Three-way, 2-position DCVs are used to ________.

• A. Control actuator speed
• B. Power actuators in one direction
• C. Power actuators in both directions
• D. Stop actuators in any position

Answer: (B)

The main idea is that a three-way, two-position directional control valve provides a path to push fluid to the actuator or to vent it, but not a path to push fluid to both ends of a double-acting cylinder. With three ports—pressure, actuator, and exhaust—and two positions, one position connects pressure to the actuator so it can move in one direction, while the other position vents that actuator port to exhaust, allowing the motion to stop or letting a spring (or the load) return the actuator. Because there isn’t a second port to pressurize the opposite side of the actuator, this type of valve drives an actuator in only one direction (often used with single-acting cylinders). To drive in both directions, a four-way valve would be required, which can connect pressure to either end of the actuator and vent the other end.