Which valve is used to control flow from hydrant side discharges, actuated by a screw closing the door top to bottom like a medieval castle barrier?

Which valve is used to control flow from hydrant side discharges, actuated by a screw closing the door top to bottom like a medieval castle barrier?

• A. Gate Valve
• B. Ball Valve
• C. Butterfly Valve
• D. Check Valve

Answer: (A)

This item tests how valve operating mechanisms translate into function. A valve that is opened or closed by a screw moving a component straight up and down resembles a door that slides to seal, like a castle gate dropping to block a passage. That describes a gate valve: a wedge-shaped gate is raised or lowered by turning a stem with a handwheel, giving a clear, linear motion along the flow path. When fully open, the gate sits out of the flow, causing minimal obstruction; when closed, it seats tightly to stop flow. Hydrant side discharges benefit from this simple, reliable full shut-off with a screw-driven, vertical movement, which is why gate valves are used here. Ball valves and butterfly valves rely on rotary motion—turning a ball or a disk to block the passage—which doesn’t match the “door top to bottom” sliding action. Check valves are designed to prevent backflow and close automatically under reverse flow, not to provide isolation with a manually screw-driven, vertical gate motion.

This item tests how valve operating mechanisms translate into function. A valve that is opened or closed by a screw moving a component straight up and down resembles a door that slides to seal, like a castle gate dropping to block a passage. That describes a gate valve: a wedge-shaped gate is raised or lowered by turning a stem with a handwheel, giving a clear, linear motion along the flow path. When fully open, the gate sits out of the flow, causing minimal obstruction; when closed, it seats tightly to stop flow. Hydrant side discharges benefit from this simple, reliable full shut-off with a screw-driven, vertical movement, which is why gate valves are used here.

Ball valves and butterfly valves rely on rotary motion—turning a ball or a disk to block the passage—which doesn’t match the “door top to bottom” sliding action. Check valves are designed to prevent backflow and close automatically under reverse flow, not to provide isolation with a manually screw-driven, vertical gate motion.