METHOD FOR DETERMINING THERMAL-OXIDATIVE RESISTANCE OF LUBRICANTS Russian patent published in 2017 - IPC G01N25/02 G01N25/12 G01N33/30 

FIELD: measuring equipment.

SUBSTANCE: method for determining the thermal-oxidative resistance of lubricants includes heating a sample of a tested lubricant of constant mass in the presence of air, mixing, photometric measurements, determining the mass of the evaporated sample during testing, and plotting the graphical dependencies, by which the oxidation process parameters are determined. According to the invention, the tests are carried out in two cycles of temperature change. One sample is tested with the stepwise temperature increase by 10°C from the minimum to the maximum value, depending on the lubricant purpose, and another sample is tested with the stepwise temperature decrease by 10°C from the accepted maximum value to the minimum. Wherein at regular intervals of the testing time for each temperature, the oxidized sample is weighed, the evaporated lubricant weight and the volatility factor are determined as the ratio of the evaporated lubricant weight to the sample weight before testing. A part of the oxidized sample is taken to determine the optical density, and, from the obtained data, the thermal-oxidative resistance is determined as the sum of the optical density and the evaporation factor. The graphical dependences of the index of thermooxidation resistance, optical density and evaporation on the cycles of rise and fall of the test temperature are plotted, the regression equations of said dependences are determined, which are used to determine the thermal and oxidation resistance parameters. According to the equations of the dependencies of the thermal and oxidation resistance index, the temperature of the beginning of the transformation processes in the tested lubricant in the cycle of increasing the test temperature and the critical temperature in the cycle of lowering the test temperature are determined, and the limiting operability temperature is determined by the coordinate of the abscissa of the intersection of said dependences. Wherein the values of these parameters are used as the thermal and oxidation resistance parameters.

EFFECT: increasing the information content of quality control of lubricants due to determining the maximum permissible operability temperature.

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