In my experience, belt driven equipment is oftentimes the least maintained of rotating machinery. Most people don't realize that v-belts are designed to last only 2-3 years, and that is only if they are properly aligned & tensioned and periodically checked for adequate tension. The sheaves are generally good for 6-8 years. So after every 3 belt changes, replace the sheaves!
Long ago I worked with a Gates engineering technician on a problem job site who proved to me how after the v-belts are installed, the tension is set so that the belts do not squeal on startup. If they squeal on startup, they are too loose! After the belts ran for 15 minutes, they must be tightened some more. (They squealed on startup again). After they ran for 1 hour-tighten again. After they ran for 3 hours--tighten again. After 1 day-re-tighten. After 1 week-retighten. And finally after 1 month, and every month thereafter, the belts have to be re-tightened! How many maintenance departments do you know of where this schedule is followed?
More importantly, what is the proper tension? In the past, the belt manufacturers printed charts whereby the tension for a particular drive was calculated for "general" applications. Those charts have now been replaced with the internet. Gates has 'Design Flex Pro' software you download free from the web at: www.gates.com . This is by far the best way to be sure you have the proper tension calculation for your application. Where do you find a tension meter? I am sure there are other places, but I simply go to the Gates website and order them for about $20 each.
The industry standard for v-belt alignment is 1/10" per foot of distance between the center of the shafts. We use a Laser alignment system to align the sheaves, so our final alignment is considerably better than the minimum required, and it is easier to achieve with our "modern" tools. Belt misalignment is the most common cause of premature belt failure. Misalignment increases overall vibrations, which in turn, decreases the efficiency losses of the motor. Loss of motor efficiency can be calculated into $$'s for each motor. When multiplied by the # of motors in a facility, the money lost through poor alignment & belt tension can be considerable-into the thousands!
A relatively easy way to check the condition of your v-belt drives is with an infra-red thermometer. According to Dayco and Gates reference guides, belt life is cut in half by every 35O F temperature rise above 85O F. Measure the temp inside one of the grooves of the sheave. If it is more than 20O-30O F over ambient, there is a problem with the belts, or the sheaves. There are sheave gauges available from any belt supplier to check the depth & pitch of the grooves. If the groove is shiny at the bottom, or shows more than 1/32" of wear, the sheave is ready for replacement.
PM for belt driven equipment involves sheave alignment and/or wear, and v-belt condition and/or tension. Regular monitoring is the key. Invest in PM, it will save you money.
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