Which cylinder type allows fluid pressure to move the piston rod in both directions?

• A. Pilot Valve
• B. Leak
• C. Double Acting Cylinder
• D. Shuttle Valve

Answer: (C)

Moving fluid pressure on both sides of a piston is what makes a cylinder able to extend and retract under power, not just return by spring. This bidirectional actuation is the hallmark of a double-acting cylinder. It has two ports, and a control valve directs pressurized fluid to either side of the piston. When pressure is applied to the front side, the piston extends the rod; when pressure is applied to the rear side, the piston retracts. There’s no need for a spring to push it back, because fluid pressure on the opposite side drives the movement in that direction.

In contrast, the other items aren’t cylinder types. A pilot valve is a small valve that starts or controls a larger valve. A shuttle valve is a device that selects the higher pressure from two sources. A “leak” isn’t a component type at all.