Radial Variable Inlet Vanes

With centrifugal fans one has a choice to control the flow using dampers.

On the inlet side we can use Variable Inlet Vanes (VIVs) or Inlet Louver Dampers (ILDs). Variable inlet vanes offers the highest efficiency of damper control of a centrifugal fan. VIVs can work inside an inlet box or be directly in the duct.

They are more expensive than the ILD as the manufacturing process is more complex and the components tend to be more expensive. The benefit is improved control and savings of energy at reduced flows.

The blades are angled such that they introduce a swirl into the fan and set up optimum streamlines for the air flow into the fan inlet.

Inlet Louver Dampers

Inlet Louver Dampers are a parallel bladed louver damper used on the inlet of centrifugal fan. As with VIVs the orientation and positioning is important in order to introduce a pre-swirl to the flow as it enters the eye of the impeller of the fan.

Often the fan may be a double inlet double width fan in which case two inlet louvers are required to work in tandem. One actuator can be used to control the two ILDs in tandem. Specify EFFOX Flextor brand Inlet Louver Dampers to your fan vendor.

Outlet Louver Dampers

Outlet louver dampers go on the outlet, or discharge, of a centrifugal fan. The efficiency in this area is less than either the Inlet louver or Variable Inlet Vane Dampers. Mainly because they simply work to throttle the flow back but at the full fan pressure. The ILD or VIV actually reduces flow by essentially drawing a new curve. All the various curves are called a “family of curves”. See below for one family.

Outlet louver dampers may be used in conjunction with inlet louver dampers. In this way they can hit a wide variety of points within the envelope of the fully open or unthrottled fan curve (the area under the 100% curve).

EFFOX Flextor is represented by CB Power and Industrial Equipment