity by 80 per cent.

Corrosion resistance is, of course, an important consideration for outdoor use and the Kaydon wind turbine bearings are therefore available with a range of suitable surface treatments. Selection of the most appropriate materials is also critical for operating temperatures that may be as low as -40degC; special sealing arrangements are available for severe conditions.

While other manufacturers may specialise in one or two specific bearing types, Kaydon has the experience and manufacturing flexibility to match the product to the exact requirement. This includes accommodating special needs without sacrificing system performance or increasing cost.

Further information on the Kaydon wind turbine bearings and custom options is available from R A Rodriguez.