Machinery Lubrication

Machinery Lubrication March April 2014

Machinery Lubrication magazine published by Noria Corporation

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As I see It 2 | March - April 2014 | In a previous issue of Machinery Lubrication, I discussed the concept of Overall Machine Criticality (OMC) and its importance on a wide range of decisions relating to machinery lubrication and oil analysis. These decisions, when optimized, define the Optimum Reference State (ORS) needed to achieve the desired level of machine reliability. It is intuitively obvious that smart maintenance decisions require a heightened sense of both the probability and consequences of machine failure. However, when lubricants fail, there are consequences that are, at least initially, independent of machine failure. These include the lubricant replacement cost (material, labor, flushing, etc.) and associ- ated downtime. These costs can exist in the presence of a perfectly healthy and operating machine. Of course, lack of timely replacement of a defective lubri- cant will invariably lead to dire machine failure consequences. For some machines, these cascading events can produce enor- mous collateral damage and financial hardship to an organization. In the next issue of Machinery Lubrication, I will explain how nearly all decisions related to lubricant analysis and inspection depend on four factors: Overall Machine Criticality, Overall Lubricant Criticality, Machine Failure Modes Effects Analysis (M-FMEA) and Lubricant Failure Modes Effects Anal- ysis (L-FMEA). For instance, regarding inspections, these factors influence what to inspect, when to inspect and how to inspect. In relation to oil analysis, these factors affect where to sample, how often to sample, which tests to conduct, which alarms to set and the general data-interpretation strategy. Machine Criticality vs. Lubricant Criticality Figure 1 shows the relationship between machine and lubricant failure. On the left are common causes of lubricant failure and machine failure. For example, heat, aeration and contaminants are known to be highly destructive to lubricants. In a similar sense, overloading, misalignment and contamination can abruptly cause a machine to fail. Note how contamination not only can fail a lubricant but also can fail a machine directly without the need to harm the lubricant first. You could say the lubricant is complicit by transporting contaminants to sensitive and critical fric- tional surfaces. When a lubricant fails, there is imminent danger of machine failure, hence the downward arrow from lubricant failure to machine failure. It is best to not only list failure causes but also rank them in terms of probability and severity. This helps allocate resources by priority. From lubricant and machine failure come specific consequences, which are listed on the right in Figure 1. Again, these consequences are mutually exclusive. Lubricant failure consequences include oil replacement costs, downtime during the oil change, labor to change the oil and flushing costs. Machine failure consequences relate to safety, spare parts, labor to repair and downtime (e.g., production losses). There is slight comingling of these failure consequences. For instance, lubricant don't Forget lUBrICANt CrItICAlItY when designing oil Analysis Programs m a i n t e n a n c e a n d r e l i a b i l i t y JIm FItCh NorIA CorPorAtIoN Figure 1. The relationship between machine criticality and lubricant criticality

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