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In oil analysis, defining contamination is relatively easy. Contamination is a particle in the oil that is not specifically part of the oil itself. Identifying, removing and controlling contamination, however, is not as easy as defining it.
When receiving data for several hundred oil samples, it is common to return more than 85 percent of the oil reports to the customer in an "action required" status for contamination. This contamination varies between excessive levels of cleanliness to water contamination, with the occasional incorrect lubricant used as a top-up. This number suggests a definite problem in relation to contamination control. It is commendable that end users are utilizing an appropriate test slate to monitor for contamination. The problem lies in the following month: again, data for several hundred oil samples, most of which were sampled the previous month due to a 30-day sample interval, and 85 percent being returned in an "action required" condition due to contamination.
Let's first look at what I consider "action required". Most oil analysis reporting strategies are categorized with three to five levels of alarm. The three basic levels are defined as follows:
Normal - No action is required. All tests performed had results within the established parameters for that specific sample point. If measured, the ISO cleanliness level is at or below the target level. The lubricant properties measured indicate no adverse lubricant health condition exists and continued use of the current lubricant is acceptable.
Caution - An initial alarm has been broken. Further action is required in order to avoid a critical condition taking place. This action can be anything from drawing a new sample for data confirmation to installing permanent kidney loop filtration. It is at the caution alarm where exception testing would take place for samples showing increased levels of wear, possible water contamination, etc.
Critical - A second, higher level of alarm has been broken. This level indicates a condition that requires attention in relatively short order.
Table 1 shows various conditions and actions for the various levels of alarm mentioned above. This table does not cover all instances or possible conditions of a machine or an oil sample, but is meant as a general overview for better understanding as it relates to the scope of this article.
With a better understanding of what "action required" consists of, we can now explore contamination on a new level.
Monitoring contamination via particle counting is paramount for process critical machinery. While particle counting can be used as a confirmation tool for wear debris, its main purpose is as a proactive test. When the ISO cleanliness level of a sample point exceeds the desired target, appropriate action must be taken in order for that point to return to an acceptable condition.
Water contamination is commonly misunderstood. A lubricant change does not fix a water contamination problem. This is an important statement worth repeating. A lubricant change does not fix a water contamination problem. All too often, recommendations are made to investigate for the source of water and to repair appropriately. More precise recommendations have also been given to help deter water ingress, such as the instruction to "replace the current desiccant breather with a high-quality hybrid-style breather, incorporating the benefits of desiccant to remove internal condensation and an expansion chamber to seal against external ingress." Even with precise recommendations, it is common to hear that the client simply changed the oil, only to find the next sample to have high levels of water contamination as well.
Table 1. Alarm Levels
Steps in Contamination Control
In Noria's Oil Analysis Level I training seminar, we teach three steps in contamination control. These include the following:
Set target cleanliness levels. This also includes setting a maximum water contamination level. These levels should reflect the reliability goals of the end user. If you do not desire a high level of reliability for a component, you may not need to set the targets values as tight as a mission-critical component of the same type.
Take specific actions to achieve targets. This is the step that is often missed. If you have set a target value of 16/13 for a gearbox, then you must set that gearbox to achieve and maintain this level of cleanliness. This includes appropriate sample porting, quick-connects for proper filtration, and an appropriate breather for the environment. Failure to deploy all required action will result in missed opportunities and frustration.
Measure contaminant levels frequently. If you are sampling a component only on an annual or semiannual basis, it is likely you are not concerned with contamination control. For components critical enough to warrant contamination control monitoring, a 30-day interval is highly recommended. This will achieve a high level of trending and allow for early detection of ingression.
Contamination is the leading cause of equipment failure. A quality analysis program will help guide you in the direction as it relates to contaminant removal and exclusion however; the most important proactive maintenance step lies in the hands of the end user: work order execution. Without properly executing the recommendations for contamination monitoring, you can never expect to achieve lubrication excellence.