Ferrography is an analytical technique in which wear metals and contaminant particles are magnetically and gravimetrically separated from a lubricant and arranged according to size and composition for further examination. It is widely used in oil analysis to determine component condition through direct examination of wear metal particles.
Complete ferrographic analysis consists of three parts:
- direct reading (DR) ferrographical analysis
- creation and examination of an analytical ferrogram
- interpretation and reporting of the results of an analytical ferrogram
DR ferrography precipitates the wear particles from a sample and electronically determines the quantity of “large” (over 5 microns) and “small” (1 to 2 microns) particles present in the sample. Wear calculations from these results indicate the rate, intensity and severity of wear occurring in the sampled machine. In cases where the DR ferrography wear trends indicate an abnormal or critical wear condition, analytical ferrography can reveal the specific wear type and probable source of the wear condition.
Analytical ferrography uses the Ferrograph Fluid Analyzer to concentrate and distribute particles directly onto a microscopic ferrogram slide by drawing the oil sample across a glass or plastic plate in the presence of a strong magnetic field. An experienced evaluator then examines the ferrogram to determine the composition and sources of the particles and the type of wear debris present.
An analytical ferrography report includes specific type and quantity classifications of the metallic and non-metallic debris present on the slide, a color photomicrograph of the ferrogram, an assessment of the sampled machine’s overall-wear status and a detailed interpretation of the ferrography results.