Parallel Blade Dampers

Parallel blade type inlet box dampers may be used to control the airflow through the system. The airfoil shaped blades are parallel to the fan shaft and remain parallel to each other as the damper is closed. Thus, in a partially closed position, a forced vortex with the same rotational direction as the fan impeller will be generated within the inlet box. The effect on the fan characteristics will be similar to that of a variable inlet vane control.