Boilers that are equipped with air heaters and economizers usually have _____ draft fans.

Boilers equipped with air heaters and economizers typically require efficient draft management to optimize combustion and enhance thermal efficiency. The presence of both forced and induced draft fans in such systems plays a crucial role in maintaining the necessary airflow.

Forced draft fans are used to push ambient air into the combustion chamber. This assists in ensuring that sufficient air is supplied to support complete combustion of the fuel, which is essential for energy efficiency and reducing emissions.

Induced draft fans, on the other hand, are installed to pull flue gases out of the combustion chamber and through the exhaust stack. This creates a negative pressure within the boiler, which is beneficial for combustion as it helps in drawing in the necessary airflow from the forced draft system.

The combination of forced and induced draft fans ensures that the boiler operates efficiently under various load conditions, which is vital for maintaining optimal performance and safety standards in steam engineering applications.