When you are performing condition monitoring tasks, don’t just rely on expensive condition monitoring tools, some unusual and simple tools can be used. Here’s a preventive maintenance example from my early days in maintenance management consulting.
The bearing was not hot, but it the sound was getting worse during the last month. The maintenance manager in the board mill in Arusha, Tanzania was worried. The bearing was used in a slow-moving press roll, and if it failed the plant would shut down. This was 1978 and it would take time for the maintenance manage to get approval to import a new bearing which had to be paid in US$ not Tanzanian schillings. The delivery time for a new bearing was six months and in the best case only three months.
“I cannot prove to top management that something is wrong with the bearing. Any way you can help?” the maintenance manager asked.
I was in Tanzania for four weeks to set up maintenance centers and train plants in maintenance including preventive maintenance. I could have suggested methods like Shock Pulse Measurement (SPM), Wear particle Analyses in oil samples and more. These methods were, for this plant, too expensive and not available. I always travelled with a SPM instrument, but back then this instrument wasn’t reliable to prove something was wrong with very slow-moving bearings. Today this method has developed, and it can be used also for very slow-moving bearings.
By necessity, a big part of the training focused on basic and affordable inspection methods. For example, how to check misalignment and wear of a coupling using a stroboscope, checking the position of a by pass valve to find out if a heat exchanger needed to be cleaned before overheating a system, visual inspection of a V-Belt drive to see if pulley and/or belts were worn out , discovering and documenting level of pitting in gears, using lead wire to measure clearances, alignment and roundness of rollers in cement kilns and many more.
Simple and unusual condition monitoring tools
When you go to the dentist, he/she will use a hook to gently scratch the surface of your teeth. That way small uneven areas and cavities can be discovered. The dentist’s hook is one of the condition monitoring tools I still bring with me when visiting plants.
Both the upper and the lower bearing elements was accessible from the side by removing a cover plate. I suggested we use the dentist’s hook as a condition monitoring tool to examine the inner and outer ring surfaces for any unevenness during the next short scheduled shut down.
When we did the inspection, we discovered a damaged area in the load zone of the outer ring. We took polaroid pictures of the damaged area and then rotated the out ring 180 degrees to get the damaged area out of the load zone.
Using this very simple and inexpensive method for condition monitoring, the maintenance manager could convince decision makers to order a new bearing. The delivery time was four months and the bearing lasted until the new bearing arrived.
In this era of new technology, it’s easy to lose the knowledge of basic and simple methods. Most experienced mechanic crafts people most probably have a dentist’s hook in their tool box, but the next generation might not even know about this, and other basic methods.
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