Slewing Bearings for Wind Turbines

Wind Turbines Slewing ring bearings can be classified into three types: the yaw bearing, pitch or blade bearing, driving system bearing (spindle bearings and gearbox bearing).

The yaw bearings install into the joint between tower and cabin, the pitch bearing installed into the joint between the blades and hubs. Each wind turbine has a set of yaw bearing and three sets of pitch bearing.

Structure of Yaw and Pitch Bearing

Generally, the structure of yaw and pitch bearings is single row ball slewing ring four-point contact bearing and double row ball slewing ring four-point contact bearing. and both these two types can be further divided into bearings without gears, bearings with internal gears ,bearings with outer gears according to gear position . 

Single-row four contact ball slewing ring reference number

Double-row ball slewing ring reference number

Technique Requirement

1, Material and heat Treatment

 Rolling elements in yaw and pitch bearing are usually made of GCr15 or GCr5SiMn according to GB/T18254-2002.The heat treatment should comply with JB/T 1255-2001.Other materials with similar or better properties can also be used.

 The material of rings in yaw and pitch bearing is 42CrMo or others that meets technique requirement according to GB/T3077-1999.. The value of notched bar impact work shall be  no less than 27J at -40℃。

Rings of yaw and pitch bearing should be applied magnetic particle testing with requirement

Stricter than grade II according to GB/T 7736-2001.Hardness after hardening and quenching should be 229HB~269HB,for raceway after quenching 55HRC~62HRC.The effect hardened thickness of raceway should meet the requirement  in Table 4.Also ,it can be calculated  according to the loads on the bearing.

Table 4 Raceway effect hardened thickness Ds

2, Gear in yaw and pitch bearing

Gear in yaw and pitch bearing usually is in volute cylindrical gear with radial modification coefficient x=+0.5 or other values according to different requirements. Gear modulus should meet GB/T1357-1987.Gear precision should be no lower than 998GK OF GB/T 10095.1-2001 and GB/T10095.2-2001.

3, Tolerance and clearance

Generally radial and axial clearance of yaw bearing is 0~50 µm.

They can be adjusted according to customer requirement.

Radial and axial clearance of  pitch  bearing is less than 0.

Tolerance of yaw and pitch bearing is listed in table 5.

Table 5 Dimension Tolerance  unit:µm

Table 6  Rotating Precision   unit:µm

4, Seal

For yaw and pitch bearing, seal material should be NBR according to HG/T2811-1996 or better material.

We use world famous seals with good propertied and reliable quality for our pitch and yaw bearing.

5, Spacer and cage

Yaw bearing of our company has spacers that are self-lubricated, so best lubrication status between ball and groove contact areas could be maintain no matter whether the lubrication is evenly or unevenly distributed.

Our pitch bearing uses integrated steel cage which has simple structure and can save space and contain more balls to increase load capacity. Compared with traditional segmented cage, integrated cage is not only easier to assemble, but also more stable and reliable.

6, Anti-corrosion treatment

For yaw and pitch bearing, except for groove and gear , other surfaces should be  applied spraying anti-corrosion treatment according to GB/T9793-1997 and GB/T8427-1996 .When applied zinc coating , the thickness of anti-corrosion should be no less than 160µm. Other treatment can also be applied if it meets performance requirements of the machine

7, Other requirement

 If there are other special requirement, please contact with us.