The INLET-DAMPER valves (or louvers) are very common in induced draft fans and gas recirculation fans. For their use it is necessary to install an air inlet box at the fan air intake.

All the blades of an Inlet-Damper turn in the same direction and they are made of hollow section with airfoil shape, each blade having inside a passing shaft for driving it.

PRINCIPLE OF OPERATION:

All what has been explained in respect to the Inlet Vanes will apply to the Inlet Dampers. Notice however, that Inlet Dampers are placed at a greater distance from the intake and that fluid must turn 90º before entering the rotor.

Hence pressure losses are greater in an Inlet Damper, for which reason this type of valve is less efficient. In heavy working conditions it offers, nevertheless, important constructive advantages.