Variable Inlet Vane Dampers (VIV)

Variable inlet vane dampers (also called vortex dampers) are mounted on the fan inlet to conserve fan horsepower at reduced airflow conditions. They are arranged to generate an inlet vortex (pre-rotation) in the same direction as the fan impeller, causing a reduction in power, consumption as the air flow is reduced. This type of control is most effective when the fan is expected to operate at reduced performance conditions for extended time periods or if the system requires modulation during operation. It will alter the fan operating characteristics and reduce the likelihood of instability. A wide-open VIV will produce a system effect which must be accounted for in the original fan selection.