After a motor with large vibration is disassembled, the grease in the bearing turns silver gray (originally milky white), what is the problem caused? Is it normal for bearing grease to change color? What color is normal for oil to turn? To what extent is normal? Some bearing grease is also discolored, from milky white to brown, and the discolored part is around the rolling body, what is the reason? If it becomes silver gray, it is caused by tight fit, small clearance and large friction, but the same bearing has the phenomenon of running in the outer ring. Why is that?

Grease placed (or running) for a period of time, there will be a lot of contact with oxygen, and metal (bearing itself) acts as a catalyst in this oxidation reaction. Therefore, when calculating the replenishment time interval of grease in bearings, the problem of oxidation should also be considered. Many greases now have antioxidant additives. That doesn’t mean it won’t oxidize.

The temperature (bearing itself, or the environment) will change, which leads to the base oil in the grease constantly in and out of the thickener, and each time the base oil goes back, it may not go back completely. After a long time, the performance of grease will change and lubrication will not be satisfied, so lubrication should be re-applied. Insufficient base oil grease, color may change. In addition, if the temperature is abnormal, the performance of the oil changes greatly, so that there will be discoloration. If the temperature is very high, it will carbonize. The color will get darker.

During the operation of bearings, impurities are mixed into the grease. This impurity may be the bearing itself peeling off, or it may be the outside into. May be solid, may be liquid, these will affect the properties of grease.

In addition, tight fit, small clearance, resulting in oil discoloration. The reasoning should be as follows: tight fit, small working (residual) clearance, increased bearing load area, heating, resulting in oil degeneration, resulting in oil color change. As for running laps, first of all, there may be problems with the coordination of the bearing chamber. Second, the internal clearance is too small and the friction is large, leading to running laps. The latter possibility can not be achieved by adjusting the fit. The overtones are worse.

In addition, according to the color of the grease to determine whether the situation is normal. This judgment is very difficult. Different lubricating grease has different internal additives, different operating conditions and different temperature ranges, so it is impossible to have a unified standard. Even for the same grease, the formula may be slightly different due to the different batches of the factory. It is not reliable to use color variation as a basis.

If  you have anyquestions,pls feel free  to contact us.

e-mail:bearing6@hyzcgroup.com