Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/544388
JIM FI T CH | NORI A CORPOR AT ION AS I SEE IT few years ago, someone mentioned to me that many of his machines were not good candidates for oil analysis because they used little oil that wasn't worth saving. He added that by the time you fl ushed the sampling port and pulled a proper oil sample, you've almost done an oil change. Why bother with oil analysis? I'm sure you recognize the misguided purpose of oil analysis in the mind of this individual. While oil analysis can certainly aid in better timed oil changes, it has so much more to offer. In fact, for machines that are mission-critical, the cost of changing the oil is small potatoes in comparison to the value gained from averting a catastrophic machine failure. If oil analysis was only about tracking the remaining useful life of the lubricant, only a fraction of the oil samples analyzed every year could be economically justifi ed. Think of the oil more as an information messenger of numerous failure modes and root causes of failure. As I've said many times, it's hard for a machine to be in trouble without the oil knowing about it fi rst. For most labs, the number of non-conforming samples from oil analysis will generally exceed 20 percent. In other words, more than one out of every fi ve samples has a reportable condition that requires a corrective response. For this reason, you must be prudent about which machines are selected for oil analysis as well as the sampling frequency. Like most reliability decisions, being wise in selecting machines to include in an oil analysis program requires a strategy of precision and optimization. This selection is a critical attribute of the Optimum Reference State (ORS) and demands careful consider- ation. Included in this is an assessment of machine and lubricant criticality, as described below. The Importance of Saving the Machine So many reliability and maintenance decisions hang on the assessment of Overall Machine Criticality (OMC). This includes oil analysis and all other machine condition monitoring methods. Critical equipment should be checked more frequently than less critical equipment. Based on the defi nition of "critical," this refers to the machines with the highest importance to you, your company and your process. Of course, it is essential to know how to defi ne an asset as crit- ical. There are many approaches to determine an asset's criticality. Some plants employ a simple 1 to 10 grading scale and subjectively assign numbers. The OMC assesses criticality in the context of lubrication. It is calculated at the multiplied product of the Machine Criticality Factor (MCF), which relates to the consequences of machine failure, and the Failure Occurrence Factor (FOF), which corre- sponds to the probability of failure. For a more detailed discussion of these factors and the OMC, see www.machinerylubrication. com/Read/29346/machinery-criticality-analysis. Using the OMC, a machine's candidacy for oil analysis is known by infl uencing factors such as: • whether the machine is exposed to failure-inducing conditions (loads, speeds, shock, contamination, etc.); • whether the machine is a bad actor (chronic problems); • whether the consequences of failure are high (safety, down- time, repair costs, environmental effects, etc.); • whether failures can be lubricant-induced (degraded or contaminated oil); • whether failures can be revealed by the oil (e.g., wear debris from shaft misalignment); and • whether early detection is important. O i l A n a l y s i s 4 | July - August 2015 | www.machinerylubrication.com HOW TO SELECT MACHINES FOR OIL ANALYSIS A What's in the Bottle? Oil Degradation Alerts Machine Impending Failure Alerts