Inspection Time - How quickly should an electric motor be inspected? - HECO

How detailed do you want the inspection to be? A more detailed inspection can take time. Do we rush detectives to solve crimes or would we rather they spend a bit more time to make sure they get the right guy? The same applies to an electric motor inspection.

You can rush an inspection and get good results, I’m not saying you cannot. However, if you have a problem that will require out of the box thinking to try and solve, rushing the inspection process will probably lead to more of the same problems you have already been encountering.

However, stepping back and looking at things from a new angle; performing a site assessment to identify what the entire motor driven system is doing, evaluating and analyzing any historical information, reviewing predictive maintenance, vibration, etc. records, this all takes time. Now, not every motor inspection should require all of the steps, but to really dig into the root cause of an issue you must look at more than just the motor, which may have just been treated as a fuse if there is a bigger issue somewhere else in the power train.

Wanting to know what is wrong with the motor and the lead time associated with correcting those deficiencies is different than a root cause failure analysis. It isn’t rocket science to tear apart a motor and see what is wrong with it. If the bearing failed, you can see it. If a winding failed, there may be a big blow hole in the winding. However, in finding what truly caused the issue may not be so obvious. Here is an example:

A motor is received into a repair shop because it “blew up”. OK, we know going into the inspection that it is most likely an electrical issue. So, we go through the inspection process and check everything out with the motor. As soon as we pop the drive end end bracket off, we notice the drive end bearing failed. There are signs of rust and water just fell out of the end bracket. We continue on with the inspection and do indeed find a spot where the winding blew to ground. Looks like water getting into the stator/winding area must have caused this.

OK, inspection is done. We can replace both bearings, rewind the stator, balance the rotor, and re assemble everything and move forward. The motor will run smooth and there will be no issues…

WRONG!

We put a band-aid on the result of a failure versus realizing that the water contamination is what caused all of the issues. What should be done to stop the water ingress from taking place again? Is it in an area where a different motor should be sold instead? OR can you modify the motor with a different seal in order to stop the water from getting in again? Was water being around the motor an odd occurrence due to a flood and is unlikely to happen again?

A quick inspection and repair would have fixed what was wrong with the motor and the plant would have gotten up and running again, quickly. However, there were no steps taken to prevent this from happening again.

Failures will happen, mistakes will happen. The best we can all do is to learn from those issues to try and stop them from happening again. To do this, many times it takes out of the box thinking and not simply just fixing the obvious, quickly identified, issue.

Posted in Field Service