In a globe valve, what best describes the interaction between the disk and the seat?

• A. The disk moves against a stationary seat to regulate flow
• B. The disk remains stationary while the seat moves
• C. The ball rotates to seal
• D. The gate slides to seal

Answer: (A)

Globe valves regulate flow with a closure element that moves toward and away from a stationary seat. The disk (or plug) is attached to a stem and is the moving part, while the seat remains fixed to the valve body. When the disk is raised, a larger flow area exists and flow increases; when the disk is lowered, it approaches the seat, narrowing the flow path and throttling the flow. When fully closed, the disk seats against the stationary seat to form a tight seal.

This interaction—disk moving against a stationary seat—is what makes a globe valve well-suited for precise throttling and shut-off. The other described configurations correspond to different valve types: a rotating ball seals by the ball turning against seats, and a sliding gate seals by the gate moving in line with the flow.