VIV Dampers are designed with mechanical principle of -Inlet guide vanes are synchronously adjustable in the same angular position by a connecting element. Adjustment can be made either automatically via an adjusting element from pulse generator by hand. Energy Savings with fans utilizing variable inlet vanes. VIV Dampers are often used for capacity modulation. They give accurate modulation and power savings over other styles of dampers at reduced air flow. When an inlet vane is partially closed, each blade directs the air into the wheel in the direction of rotation and so the air is prespun. This brings about a reduction in the Capacity, Static Pressure and BHP. The amount of BHP savings at reduced capacity is determined by the type of system and type of fan-vane combination.