Wind power turbines are located in remote areas where favourable wind conditions for maximum power generation are guaranteed.
Nevertheless, the environmental conditions of these specific areas change from day to night, from winter to summer, in Arctic or desert areas, on-shore and off-shore, etc. In fact, the temperatures can vary from -40ºC to more than 50ºC and the wind direction and speed can change suddenly.
There are wind farms where the relative humidity, for example, is very high, and in off-shore farms the salt concentration is very high and tremendously abrasive. Dust also has a significant abrasive effect on the components of wind power turbines.
All of this makes the operating conditions of wind power turbines are very harsh, requiring high performance in the various mechanical systems.
In addition, due to the difficulties in accessing the turbines, one of the main priorities is to prolong the regreasing periods and use specific greases for each component of the turbines.
The main bearing is subject to large fluctuations due to the wind, generating high loads of thrust. Working conditions such as high loads, low speeds, vibrations, etc. make the conditions of elastohydrodynamic lubrication (EHL) are very difficult to achieve, so the use of greases formulated with oils with a viscosity of up to 460 cst, with good stability against oxidation, good behaviour against water and low temperatures.
The generator bearings are subject to moderate and high speeds, high loads, high vibrations and high temperatures so we recommend using medium viscosity greases (ISO VG 100), which have excellent behaviour at low temperatures, high resistance to vibrations and good stability against oxidation. Generally greases with a degree of consistency NLGI 2 are used.
The blade bearings work at high loads and vibrations, with an oscillating movement. Vibrations give rise to problems of fretting (corrosion and wear), so greases with a high resistance to corrosion, excellent resistance to the false brinelling and fretting, excellent stability against oxidation and resistance to water are used.
The general tendency is to use the same type of grease in the main bearing, the blade bearings and the yaw bearings. Nevertheless, for the generator bearings a grease with a lower viscosity is usually applied.