What are the two principal types of rotary valves?

• A. Gate and Globe
• B. Plug and Ball
• C. Ball and Gate
• D. Check and Swing

Answer: (B)

Rotary valves control flow by rotating a closure member rather than moving it linearly. The two main designs used in water distribution are plug valves and ball valves. A plug valve uses a cylindrical or conical plug with a bore that aligns with the pipeline when open and blocks flow when rotated to a closed position; the seal comes from seating surfaces around the plug. A ball valve uses a spherical ball with a bore; a quarter turn aligns or blocks the bore to open or close, and the seating surfaces around the bore provide the shut-off seal. These designs are favored for their compact size, quick operation (often a 90-degree turn), and reliable shut-off, making them the most common rotary options in distribution systems. The other choices are not rotary valves: gate and globe valves operate with linear motion of a closure along the stem, and check valves (including swing check) rely on flow direction and hinges rather than a rotating closure.