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Viscosity conversions are based on fluids with specific gravity of one. W. A. Wright Past Chairman vRnesearch and Development Division ASTM Committee D-2, Acknowledgment of Work Personnel of Research and Development Division VII of ASTM Com-mittee D-2 responsible for the development of ASTM Standard MethodD 2270-74, Calculating Viscosity Index From Kinematic Viscosity at 40and 100°C on which these viscosity index tables are based. first two years of college and save thousands off your degree. Take any river you may have seen. Normal laboratory practicesshould not be expected to provide significantly better viscosity or viscosityindex accuracy than provided for in the tables.References The following references do not constitute a complete coverage of theliterature, but will be helpful in following the history and development ofthe viscosity index. If the exact viscosities of an oil are not found in the table, the informa-tion desired can be obtained by linear interpolation between the propertabulated values. You already know this, but by a different name - stickiness. Many lubricant applications require the lubricant to perform across a wide range of conditions, for example, automotive lubricants are required to reduce friction between engine components when the engine is started from cold (relative to the engine's operating temperatures) up to 200 °C or 392 °F when it is running. 215, 1956, pp. The hotter something is, the more energy and movement the molecules have. [3], VI improving additives and higher quality base oils are widely used nowadays which increase the VIs attainable beyond the value of 100. The lower the VI, the more the viscosity is affected by changes in temperature. 0000283885 00000 n Did you know… We have over 220 college vi, H = kinematic viscosity in centistokes at 40°C of an oil of 100 viscosity index, and having the same kinematic viscosity at 100°C as the oil whose viscosity index is to be calculated. Since the viscosity index for a fluid is better understood as the ability to protect its viscosity from temperature changes, it follows that a high VI oil shows a greater resistance to viscosity change. It is wise to follow the manufacturers recommendation as to what grades of oil or types of lubricants should be used in or on any equipment relative to the seasonal temperature ranges of the environment that the equipment is used in. Gases & liquids are more free to flow as compared to solids and are known together as fluids. However as the oil is heated further, the oil becomes thinner and thinner until it is nearly smoking and it is almost as thin as water — and thus it has almost no capacity to keep moving parts separated — resulting in metal to metal contact and damage of the components that are supposed to be kept apart with a thin film of oil. Viscosity Index (VI) is a scale used to measure how much an oil's viscosity, or resistance to flow, changes depending on its temperature. The viscosity index is a measure of viscosity fluctuations with changes in temperature. Some of our calculators and applications let you save application data to your local computer. Check ASTM D 2161 "Standard Practice for Conversion of Kinematic Viscosity to Saybolt Universal Viscosity or to Saybolt Furol Viscosity". Thus the multigrade oils are recommended for use based on the ambient temperature ranges of the season or environment. For example, the viscosity of a lubricating oil at 100 degrees Fahrenheit would be very different than at 200 degrees Fahrenheit. Now try and picture it as a stack of hundreds of super-thin sheets of water, flowing together - each with their own speed. Take boiling water for example - as the water molecules are heated, their energy and movement rise to the point of bubbling. Google use cookies for serving our ads and handling visitor statistics. However, in hot climates where temperatures range from 30*C to 45*C, a 50 weight oil would be necessary so it would remain thick enough to hold up an oil film between the moving hot parts. 0000001186 00000 n For any oil, the viscosity index or VI is given by the equation : Get access risk-free for 30 days, just create an account. All other trademarks and copyrights are the property of their respective owners. Study.com NCLEX Scholarship: Application Form & Information, Signing Up for Study.com Courses with a Student Premium Account, Top 20 K-6/8 School Districts for Teachers in Massachusetts, Tech and Engineering - Questions & Answers, Health and Medicine - Questions & Answers, Working Scholars® Bringing Tuition-Free College to the Community.

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