Which disk valve requires very little pressure to the handwheel but is excellent for fine throttling?

• A. Needle
• B. Conventional
• C. Composition
• D. Plug

Answer: (A)

The needle valve is specifically designed for precision flow control and is excellent for fine throttling. This type of valve has a long, tapered seat that allows for a small amount of flow at low pressure. As the handwheel is turned, the needle moves in a linear motion, enabling very fine adjustments to the flow rate. This is particularly important in applications where precise control of liquid or gas flow is crucial.

Unlike conventional valves, which are better suited for on/off control, or composition valves, which may not provide the same level of adjustability, the needle valve excels because of its design and the control it offers. The plug valve also does not facilitate fine throttling as effectively as a needle valve, since it is typically used for quick shut-off rather than precise adjustments.

In summary, the needle valve is the ideal choice when very little pressure is required at the handwheel while allowing for excellent control in throttle applications.