Motor Repairs and Failure Analysis, Part 1

One common view of motor repair goes as follows:

1. Repair or replace motor.
2. Return to service.

This often results in a third step: repeat. If you have déjà vu with any of your motor repairs, the underlying problem is that your repair isn’t complete. You’re fixing the symptom (motor stopped, production down), not the problem.

Failure analysis allows you to determine why motors failed so you can solve for that cause. Several failure analysis methodologies exist.

Some involve diagramming (e.g., the wishbone diagram) and some involve charts or other techniques to help you isolate the failure cause. With one system, the first step is to eliminate potential causes so you deal with a shorter list of possibilities. With another, you sort failures into most likely, somewhat likely, and unlikely.

All of these systems rely on good data. Unless you have a failure analyst who evaluates every motor failure after the repair crew is done, the repair crew itself will collect the data. That crew needs to be trained in properly observing and identifying the clues that a motor failure leaves. They also need a quick, accurate way of recording and reporting those clues.

In our next issue, we’ll look at ways to get the correct information from the field so a maintenance engineer or other qualified person can determine the root cause. Good data will also help identify root causes that have been contributing to multiple motor failures, such as deficiencies in bonding, power anomalies, and incorrect lubrication practices.