Technical Papers

Efficiency Advantages in Vane, Piston and Gear Pumps -What High VI Hydraulic Fluid can do for you!

Authors: Michael Alibert, Dr. Hans Görlitzer, Steven Herzog, Christian Neveu

presented at:   5th International Fluid Power Conference (IFK)
                            Eurocongress
                            Aachen, GERMANY
                            March 20-22, 2006

The increasing demand for improved economics leads to mobile hydraulic systems running under higher pressure fitted with smaller oil reservoirs. Under these severe conditions the proper selection of the hydraulic fluid is critical to operate the equipment efficiently and to provide adequate wear-protection. Viscosity is one of the most important selection criteria of a hydraulic fluid since it controls the efficiency of hydraulic pumps and motors. At high temperature, a too low viscosity may result in excessive wear that reduces equipment life. Furthermore, insufficient viscosity will increase the pump leakage, consequently reducing the volumetric efficiency which deteriorates the overall economics.

In this paper, we have reviewed different hydraulic pumps such as medium and high pressure vane, piston and gear pumps and studied the influence on pump efficiency of various hydraulic fluids covering both monograde and multigrade fluids. The effects on the pumps’ performance of specific fluid characteristics like ISO Viscosity Grade, Viscosity Index and Shear Stability have been examined. Our results clearly show that “in-service viscosity” of high-VI, highly shear stable hydraulic fluids significantly improve the overall efficiency irrespective of the pump type used.

After describing the equipments and the test fluids used in the program, we will analyse the data obtained for the three types of pumps studied and demonstrate that at 80 °C and above a gain of approximately five percent in global efficiency can be obtained by simply using an appropriate high-quality, high-VI oil instead of a conventional HM fluid of the same ISO grade.

This, of course, is of particular importance since the lower the volumetric efficiency, the higher the energy needed at the pump shaft to produce a given level of work. Thus, increasing the pump’s efficiency does directly translate into energy savings or allow for an increase in the productivity and performance of the system: This paper will demonstrate how an equipment user can improve the performance and reduce his fuel consumption during operation by using a Maximum Efficiency Hydraulic Fluid.

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