EFFECTIVE USE OF THE PATCH TEST FOR SIMPLE ON-SITE ANALYSIS

The very best oil analysis programs incorporate some degree of onsite analysis. For most plants, mills, and mines, particle monitoring is the most productive onsite oil analysis activity available.

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Studies show that particle contamination is responsible for up to 80% of lubrication-related machinery failures. Hard particles can enter the system through seals, breathers, new oil changes, and top-offs. They can also be generated within the system from component wear. These particles can abrade, fatigue, and erode component surfaces - robbing them of precious life.

Because particles cause so many problems, they should be monitored regularly and controlled by filtering the oil or changing it as required. Particles are generated when a machine fails, and monitoring for increased generation of wear debris alerts the technician of an impending failure.

The simple patch test enables the technician to quickly identify abnormal levels of contamination and wear debris so that corrective actions can be scheduled accordingly. While several excellent automatic particle-monitoring devices (particle counters and wear debris meters) are available, low-cost patch microscopy allows onsite particle monitoring without spending a great deal of money.

The patch test can help maintenance personnel determine if onsite particle monitoring suits their needs. It can also provide them with experience and information that will help them determine if a more sophisticated particle-monitoring device is needed and, if so, which device best suits their needs.

The procedure for performing low-cost patch microscopy is explained below.

Analyzing Debris on the Patch

After the patch has been prepared, a number of things can be determined by visually examining the debris collected on the patch.

First, by using the 100 X magnification microscope, a comparison may be made with a catalog of standard patches, which can be obtained from numerous sources. The appropriate ISO Cleanliness Code can then be estimated.