Electric motors are moving countless industries and as essential as the bearings are to make them work so is knowing what causes bearing failure. Most of the time bearing failure is caused by improper use or lack of maintenance. Knowing the most common factors that cause it, bearing failure can be prevented or minimised.

Electrical erosion

It is caused by unintended currents flowing through the rolling elements from one ring to another. The currents are often generated by asymmetries in the magnetic field of an electric generator. It results in damaged rolling elements, degrading lubricant, and bearing failure.



Insufficient lubrication

To avoid metal-to-metal contact between the rolling elements the lubricant film between them needs to be thick enough and uncontaminated. In case of re-greaseable bearings make sure you maintain them regularly and with the right lubrication. If the lubrication is contaminated, the seals need to be checked for replacement. On the other hand, if the bearings are excessively greased this can lead to overheating and failure of the bearing.




Excessive vibration can also cause bearing failure. This can be caused by mechanical imbalance, rubbing parts, resonance or due to electromagnetic cause. Usually, this happens if a motor is transported without a secured rotor shaft or because it is stored in a place where it`s subjected to constant vibrations.



Improper installation

Making sure we use the right tools and are following the right procedures to install the bearings are the basics to avoid misalignment imbalance, belt tension or overloading.



Insufficient bearing load

If not preloaded, bearings always need a minimum load to function properly. This can be seen as  a smearing on the rolling elements or raceways and prevented by applying enough external load to the bearings. Note that especially when using cylindrical roller bearings which are intended to carry heavy loads.




This can be caused by high temperature in operating environment or bad power quality.

Bearings have different clearances to allow for thermal expansion in operation. Ensuring correct grease is applied to bearings and keeping the operating environment as cool as possible are some of the basic solutions to prevent overheating.


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