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Inlet Vane Controls (IVC)

Inlet vane controls (Radial Vane Controls) are often used to control the flow through the fan.

They must be mounted close to the fan inlet to provide effective control and must have the correct orientation so that the gas is swirled in the same direction as the impeller rotation.

There are two main menthods of mounting:

1) The vanes are constructed within the fan inlet cone. This provides the greatest control and generally gives stable performance down to very low flow. The mechanism however is often in the air stream which can be a disadvantage in dirty applications causing increased wear or seizure.

Vanes mounted in the inlet cone provide the best mechanical method of controlling flow through the fan and giving substantial power savings at off design duties. Cheaper in first cost than variable speed controlers for large motors.

2) The vanes are mounted in a separate barrel bolted to the fan inlet. Flow control is still very good and the mechansim can be external to the gas stream. Cantilever types can be used for dirty applications.

An offset vortex can sometimes be generated by both types at around the mid point opening. This vortex can cause very large vibrations whch may cause fan failure. This problem can be fixed by using dorsal fins or a central jet of air to stabilize the vortex.