The term fan shaft has two meanings. The most common refers to the rotating spindle on which a fan blade is mounted. The blade is usually mounted on one end of the fan shaft, and the other end is attached to the motor, which is often electrically driven. The term is also used to denote a type of ventilation shaft that is found in industrial settings, especially mining. A fan shaft differs from passive ventilation in that a fan is mounted in the shaft to actively move the air.
Most electric motors used to power fans have a shaft that is integral to the motor itself and to which the fan blade is mounted, without any other parts or mechanisms involved. While there are several modifications to this basic design, all fans work on the basic principle of a blade rotating around a central axis. The blades, regardless of the configuration of the fan, are almost always mounted radially around the fan shaft.
An axial fan moves air in a direction parallel to the shaft, while a crossflow fan moves air in a plane perpendicular to the shaft and usually has a venting or cowl mechanism to direct the flow. A centrifugal fan also moves air perpendicular to the fan shaft, but it differs from a crossflow fan in the configuration of the intake. A crossflow fan takes in air along an axis perpendicular to the shaft while a centrifugal fan takes in air along its axis, usually at one end.
In industrial settings, a fan shaft is a type of ventilation shaft used for maintaining air quality in an enclosed space, like a mine or other subterranean installation. A fan is mounted in the shaft in order to increase air flow as well as to move the flow in a certain direction. Most fans of this type are axial fans, and some of them may be extremely large. The drive mechanisms of these types of fans can vary and may be electrical, internal combustion, or hydraulic. The power transfer method may also vary, and these fans may be driven by belts, gears, or even a chain and sprocket assembly.