CF-450 Backward-Curved Centrifugal Fan

The CF-450 uses a welded backward-curved impeller in a scroll casing. Backward-curved blading is non-overloading: as the system resistance falls away, the absorbed power flattens rather than climbing, so the motor cannot be dragged past its rating by a filter bank that turns out to be cleaner than the design assumed.

Where it sits on the curve

Peak total efficiency falls between roughly 55 and 70 per cent of free delivery. We quote the duty point on the measured curve rather than at the end of it, because a fan selected close to free delivery will be noisy, and one selected far left of peak will run unstable in the stall region.

Construction

Casing and impeller are mild steel as standard, with the impeller welded and then dynamically balanced in two planes. Bearings are grease-lubricated and mounted outside the airstream on the arrangement 9 build, so bearing life is not tied to the air temperature.

Motor and drive

Belt drive as standard, with the pulley ratio set after the duty point is confirmed, so the same casing covers a range of speeds. Direct drive is available where the required speed matches a standard IEC frame pole count. Motor frame sizes follow IEC 60072 dimensions, which keeps replacement motors sourceable locally.

Sound

Sound power levels are given in octave bands, measured by the ISO 13347 method, and stated separately for inlet, outlet and casing radiated. Ask for the value that matches where your acoustic problem is; a single A-weighted number for the whole fan will not tell you whether to lag the casing or fit an attenuator.