You may have encountered that the bearing works well, but from time to time there will be grease seeping out of the sealing ring....
You may have encountered that the bearing works well, but from time to time there will be grease seeping out of the sealing ring. If there is more leakage, it may cause oil everywhere. There are many possible reasons for oil leakage. This article tries to list some possible reasons for your reference in diagnosis.
First of all, we want to say that the scope of discussion in this paper is only for the normal operation of bearings, and the grease leakage caused by deformation and damage of ball and cage or sealing problems will not be discussed.
The first possible reason is that too much grease is filled. Generally, the filling amount of bearing grease is 1/3-1/2. Of course, the specific content also depends on the bearing type and speed coefficient. Generally, we can select bearings according to the filling amount of the manufacturer (except for those with special requirements), without any problems. When the amount of grease is filled too much and more, it occurs during bearing maintenance. The maintenance personnel want to add more grease, and the service life is longer. At this time, the grease leakage will occur. However, with the continuous reduction of grease, once the normal state is reached, the leakage will usually stop.
The second reason is the pressure difference between the inside and outside of the bearing. The reasons for this pressure difference are also diverse. For example, it is caused by internal gas expansion caused by high temperature, blockage of exhaust and oil drainage channels, strong convection of air on bearing seat, or vacuum adsorption effect caused by oil seal/inner ring rotating too close to a plane at high speed. These need to be considered during design.
The third is high temperature. In addition to the pressure difference mentioned above, high temperature will also make the grease soften with the increase of temperature. The softer the grease is or the stronger the fluidity is, the greater the tendency of seepage is. Bearing operating temperature is affected by ambient temperature, air flow, load, speed and operating time. These need to be considered in the analysis.
The fourth is the influence of external dynamic load. When external vibration and shock load are transmitted to the bearing, the sealing lip and sealing ring may be separated instantaneously, especially when the bearing is operating under internal thermal pressure. This separation gives oil a chance to spill. In addition, when the shaft has feed motion or brings tilting force to the bearing, the grease may be alternately deformed, resulting in the thixotropic flow of the grease, which may lead to leakage.
These are the four possible factors that cause bearing grease leakage. I hope you can help us with the problem analysis!
