After the motor with big vibration is disassembled, the grease in the bearing becomes silver gray (originally milky white), what is the problem caused? Is it normal for the bearing grease to change color? What color is it normal for the grease to become? 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 the silver gray 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 this?

Grease changes color in bearings, even if it is not placed in bearings, it will change color. This is because:

First, there are oxidation problems in grease. 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.

Second, the bearing runs itself, and the temperature (the 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 and turn dark.

Third, during the operation of the self-aligning roller bearing, 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.

Many people do not understand why bearings can not work under long-term load? This is because if the bearing is working under load for a long time, it may make the bearing strike in advance at any time, and some damage that cannot be estimated will appear, so do not let the bearing work under long-term load.

The importance of bearing installation

Correct installation of bearings is the guarantee of its service life extension. Many people without professional knowledge in this regard are not particularly in place when they are installed, which is prone to improper bearing installation and mechanical operation accidents. As a professional mechanical maintenance engineer, we must have some understanding of bearing installation.

Bearing long-term load work should pay attention to observe the track of raceway surface.

When the bearing rotates, the raceway surface of the inner ring and outer ring of the bearing is in rolling contact with the rolling body, so the running track is dark. The running track attached to the raceway surface is not abnormal, so the load conditions can be known. Therefore, when removing the bearing, please pay close attention to and observe the running track of the raceway surface.

If you carefully observe the running trajectory, you will know the radial load and axial load of the bearing, and whether there is extreme rigidity inequality on the bearing box. It can check whether the self-aligning roller bearing is added with unexpected load and whether the installation error is too large, and become a clue to investigate the cause of bearing damage.

e-mail:bearing6@hyzcgroup.com