Which type of valve restricts flow in both directions?

• A. Ball valve
• B. Check valve
• C. Needle
• D. Gate valve

Answer: (C)

Needle valves are built for precise flow regulation. They use a slender needle that seats into a small, adjustable orifice. Turning the handle moves the needle a tiny amount, finely throttling the flow. Because the restriction comes from that adjustable opening, you can throttle flow in either direction, giving bidirectional control. Ball and gate valves are designed mainly for on/off service with minimal restriction when open, not for fine throttling. A check valve, on the other hand, is intended to block flow in one direction and permit it in the other, so it doesn’t provide restricted flow in both directions. That bidirectional throttling capability is why the needle valve is the best answer.