Method of measuring thermal-oxidative stability of lubricants

FIELD: inspection of quality of oil products.

SUBSTANCE: permanent-weight lubricant is subject to heating in thermo-stable glass cup at three temperatures at least, which temperatures exceed that one of beginning of oxidation and then it is subject to mixing by glass mixer at constant speed during 12 hours or less. Samples for photometry are selected in equal time intervals. Factor of absorption of light flux by oxidized oil Ability to evaporation is measured by weighing sample before and after test. Graphical dependences of theses parameters are built relatively temperature of testing. Thermal-oxidative stability of lubricant is determined by critical temperature of service ability, by temperature of beginning of oxidation and by temperature of beginning of oxidation.

EFFECT: improved efficiency of measurement.

2 dwg

 

The invention relates to measurement techniques, in particular for determining the quality of oil products, and can be used to control thermal stability of thermal-oxidative processes lubricants.

There is a method of determining stability, which consists in heating oil at 200°With the device DK-US, accompanied by oxidation, mixing it with petroleras ether in the ratio of 1:40, aging the mixture for 12 h, filtering the resulting precipitate, drying the last in a drying Cabinet and determining the amount of sludge and viscosity of the oxidized oil (GOST 11063-77).

The known method has insufficient information about the oxidative stability of lubricants, not because temperature determines the scope of their application and the critical temperature at which begins the intensive oxidation and evaporation.

The closest in technical essence and the achieved result is a method for determining oxidative stability of lubricants, including heating the lubricant in the presence of air, mixing, determination of the parameters of the oxidation process. The test subject sample by heating at certain intervals of time to a certain temperature with the temperature increase at the beginning of the interval from exposure to the giving of the interval, determine the optical density at the end of each time interval, build graphical dependence of optical density on temperature oxidation, the inflection point which determines the temperature oxidation (RF patent No. 2057321, G 01 N 25/02, 1996).

The known method cannot provide sufficient information about the quality of lubricants and objectivity in determining the temperature of the beginning of oxidation of the lubricant, since it is in this way depends on the duration of the test sample. The longer the duration of the test, the at a lower temperature will bend dependence. In addition, the known method does not take into account changes such important performance properties of lubricants, as evaporation and the critical temperature of the health of the lubricant.

The objective of the invention is to increase the information content in determining the quality of lubricants using three criteria: the critical temperature performance, temperature of the beginning of oxidation and temperature of the beginning of the evaporation of the lubricant.

The problem is solved in that in the method for determining oxidative stability of lubricants, including heating the lubricant in the presence of air, mixing, photomatrixovina, graphing C is Wiimote, which determine the parameters of the oxidation process, according to the invention, the lubricating material constant mass is heated in a heat resistant glass beaker at least at three temperatures higher than the onset temperature of oxidation, and stirred with a glass stirrer at a constant speed of rotation for a period of not more than 12 hours, and at equal intervals of time take samples for photometric measurements, determine the absorption coefficient of the light flux of oxidized oil and evaporation by weighing the samples before and after testing, build the graphical dependence of these parameters on the test temperature, and thermal-oxidative stability of a lubricant is determined by the critical temperature performance, the oxidation onset temperature and the onset temperature of evaporation, with the critical temperature operability is determined by the curve of the dependence of the absorption coefficient of the light flux on temperature, the temperature at which oxidation of lubricants is determined by the extension of the linear dependence of the absorption coefficient of the light flux to the intersection with the abscissa for oils, absorption coefficient of the light flux which in the initial state (before the test) is equal to zero, or to the value of the absorption coefficient of the light flux that characterize the initial state is of asle, and the onset temperature of evaporation is determined by the extension of the dependence of evaporation on temperature to the intersection with the x-axis.

Comparative analysis of the prototype and the proposed method showed that the latter has the following distinctive features.

The determination of the critical temperature performance and temperature of the beginning of oxidation on the graphical dependence of the absorption coefficient of the light flux from the test temperature increases the informativeness of the proposed method and sets the temperature in the region of application of the test lubricant.

The onset temperature of evaporation of the lubricant determines the optimal temperature in the region of its health. All accepted criteria are aimed at solving the problem.

Figure 1 shows the dependence of the absorption coefficient of the light flux from the test temperature of engine oils: 1 - Zic 5000 10W-40 CG-4/SH (semi-synthetic); 2 - Zic A 10W-40 SL (semi-synthetic); 3 - Mobil 10W-40 SJ/CF (synthetic); 4 - Mobil 10W-40 SC/CC (mineral); transmission oils: 5 - CUP-14The ISU(mineral); 6 - CUC- 9The ISU(mineral); 7 - Rotra FE 75W-90 GL-4 (semi-synthetic); figure 2 - dependence of evaporation on temperature tests.

The method for determining oxidative stability of lubricants made tsetse as follows.

The sample studied lubricant constant mass (100 g) is poured into a heat resistant glass beaker, which is installed in a cylindrical furnace, and heated to a temperature higher than the onset temperature of oxidation, mixed with a glass stirrer with electric drive. The temperature of the test oil sample is maintained automatically with an accuracy of ±1°C.

The use of glass cups and stirrers eliminates the influence of materials on oxidative processes. Testing is carried out for 12 hours, at least at three temperatures higher than the onset temperature of oxidation, such as motor oils, 170, 180, 190 and 200°With, for transmission 150, 140, 130°C, and after 2, 5, 8, and 12 hours of testing, take samples for photometric measurements and determine the ratio of the luminous flux of oxidized oil and evaporation by weighing the samples before and after testing for agreed periods of time.

The results analysis is performed using the graphical dependence of the absorption coefficient of the light flux To aP(figure 1) and evaporation (G (2) from the test temperature for the test time, for example 5 hours. For oils with high thermal-oxidative stability at the time of test 2 or 5 hours factor KPcan be equal to zero, then the selected time 8 or 12 hours.

Correlation coefficient is ecient absorption of the light flux from the test temperature of engine oils (1) are linear in the temperature region, for which there is no decomposition of antioxidant additives. However, when a certain temperature is the decomposition and the formation of new compounds, catalytically acting on the oxidation process. In this case, the bending dependencies, so this temperature is taken for critical.

For oils No. 1, 2 and 3 the critical temperature of their working capacity was 190°With as 200°C is the curve of dependence and oil No. 4 - 180°C.

The critical temperature operability transmission oils were: 150°oil No. 6 and 7 and 140°oil No. 5.

The onset temperature of oxidation of lubricants is determined by the extension of dependency (figure 1) to the intersection with the abscissa for oils, absorption coefficient of the light flux To aPwhich in the initial state (before the test) is equal to zero or to a value of KPcharacterizing the initial state of the oil (oil No. 5).

The onset temperature of oxidation of engine oils (1), respectively, were as follows: No. 1 - 178°C; No. 2 - 168°C; No. 3 - 176°C; No. 4 - 166°C. To gear it was: No. 5 - 117°C; No. 6 - 130°C; No. 7 - 140°C.

Evaporation of lubricants G (2) is determined by weighing the oil sample before and after testing. The dependence of the evaporation G temperature tests for them is no linear within a certain range of temperatures, therefore, the extension according to the intersection with the abscissa axis defines the onset temperature of evaporation. For engine oils she accordingly made: No. 1 - 140°C; No. 2 - 145°C; No. 3 - 152°C; No. 4 - 150°; gear: No. 5 - 97°C; No. 6 - 110°C; No. 7 - 117°C.

The proposed solution allows to obtain additional information when determining the oxidative stability of lubricants, such as: critical temperature performance, the onset temperature of oxidation; the onset temperature of evaporation and is industrially applicable in the identification or establishment of the group's operational properties.

The method for determining oxidative stability of lubricants, including heating the lubricant in the presence of air, mixing, photomatrixovina, the construction of the graphical dependencies, which determine the parameters of the oxidation process, wherein the lubricating material constant mass is heated in a heat resistant glass beaker at least at three temperatures higher than the onset temperature of oxidation, and stirred with a glass stirrer at a constant speed of rotation for a period of not more than 12 h, and at equal intervals of time take samples for photometric measurements, determine the absorption coefficient SV is preset flow oxidized oil and evaporation by weighing the samples before and after the test, build the graphical dependence of these parameters on the test temperature, and thermal-oxidative stability of a lubricant is determined by the critical temperature performance, the oxidation onset temperature and the onset temperature of evaporation, with the critical temperature operability is determined by the curve of the dependence of the absorption coefficient of the light flux on temperature, the temperature at which oxidation of lubricants is determined by the extension of the linear dependence of the absorption coefficient of the light flux to the intersection with the abscissa for oils, absorption coefficient of the light flux which in the initial state (before the test) is equal to zero, or to the value of the absorption coefficient of the light flux that characterize the initial state of the oil, and the onset temperature of evaporation is determined by the extension dependencies the evaporation temperature to the intersection with the x-axis.



 

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