Which component regulates the flow of water into a boiler?

The component that regulates the flow of water into a boiler is indeed the feedwater control valve. This valve plays a crucial role in maintaining the proper water level within the boiler, which is essential for its efficient and safe operation. By controlling the amount of water entering the boiler, the feedwater control valve ensures that the system does not become either overfilled or underfilled.

When the water level in the boiler drops below a predetermined setpoint, the feedwater control valve opens to allow more water to flow in. Conversely, if the water level rises above the setpoint, the valve can close to prevent excess water from entering. This regulation is vital for maintaining optimal heat exchange efficiency and preventing damage to the boiler from overheating or water hammer.

This specific function distinguishes the feedwater control valve from other components listed. For instance, while the pressure relief valve is critical for safety, providing a means to relieve excess pressure, it does not regulate water flow. The expansion tank serves to accommodate fluctuations in the water volume due to temperature changes, and the water level gauge provides visual indications of the water level within the boiler, rather than actively controlling it.