We looked at the motor maintenance activities in seven of our companies in six different countries. Each was a company plant built to corporate standards, with most rotating equipment having an installed spare. However, there were a variety of maintenance strategies in place.
Figure 39.1 summarizes our findings. It gives the percentage of each site's inventory of motors removed to the workshop for significant repair each year. These percentages have been broken down by reason for removal:
• Breakdown (i.e., the motor had been run to failure)
• Condition monitoring had indicated imminent failure
• Time-based overhaul regime in place for some or all of the motors
Considering this, we found that:
• The large proportion of time-based overhaul activities of Location 7 did not seem to reduce breakdowns significantly.
• Location 6 did seem to be somewhat more effective, but arguably was still not cost effective.
• Location 5 had many breakdowns, even though a significant percentage of motors were repaired because condition monitoring was predicting imminent failure.
• Their condition monitoring did not seem very effective in predicting and/or pre-empting failures.
• The site had an extreme blame culture.
• Location 1 had minimized repair efforts by using run-to-failure as a default strategy.
• The small amount of time-based maintenance was for a very few unspared furnace fans which were overhauled when the plants were shut down every four or five years.
• This location had a fairly skeptical view of the merits of condition monitoring. They would keep motors running until imminent failure was very apparent.
• What they also had found was that running motors less than 30 hp to failure did not result in significant additional consequential damage and cost compared to pre-emptive action.
• The proportion of breakdowns is fairly constant whether you do condition monitoring and/or overhauls or just let things run to failure.