A centrifugal fan usually has a distinctive “snail shell” appearance. From the outside, you see a spiral, scroll-shaped steel housing with a circular inlet on one side and a rectangular or round outlet on the rim of the scroll. Mounted on a frame or baseplate, the fan is driven by an electric motor through a direct coupling or belt drive.
Inside the scroll is the impeller, which looks like a wheel with multiple blades. Depending on the design, the blades may be radial (straight out from the hub), backward-curved, airfoil-shaped or forward-curved. The impeller is mounted on a shaft supported by bearings in a bearing housing. In industrial and mining fans, these bearings and housings are robust, often with lubrication lines and seals suitable for continuous heavy-duty operation.
On the inlet side, you typically see a circular opening with an inlet cone or bellmouth that guides air smoothly into the impeller eye. A safety guard or inlet box may be installed to prevent accidental contact and to connect the fan to inlet ducting. On the outlet side, the scroll housing narrows into a discharge opening that connects to a duct, stack or mine airway. The orientation of this outlet (up, down, left or right) can be chosen during installation to suit the layout.
In many industrial installations, the motor is mounted on the same base as the fan. For belt-driven centrifugal fans, you will see pulleys and belts between the motor shaft and the fan shaft, protected by a guard. For direct-drive designs, the motor is connected directly to the impeller shaft, and the assembly may appear more compact. Large mining or process fans may be housed in fabricated steel structures with access doors, inspection ports and lifting lugs.
Compared with a typical axial or household fan, a centrifugal fan looks more like a closed industrial blower than an open propeller. You do not usually see the blades from the outside because they are enclosed in the housing. This enclosure is what allows the fan to build higher pressures and connect efficiently to ducting, filters and process equipment.
In summary, a centrifugal fan is recognisable by its scroll-shaped housing, wheel-like impeller, and motor-and-frame assembly. This compact yet robust shape is designed for reliable operation in industrial plants, HVAC systems and mining ventilation where controlled airflow and pressure are required.
