Why is a 4-3 way valve preferred for controlling the direction of a double-acting actuator?
It can reverse flow and provide a neutral position
A double-acting actuator (cylinder) is powered in both directions, receiving pressurised fluid on one side to extend and on the other side to retract, so its control valve must be able to route fluid to either port on demand.
A 4/3 way directional control valve has four ports and three switching positions, which is exactly what such control requires.
In its first working position it sends fluid to one side of the cylinder while returning fluid from the other, extending the actuator; in its second position the connections swap, reversing the flow to retract it.
Its third, central position is a neutral setting that can block or vent the ports, letting the actuator stop and hold, or allowing the pump to unload.
This combination of reversing capability plus a neutral hold is precisely why the 4/3 valve is preferred for a double-acting actuator.
A one-way valve (option 2) allows flow in a single direction and cannot reverse the cylinder, while being smaller (option 3) or raising pressure (option 4) are not functions this valve provides, since pressure is set by the relief valve, not the direction valve.
Hence, the answer is It can reverse flow and provide a neutral position.
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Important Questions from Pneumatics and Hydraulics
The study of pneumatics deals with system operated with,
- The hydraulic accumulator is fitted
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