How Efficiency Is Achieved in Hydraulic System Oil?

How Efficiency Is Achieved in Hydraulic System Oil?

How Efficiency Is Achieved in Hydraulic System Oil?
Machines and oils protecting machines are often subjected to a wide range of ambient and operating temperatures. As a result, oils often have to maintain good pumpability at low temperatures and sufficient film strength at high temperatures. The best examples are hydraulic fluids used in industrial and mobile equipment applications operating in a wide range of environments and temperatures. Finding an oil that can meet these requirements is not difficult; however, performance issues can occur if the fluid is not formulated correctly. To improve viscometric properties at high and low temperatures, fluids with a wide operating temperature range are often formulated with special viscosity enhancing additives, which are subjected to shear forces during use, which can reduce their effectiveness. Viscosity-temperature relationship The viscosity of oils changes depending on the temperature. The viscosity decreases as the temperature increases and the viscosity increases as the temperature decreases. Measurement of the rate of change of viscosity with temperature, the viscosity index of the liquid
It is known as viscosity or VI. Viscosity Index is an empirical, unitless number used to measure the change in viscosity with respect to temperature. The viscosity of a liquid with a high VI does not change with temperature as rapidly as the viscosity of a liquid with a low VI. Typical VI for mineral hydraulic fluids is between 90 and 110.

Viscosity Index Improvers
The VI of a liquid can be increased by using special additives known as Viscosity Index Enhancers. These additives are usually high molecular weight polymers designed to minimize the effect of temperature on viscosity. VI improvers swell with rising temperature, offsetting the effect of the lower viscosity of the base fluid. As a result, a liquid is obtained that maintains sufficient oil film thickness at high temperatures. At low temperatures, the VI improvers shrinks and the properties of the base oil determine the viscosity of the fluid. Shear Strength of Hydraulic Fluid