Electronic Detection of Synthetic Lubricant Oxidative Breakdown

Abstract

The oxidative breakdown of lubricating oils is accompanied by by monitoring volatile oxidation products with an electronic the liberation of vapor-phase oxidation products. A simple apparatus which uses a semiconducting tin oxide gas sensor has been employed to monitor the evolution of these products and determine the length of the induction period.The method provided reliable end-point detection with ester-base lubricants of moderate stability, simplifying the oxidation testing procedure and providing useful data for studies of lubricant stability.A sensor calibration technique was developed, and the sensors were found to have adequate sensitivity, response speed, and reliability.

Comprehensive and Critical Literature Review on Insitu Micro-Sensors for Application in Tribology

“…Once the inhibitor concentration has fallen below a certain level, then the acid number, viscosity, and volatility of the oil all start to increase [ Figure 1]. This suggests that the use of a dielectric sensor (e.g., [22,23,46]), backed up by an electronic gas sensor [19,26,27], would provide confirming signals of the onset of oil degradation. Preliminary results [23] have shown that the dielectric constant decreases slowly during the useful life of the lubricant.…”

“…The conductivity of the semiconductor increases significantly with increasing concentration of vapors and provides a dear signal of their presence. Ravner and Wohltjen [19] and Bolster and Wohltjen [26] have shown that this approach has merit. They demonstrated that an increase in gas evolution also marked the point at which the antioxidant was practically depleted and the acid number and viscosity were increasing rapidly.…”