Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/704613
AS I SEE IT Align Inspection Strategy with Failure Mode Ranking As with any condition monitoring program, inspection strategy needs to be aligned with a ranking of failure modes for individual machines. The order of the ranking is risk-based, i.e., probability of occurrence times the consequences of occurrence. This alignment ensures efficient use of inspection resources and proper deployment of inspection methodology based on need. In other words, each failure mode on the ranking requires a corre- sponding inspection task or observation that enables the earliest possible detection. For each machine, start by ranking failure modes based on the probability and consequence. See the articles on failure modes and effects analysis (FMEA) at MachineryLubrication.com. Next, apply one or more inspection fault detec- tors for each failure mode. This may require training. For more on condition monitoring alignment to failure mode ranking, read my "Advantages of a Unified Condition Monitoring Approach" article at Machinery Lubrication.com. Beware of Short P-F and Sudden-death Failures As mentioned, the P-F interval is almost impossible to predict for a variety of machine-specific reasons. In fact, the interval can vary from seconds to decades. Maintenance departments like long reaction times to schedule needed corrections. Still Murphy's law always looms to ruin an otherwise perfectly good day. The best strategy to mitigate sudden- death failures is to focus on the early detection of root-cause fault bubbles. This is a fundamental proactive mainte- nance strategy (see the left side of Figure 1). Fault bubbles are escalating condi- tions that threaten the onset of an active failure event. As much focus should be spent on preventing the inception of failure as on detecting a failure in prog- ress. Every failure mode has one or more root causes. Ensure good root-cause alignment with your inspection strategy. Following are a few examples of short P-F and sudden-death failure modes and fault bubbles. What intervention strategy focused on root causes would you apply to detect and neutralize these threat- ening conditions? • Oil filter rupture • Wrong oil or severely degraded oil • Fish-bowl conditions (disturbed and mobilized bottom sediment) • Severe shaft misalignment • Stiction/silt lock of hydraulic valve (motion impediment) • Grease "soap lock" starvation of an autolube system • Impaired oil supply of a splash-lubed gearbox • Heavy fuel dilution of a diesel generator • Heavy chemical contamination of a compressor oil • Gross seawater contamination of a shipboard hydraulic fluid • Shock loading of a large thrust bearing Inspection Windows and Zones Inspection 2.0 is searching, detective work. It puts the machine under the micro- scope day by day. To do this, the machine's exoskeleton must be penetrated. You have to find ways to see through steel plate and cast iron. You must also "ready" machines for world-class inspection. New products, including modernized sight glasses, are being developed to bring vision to critical zones within the machine. One of my favorites is the bottom sedi- ment and water (BS&W) bowl. If this sight glass is properly positioned, anything that is heavier than the oil will accumulate there for quick inspection with a good light. This includes sediment, water, sludge, wear debris, coolant, dead additives and dirt. If your BS&W bowl is clear, bright and without sediment, there are many things that could be going wrong with your oil and machine that are not going wrong simply because this sight glass passes inspection. 4 | July - August 2016 | www.machinerylubrication.com This inspection window finds an active, threatening root-cause fault. Act now! Don't wait for lab results on percent water. Inspection 2.0 is intense and purposeful. It seeks to penetrate and extract information from what's been referred to as machine sign language. 70% of lubrication professionals perform daily visual inspec- tions of the oil at their plant, based on a recent survey at MachineryLubrication.com