The higher the viscosity index is on a particular fluid, the less of a change in viscosity. The desired temperature at which the viscosity is to be measured is maintained by the stirring the water and oil in the heating bath and the oil cup respectively. Heating tends to make lubricants thinner cooling makes them thicker. An empty Kohlrausch flask is kept just below the jet. Test oil is filled in the oil cup up to the tip of the indicator. Working: Water is filled in the bath and the brass ball is kept in position to seal the orifice. Its capacity is 50 ml to the mark in its neck. Kohlrausch flask: It is a special type of receiver for receiving the oil. Heating Bath: oil cup is surrounded by a cylindrical cooper bath containing water having an outlet for talking out water a stirrer with four blades and thermometer.ģ. The lid of the cup is fitted with a thermometer which indicates the oil temperature.Ģ. The bottom of the cylinder is fitted with an agate jet that can be kept closed or open by a value rod fitted with a boll made of brass. Oil cup: It is silver plated brass cup, which is open at the upper end. Redwood viscometer: It consists of the following parts:ġ. Thus a good lubricating oil should possess high V.I. lesser is the variation of viscosity with change in temperature. Viscosity of liquid is decreases with increasing temperature so that lubricating oil become thinner as the operating temperature is raised, and lubricant can be squeezed out from the subbing parts. Viscosity index: The rate at which viscosity of a lubricant changes with temperature is measured by any arbitrary scale is known as viscosity index. If the viscosity of the lubricating oil is too high, excessive friction may take place. If the viscosity of liquid is too low, the fluid lubricant film cannot be maintained between the moving surfaces, as a result of which excessive wear may take place.ģ. Viscosity of lubricating oil determines its performance under operating conditions.Ģ. It is mainly due to forces of cohesion between the fluid molecules.ġ. Viscosity is the property of the lubricants by virtue of which it offers resistance to its own flow. Viscosity: Viscosity is most important and representative property of lubricants. How the viscosity is determined by Redwood viscometer?Īns. Viscosity Index (VI) Shear Stability Index (SSI) 100 90 80 70 60 50 40 30 20 10 0 PIB PMA PAO Asteric VM Technology Blended to the Same Viscosity at 100C in 4 cSt Oil Passenger vehicle manufacturers, heavy duty equipment OEMs, along with lubricant end-users are demanding higher performing, longer lasting and more fuel efficient lubricants. Discuss the significance of viscosity in lubricating oil.
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