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.

Actuating both operators simultaneously extends the cylinder. According to valve size and inlet air flow, the cylinder might not extend if just energizing the valve.

Shows a circuit that operates a single-acting cylinder with 2-way valves. One and one 2-way directional valve piped to the cap end cylinder port allows fluid to enter and exhaust from it.

With the control valve in neutral , the pump is "De-stroked" to zero flow. 5-way, 3 position, spring-centered pressure to cylinder ports, exhausts blocked center condition, solenoid-pilot operated, line mounted.

This prompts a pilot signal to an integrated pilot-operated check valve , which opens, and creates a direct passage from the cylinder through the intensifier and back to tank. The schematic drawing in Hydraulic Valve 8-79 shows a cylinder with pilot-operated check valves at each port and meter out flow controls downstream of the reverse flow outlet port. If this circuit did not have externally drained pilot-operated check valves, the cylinder would operate in jerks or not at all when the directional valve shifts. Backpressure from the flow controls can push the pilot piston closed and stop the cylinder, then pressure would drop and it would start again. This oscillating movement would continue until the cylinder competes its stroke.