Why does the motor bearing grease deteriorate or lose?
March 09, 2023
In the motor fault cases, more than half of the faults are caused by the quality problems of the bearing system. The light ones are manifested as bearing noise, and in serious cases, the bearings are scattered, which may also lead to the motor bore cleaning or winding burning accidents. At least one of the following appearances can be found in the dissection process of this type of fault motor: dry wear state of bearing or lack of oil; The grease turns black and agglomerates; The bearing has obvious mechanical or electrical corrosion damage. The motor with such problems will appear as bearing noise at the early stage of the fault. Because the object of the failure is clear, people will probably attribute the problem to the quality of the bearing, and naturally ignore the influence of lubricating grease and its related factors. 1. The lubricating grease is thrown out due to the rotation and movement of the bearing The design of bearing system is the key link to determine whether the motor can drive the equipment reliably. For cylindrical roller bearings with separable inner and outer rings, especially when the positioning end is not well controlled, there will be a certain amount of axial movement. Sometimes the frequency and strength of the motor shaft movement just reach the level similar to that of the vibrating screen, causing the grease in the bearing to continue to move in a certain direction, so under the centrifugal action during the rotation of the bearing, the grease is constantly thrown out of the bearing cavity. During the actual inspection, it was found that for the large cavity in the bearing system, there was no good restriction on the thrown grease, which could not play a role in the final lubrication, and would also hinder the heat dissipation of the bearing system.
To solve this problem, the following measures should be taken according to the specific situation: appropriately change the size of the inner cavity through the inner and outer covers of the bearing, add an oil baffle plate or oil slinger, and check the positioning relationship of each bearing pivot. 2. Why does the grease deteriorate? The main reason for the deterioration of lubricating grease is that the heating degree of bearing is higher than the working temperature of lubricating grease. If the processing and assembly accuracy of the bearing system is not bad, it may be related to the selection of lubricating grease, especially for motors operating in high temperature environment. There are more bearing heating problems caused by other reasons, which will not be repeated here.
Bearing heating and grease degradation failure are two factors directly related. Bearing heating to a certain extent will lead to grease degradation, and grease degradation will aggravate bearing heating. The lubricating grease running in the bearing is damaged by mechanical force, which causes the fiber of thickener to break and shorten, and reduces the ability to maintain the structure of lubricating grease, that is, the consistency change. If the consistency change is very large, it will cause loss from the working surface. At the same time, during operation, the lubricating grease will be affected by the temperature rise, and the Base Oil will evaporate and reduce or part of the base oil loss due to the oil colloid damage, which will reduce the oil content of the grease, and may also cause oxidation deterioration.
From the analysis of the actual operation effect of the motor products, the matching relationship between the lubricating grease and the bearing system and the environmental conditions is very important. Moreover, for any motor, the cost of lubricating grease is very small. Using high-quality lubricating grease can greatly reduce the bearing system failure.
