Motors and Burned Bearings, Part 2

Bearing failures are a major cause of motor failure. Can you name some common causes of bearing failure?

Here’s a list of five common failure modes:

1. Improper lubrication. Mixed grease, too little grease, or too much grease can quickly kill a bearing. Motor bearing lubrication isn’t a grunt job, it’s a job that requires expertise.
2. Mechanical factors such as misalignment or a bent shaft. Ensure any critical motor has been balanced by a motor shop; check shaft runout on the other motors using a dial indicator. Perform laser alignment on all motors.
3. Excess loading. Check gear boxes for lubrication and operation issues. Ensure the motor is correctly sized for the application.
4. Harmonics, low power factor, or other anomalies. These can make the motor run hotter and that doesn’t help bearings.
5. Unbalanced current flowing through the bearings. If you see a ground rod near a motor, suspect someone tried to fix this problem. The ground rod won’t fix it, however. Bond all metallic objects (to help provide a path around the motor rather than through it). Ensure 100% integrity of grounded conductors (i.e., return path for 277V).