The hydraulic system first determines how much thrust (or torque) the machine wants you to provide, whether it needs to maintain the thrust for a long time, how much speed is needed, whether the speed is constant or variable, whether the inertia at start and stop is large, and when to reduce the impact.

After determining the speed and thrust of the actuator, the power source can be selected, including prime mover and oil pump. In the workshop, enough power, preferred motor, small flow system on the production line can be used pneumatic, field flow to use diesel engines. And so on. Consider which plunger A2F pump to use, depending on the machine's operating environment, frequency, pressure level, flow range, cost, etc.

According to the mechanical action requirements, determine the selection of hydraulic valve. Electromagnetic ball valves and accumulators are required to maintain pressure, and proportional valves are required to change thrust at any time. High speed reciprocating servo valve and so on. Complex systems often need to adjust the pressure and flow at any time, and several different pressure cylinders at the same time, all rely on hydraulic valves to complete. The development of hydraulic valves is much more complex than that of hydraulic pumps.

The rest of the system is called "accessories", filters, coolers, fuel tanks, pipes and fittings, etc. These components should not be ignored. "running and leaking" is an old problem of the hydraulic system, which has not been solved yet.