Bearing knowledge: the difference between pitch bearing and yaw bearing

1. Anti-corrosion treatment on the outer surface of pitch bearing and yaw bearing

According to the anti-corrosion requirements of yaw bearings, we adopt arc spraying long-term anti-corrosion technology. It uses special arc spraying equipment to melt, atomize, and spray corrosion-resistant metal (pure aluminum or zinc) on the surface of the workpiece to form a metal arc spraying layer, and then seal it with a corrosion-resistant coating with strong permeability to form a long arc spray. Effective anti-corrosion composite coating. Its technical characteristics are: ①Long anti-corrosion life, up to more than 20 years; ②High coating bonding force; ③Good coating quality. The process route: preparation of bearing inner and outer ring semi-finished products→pre-cleaning→workpiece pre-protection→sand blasting→arc spraying→sealing treatment.

1) Preparation of semi-finished products for bearing inner and outer rings

In order to ensure the high appearance quality of the yaw bearing, the anti-corrosion spraying process is arranged after all the mechanical processing, and the sprayed bearing parts are directly stored in the warehouse after the assembly is completed to ensure that the anti-corrosion layer will not be scratched.

2) Pre-cleaning

Use organic solvents for degreasing treatment. There may be oil stains on the surface of semi-finished bearings after mechanical processing. In order to ensure the quality of spraying, a cleaning process must be arranged before spraying.

3) Workpiece pre-protection

Before sandblasting and spraying, special surface pre-protection tools are used to protect the arc raceway, threaded holes and surfaces that do not need to be sprayed.

4) Sandblasting

Roughen the surface of the inner and outer rings of the bearing, increase the contact surface between the coating and the workpiece, make the surface of the workpiece more activated, and improve the bonding strength of the coating.

5) Arc spraying.

Arc spraying (pure aluminum or zinc) equipment mainly includes DC power supply, spray gun, air compressor and air filter, etc. It mainly controls parameters such as arc voltage, current, wire feeding speed, compressed air pressure, spraying distance and so on.

6) Closed treatment

Because there are pores in the sprayed coating, it must be sealed to increase the corrosion resistance.

After spraying and assembling, the main exposed processing surfaces of the yaw bearing are gear surface, mounting thread surface and arc raceway surface. The first two are coated with anti-rust oil after assembly, and the latter is coated with lubricating grease during assembly. The inner packaging of the finished product is wrapped with plastic film, and the outer layer is wrapped with plastic braid to meet the requirements of rust prevention.

2 Damping torque

2.1 The difference in formation mechanism of pitch bearing and yaw bearing

The damping torque after assembly of the yaw bearing has two sources: one is the friction resistance of the raceway part, and the other is the friction resistance between the sealing strip and the sealing surface. The latter is generally constant under the same processing conditions, so the damping moment after the yaw bearing is assembled mainly depends on the former.

The frictional resistance moment generated by the raceway part during rotation mainly depends on the size of the bearing clearance. Large gaps result in low resistance, and small gaps increase resistance accordingly. The yaw bearing requires zero or negative clearance, and the amount of negative clearance is determined by the friction damping torque after assembly. Therefore, the friction damping torque after assembly basically depends on the assembly clearance value of the yaw bearing, and the formation of this value mainly depends on: the size of the finishing before the raceway quenching, the raceway surface quenching, and the raceway quenching There are four options for grinding size and rolling element size.

Wind power bearings (yaw bearings, pitch bearings) have complex forces, and the bearings bear relatively large shocks and vibrations. Therefore, the bearings are required to withstand both shocks and large loads. The life of the wind turbine main engine is 20 years, and the cost of bearing installation is relatively high. Therefore, the life of the yaw and pitch bearings must also reach 20 years.

Wind turbines may work in extremely cold areas, the ambient temperature is as low as -400c, the bearing's operating temperature is around -200C, and the bearing must be able to withstand large impact loads under low temperature conditions.

Yaw and pitch bearings have special requirements in terms of clearance. Compared with the yaw bearing, the impact load of the pitch bearing is relatively large, and the wind blows on the blades and the vibration is also large. Therefore, the clearance of the pitch bearing should be zero clearance or a slight negative clearance value, so in the case of vibration It can reduce the fretting wear of the bearing. The yaw bearing requires a small clearance value.

The wind turbine equipment is working in the field, and part of the yaw and pitch bearings is exposed outside, which will be polluted by the atmosphere. The high humidity environment will also corrode the bearing substrate. Therefore, the exposed yaw and pitch The position of the pitch bearing requires surface anti-corrosion treatment.

The difference between the pitch bearing and the yaw bearing, that's it, I believe everyone has a certain understanding of the pitch bearing and the yaw bearing.