ACHIEVING EFFICIENCY GAINS THROUGH HYDRAULIC FLUID SELECTION: LABORATORY PREDICTION AND FIELD EVALUATION

Studies completed in medium and high pressure vane and piston pumps showed that their efficiency depends on discharge pressure and on oil viscosity. Recently, a limited field test completed in a medium size excavator confirmed that significant gains in efficiency and productivity even under moderate operating temperatures could be achieved by substituting the OEM-recommended oil with a Maximum Efficiency Hydraulic Fluid (MEHF). To understand the origin of the efficiency gains observed in the field test, we instrumented an Eaton-Vickers V104C pump to record pressure, temperature, flow rate and power input at the pump shaft. Tests were completed at 69 and 138 bars and temperatures ranging between 30 and 90°C. Candidate hydraulic fluids included the two field test oils and an ISO VG 46 HM oil. The efficiency gains in the pump stand are consistent with those generated in the field test making the former a valuable tool to assess the potential benefits of MEHF oils in actual service. Thermodynamic models determined earlier can be used to estimate the temperature of the oil leakage stream and the actual oil temperature inside the pump.