Valves that use rotational motion to make a seal are called:

• A. Globe valves
• B. Ball valves
• C. Gate valves
• D. All of the above

Answer: (B)

Rotational motion to seal is a hallmark of a ball valve. Inside, a spherical ball with a bore rotates to open or close the flow path. When the bore aligns with the piping, fluid passes through; rotate the ball 90 degrees and the bore is blocked, and the seal is created by the ball pressing against seats. This quick, rotational action provides a tight shutoff with relatively low torque and fast operation.

Globe valves and gate valves, by contrast, seal through linear movement. A globe valve moves a disk toward or away from a seat along the axis, while a gate valve raises or lowers a wedge-shaped gate to block flow. Their sealing relies on axial motion rather than rotation, so they aren’t described as using rotational motion to seal.