METHOD FOR DETERMINING THERMAL-OXIDATIVE STABILITY OF LUBRICANTS Russian patent published in 2017 - IPC G01N25/02 G01N33/30 

FIELD: measuring equipment.

SUBSTANCE: method for determining thermal-oxidative stability of lubricants, in which the lubricant samples of the constant volume are tested in the presence of air with stirring at optimal, at least, three temperatures below the critical value, selected depending on the basic foundation, the lubricant target and the group of the performance properties within the time characterizing the same oxidation degree. At the regular time intervals, the sample of the oxidized lubricant is selected, scanned photometrically, kinematic viscosity of the initial lubricant and the oxidized lubricant is determined, the thermal-oxidative stability value is determined, the characteristic curves of the said photometric parameter value are built for the selected temperatures, and the oxidation process is evaluated. The new is that optical density is determined in the photometry, kinematic viscosity is determined at the temperatures of 40°C and 100°C. At the same time, the viscosity index and the value of the relative viscosity index are determined as the ratio of the oxidized lubricant viscosity index to the product index, and the thermal- oxidative stability value is determined as the ratio of the optical density to the relative viscosity index value. Herewith the effect of the temperature and the oxidation products on the viscosity-temperature characteristic of the tested lubricant is determined, and the lowest change rate of the thermal-oxidative stability value is identified by increasing the oxidation temperature relative to the characteristic curves of the thermal-oxidative stability value from the optical density, built according to the results obtained at the selected testing temperatures.

EFFECT: increasing the method informativeness for determining the thermal-oxidative stability of lubricants by considering the effect of temperatures and oxidation products on the viscosity-temperature characteristics of lubricants.

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