Patent ID: 9551319
Date: 2017-01-24
CPC Classifications: F03D,F05B,F16H,Y02E,Y10T

Claim:
1. A method of operating a yawing system for a wind turbine, the yawing system including a hydraulically driven preload mechanism having a hydraulically operated piston, an accumulator, and a valve switchable between a first position establishing a fluid connection between the hydraulically operated piston and the accumulator and a second position establishing a fluid connection between the hydraulically operated piston and a tank, the method comprising the steps of: applying a preload force to a yaw bearing of the yawing system when the yawing system is not performing yawing movements, wherein the valve is in the first position so that pressure in the accumulator causes the hydraulically operated piston to apply the preload force, moving the valve to the second position, thereby allowing fluid to flow from the hydraulically operated piston to the tank, via the established fluid connection, to release the preload force provided by the hydraulically operated piston, and operating the yawing system to perform yawing movements, wherein said operation of the yawing system automatically causes a pump to operate to supply fluid to the accumulator.