Electronic system for wear-debris condition monitoring

Abstract

Wear-debris condition monitoring involves detecting and identifying wear-debris particles in the lubricant flow of a machine to obtain an estimate of the machine's 'health'. In this work a wear-debris condition monitoring system using an inductive transducer has been investigated and a prototype system has been developed, constructed and successfully tested. The general field of condition monitoring has been reviewed and the more specific area of lubricant wear-debris monitoring has been examined in detail. The wear-debris monitoring system comprises an inductive transducer, a marginal oscillator, and AM and FM demodulation circuitry. A wear-debris particle passing through the transducer interacts with the system to generate a pair of output pulses; an estimate of the particle diameter and material is obtained from analysing pulse heights. The theoretical foundations of the present method are described in detail.

The system has been tested using particles of lead, brass, copper, steel and ferrite, in the approximate diameter range 100~m to 400~m, and the experimental results confirm the theoretical predictions. Limitations of the present system have been identified, a major problem being noise which limits the minimum detectable size of particle to -100~m diameter for ferrous materials and -200~m diameter for non-ferrous. Also, distortion limits the maximum diameter of particle which can be analysed to -400~m for ferrous materials and -- 500~m for non-ferrous.

A comparison between the performance of the present system and the characteristics of commercially available wear-debris monitoring systems is made with the conclusion that the present system offers significant advantages.

Finally, possible future improvements for the system are identified and a recommended programme for further work is given.