An Energy Audit for a Three-Function Hydraulic Control System: A Consideration of Pump Arrangements

When designing a hydraulic circuit, there are a number of ways to power each hydraulic function in the circuit. For instance, a single hydraulic function may be powered by its own dedicated pump; or, a hydraulic function may share a pump with additional functions in the circuit. The design question is this: “What is the optimal arrangement of pumps for a given circuit that will result in the lowest energy consumption and the smallest machine size?” This research documents an example study in which a duty cycle from the typical wheel loader is used to study the five possible pump-combinations that exist for powering the lift, tilt, and steering functions of the machine. It is shown that the lowest efficiency for the machine is observed when all three functions are powered by a single pump, and that a 15% efficiency increase may be realized over the single-pump design by giving each function its own dedicated pump. In order to achieve this efficiency increase, the original single pump is replaced by the following pump combination: 1) a pump 69% the size of the original pump for the Lift function, 2) a pump 86% the size of the original pump for the Tilt function, and 3) a pump 31% the size of the original pump for the Steering function. This solution increases the overall pump volume on the machine by 86%, nearly doubling the pump volume on the machine.