May 2009

How Rate of Wear Impacts Oil Analysis
by Andy Widay
Business Manager, Eastern U.S. Region

When clean oil is first put into an engine, detectable wear metals are relatively low and can be attributed to carryover from oil trapped in the engine. As the engine operates, wear metals begin to accumulate. The rate at which wear metals are added can vary based upon a multitude of factors, including oil condition, operating problems, and the load demands placed on the engine. If wear particles do not have a way in which to exit the oil (such as filtration, magnetic drain plugs for ferrous particles, or oil leaks), they will continue to accumulate as long as the engine is in service. If the time interval between samples is not consistent, the effects of the variance will impact the accuracy of preset limits.

In 1996, ALS Staveley Services began working on “Rate of Wear” analysis as a means to eliminate varying drain intervals as a source of oil analysis error. The project was initiated to improve determinations made as a result of readings on wear metals that continuously accumulate the longer oil is in service. Extensive studies conducted on wear levels throughout oil drain intervals have since proven valid the theory that factoring the service life of the oil into threshold limits is imperative. In conjunction with statistical tools used to regularly condense the wealth of available sample data, these studies have helped to refine to a statistical science the process of setting limits for flagging abnormal data.

Normalizing test results using the service life of the oil requires that the information from the customer be complete and accurate. With today’s available technology, handwritten information on paperwork accompanying the sample is no longer the most economical way of accomplishing this. This information is often already stored electronically by the equipment owner for other purposes. Automating methods to transmit this information to the laboratory results in labor savings for the customer because customers spend less time completing forms. There are only two requirements to accomplish this operational efficiency: a data export file and a unique identifier on the bottle, such as a barcode. The testing laboratory’s laboratory information management system matches the customer data to the sample via the barcode scan.

The payback for accurately recording the in-service life of the oil and incorporating it into the interpretation of results is a higher level of precision that only adds value to the conclusions reached.

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