Wear detection by oil analysis

When wear is the most likely failure mechanism, oil analysis can be a powerful tool in identifying the early stages of wear. Almost by definition, wear implies a loss of material and that lost material has to go somewhere! Commonly this debris is swept away by the lubrication system. Oil filters are able to remove the larger particles but are likely to pass particles smaller than 5 microns in size.

Oil Analysis can be applied to systems that use oils as a lubricant such as engines, hydraulics, gear cases and compressors. The design of many of these systems has changed significantly in recent years. New surface hardening techniques have allowed smaller components for a given rating. These harder surfaces, while more resistant to particle induced sliding wear, are highly susceptible to particle induced rolling wear that can fatigue the hardened surface, but initially generate little wear debris. This results in small plastic-deformation craters, complete with raised rim, that become sites for rapid wear.

Oil analysis

Oil can be analyzed in line, or by used oil analysis in the laboratory. Due to the complexity of many analysis techniques, in-line analysis is usually simple and not as sensitive as laboratory methods such as:

• soot measurement
• spectrochemical analysis for metallic elements
• water content
• wear debris particle size analysis
• fuel dilution
• ferrography
• viscosity measurement
• dissolved gas analysis

References

An excellent general site for oil analysis is http://www.oilanalysis.com - and go to the "Learning Center"