A connective valve which selects one of two or more circuits because of flow or pressure changes between circuits.

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

Answer: (B)

The function here is to automatically pick which circuit feeds the load based on pressure differences. A shuttle valve does exactly that by using a movable shuttle (ball or piston) inside a three-port body. When two input circuits are connected, the shuttle shifts toward the lower-pressure side and away from the higher-pressure side, effectively blocking the lower-pressure input and connecting the higher-pressure input to the output. This creates an OR-like effect: the actuator is fed by whichever circuit has the higher pressure, and if one circuit drops pressure, the other takes over without manual switching.

This isn’t a leak valve, which is used to vent or bleed, nor a pilot valve, which uses a small pilot flow to control another valve, nor a double-acting cylinder, which is an actuator.