Wind turbine works in the field all the year round, working conditions are bad, temperature, humidity and bearing load change greatly, wind speed up to 23m/s, and with impact load, so it requires bearings to have good sealing and lubrication performance, impact resistance, long life and high reliability. Because the generator will start in level 2-3 wind and can rotate with wind direction changes, special bearing structure design is needed to ensure low friction and high sensitivity requirements. In the design and manufacture, the material processing, heat treatment, lubrication, sealing and anticorrosion of large yaw bearings with outer ring teeth have special requirements, which require special design and research. The host life of wind turbine is set as 20 years. Therefore, the reliability life of wind turbine bearings is required to be the same as the unit life, and more than 20 years, because the bearing installation location is not easy to disassemble, and the disassembly cost is high, and the cycle is long.

Bearings are used in the rotor spindle, gear box (speed up machine), generator, yaw gear box (reducer), yaw rotating seat, blade moment rotating seat, hydraulic pump and other parts of the fan. The yaw bearing is installed at the connecting part between the tower and the cockpit, and the variable rotor bearing is installed at the connecting part between the root of each blade and the hub. The variable rotor bearing and yaw bearing used in the variable rotor and yaw system are the super large rotary bearing.

The main shaft bearing of the rotor needs to be started, accelerated, decelerated and stopped irregularly repeatedly while undergoing variable load. Therefore, in addition to the research on the design of rotor spindle bearing, bearing type, bearing clearance, bearing roller number, convex processing, cage structure and other conditions, especially the minimum load, average load, maximum load of bearing parts, as well as the best technical conditions are particularly important.

The design should take into account the maximum load, the necessary strength of the axle box and the deformation of the axle box under the average load. It is necessary to study the bearing life, select the thin axle box design that meets no extra burden, and fully calculate the life of the spindle bearing in practice.

In addition, it is necessary to consider the deformation of the axle box and outer ring raceway surface, calculate the load of each rolling body, and calculate the life of the rotating ring and the fixed ring respectively.

The sheer size of offshore turbines — which are typically double the capacity of onshore machines — and extreme wind loads mean great demands are placed on a turbine’s gearbox and main-shaft bearings. The potential for costly failures in offshore wind turbines runs high. This means it is vital to choose high-quality components with reliable system designs for efficient operation and minimal downtime.

Ideally, a bearing’s geometry, clearances, and load capacity are custom-engineered for the application’s operational conditions and this is particularly important in offshore turbines.

An improperly engineered bearing may cause too much pre-load, which may result in high stresses, high bearing temperatures, and a shorter life. Additionally, a bearing with too much clearance may experience excessive deflections, improper roller load sharing, higher stresses, misalignment, and edge loading, premature cage, or sliding damage. There’s a lot that can go wrong. (“Clearance” is the total distance that one bearing ring moves relative to another.)

Regardless of the form of damage, however, the result is the same: compromised performance of the turbine. Eventually, the bearing requires repair or replacement, leading to turbine downtime and lost operation. Technical expertise and product quality are necessary to successfully capitalize on the asset’s longevity and potential.

Offshore component repairs and replacements are also typically more costly than onshore ones. Replacing a damaged bearing in an offshore turbine requires a specialized O&M team with a transport vessel and the necessary equipment to correctly diagnose the problem. Additionally, it’s necessary to disassemble the turbine to repair the damage, which requires a costly offshore carane rental.