hat useful life can you expect from a motor if it is installed and maintained with an eye toward precision?
Reducing vibration, no doubt, reduces fatigue and failure – as proven by Dr. Wernher von Braun and leading reliability engineering schools – therefore, increasing a component’s life span. It’s the easiest path to lower costs, improved uptime and improved morale. Yet, 80 to 90 percent of organizations pay little to no attention to this initially.
The rule of thumb is lower vibration by 20 percent and double the life of the bearings. Keeping an eye on precision through vibration reduction has a lasting effect on numerous mechanisms that play a large role in a company’s success.
Figure 1 shows actual results obtained by implementing and
insisting on precision installation and maintenance at the world’s largest pulp and paper mill.
Figure 1: The yearly decline in total motor failures following precision installation and maintenance
Prior to precision state, the average life of the mill’s motors was 19.6 years. By concentrating its efforts on the troublesome and costly motor positions first and insisting that the hundreds of others vibrating at higher than new minimum acceptable levels be put into a precision state, the mill could easily double the life of its electric motors. Conversely, the mill could cut the failure rate in half in just four years, which it did, achieving an average life of 46.1 years. Some eight years later, the rate has been sustained and now reflects an even higher average motor life of 52.8 years.
Reducing vibration will exponentially improve bearing life and, since bearing clearances control most of rotating equipments components’ life, by association, rotating equipment life is also increased. For every 20 percent that you lower vibration, you easily double the life of the bearings. Do this on a systematic basis across the plant and you will not believe the other costs that will go down and the uptime that will go up. This is accomplished by applying the following vibration and precision actions and using the plant’s fleet vibration, downtime, cost, or similar metrics.
- Identify the Top 10 equipment vibrations in each area. Assign responsibility to individual mechanics to put the equipment in precision state after defining proper expectation settings of what precision state is and how to get it without spending more than a few hours of mechanical downtime.
- Go beyond the Top 10. Some plants make the huge mistake of only working on the Top 10.
- Set monthly or quarterly expectation goals. For example, in one company, crew leads were expected to put a certain amount of additional equipment in a precision state each quarter and the results were audited (i.e., no pencils or keyboards “whipping the number”).
- Be sure to eliminate errors. Mechanics responsible for precision expectations should identify and eliminate common assembly errors made daily in every plant by mechanics and construction workers.
- Work to establish
strict precision measurements for fit and tolerance in plant repair shops and audit outside repair shops, bringing along mechanics and one engineer, to ensure these shops work to your standards not theirs, unless their standards are better.
- Ensure all field installs have zero pipe strain, no soft foot and are aligned for thermal growth, if needed, and to precision alignment expectations.
- Purchase new and rebuilt rotating equipment to G 1.0 balance specs.
- Ensure mechanics fill out and submit to the planner a precision field maintenance worksheet stating whether or not equipment was left in a precision state. This is most important and vital. No one should be scolded if the equipment isn’t left in a precision state, but they should note why they weren’t able to do so. Some reasons might be pipe strain; no time to correct; bearing housing worn out, none in storage, need to order; or precision alignment not possible because 60-year-old base is corroded away.
- Emphasize follow-up on the problems turned in by mechanics and first-line personnel of emergencies. It is vital that the planner, superintendent, or whomever knows that they have the responsibility to order parts and get back on schedule for repair.
It is a proven fact that vibration significantly decreases the overall life of all rotating equipment, including, but not limited to, bearings. If you want to dramatically reduce your overall maintenance costs and substantially increase uptime and profits, start by lowering the overall vibration of your plant’s equipment.
From Your Site Articles
Related Articles Around the Web