Inexpensive test methods do not provide all the information about the causes of wear. For example, determination of metals with AES is limited to particles smaller than 5μ. The PQ index shows only magnetizable iron particles.
Particle counting does not distinguish between soft or hard particles. With the O.P. A., the individual particles in the oil stream are imaged by photography. With the help of the computer, the particles can be enlarged and measured. Using the outline, size and appearance, the individual particles can be cataloged into different types of wear and aged oil components.
Particularly in the case of slow-running planetary gears (oil circulation systems, large engines, complex hydraulic systems, oil-lubricated systems), which are difficult to monitor with vibration or other sensors, the O.P. A. provides essential information about the wear condition and its cause.
The typical images of an optical particle analysis are sent together with the well-known laboratory report as a 3-page printout. The result is commented on separately in detail.
The following images are taken from an examined industrial gear oil CLP 320, as used in gears of wind turbines, in screw presses in the sugar industry or in extruders in plastics production. The oil, which has been in use for about 11,000 h, shows a significant increase in wear particles in the conventional analysis and a simultaneous degradation of the oil additives. An oil change and gear inspection for micropitting and fatigue wear was recommended. Details of the analysis are clear from the figures and the number of particles per type of wear using optical particle analysis.