Value of Particle Counting in Oil Analysis

Noria Corporation

"Our power generation company uses a central laboratory for oil analysis. It performs routine particle counts using an optical particle counter on lubricants sampled from critical equipment (compressors, hydraulics, turbine oils, etc.). Recently, the lab manager recommended that the particle counting activity be discontinued. His reasoning is that our fluids have always been clean (less than 1 percent reportable), and therefore there is no justification for spending the extra time and money. Are there any risks associated with discontinuing the particle counts, and should another alternative be considered?"

If the central laboratory does not report significant variations in the solid particle contamination code, you might think that the oil in the machines is in good condition, that the oil supplier is excellent, that the machines do not have any wear, and that the oil filters and breathers are perfect. However, none of these things should be assumed until they are verified first.

Review the machine historical fails record. If the oil has always been clean, there should be a low fail rate associated with the lubrication in most of the machines.

Also, assess the oil change frequency. It is possible that the oil is always clean because it is frequently changed.

Next, confirm that the sampling is truly representative of the lubricant condition, and make sure that inspectors are collecting the oil in the correct form. If samples are being taken immediately post-filter, then particle counts will always be low.

Don't forget to evaluate the characteristics of the optical particle counter being used and its limitations. Check its calibration and the capacity of the personnel using the instrument.

Finally, take a series of samples and send them simultaneously to the current laboratory and two or three external laboratories to compare the results. Be sure that at least one of these laboratories uses the method of the current laboratory as well as another available method, such as the blockade of pores.

If you discover that any of these things are not true, take the appropriate actions to correct them. Specialized training or consultation may be required. If all of these things prove to be correct, you may want to consider changing the sampling frequency. However, do not stop the solid particle contamination monitoring. Remember, all it takes is one abnormal result to contribute to a major problem, and catching this one problem will more than provide the justification for spending the extra time and money.

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