Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/680544
14 | May - June 2016 | www.machinerylubrication.com With increasing pressure to drive down operating costs in order to boost operating profits, there is a real need to define an optimum approach. In the past, many organizations have exclusively used interval- based oil change criteria. The interval was based on an assortment of considerations, such as the calendar, operating hours (meter), fuel consumed, miles/kilometers driven or production/work performed. In many cases, an approaching outage and shutdown have a driving influence on the decision, coming from the desire to avoid unscheduled downtime later or the need to change lubricants "on the run." In addition, new equipment still under warranty may have OEM-specified lube change-out intervals, which can make the matter far less subjective (and optimized). The condition-based oil change strategy is indeed important in reducing oil consumption and associated costs. However, there are many situations with certain machines when maintenance and reli- ability are not "optimized" when the strategy is applied. In order to perform a condition-based oil change, there is added cost to moni- toring the conditions, namely oil analysis. There may also be added risk from running the oil too close to its end of life, which could lead to such challenges as the following: • a sudden and inconvenient need to change the oil, • wear and damage to the machine, and • the need to perform an expensive system flush prior to intro- ducing new lubricants (resulting from oxidation of the belatedly changed oil). Regardless, for most companies and machinery applications, the benefits of the condition-based oil change far outweigh the risk and cost. Corrosion costs companies billions of dollars each year. Much of this loss is due to the corrosion of iron and steel. When exposed to moisture and oxygen, iron and steel will react, forming an oxide. This oxide does not firmly adhere to the surface of the metal and will flake off, causing pitting. Extensive pitting eventually results in weakness and disintegration of the metal, leading to failure. The best way to stop rust and corrosion is not to allow the metal to come in contact with water, oxygen or acid. In essence, this is exactly what rust and corrosion inhibitors do. These additives are typically compounds that have a high polar attraction toward metal surfaces. They chemically bond to the metal surface, forming a protective film over the underlying metal. This film acts as a barrier that does not physically allow the metal to come in contact with anything that could promote corrosion. Some popular compounds being used are amine succinates and alkaline earth sulfanates. If rust formation cannot be prevented, the rust particles can flake off and contribute to abrasive wear. The iron oxide is much harder than the steel surfaces it comes in contact with, so massive amounts of three-body abrasion occur. Rust and corrosion are detrimental to your reliability program. Remember to always fight it at its root causes. Eliminate the root causes of a failure and you will reduce the likelihood of that failure's occurrence. Knowing when a piece of equipment is going to fail (predictive maintenance) is much more difficult than making it last long (proactive maintenance). Even more complex is root cause analysis (RCA), which is performed post-mortem, like an autopsy. Still, reli- ability professionals are increasingly stressing the importance of performing RCAs following all failures of critical machinery. As odd as it sounds, it is more productive to study failures than successes. After all, an apparent success may actually be a failure in disguise, more like a problem waiting to happen. Studying failures teaches insightful lessons in developing predictive and proactive mainte- nance strategy. Root cause failure analysis is a process of working backward through a sequence of events or steps that led to functional failure of the machine. This process is often referred to as "asking the repetitive why" or "the five whys." The first "why" is intended to reveal the obvious and more immediate cause, sometimes referred to as the direct cause. This is the suspect that first, and most often, bears the blame. However, by continuing the series of questions, one can often expose hidden causes that include contributing causes (partners in crime) and intermediate causal agents. With a little luck, your interrogation will lead you to the root cause. Keep in mind there may be multiple root causes. Interpreting an oil analysis report can be overwhelming to the untrained eye. Oil analysis isn't cheap, and neither is the equipment 5 Inhibit Rust and Corrosion (from September-October 2012) 6 Search for the Root Cause of Failures (from March-April 2006) Machinery Lubrication's 15th Anniversary 7 Learn to Interpret Oil Analysis Reports (from November-December 2013)