Question

What type of directional valve is used to control the forward and reverse of a double-acting hydraulic piston?
a) 3 way/ 2 position
b) 4 way/ 2 position
c) 4 way/ 3 position

and why?

Answer 1

A double-acting actuator requires a 4-way valve. A 4-way valve pressurizes and exhausts two ports interdependently. A 3-position, 4-way valve stops an actuator or allows it to float. The 4-way function is a common type of directional control valve for both air and hydraulic circuits. A 3-position, 4-way valve is more common in hydraulic circuits.

The four-way, two-position DCVs used are sometimes impractical because they continually send pump flow and pressure to the actuator in one direction or the other. Many cylinder and motor applications require a third DCV position or neutral in which the actuator is subjected to pump pressure. Four-way three-position circuits are therefore used in many hydraulic circuits.

Ans is (c) 4 way / 3 position.