By Jim Fitch & Holly J. Borden
Diagnetics Publishing
The inclusion of particle counting in the periodic analysis of hydraulic and lubricating fluids has provided an important new advancement to machine diagnostics. With particle counting, machinery users can monitor the principal cause of failure, not just the symptoms, or results, of failure. The benefit, when particle levels are controlled, is extended machine life and reduced failure frequency. This is the objective of the growing practice of proactive maintenance.
Along with this important trend has come the practical questioning of particle counter accuracy. It is estimated that by the year 2000, as many as 50 million particle counts will be performed on fluid samples each year. Hence, a failure to do particle counting with reasonable accuracy could effectively undermine user confidence and erode this incredible rate of growth.
While calibration techniques are available for most types of particle counters, the frequency and proper use of these techniques is not well understood. Likewise, it can be questioned whether the type of fluid and test particles (calibration fluid) used in calibration of particle counters is sufficiently close to field oils and field contaminants. Additionally, accuracy is also influenced by bottle cleanliness, fluid agitation, deaeration, dilution, dilution fluid cleanliness, and operator error.