Machinery Lubrication

Machinery Lubrication Jan-Feb 2018

Machinery Lubrication magazine published by Noria Corporation

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36 | January - February 2018 | www . LESSONS IN LUBRICATION • To what type of application is the bearing subjected? • What function does the application perform for the organizational goals? (How critical is the piece of equipment containing the bearing?) • What are the potential failure modes? (In what ways can the machine fail?) • What are the effects of the failure modes? (What is the consequence of failure on operations?) • What is the severity of each of these effects? (What's the relative impact of these failure modes on operations?) • What are the failure mechanisms for each failure mode? (What is the underlying root cause?) • How likely is it for the failure mechanism to exist? (What is the probability of the failure mechanism?) • What failure detection mechanisms are deployed? (What methods are there to predict the failure?) • How effective is the detection mechanism? (What is the probability of detecting the failure early?) With the answers to these questions, a risk/priority number can be calculated and recommendations for the best maintenance strategy determined. is article will highlight the most common failure mechanisms for a bearing as a result of lubrication (or lack thereof ). When analyzing these failure mecha- nisms, one can perform a lubricant FMEA. With this approach, questions are asked similar to those in the machine FMEA discussed earlier, but in this case the lubricant's failure root causes are identified as well as how they can result in a failure to provide lubrication to the machine. In his book, Machinery Failure Analysis and Trouble- shooting Vol. 2, Heinz Bloch states, "Lubrication-related bearing problems, according to our experience, are most frequently caused by lack of lubrication or lubri- cant contamination." is information is not new and has been reiterated by bearing manufacturers and end users through countless failure root cause analyses (FRCA). But why? Consider that rolling elements in bearings ride on a thin film of lubricant (often less than 1 micron) at the mating surface of the bearing race. With small contact areas, the pressure exerted on the surfaces can exceed 500,000 pounds per square inch (psi). If any lubricant is displaced by a foreign contaminant, such as dirt or water, at these critical load zones, the bearing eventually will experience increased wear. If the wear is excessive, the life of the bearing will be reduced significantly. e result is a contamination-induced bearing failure. But even when contamination is minimized, if the lubricant selected for the application does not meet the operating and environmental requirements, a lubri- cant- induced bearing failure will occur. erefore, whether it's excessive contamination or an incorrectly 42% of lubrication professionals say contamination is the most common cause of bearing failures at their plant, according to a recent poll at

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