Fundamental characteristics of wear particle deposition measurement by an improved on-line ferrographic analyzer

Abstract An improved on-line ferrographic analyzer and its specific characteristics are presented. This analyzer is very convenient for detecting wear debris in a transparent oil pipe of a machine by using an electromagnet and a photoelectric sensor with a microprocessor. To eliminate the detection error of background colour of the oil sample, the wear index is redefined and can be directly calculated by the microprocessor in this analyzer. This detected value can represent the covered area rate of deposited wear debris and is able to present accurately the debris concentration. Results show that the wear index is slightly decreased by higher viscosity, and that the effects of a flow rate of the oil sample lower than 2 ml min −1 on the wear index are not obvious. A simple theory, accounting for the balance between the magnetic and fluid drag forces on the wear particles, is presented and shows very good agreement with experimental results.