Equipment Particle Analysis is often confuses with Oil Analysis.  However, ferrography uses precision magnets to strip iron-laden and other susceptible particles from a used lube oil for study; results indicate extent of equipment wear and likelihood of imminent failure.

Direct-Reading Ferrography uses optical sensors to measure the density of particles collected and the ratio of large particles to small (fatigue-related catastrophic failure generally is characterized by generation of particles larger than 10-15 microns or um).  The DR obtains two-(2) sets of readings: first for Direct Large (D_L) >5um and the second for Direct Small (D_S) ≤5um  particles. The Wear Particle Concentration (WPC) is calculated by adding D_L + D_S = WPC divided by the volume of sample, establishing a machine wear trend baseline.  Other helpful particle calculations include:

Wear Particle Concetration	(WPC)	DL + DS = WPC
Percentage Large Particles	(PLP)
Wear Severity Index	(WSI)	(DL + DS) (DL - DS) = WSI

Analytical Ferrography employs photo and optical microscopic techniques for evaluation of equipment particles.  This evaluation involves discriminating the particles by Size, Shape, Composition & Concentration and relates these characteristics to the four-(4) known wear mechanisms or Rolling, Sliding, Spinning and Impaction. The test provides in-depth analysis of particle makeup discriminating metals from non-metal and ferrous metals from non-ferrous metals (e.g., high carbon steel (~12%), case hardened steel, cast iron, copper alloys, brass, bronze, aluminum, tin and corrosion or oxides).