An Experimental Study on High-Flowrate Ultrasonic Particle Monitoring in Oil Hydraulics

In this article an experimental analysis on detection of particles in oil hydraulics by an in-line, high flowrate ultrasonic sensor is presented. This experimental study is conducted by the implementation of a particle concentration sensor prototype in a simple hydraulic circuit. In this system the contamination particles are introduced in an open tank. The sensor prototype is based on the particle scattering of ultrasound measured in a 90° angle in relation to the incoming wave. An experimental analysis of the sensors ability to detect specific concentrations of silicon dioxide particles in oils of varying viscosity grade is presented. Furthermore, an experiment involving a used hydraulic oil from an industrial plant is shown, where the sensor is able to detect increased particle contamination in the system, when the open tank is actively stirred. It is from the experimental analysis found that the prototype can detect particles of above 40 microns in common hydraulic oils, however the background field intensity and frequency could be increased to lower the size of the detectable particles. The paper is concluded with a theoretical analysis, which is examining the background field intensities and frequencies needed to meet standards within measurements of oil cleanliness.