Fans are flow machines for transporting air or other gases. The possible flow is from the premises to the environment or vice versa, and through process equipment, via ventilation ducts. The transfer of energy to overcome the flow resistance takes place in the impeller, the basic component of the fan. The drive source of the fan is an electric motor. The drive can be implemented as direct, belt or clutch drive. The fan impeller must operate in a spiral or tubular housing, terminated with stubs at the suction and discharge. The mechanical energy supplied to the fan is converted into the static and dynamic pressure gain needed to overcome the gas pressure flow losses in the equipment and ductwork.
With regard to their construction, fans are divided into:
They are used in car radiators and are also used as table, cabinet, ceiling and wall fans.
Diagonal fans bridge the gap between axial and radial fans. In this type of fan, the flow from the impeller flows onto the impeller blades in an axial direction, or is introduced into the scroll housing by flowing out through the discharge port.
In radial fans, the energy to the gas is transferred in the radial direction of flow. The inflow to the fan and impeller is axial. In the inlet chamber of the impeller, it changes to radial. A centrifugal effect occurs, further increasing the pressure build-up. This phenomenon is not present in axial fans. Thanks to it, higher pressure increments are produced. A high pressure build-up is achieved at a relatively lower capacity. Radial fans are most widely used. They are used in industry for ventilation, pneumatic conveying, dust extraction and blowing systems. They make it possible to transport the medium over long distances.
Fans are also divided according to the amount of backpressure generated:
When selecting a fan, in addition to the capacity, it is important to take into account the pressure losses that will be present in the system in order to ensure the intended fluid flow. Pressure losses occur in straight sections of ducts, elbows, fittings, inlets, outlets, filters, cyclones, etc. Velocities in the ducts range from 4-25 m/s (and higher). Higher velocities result in greater pressure losses and noise. Where pneumatic conveying is not required, we recommend speeds of a few m/s. For pneumatic conveying, velocities need to be higher - 16 m/s and above; this also depends on a number of other factors taken into account when designing and manufacturing the fan.
UNI-PRO Industrial Fans manufactures radial industrial fans: low-, medium- and high-pressure fans. It is possible to calculate and produce a fan of a given pressure and capacity. We manufacture fans from common steel sheets and acid-resistant sheets.
We manufacture special radial fans, tailored to individual customer wishes and requirements:
Belt drives are often used in air heater fans. Several technical problems requiring attention can be encountered with this type of drive. The first problem concerns the alignment of the pulleys to ensure that the belts work properly. This is particularly important in the case of multiple-belt drives (3 or more). The belts must be of equal length. Misaligned pulleys cause them to heat up. The belts also heat up. The gearbox runs noisily and the belts wear quickly. The drive configuration should be such that the lower part of the belt is stretched. This is important for long belts and for systems without tensioners. The loose part of the belt has a tendency to ‘flutter’. All housing and guard components must be kept at a safe distance to prevent rubbing or accidental flapping of the belt. Uncontrolled accelerated wear (belt fraying) is not difficult in such systems.
The fan impeller is supported by two bearings. Housings with open bearings or closed housings with seals can be used. UNI-PRO fans for heaters are fixed on a bearing system with the possibility of compensating for the thermal lapping of the shaft. As a result, the bearings do not transmit additional axial forces and the internal bearing clearance is maintained at a constant level. This solution extends bearing life and ensures a lower noise level.
Another issue is the lubrication of the bearings. The temperature of the housing can be 80-90 oC. In each design solution, the bearings must be lubricated with a suitable grease and re-lubricated at specified intervals during operation. The re-lubrication interval depends on the conditions and the operating time of the bearings. Closed housings allow the grease to be retained inside the bearing for longer. However, the grease gradually leaks out of the housing (outflow holes are drilled into the housing for this purpose). New grease is applied via grease nipples screwed into the housing. The space inside the housing must not be tightly filled with grease. Too much of it creates additional resistance to bearing movement and leads to excessive heating of the bearing node.
