the operation of electric vehicles, machinery, and electronics but also support sustainability goals through reduced maintenance and environmental impact.
Hydraulic efficiency study
The Fluid Power Institute at the Milwaukee School of Engineering (MSOE) (led by Director Paul Michael) conducted a comprehensive hydraulic efficiency evaluation to measure the performance impact of an SPE®
• Pump Speed: Varied to achieve target motor speed (rpm) and system pressure (MPa).
Each test condition was repeated six times for reproducibility. Torque, flow, and temperature data were measured and averaged across steady-state intervals.
Typical physical properties of test fluids
formulated EAL (environmentally acceptable lubricant) hydraulic fluid compared to a mineral oil-based reference fluid. The goal was to quantify differences in frictional (torque) and volumetric (flow) losses under realistic operating conditions using a hydraulic dynamometer test stand.
Test stand and equipment
Table 1: Mineral Oil Industrial Hydraulic Reference Fluid compared to VBASE EAL HF (*formulated to meet ISO 15380).
Figure 1: MSOE Fluid Power Institute hydraulic efficiency test stand showing pump–motor loop and instrumentation setup.
Testing was conducted using a closed-circuit hydraulic test stand (Figure 1) and consisted of: • Pump: Linde HPR-75 axial piston pump. • Motor: Poclain radial piston motor . • Reservoir: 25-gallon capacity with inline heating and cooling for temperature control .
• Instrumentation: High-accuracy torque transducers, flow meters, pressure sensors, and thermocouples to record torque, flow rate, pressure, and temperature.
• Control: Proportional relief and load valves to regulate system pressure.
The circuit was designed to simulate typical mobile hydraulic operation with precise control over pressure, flow, and temperature.
Test conditions • Temperature: Maintained at 80 °C ± 1 °C (bulk oil) .
• System Pressure: 13.8, 20.7, and 27.6 MPa (2,000, 3,000, and 4,000 psi).
• Motor Speed: 400, 600, and 800 rpm.
Two fluids were tested (Table 1 compares typical properties): 1. Industrial Hydraulic Reference Fluid is a leading SAE 10W (ISOVG-46) mineral oil hydraulic fluid that is an approved factory fill product.
2. VBASE EAL Hydraulic Fluid is a formulated hydraulic fluid using SPE®
base oils, (ISOVG-46) and
comprises an ashless anti-wear additive package with components that are EU-LuSC listed. The formulation is targeted to meet ISO-15380 (for environmentally acceptable hydraulic fluids).
The mineral oil reference fluid exhibits good low temperature properties but a comparatively low viscosity index. It is speculated it contains no Viscosity Index Improver (VII) due to the risk of shear degradation under high pressure conditions. The product also offers good corrosion inhibition. The presence of zinc and phosphorus suggests it contains a classical zinc dialkyldithiophosphate (ZDDP) antiwear additive.
The novel SPE® EAL hydraulic fluid exhibits a
significantly higher VI (and does not contain VI Improvers) and good low temperature properties. Interestingly, it exhibits a remarkably low air release time and low foaming. Smaller equipment reservoirs are being designed, in part, to reduce capital costs incurring even greater stresses to the fluid. Its ability to rapidly release air and avoid issues such as
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