Design and Development of Opto-Resistive Type Quasi-digital Sensor and Instrument to In-situ Monitoring of the Quality of Lubricant Oil

In large rotating machinery, lubricating oils are employed to reduce the wear, minimize the friction between gears and bearings, remove heat, takeaway wear particles and to protect against corrosion. Lubricant oil slowly degrades over a period of time due to oxidation and contamination. Consequently looses its defensive properties and effects the machinery performance. This may leads to catastrophic failure, unplanned shutdown and capital loss. Replacing the in-service oil with fresh oil before degradation can prevent the above consequences but changing the lubricant too early is uneconomical. Therefore, it is better to predict the remaining effective life of the oil under operating conditions. Monitoring the healthiness, predicting the remaining useful life of the lubricant oil and warning the operator with an alarm can prevent catastrophic failure. It is observed that the oil color becomes darker with contamination, oxidation, and aging. Thus, the color of the lubricant is considered as an essential parameter for describing the quality of the oil. This paper describes the design and development of a lowcost, low power instrument and Opto-resistive quasi-digital sensor. It explains the capability of the instrument about in-situ monitoring of quality, predicting the effective life of lubricant by measuring the transmittance of the light through lubricant oil and alerting the operator by annunciation cum display.