A complete guide to hydraulic jack oil

With externally drained pilot-operated check valves, the cylinder is easy to control at any speed. Rotary hydraulic motor circuits are basically the same as cylinder circuits. The amount of rotary force available from the motor is a function of pressure and motor size. All of the systems described above are open center systems due to the oil flowing through the control valve back to the tank. Closed center systems use control valves with the inlet port blocked and variable displacement pumps.