The needle valve adjustment screw has a tapered end to adjust the size of the ______.

• A. Orifice
• B. Vane
• C. Valve Body
• D. Pressure

Answer: (A)

Fine control of flow is achieved with a needle valve because its tapered tip acts as a precise plug that meters the opening through which fluid can pass. As you turn the adjustment screw, the needle moves into or out of the small seating area, changing the effective size of the orifice. A smaller opening restricts flow and can raise downstream pressure, while a larger opening allows more flow. This is why the tapered end is designed to adjust the size of the orifice. The other options don’t fit because a vane is a part of a pump or turbine, the valve body is just the housing, and pressure is a condition, not a physical opening whose size is controlled by the needle.