This article is based on Chinese national standard (GB/T 29717-2013) which regulates the structure, dimension, technical requirements of wind power generators yaw and pitch bearings.

The structure of yaw bearing and pitch bearing

1. Single row four point contact ball bearings

Dimension range of single row four point contact ball slewing ring: id 200 ~ 3000mm; OD 400 ~ 4000mm

2. Double row four point contact ball bearings with rolling elements of same diameter

Dimension range of double row four point contact ball slewing ring: id 1000 ~ 5000mm; OD 2000 ~ 6000mm

Technical requirements of yaw bearing and pitch bearings

1. Material and heat treatment
The slewing bearing rings material usually adopt 42CrMo, and can also use other materials based on customers requirements. Rolling elements material usually use GCr15 or GCr15SiMn. Normally Yaw bearings cage material is polyamide resin, while pitch bearings cage material is steel. The sealing rings are made of nylon for common working conditions. For severe environment such as strong acid, base or uv, please contact BRS technicians.

2. After quenching and tempering, the slewing rings low temperature impart energy(-40℃）KV2 should not be lower than 27J. Hardness 260 HBW ~ 300 HBW.

3. Slewing rings(after quenching and tempering) average grain size shouble comply with level 6~9 in GB/T 6394-2002.

4. After case hardening, the slewing bearings raceway hardness should be 55 HRC ~ 62 HRC, and the effective case depth should meet standards below:

Dw （Ball Diameter )	≤30mm	＞30~40mm	＞40~50mm	≥50mm
Effective Case Depth (min.)	3.0mm	3.5mm	4.0mm	5.0mm

5. Yaw bearing and blade bearings gear teeth surface and root should be case hardened, with surface hardness 50 HRC ~ 60 HRC. The effective case depth as below:

Module		＞6~10	＞10~16	＞16~22	＞22~28	＞28
Effective Case Depth (min.)	Tooth Surface	1.2mm	2.0mm	2.5mm	3.2mm	3.6mm
	Tooth Root	0.6mm	1.0mm	1.4mm	1.8mm	2.2mm

6. The width of the soft spots should not be exceed the load plug hole's diameter plus 35mm.