Laboratory evaluation of the on-line ferrograph

A laboratory evaluation of the on-line Ferrograph for fluids containing well-characterized debris indicates that the wear concentration, as measured by the instrument, is unaffected by variation in fluid pressure (0.21–0.65 MPa (absolute); 30–80 lbf in −2 (gauge)) and temperature (65–99 °C) within the range examined, that the difference between L, the concentration of large debris particles, and S, the concentration of small debris particles, describes the severity of wear and that changes in debris concentration at or near the level of 1 ppm can be detected. Correlation of on-line and analytical ferrographic data was apparent; such correlation was not found for spectrometric oil analysis, colorimetric iron analysis or particle count data. Start-up and low fluid temperature problems encountered with the unit may be avoided by sensor insulation and preheating. Additional field evaluations are required to determine suitability for many potential applications.