Which valve enables steam to flow from the Auxiliary Exhaust Line to the Deaerating Tank when the tank pressure is less than the exhaust line?

Which valve enables steam to flow from the Auxiliary Exhaust Line to the Deaerating Tank when the tank pressure is less than the exhaust line?

• A. Check Valve
• B. Gate Valve
• C. Ball Valve
• D. Relief Valve

Answer: (A)

A check valve is the one-way flow control device designed for this situation. It automatically opens to allow steam to move from the Auxiliary Exhaust Line into the Deaerating Tank when the line pressure is higher than the tank pressure, and it closes if the tank pressure becomes equal to or greater than the line pressure, preventing any reverse flow back toward the exhaust line. This automatic, directional behavior is exactly what’s needed to feed the deaerator without letting steam backfeed. Gate and ball valves are manual shutoffs; they don’t automatically prevent backflow and would require operator action to control flow, making them unsuitable for this purpose. A relief valve, on the other hand, is a safety device that vents excess pressure and is not used to route normal flow from the exhaust line to the deaerator.

A check valve is the one-way flow control device designed for this situation. It automatically opens to allow steam to move from the Auxiliary Exhaust Line into the Deaerating Tank when the line pressure is higher than the tank pressure, and it closes if the tank pressure becomes equal to or greater than the line pressure, preventing any reverse flow back toward the exhaust line. This automatic, directional behavior is exactly what’s needed to feed the deaerator without letting steam backfeed.

Gate and ball valves are manual shutoffs; they don’t automatically prevent backflow and would require operator action to control flow, making them unsuitable for this purpose. A relief valve, on the other hand, is a safety device that vents excess pressure and is not used to route normal flow from the exhaust line to the deaerator.