What are induced draft fans? And how do they work?
Draft, is commonly referred to as the difference between the atmospheric pressure and the pressure existing within a flue gas passage or the furnace of a boiler system. When the flow of flue gas and air become influenced by the effect of a gradually decreasing pressure below atmospheric pressure, this is referred to as induced draft.
Induced draft fans or ID fans are used in systems such as steam boilers and thermal oil heaters to draw out and remove flue gases from combustion chambers, by creating a vacuum of negative air pressure (typically -10 mm Hg). This is achieved by using a blower to to suck air through the combustion chamber and the rest of the system, before discharging the air and flue gas through a stack or chimney.
In this way, not only do induced draft fans enable the regulation of pressure within systems such as boilers, but they work to facilitate the combustion process in boilers and other systems, by supplying the necessary air needed for the combustion of fuels.