Centrifugal Fan Sheave

The speed at which a belt-drive centrifugal fan will run is completely determined by one component and that is the driven sheave, which is mounted directly on the fan shaft. The actual RPM of the fan is determined by the ratio that this Centrifugal Fan Sheave creates with the motor-side sheave. A slight mistake or mismatch in its pitch diameter changes the entire calculation of airflow, static pressure and motor loading. A small or worn fan sheave slips under load, causing the motor's power to be wasted as heat instead of airflow.

A perfect fan sheave selection depends on calculating the target fan RPM, motor speed and pitch diameter in conjunction with the motor sheave diameter. This is the standard drive-ratio calculation, which is used in fan engineering references. For larger diameter and higher torque fan-side sheaves, it is best to use taper-bushing mounting instead of set-screw mounting. There are two excellent reasons behind this. First, it spreads the pressure or clamping force very evenly around the shaft. And secondly, when maintenance or servicing is needed, the sheave can be easily removed without causing any damage. It is absolutely mandatory to check the alignment of any Centrifugal Fan Sheave with a straightedge after installing or replacing it. Also, you must verify whether the belt speed is within the maximum recommended limit.