On-Line Wear Particle Monitoring Based on Ultrasonic Detection and Discrimination

Abstract : An ultrasonic technique is developed for the nondestructive evaluation of shipboard machinery conditions. The ultrasonic wear particle sensor (UWPS) quantitatively measure the amount and size of war-generated debris in the machinery lubricating oil by employing wide-band, ultrasonic pulse echo techniques. In addition to its present capability to detect, count, and size wear debris over a broad range of sizes, several methods of electronically discriminating contaminant particles from air bubbles have been demonstrated experimentally. The UWPS presently exists as a microprocessor-controlled laboratory instrument. the instrument initially did not discriminate air bubbles from wear debris but was successful in detecting abnormal bearing wear. Three methods to identify scatterers as either air bubbles, water droplets, or debris particulate. One method uses the intensity vs. the angle of scatter of the ultrasonic pulse to discriminate air from debris. Another method is based upon phase measurements of the reflected pulse echo. The latest method investigated measures the spectra of the individual pulse echoes and correlates the spectral features with particle composition. This report discusses the theory of operation of the UWPS, methods used for determining the size of individual scatterers, and the various methods of discriminating war debris from entrained air. This instrument will be a powerful tool for nondestructively determining the wear condition of hydraulic and lubricating oil machinery.