What is the main function of a blowdown valve in a boiler system?

The primary function of a blowdown valve in a boiler system is to remove impurities and sludge that accumulate in the boiler water over time. As water is heated in the boiler, dissolved solids can concentrate due to evaporation. These solids, along with any suspended particulate matter or sludge, can negatively impact boiler efficiency and increase the risk of corrosion and scaling.

To maintain water quality and ensure efficient operation, regular blowdown is conducted. The blowdown process involves opening the valve to allow a portion of the concentrated water from the bottom of the boiler to be expelled, thereby reducing the concentration of impurities. This helps in maintaining overall system health by facilitating better heat transfer and preventing other operational issues, ensuring the boiler operates efficiently and safely.

In contrast, other functions mentioned in the choices do not accurately reflect the role of the blowdown valve. Releasing steam into the environment, controlling the feedwater supply, or increasing pressure, while relevant to boiler operation, do not pertain directly to the specific role of the blowdown valve.