Electrical Testing
Tip of the Week: Have You Reviewed Your Motor PM Procedures Lately?

Tip of the Week: Have You Reviewed Your Motor PM Procedures Lately?

Strive to correctly identify a maintenance problem before pursuing a solution.  

Sometimes, PMs get adjusted to solve a recurring problem. That is often a good thing, but it can go disastrously wrong. Make sure your adjustments solve, not exacerbate, the problem they are intended to solve.

Consider the following case history: A three-shift manufacturing plant in Georgia started experiencing a fairly high rate of motor failure. The response from the electrical maintenance manager was to increase the PM frequency.

Photo credit: stalkerstudent/iStock/Thinkstock

This manager was an individual who started as a floor sweeper and moved up over 20 years at the plant. Because of his lack of credentials, he was insecure and didn’t like having his authority challenged. Two electricians who had worked at other plants disagreed with his solution, so he found an excuse to give each of them a disciplinary write-up.

To increase the frequency with the existing resources required trimming back the PMs. The electrical maintenance manager needed to decide where to focus. After looking into the motor “autopsy” reports, he found the main problem was bearing failure.

Because the plant manager was not meeting his numbers, the electrical maintenance manager went all out to fix the problem. He put every motor on a monthly PM that consisted of greasing the motor and conducting vibration readings. The motors still failed at the same rate.

The Division VP now was not making his numbers because of the problems at this plant. So he fired the plant manager and brought a company veteran over from the division’s top-performing plant to get things under control.

The replacement plant manager looked at the resumes of the existing plant engineer and maintenance managers. He hired a new plant engineer, and together they hired a new electrical maintenance manager and a new mechanical maintenance manager.

The new hires re-assessed the failure data and concluded that motor bearing failure was the cause in all cases where a post-mortem was done. When told that PMs were done monthly, the plant manager expressed his amazement and said the PMs must be faulty. He was correct.

Here is what the plant engineer and two new maintenance managers found wrong with the PMs:

• Various greases were being used, some of which were incompatible and basically turning into sand inside those bearings.

• Nobody was trained on motor lubrication, and everyone involved was doing it incorrectly.

• It’s not that the motors were starving for grease, they were over-greased. The excess grease created so much heat, it caused grease to melt and drip onto the floor under the motor.

• No insulation resistance testing was done.

• No voltage measurements of the motor controls were being done.

The new motor PMs eliminated the greasing entirely. This would be handled by two technicians once they completed formal lubrication training. Each motor would receive only the recommended amount of grease and only by the recommended procedure.

What are some lessons learned here?

First, if you are a manager, you need to listen to your experienced people. Check your ego or insecurities at the door. If you are an experienced person dealing with a difficult manager, try to state your case in such a way that it looks like your manager’s idea; that is one way to get it accepted.

Second, don’t make assumptions about what solves a problem. Consider what often happens when a motor exhibits excess vibration. The technician tightens the mounting bolts. But this “solution” normally exacerbates the problem by warping the motor feet. To know how to solve a problem, correctly identify it first. In the case we looked at, that did not happen until new managers examined the problem.

Third, set up metrics for your solution. Measure before and after performance. If the inept manager had done this, he would have seen his solution wasn’t working.

Fourth, there are standard frequencies for PM tasks. A high failure rate doesn’t mean increasing those frequencies will fix the failure rate. Usually, the cause is the tasks are being done incorrectly. Making mistakes more often doesn’t produce a positive outcome. Always examine how the work is being done first.

Hide comments

Comments

  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
Publish