In a pneumatic system, which valve throttles or limits flow in the reverse direction through a needle valve?

In a pneumatic system, which valve throttles or limits flow in the reverse direction through a needle valve?

• A. Flow control valve
• B. Check valve
• C. Pressure regulator
• D. Relief valve

Answer: (A)

Controlling how fast air moves through a line is done with a flow control mechanism that provides an adjustable restriction. A needle valve gives very precise control of the opening, but to regulate or throttle the flow in the path—especially when you want to limit flow that could move back through that path—you use a flow control valve. It introduces the calibrated resistance that sets the rate at which air can pass, so you can dial in the desired speed in the circuit. A check valve, on the other hand, mainly stops flow from returning in the opposite direction rather than setting a reversible, adjustable flow rate. A pressure regulator keeps the system at a set pressure, not the flow rate through the needle path. A relief valve opens to vent when pressure gets too high, also not about metering flow in the needle valve path. So the valve that provides the throttling or limiting effect through the needle valve path is the flow control valve.

Controlling how fast air moves through a line is done with a flow control mechanism that provides an adjustable restriction. A needle valve gives very precise control of the opening, but to regulate or throttle the flow in the path—especially when you want to limit flow that could move back through that path—you use a flow control valve. It introduces the calibrated resistance that sets the rate at which air can pass, so you can dial in the desired speed in the circuit.

A check valve, on the other hand, mainly stops flow from returning in the opposite direction rather than setting a reversible, adjustable flow rate. A pressure regulator keeps the system at a set pressure, not the flow rate through the needle path. A relief valve opens to vent when pressure gets too high, also not about metering flow in the needle valve path. So the valve that provides the throttling or limiting effect through the needle valve path is the flow control valve.