Open Cut » Maintenance & Equipment
Issues
The repairs and downtime caused by oil-related engine or other machine failures represent about 30-50% of the operational cost in the Australian mining industry. The reliable monitoring of the effectiveness of working lubrication oils and the condition of lubricant wetted components is crucial to preventing oil related failures of mining equipment. However, current diagnostic tests based on Scheduled Oil Sampling and used oil analysis cannot promptly detect a rapidly progressing component failure or a sudden ingestion of oil contaminants, as well as oil degradation ahead of time. Moreover, it can be wasteful to change oil before it becomes necessary, and the service schedule recommended by equipment manufactures may not be suitable to specific operating conditions that shorten the oil life. The use of "Oil Burn" technology will result in oil contamination and degradation in the high level range for a long period of time. Therefore, a small change in contamination and degradation levels may be sufficient to trigger an unacceptable condition. If the "Oil Burn" technology is widely adopted by Australian coal industry, it will become very necessary to have an on-board system to monitor and predict oil condition over the 10 to 12 month life of the oil.
Objectives
The overall objective of this project is to develop an on-board and/or portable detector for monitoring the condition of lubrication oil and the concentration and the average size of ferrous wear particles. The specific aim at this stage is to develop prototypes of the detector and investigate its capability on oil samples with identified contaminants and degradation levels.
The Approach
The on-board detector is based on the Electrical Impedance Spectroscopy (EIS) technique, in which the electrical impedance spectrum of oils is measured over the frequency range of 0.1 Hz to 1 MHz. Changes in the frequency response reflect a change in the oil composition, and by deconvoluting the signals attributable to different components in oils, one can detect or determine the type and level of oil contaminants and degradation. The measurements of impedance spectra require relatively simple instrumentation. Thus, the detector is low-cost, robust and fast. The detector can be constructed in either on-board or portable type, and the latter can be used in routine inspections of multiple vehicles and equipment. In order to increase the sensitivity of the detector for low concentrations of ferrous wear metals, an electromagnet is used to attract ferrous wear particles into the gap between electrodes.
Conclusions
An effective detector based on electrical impedance spectroscopy has been developed and can be used for:
- Detecting the oil brand and/or type of a fresh oil added into the oil sump and therefore reducing the chance of using inappropriate or incompatible oils,
- Detecting abnormal levels (>0.5%) of water contamination,
- Detecting abnormal levels of coolant and fuel contamination,
- Monitoring depletion of additives in lubrication oils,
- Quantitatively determining oxidation degrees of lubrication oils,
- Detecting excessive levels of soot,
- Detecting excessive level of sulfur products,
- Quantitatively determining the concentration of ferrous wear particles,
- Determining the average size of ferrous wear particles.