1. The quality of the bearing itself
The bearing has problems before unpacking and assembly, such as loose cage rivets, cage deformation and bumps, scratches on the rollers or raceways, and even the bearings are rusted. Because the bearings are newly manufactured by random inspection, individual bearings with these defects are likely to be loaded and used as qualified products. Once loaded and used, the bearing will inevitably be alarmed.

2. Improper assembly leads to bumps on the bearing
When assembling motor bearings, a hydraulic machine is generally used to press the outer ring of the bearing into the bearing chamber. If biased during the press-in process, the outer ring is likely to be deformed and damaged. It is not allowed to use percussion to install the bearing into the bearing chamber. When the rollers of the inner ring and outer ring are assembled, if there is any deviation, it is easy to produce axial scratches on the roller and raceway surfaces, which will cause an alarm when the bearing is running.

According to the analysis of dismantling and inspection:
1) There is an equilateral triangle bump on the edge of the raceway surface of the inner ring of the bearing, which is caused by the bump between the roller and the raceway surface of the inner ring during assembly.

2) There are obvious circumferential scratches on the inner ring of the bearing, which is caused by foreign matter entering the bearing.

3. Cleanliness impact
3.1 Grease cleanliness
Bearings have high requirements for the cleanliness of grease. If the added lubricating oil is mixed with particles such as quartz sand, iron filings, etc., it will cause permanent damage to the bearing during the operation of the bearing, which will seriously affect the use of the bearing.

3.2 Cleanliness of parts
Bearing-related parts include bearing caps, oil guide tubes, end cover bearing chambers, etc. If these parts are not thoroughly cleaned, impurities will be mixed into the bearing during assembly, which will affect the use of the bearing.

3.3 Assembly environment
When the bearing is assembled, the surrounding environment has a lot of dust, which is mixed into the bearing chamber or bearing grease during the bearing assembly process, which will also cause bearing failure

4. Current corrosion
After the bearing is assembled and in use, due to external reasons, an unknown current flows through the bearing, which will cause current burning points on the bearing raceway surface and rollers, which will affect the service life of the bearing. This type of current corrosion is generally nothing more than two types. One is that after the completion of the locomotive, the incorrect lap position of the return wire during the electric welding construction causes the bearing to be energized and causes electric corrosion; the other is that the motor itself generates leakage current or the motor is running. After the blasting occurs, electric current flows through the bearing to produce electric corrosion.

5. Use and maintenance
When the locomotive was used in the section, it did not receive normal and effective maintenance. Such as: regular quantitative refueling is not carried out, the cleanliness of refueling and the amount of refueling are not controlled, the type of grease added is not uniform, and problems such as bearing oil leakage occur from time to time.