Directional control valves are one of the most fundamental parts in hydraulic machinery. They allow fluid flow into different paths from one or more sources. They usually consist of a piston inside a cylinder which is mechanically or electrically controlled. The movement of the cylinder restricts or permits the flow, thus it controls the fluid flow.
These valves are used to control conditions such as flow, pressure, temperature, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a “set point” to a “process variable” whose value is provided by sensors that monitor changes in such conditions. they control the direction of the actuator, also if you have a hydraulic motor the valve would control which rotation it would turn, such as forward and reverse or clockwise and counter clockwise.
Furthermore if you are controlling a cylinder, the valve would tell it to extend and retract. A selector valve controls the flow from the pump to one line or another, giving the system an extra path to be used from the same pump.
Finally a 4-way control valve is essentially the directional control valve. Consequently controlling pump flow direction from the control valve to the actuator and allowing return flow to go through the control valve and back to the tank. In one spool position of the valve, the flow from the pump is ported from the inlet port to the A work port (which then goes to the actuator) and (coming from the actuator) to the B work port the flow is ported to the outlet port. Hence flow passes through the valve twice. Opposite of that spool position. The flow is ported from the inlet to the B work port (which then goes to the actuator) and (coming from the actuator) to the A work port the flow is ported to the outlet port. Flow passes thought the valve twice.
With the 2 positions of the spool, the flow has the ability to pass through the valve 4 times – 4 way valve.
Choices of Directional Control Valves
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