Industrial hydraulic systems were introduced as a useful medium for power transmission during the beginning of the 20th century. Since then the technology has undergone continuous evolution by responding to the challenging demands. It has competed with other power transmission technologies to find its present place. The strengths of hydraulic drives that make them the preferred choice are their high force and acceleration capability, ability to operate at full torque even at zero speed, continuous speed variability and stiffness.

In Industrial hydraulic systems, the actual input is some kind of prime mover such as an internal combustion engine or an electrical motor. The speed and torque of the prime mover is converted to the hydraulic power parameters at the hydraulic pump, the directional control of the hydraulic power is provided by a valve, while the output can be the force and velocity of a reciprocating cylinder (or a hydraulic motor) which may actually connect to the load through linkages and gears. The input to the valves can be electronic, hydraulic, or maybe manual. It is imperative that the design engineer be able to perform some kind of analysis to insure the proper functioning of the system such as energy analysis. Such an analysis can be performed in the laboratory through the use of prototype systems, or it can be performed through computerized simulation. In order to evaluate the total energy performance, from input to output, of a hydraulic system analytically, a software program is used, which will carry out the calculation of the energy balance for each component in the hydraulic system and also will integrate the interactions of the diverse components involved.

In this computer program, initially the required mechanical power (output power) should be determined, and then the corresponding hydraulic power through the reciprocating cylinder and/or hydraulic motor will be estimated. The type of way valve will be selected following the directional control needed for the hydraulic circuit. Next, the necessary control valves, to insure the correct functioning of the circuit, and the corresponding linking pipes and conduits will be chosen. The last step, in this stage, is the dimensioning of the hydraulic pump and tank.
In the next stage, the performance characteristics of hydraulic components will be studied, where the pressure and flow rate at the inlet and outlet of each component are calculated. Then detailed calculation of force, velocity, inlet and outlet powers, pressure losses and flow rate losses in the various components is achieved. In the last stage, the volumetric, mechanical, and total efficiencies for individual components and overall efficiency for the whole hydraulic system are evaluated.

The aspects involved in this computerized analysis will be discussed, followed by the illustration of the concepts through the study of a typical system. This typical system will be simulated and the output information will be presented and discussed.