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When to Perform Wear Debris Analysis - Part II
By Micheal D. Holloway, CLS, OMA I, MLT I, Manager - Strategic Accounts and External Training

Each asset has a life span. Often, it isn’t until premature failure occurs will an in depth investigation ensue. While inadequate lubrication, new component defects, the use of wrong components or materials, poor installation, or poor maintenance practices or workmanship are to blame, routine oil analysis combined with wear debris analysis might have indicated a pending failure. It is not realistic to have wear particle debris analysis performed on every asset but it is entirely reasonable to test critical assets for wear debris on a scheduled basis. It is also recommended to perform wear debris analysis when beginning an oil analysis program. This will help establish which assets may be most vulnerable to failure.

Lubricants have several functions; reduce friction and wear, protect against rust, corrosion, oxidation, transfer power, act as a seal, clean and flush surfaces, keep contaminants in suspension. These are all well-known functions. A lesser considered function yet not less important is to act as a conduit of information. The lubricant can provide insight into what is occurring within a system without having to disassemble and inspect. Prior to an oil sample being drawn for wear debris analysis, it is prudent to consider the following observations; overheating, high vibration, high system pressure all may indicate it is time to analyze the oil for wear debris. Once an oil sample is tested, there will be a indicators which will encourage the use of wear debris analysis. Data can only be meaningful if a there are more than one test performed. The first indication will be an increase in wear metals (Fe, Pb, Sn, Al, Cu) over a period of several tests. These metals are common in lubricated systems. Secondly if there is an increase in the Particle Quantified Index value (PQI). The PQI is a test which measures the distortion of a magnetic field applied to the sample while still in the bottle. It is used to quantify ferrous particulate. The test has limitations. It does not measure non-ferrous metals and a single large particle reads like many smaller particles. The Particle Quantified Index is useful when used in conjunction with the wear metal concentration. When PQ Index is lower than the iron (ppm) from ICP, chances are there are no particles larger than 10 microns. If the PQ Index increases dramatically while the iron (ppm) remains consistent or decreases, larger ferrous particles are being generated. The use of this increasing trend triggers ferrography or wear debris analysis.

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