Patch Testing and Wear Particle Analysis (WPA)

Method Light Microscopy and Electron Microscopy
Standards ISO 4407 (when combined with manual particle count)

What is it used for?

To isolate individual wear particles and determine from the shape, size and condition of the particles what caused them, i.e. the wear mode responsible.


How does it work?

Wear particles suspended in the oil sample are removed, usually via magnetic, filtration or centrifugal methods. Particles and debris recovered is then reviewed under an optical or electron microscope.


The microscopic analysis identifies the types of wear debris present in terms of shape, appearance and size parameters. The quantities present can also be determined though gravimetric testing if required.


What do the results tell us?

Wear Particle Analysis (WPA) can be a powerful tool in analysing the health of machinery and determining modes of wear that are occurring within the system.


Extracted wear particles can ultimately be examined further using techniques such as SEM-EDX to determine the precise metallurgy of the wear particles formed.


In addition to wear metal detail, patch testing can provide additional info regarding lubricant content of soot (combustion related), rust (corrosion related), silicon-based material (usually dirt/dust), fibres and other residual matter.


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