![]() ![]() Frequently used to imply high viscosity.Īn apparatus for determining the viscosity of a fluid. If two know viscosity-temperature points of a fluid are located on the chart and a straight line drawn through them, other viscosity-temperature values of the fluid will fall on this line however, values near or below the cloud point of the oil may deviate from the straight-line relationship. The charts used for this purpose are the ASTM Standard Viscosity-Temperature Charts for liquid Petroleum Products, available in 6 ranges. Because of the mathematical relationship that exists between these two variables, it is possible to predict graphically the viscosity of a petroleum fluid at any temperature within a limited range if the viscosities at two other temperatures are known. The manner in which the viscosity of a given fluid varies inversely with temperature. The absolute viscosity divided by the density of the fluid. The ration of the shearing stress to the shear rate of a fluid. Lubricant additive, usually a high molecular weight polymer, that reduces the tendency of an oil's viscosity to change with temperature. Multigrade oils, which provide effective lubrication over a broad temperature range, usually contain viscosity index improvers. A gear lubricant and an engine oil having the same viscosity will have widely different SAE grade designation as defined in the two classifications. Lubricant additive, usually a high molecular weight polymer, that reduces the tendency of an oil to change viscosity with temperature. In determining the viscosity index, two temperatures of viscosity are taken, one at 40☌ and the other at 100☌. The higher the viscosity index is on a particular fluid, the less of a change in viscosity there will be over a given temperature range. Heating tends to make lubricants thinner cooling makes them thicker. The measure of the rate of change of viscosity with temperature. The reduction of lubricant viscosity caused by contamination with water or other substances.Īny of a number of systems, which characterize lubricants according to viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston, engine oils. Thin oils reduce friction in engines and help engines start quickly during cold weather. Thin oils have lower viscosity and pour more easily at low temperatures than thicker oils. it must be considered when selecting a pump and determining the friction losses in a fluid process system. Engine oil viscosity refers to how easily oil pours at a specified temperature. ![]()
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