What is the purpose of a forced draft fan in a boiler?

The primary function of a forced draft fan in a boiler is to supply air to the furnace. This is crucial for the combustion process, as a proper air supply is needed for the fuel to burn efficiently and produce heat. The forced draft fan pushes air into the combustion chamber, where it mixes with the fuel, ensuring a controlled and optimal combustion environment. This contributes to better fuel efficiency, reduced emissions, and more effective heat generation.

In a boiler system, the balance of air and fuel is vital for maximizing performance. The forced draft fan helps to maintain this balance by delivering the necessary oxygen required for complete combustion. Without this fan, the combustion might be insufficient, leading to increased pollutants, such as carbon monoxide, and potentially causing operational issues within the boiler system.

The other options do not relate directly to what a forced draft fan accomplishes. For instance, expelling excess steam pertains more to safety valves or condensate drains, while pumping water into the boiler is typically the function of feedwater pumps. Regulating pressure is typically managed through various controls and safety devices, not specifically by the forced draft fan. Therefore, the option that identifies the role of the forced draft fan accurately reflects its significance in boiler operations.