| Abstract: | Oil filters contain useful information on wear that has occurred in the oil-wetted mechanical system. However, filter analysis for wear detection is seldom performed, because the method is fairly cumbersome. On the other hand spectral oil-analysis can be economically done in highly automated laboratories and is therefore widely accepted. This paper describes the case involving a small passenger car diesel engine, where the results of the filter analysis were compared with the results of simultaneously performed oil analysis using X-ray fluorescence. Oil and filter samples were analysed after each 10,000 km, when oil and filter changes took place, over the life of the engine to 165,000 km. The results, as derived from the filter samples, showed a roughly shaped bath-tub curve development of the wear rate before the final stage of serious deterioration. However, the oil analysis did not confirm this trend. It is believed that the different in characteristics between a filter sample and an oil sample, and the effects of particle size and of oil filtration on the oil sample, may cause this discrepancy. If the latter is the case, care has to be taken in oil sampling for wear analysis, particularly in systems with fine full-flow filtration. Suggestions are made at the end of the paper for the design of dedicated diagnostic filters for wear debris detection. |
