The pitch bearing is the key component of the wind turbine. It has harsh operating environment, high maintenance cost, complicated stress conditions, and directly affects the continuity, stability and accuracy of the entire pitch action. In order to ensure the reliability of the pitch bearing life Therefore, the pitch bearing needs to be well sealed and lubricated. With the increase of the operating time of the wind turbine, the sealing ring of the pitch bearing is gradually aging, the grease is gradually deteriorated, the waste grease is not discharged smoothly and the pitch bearing is not fully rotated, resulting in uneven internal pressure, which will cause the pitch bearing sealing ring. There are different degrees of grease leakage, if not dealt with in time, it may cause poor lubrication of the pitch bearing, thereby affecting the service life of the pitch bearing and the wind turbine. There are many reasons for the grease leakage of the pitch bearing. Due to the long period of tracking observation and verification, it is difficult for the sealing test bench to simulate the actual working conditions of the pitch bearing, and the research on it is not systematic and in-depth. The reasons are analyzed and summarized. Reasons for Pitch Bearing Grease Leakage 1 Poor sealing 1.1 Aging and wear of the sealing ring Most of the pitch bearings use NBR sealing rings, which will age after long-term use. , anti-aging agent and use environment and other factors, under normal circumstances, the service life of nitrile rubber sealing ring is 5 to 10 years. The pitch bearing adopts contact seal. During operation, the seal ring is in contact with the sealing friction surface. With the increase of operating time, the seal ring will gradually wear down, resulting in a decrease in sealing performance and insufficient pressure on the seal ring. The grease may be removed from the seal ring. leaks. 1.2 Unreasonable structural design of sealing ring Pitch bearings generally use double-lip sealing rings. The outer lip can prevent moisture, dust and other harmful substances from entering the bearing, and the inner lip can prevent grease leakage. If the structural design of the sealing ring is unreasonable, the sealing effect will be affected after installation, and the sealing ring may be deformed after the operation of the pitch bearing, resulting in insufficient sealing capacity or failure of the sealing, and the grease is easy to leak. 1.3 Improper installation and maintenance of the sealing ring If the sealing ring is not installed or maintained according to the process, the force of the sealing ring will be uneven. When installing the sealing ring, the poor bonding of the interface will cause the sealing ring interface to break, and the sealing ring will easily appear after the subsequent operation of the pitch bearing grease. Bulge, warpage (Figure 1) and breakage, allowing grease to escape from seal gaps, warpage and breakage. Figure 1 Warpage of the pitch bearing seal ring 1.4 Seal ring extrusion damage When installing or maintaining the wind turbine blades, a hydraulic tensioner needs to be used to apply torque to the connecting bolts between the blades and the pitch bearing, and the distance between the connecting bolts and the seal ring is relatively short , and the external dimension of the stretching head of the hydraulic stretching device is large, and the stretching head is easy to press the sealing ring and cause serious damage to the sealing ring, as shown in Figure 2. Subsequent operation of the pitch bearing may cause deformation and tearing of the sealing ring, resulting in a large amount of grease leakage. Fig. 2 Extrusion damage of the pitch bearing seal 2 Unreasonable design of the internal structure of the pitch bearing 2.1 Channel structure The design of the pitch bearing channel affects the fluidity of the grease in the internal groove of the bearing. Under normal circumstances, the pitch bearing is filled with grease from the grease injection hole, and the pressure difference required to discharge waste grease from the grease discharge hole is less than the pressure value that the sealing ring can withstand, and is greater than the resistance value of the grease flow, then the sealing ring No grease leaks anywhere. The required pressure difference is closely related to the resistance of the grease flow. The smaller the resistance, the smaller the pressure difference is, and the larger the resistance, the larger the pressure difference. If the internal channel design of the pitch bearing is unreasonable, the flow resistance of the grease will be large, which is not conducive to the uniform distribution of the grease and the internal pressure. overflow. 2.2 Grease hole size and distribution The grease injection hole and grease discharge hole of the pitch bearing should be distributed at reasonable intervals to ensure that the bearing can smoothly inject new grease and discharge waste grease. The distance between the adjacent grease injection hole and the grease discharge hole should be moderate. If the distance is too short, the pressure of the grease injection hole will be high and the pressure of the grease discharge hole will be small during refueling, and the newly added grease will be easily discharged from the grease discharge hole. If it is too long, the local pressure on the sealing ring will be relatively large during regreasing, which will easily lead to grease leakage. In addition, the diameter of the cross section of the grease discharge hole is too small, the diameter of the mouth of the grease collection bottle connected to the grease discharge hole is too small, and the distance between the two adjacent grease discharge holes on the bearing is too large, which will also increase the resistance of grease discharge, resulting in insufficient grease discharge. smooth, so that the internal pressure of the pitch bearing is too large, resulting in grease leakage. 3 Improper selection of lubricating grease or unreasonable setting of lubrication system 3.1 Improper selection of lubricating grease The selection of lubricating grease usually refers to the actual working conditions of the pitch bearing, and also needs to consider the consistency of the grease and the type of additives. The consistency of the grease is closely related to the ambient temperature. For every 5 ℃ drop in the ambient temperature, the consistency will double, and the fluidity of the grease will become worse. The solidification phenomenon blocks the grease path system, resulting in the failure of the grease to be discharged normally and leaking from the sealing ring.As shown in Figure 3. Figure 3 Cured grease at the pitch bearing drain hole