Recent advances in wind-energy lubrication are aimed at supporting increased turbine efficiency. Synthetic lubricants have received considerable attention mostly due to their reputation for improved performance over conventional mineral-based oils. A few specialized lubricants with characteristics intended for particular tasks include low-temperature fluidity and long oil life. Such lubricants provide benefits for difficult to maintain wind turbine gearboxes. It is generally accepted that synthetic gear oils in several formulations offer protection from common failure modes, including micropitting and bearing wear. One formulation is intended for yaw and pitch drives. And greases are formulated to protect bearings against fretting corrosion, moisture contamination, and false brinelling at temperatures as low as -55ºF.
One idea suggests the reduction of maintenance costs by switching to a single lubricant for all bearings within the hub and nacelle. Sufficient lubrication of high and low speed bearings is achieved by combining the proper blend of base oil with selective additives. Pitch and main bearings are protected from wear related to false brinelling and boundary friction while generator bearings operate with the required film thickness and thermal stability. The lubricant is suitable for automatic lubrication systems and shows excellent performance at low temperatures.
In addition, a new product has been introduced for pitch and yaw gears (open gears) because the lubrication requirements for those gears are significantly different than the requirements for bearings. The recently introduced white, adhesive grease provides excellent protection against wear from high loads and corrosion from extreme environments. The thixotropic nature of the lubricant presents an opportunity to reduce the amount of grease needed to adequately lubricate open gears. Traditionally, open gear lubricants were challenging for automatic lubrication because the formulations contained base oil with high viscosities in combination with increased amounts of solid additives. But now, the developer offers a product which can be automatically applied at extremely low temperatures.
For gearboxes – enclosed gears – significant options are available. An oil life beyond five years for main gearboxes is easily achieved with formulations based on polyalphaolefins or polyalkylene glycol. The new technologies impart excellent behavior when exposed to moisture while enhancing the protection against wear across a wide range of temperatures, speeds, and loads.
Turbine operations in remote areas with extreme climatic conditions add to the lubrication challenge. Whether it’s to extend maintenance intervals and increase reliability with low-temperature hydraulic oils, or to protect blade bearings from fretting corrosion and false brinelling there is a wide range of lubricants from which to choose. Another lubricant manufacturer has developed a dry lube that it aims at extreme temperature applications. The dry lubricant incorporates graphite and molybdenum disulphide.