What is the purpose of a deaerator in a boiler feedwater system?

• A. To remove dissolved gases and preheat the water to reduce corrosion and improve efficiency.
• B. To remove dissolved solids.
• C. To dehydrate the feedwater.
• D. To equalize pressure.

Answer: (A)

Dissolved gases in feedwater, especially oxygen and carbon dioxide, promote corrosion of boiler components. A deaerator uses contact with steam to strip those gases from the water and vents them away, reducing the potential for corrosion. At the same time, the incoming water is preheated by the steam, which saves energy because less heat is needed to bring the water to boil and it reduces thermal stress on the boiler and piping.

So, the deaerator’s purpose is to remove dissolved gases and preheat the water to cut corrosion and improve efficiency. This isn’t about removing solids or dehydrating the water, and it isn’t primarily a device for balancing pressure.