Why is the motor bearing grease degraded or lost?
July 04, 2021
In motor failure cases, more than half of the failures are caused by bearing system quality problems. The lighter ones are caused by bearing noise. In severe cases, the bearing falls apart, which may lead to motor borehole sweeping or winding burnt accidents. During the anatomy of this type of faulty motor, at least one of the following symptoms can be found: the bearing or the dry grinding state of lack of oil; the grease has turned black and agglomerated; the bearing has undergone obvious mechanical or electrical corrosion damage. Motors with such problems will show up as bearing noise in the early stage of failure. Because the target of the failure is clear, people will most likely attribute the problem to the quality of the bearing, and naturally ignore the impact of grease and its related factors. 1. Bearing rotation and movement cause grease to be thrown out. The design of the bearing system is a key link that determines whether the motor can drive the equipment to operate reliably. For cylindrical roller bearings with separable inner and outer rings, especially when the positioning end is not well controlled, a certain range of axial movement will occur. Sometimes the frequency and strength of the motor shaft movement just reach the level similar to that of a vibrating screen, causing the grease in the bearing to continue to move in a certain direction, so under the centrifugal action during the bearing rotation, the grease is continuously thrown out of the bearing cavity. The actual inspection process found that for the case of a large cavity in the bearing system, there is no good restriction on the grease being thrown out, and ultimately it will not have a lubricating effect, and it will 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 bearing inner and outer cover, increase the oil baffle or oil throwing device, and check the positioning relationship of each bearing fulcrum. 2. Why does grease deteriorate? The main reason for the deterioration of grease is that the bearing heat is higher than the working temperature of the grease. If there is no problem with the processing and assembly accuracy of the bearing system, it may be related to the selection of grease, especially for motors operating in high-temperature environments. There are more bearing heating problems caused by other reasons, so I won't repeat them here.
Bearing heating and grease degradation failure are directly related to two factors. Bearing heating to a certain extent will cause grease degradation, and grease degradation will aggravate bearing heating. The grease running in the bearing is damaged by mechanical force and the fibers of the thickening agent become fragmented and shortened, which reduces the ability to maintain the structure of the grease, that is, the consistency changes. If the consistency changes greatly, it will be lost from the working surface. The phenomenon. At the same time, during operation, the lubricating grease will be affected by the increase in temperature. The Base Oil will evaporate and reduce or part of the base oil will lose due to the colloid destruction of the grease, which will reduce the oil content of the grease and may also cause oxidative deterioration.
From the analysis of the effect of the actual operation of the motor products, the matching relationship between the grease and the bearing system and environmental conditions is very important. Moreover, for any motor, the cost of the grease is very small, and the use of high-quality grease can greatly reduce the bearing system error.
