Every lubricating oil comes with a specific SAE number. The SAE number of the oil indicates its viscosity based on classification involving two temperatures. The flash point of oil can be defined as the lowest temperature at which the oil will give off sufficient inflammable vapour to produce a flash when a small flame is brought to the surface of the oil. The pour point is lowered using additives known as pour point depressants. The pour point of the oil can be defined as the temperature at which the oil stops flowing. The cloud point helps in finding out the tendency of the oil to form wax. Gradually, the wax formed crystallizes and clogs the filters. This means that lubricating oil with higher viscosity index has only a small change as a result of a large temperature difference.Īs a general practice, various additives are added in the oil to improve the viscosity index of the lubricating oil.Ī viscosity index is a dimensionless number.Ĭloud point is the term which is related to the wax formation in the oil.Ĭloud point indicates the temperature at which waxes begin to form in the oil. The higher the viscosity index of the lubricating oil better is the quality. It can be defined as the change in viscosity of the oil which takes place as a result of a change in temperature. Viscosity Index is a term which is mainly related to marine lubricating oils. Generally, the thicker the fluid, the higher its viscosity whereas thinner liquids have lower viscosity. It is the property of the liquid which tends to prevent relative movement between adjacent parts within itself. The viscosity of the oil is defined as a measure of a fluid’s resistance to flow.
Representation Image – Photograph by Captain Syed Husain KamilĨ More Engine Terms Every Marine Engineer Should Know These terms are used extensively on ship and therefore they are of great importance. In this article, there are eight more engine terms which deals with the characteristics of fuel and lubricating oils used on ships. Just as an example, to calculate viscosity index we can use online viscosity index calculator or excel tools.In the previous article, 8 Engine Terms every marine engineer should know, we talked about marine engine terms which marine engineers should know without fail.
#Define viscosity index iso
Common methods for viscosity index calculations are ASTM D2270 and ISO 2909.
#Define viscosity index how to
Q: How to calculate viscosity index?Ī: The viscosity index of a fluid (usually oil) is calculated from its viscosity at 40 and 100☌. Therefore higher viscosity index or higher VI means fluid is more stable and less changes in viscosity over a wide temperature ranges. Viscosity index indicates the change in fluid viscosity in dependence of temperature. Q: What is viscosity index?Ī: Viscosity index of a fluid is a calculated number according to ASTM D2270 or ISO 2909. For example the viscosity of honey is higher than the water. High viscosity fluid has more resistance to flow than a low viscosity fluid. If viscosity of fluid is high, most likely it is difficult to pour. Hence high viscosity fluids flow less easily or slower. Low viscosity fluids (low resistance to move) flow or pour more easily and faster. Therefore oil/fluids are usually measured at the same temperature to calculate viscosity. Lubricants Viscosity and Viscosity index Q: What is Viscosity?Ī: Viscosity is a fluid’s resistance to flow at given temperature. Press Calculate button to calculate kinematic viscosity (KV) As before, use Clear button to reset and calculate a new viscosity. Calculate Viscosity use calculator 3 to calculate viscosity (KV) Enter known viscosity index (VI) and kinematic viscosity (KV) in table 3. Click Calculate to get KV As previously stated, use Clear button to start a new calculation. Enter kinematic viscosity (KV) in the second row. Similarly with known viscosity index (VI) and viscosity It is possible to calculate viscosity For example enter viscosity index (VI) in the first row of second table. Calculate Viscosity possibility is to calculate kinematic viscosity from viscosity index. Finally, press Clear button to start again. Click Calculate button to get viscosity index (VI). In the first row table 1, Enter kinematic viscosity (KV) at 40☌, In the same way enter kinematic viscosity in the second row. To calculate viscosity index we need viscosity of an oil both at 40☌ and 100☌.
Standard practice for viscosity index (VI) calculation as per ASTM D2270 and ISO 2909.
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