Measurement of Lubricant Viscosity and Metal Particles Using Dual Coil Inductive Sensor

Lubricant is a critical component of a ship’s power plant, and analyzing the information on the change of lubricant viscosity and the wear particle it carries is of great significance to realize the condition monitoring of the power plant. In this article, we propose and design an inductive sensor capable of simultaneously detecting the viscosity, particle diameter, and velocity of lubricants. COMSOL was used to investigate the magnetic field, particle flow, and particle velocity characteristics. The inductance signal amplitude and velocity values of spherical iron particles of eight diameters passing through four levels of viscosity lubricants were collected. Based on this data, we plotted the particle diameter-inductance signal amplitude curves, viscosity-velocity (for different diameters), and diameter-velocity (for different viscosities) curves. According to the experiment, when the two unknown iron particles passed through the standard oil sample of 50 mm2/s (20 °C), the corresponding particle diameter can be obtained from the particle diameter-inductance amplitude curves as 300 and $278 \mu \text{m}$ , respectively. For the calibrated particle with a diameter of $300 \mu \text{m}$ , the viscosity–velocity (for different diameters) curve yielded the viscosity value of 53.382 mm2/s with an error of 6.76%. The estimated viscosity value of 54.73 mm2/s was obtained by diameter–velocity (for different viscosity) curve for the noncalibrated particle of $278 \mu \text{m}$ , with an error of 9.46%. This detection technology provides a new research idea for marine lubricant testing.

I. Introduction

The safe and reliable operation of the power plants of ocean-going vessels is a prerequisite to ensure the routine function of the ships. Therefore, it is significant to carry out effective condition monitoring and fault diagnosis for ship power plants [1]. It has become a novel approach to judging the health status of machinery and equipment through lubricant. In addition to noise reduction and cooling functions, it contains rich information on the lubrication and wear status of frictional subsets of ship power plants. Therefore, testing the lubricant’s performance index is a meaningful way to monitor ship power plants’ condition [2].