Open Cut » Maintenance & Equipment
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 predicting oil degradation ahead of time. Moreover, it can be wasteful to change oil before it becomes necessary, and the service schedule recommended by equipment manufacturers may not be suitable to specific operating conditions that shorten the oil life. Therefore, there is a strong need for an effective on-board detector for monitoring the effectiveness of lubrication oils and the conditions of lubricant wetted components.
In the proof of concept stage (project 9037), an on-board detector was developed and tested with over 400 used oil samples with known contamination and degradation levels. The objective of project C12037 was to carry out field trials of the oil detector, via:
· Development of a robust oil detector assembly;
· Development of EIS spectrometer with the capability of measuring high impedance in the frequency range of 1 Hz to 1MHz; and
· Development of improved approaches and automated procedures for data analysis.
Development of Oil Detector System
This project has developed a robust oil detector assembly which includes a rugged design of the electrode chamber and an electromagnet with heat dissipation.
Since there was no suitable electrical impedance spectrometer commercially available, design and construction of an on-board EIS spectrometer became the major task. Achieving the specifications required for on-board filed trials proved to be a very significant challenge. Due to the complexity of the circuitry design of an impedance spectrometer, establishing the final design of the circuitry became the major challenge.
A CSIRO EIS spectrometer has been successfully developed. The EIS spectrometer is able to measure the high electrical impedance of engine oil over the frequency range of 1Hz to 1MHz. The spectrometer has the facilities to store and transfer data, and to switch between two sets of different electrodes, and also an internal calibration circuit verifying correct instrument operation in the field.
Based on pattern recognition and algorithms, procedures for EIS data analysis have been developed, in which oil contamination and degradation are determined from EIS spectrum characteristics. The algorithms and procedures have been incorporated into a computer program which can automatically detect oil change and oil/additives top-up, water/coolant contamination, excessive fuel contamination, excessive level of soot and sulfur products and oxidation degree. The automated procedure can provide information on the remaining oil life and valid recommendations to maintenance people regarding oil change-out requirements and other actions.
Field trials of the CSIRO oil detector system were carried out on a Caterpillar 784 series coal hauler at a Bowen Basin mine site for a period of more than 8 weeks. It has been demonstrated that the oil detector system can provide satisfactory measurements of the EIS spectrum of the oil. Predictions of oil oxidation and intermediate level of soot/sulfur product contamination from EIS could be linked with those determined from SOS oil analysis over two oil changes. The determination of oxidation degree from EIS at the end of "oil burner" stage also matched the result from SOS analysis. Due to a limited period of time, contaminations by water, coolant, fuel, excessive level of soot and ferrous wear particles were not observed. Events of oil change and top-up with oil/additives were correctly detected. The prediction of the remaining oil life (ROL) in one case based on a redefined condemnation limit was comparable to that determined by SOS oil analysis.
The whole oil condition monitoring system has passed robustness testing in laboratory under conditions of oil temperature up to 1000C, a hydraulic pressure of 250 PSI (3 times expected pressure of field equipment) and a vibration intensity of 3g, and survived in field trials in a period of 2 months.