Improving Sensitivity of a Micro Inductive Sensor for Wear Debris Detection with Magnetic Powder Surrounded.

Liankun Liu,Yi Yin,Liang Chen,Xinxiang Pan,Saijie Wang,Dazhuang Liu,Sen Wu,Zhijian Liu

doi:10.3390/mi10070440

Abstract

The inductive detection of wear debris in lubrication oil is an effective method to monitor the machine status. As the wear debris is usually micro scale, a micro inductive sensor is always used to detect them in research papers or high-tech products. However, the improvement of detection sensitivity for micro inductive sensors is still a great challenge, especially for early wear debris of 20 μm or smaller diameter. This paper proposes a novel method to improve the detection sensitivity of a micro inductive sensor. Regarding the magnetic powder surrounding the sensor, the magnetic field in the core of the sensor where the wear debris pass through would be enhanced due to the increased relative permeability. Thus, the inductive signal would be improved and the detection sensitivity would be increased. It is found that the inductive signal would linearly increase with increasing the concentration of the magnetic powder and this enhancement would also be effective for wear debris of different sizes. In addition, the detection limit of the micro inductive sensor used in our experiment could be extended to 11 μm wear debris by the proposed method.

Highlights

The failure of a running machine may result in high safety risk or economic loss
It is found that the inductive signal would linearly increase with increasing the concentration of the magnetic powder and this enhancement would be effective for wear debris of different sizes
While the vibration patterns and thermal analysis can provide vital information concerning the current status of the machine, the oil particulate analysis can forecast early abnormal wear and provide a prognosis of pending machinery failure that is very important for marine engines and aircraft engines

Summary

Introduction

The failure of a running machine may result in high safety risk or economic loss. Researchers have been working to develop measures to prevent such failures. It is fact that an inductive sensor with a very small inner diameter, which is comparable to the early wear debris, could detect them. Regardless, many researchers work on improving the inductive sensor detection sensitivity without reducing the inner diameter, mainly following two directions. The outputs of the adaptive filters are thresholded in the second stage to remove the background noise mainly caused by the wiring and measurement system flaws Another way to improve the sensitivity is to increase the magnitude of the signal. Hong et al [23] designed a sensor structure based on a radial magnetic field which could detect 200 μm debris within a pipe with a diameter of 20 mm. This method is effective for detection of the early wear debris

Sensor Design and Detection Principle

Detection Limit Exploration of Magnetic Particle Enhancement

Conclusions