Wind turbines generate electricity in adverse, constantly changing conditions both onshore and offshore. The turbines are not readily accessible and are designed for a 20-year service life. This places extreme demands on all of the turbine’s components – especially the bearings. They must be able to withstand the continuous dynamic loading over a long term, at high wind speeds.
NSK bearings have gained a global reputation for outstanding quality built on their long service life, reliability, resistance and innovative design.
In 2008, NSK played a pioneering role as the first manufacturer to create an in-house standard for bearings used in wind turbines: the Wind Standard U303. This standard requires 100% traceability of components for each bearing - back to the material batch as well as all major process variables. It also defines NDT methods (non-destructive testing) to prevent grinding burns, surface cracks and structural faults in the material.
Operating conditions: variable loads
Wind turbines are enormous machines. Many 2 megawatt class turbines are being built with blades of 130+ foot in length, and a rotor hub height of 195 to 328 feet with total weight over 200 tons. Due to their size, the bearings used in wind turbines are extremely large, with bore diameters between 100 mm and 700 mm.
Very few manufacturers worldwide can offer the market a stable supply of such large bearings. Suppliers must have both production capability and the ability to provide sales and technical service in key locations around the world.
Currently, NSK bearings are used by nine of the world's top ten wind turbine manufacturers, and in turn the company is making a substantial contribution to environmental protection.
Bearing design by experienced engineers using sophisticated calculation and simulation tools: In addition to extreme and maximum conditions, load cycles, lubrication, deformation and thermal response are also taken into consideration. This allows a safe design to be created in order to achieve the desired service life using cost-optimized components.
HR taper roller bearings and cylindrical roller bearings from NSK are ideal for main gearboxes as they have high loads and remain reliable despite changing loads. They can be arranged in various constellations – as locating/non-locating bearings, adjusted bearing arrangements or floating bearings.
BOC (black oxide coating) offers longer service life: Black oxide coating is a method used to reduce the risk of white etching cracks (WEC) in bearings. An even more special material AWS-TF (Anti White Structure-Tough) is available to prevent damage caused by white etching cracks. To increase the load rating and service life, our STF material (Super-Tough) has proven to be successful, especially in applications with contaminated lubricants.