| Summary: | Problems in hydraulic systems associated with hydraulic fluids are an important area of research. Time has proven that contamination control in hydraulic and lubricating systems are fundamental to reliability and performance. Contamination control is needed to guarantee the quality of the oil and machine reliability. Among the several condition monitoring techniques, oil and wear analysis are the most effective for contamination control in hydraulic equipment. An emerging maintenance philosophy is oil condition based maintenance, in which the active monitoring of oil parameters determines the machine health and the variable service intervals. This new maintenance philosophy requires sensor technology able to provide real time indicators of the status of the system.Nowadays, oil condition monitoring sensors are not a mature technology and their performance has not been widely assessed under controlled experimental conditions. This research explains the physical fundamentals of commercially available sensors and it discusses and evaluates their effectiveness under controlled experimental conditions.Tribology tests were performed for sliding contacts as they are the most predominant type of contacts within hydraulic systems. Results reveal that several characteristics of the sensors must be improved for a more meaningful output and for an earlier detection of abnormal trends which are typical indicators of the onset of faults.Finally, of all the future trends of oil condition monitoring sensors, the novel methodology to calculate the particle size distribution from ferrous debris density measurements is the most useful and important contribution to knowledge of this research. The proposed method when compared to current technology would bring a new type of particle counter that could break the technological size limitation of particle counters based on magnetometry (the most extended type in industrial and military machinery), leading to earlier fault detection. Improvements of this methodology would allow further development of low cost particle counters in the micrometer and submicrometer range which can be widely applied in many industrial processes and scientific disciplines.
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