![]() ![]() The majority of equipment was found to provide satisfactory performance with an operating viscosity range of 13 to 860 cSt. Hydraulic pump and motor manufacturers were surveyed regarding the fluid viscosity requirements for their pumps and motors. ![]() Effect of Viscosity upon the Volumetric and Mechanical Efficiency of Hydraulic Pumps To accomplish this, the requirements of the hydraulic components, as well as the operating temperature range, must be taken into consideration.įigure 1. Therefore, selecting the proper fluid involves optimizing oil viscosity in terms of volumetric and mechanical pump efficiency, as shown in Figure 1. A fluid that is too high in viscosity, on the other hand, will cause poor mechanical efficiency, startup issues and wear due to cavitation. In addition, low viscosity fluids can lead to increased friction and pump wear. This is because a hydraulic fluid that is too low in viscosity will reduce the volumetric efficiency of pumps and cause fluid overheating. There is a common misconception that reducing hydraulic fluid viscosity will decrease operating temperatures, when in fact higher viscosities may lead to a reduction in operating temperatures in hydraulic applications. One of the most important criteria in the selection of a hydraulic fluid is viscosity. Other factors such as machine builder specifications, additive requirements and compatibility must also be considered. The guidelines shown in Figure 2 are designed to assist in this analysis. ![]() Consolidating hydraulic fluids can enhance system performance and reduce costs however it requires a careful analysis. An abridged version of ISO viscosity grades is listed in Table 1.Īccommodating a variety of equipment builder preferences can lead to an abundance of fluids and high inventory costs. They may also identify qualified lubricants by brand name or the ISO viscosity grade. If we know the and values for a given polymer solution the intrinsic viscosity and molecular weight can be calculate using the above equation.Machine builders recommend hydraulic fluids for their equipment by specifying characteristics such as viscosity, antiwear performance and oxidation stability. Where is the intrinsic viscosity, is Molecular weight, and are constants for a particular polymer solvent system. The molecular weight of the polymer solution is very high so the viscosity of polymer solution is very high compared to that of pure solvent.įrom the Mark-Houwink equation the relationship among the molecular weight and viscosity are given below The molecular weight of the polymer is measured by using viscometer and the molecular weight obtained by this technique is called viscosity average molecular weight. The unknown composition can be determined by plotting a graph for the time of flow and compositions. In this method the flow times are measured for different known compositions and a graph is plot for time of flow and compositions. The time of flow of liquid depends on the viscosity and composition. Various mixtures of two non-interacting liquids viscosities will lie among the viscosities of those pure components. And η 1 is the coefficient of viscosity of water.įor a given liquid η has a specific value at the same temperature. Here t 1 and t 2 are the time of flow of the liquids and ρ 1 and ρ 2 are the respective densities. Then the coefficient of viscosity of liquid (η 2) is given by equation In this method viscosity of liquid is measured by comparing the flow times of two liquids of equal volumes using same viscometer.Ĭonsider two liquids are passing through a capillary of same viscometer. The Ostwald method is a simple method for the measurement of viscosity, in which viscosity of liquid is measured by comparing the viscosity of an unknown liquid with that of liquid whose viscosity is known. Many methods are available for measuring viscosity of polymer solution. It is due to the internal friction of molecules and mainly depends on the nature & temperature of the liquid. Viscosity is an internal property of a fluid that offers resistance to flow. Determine the viscosity average molecular weight of a polymer.Determine the absolute viscosity of Polymer solutions of different concentrations. ![]()
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