Radial fans are machines used to pump gas, usually air. This results in the flow of air in ducts or its mixing in rooms. UNI-PRO is a manufacturer of industrial radial fans in which the direction of gas flow is radial centrifugal.
In the offered fans, air or other gas is drawn in axially, speed is imparted and flow is forced perpendicular to the rotor axis. The compression of the air or other gas is caused by centrifugal force. The required energy is obtained through the work of an electric motor, and the air flowing through this type of device changes direction by 90°. The radial fan sucks air axially through a circular opening located along the axis of the motor. The outlet of the performed radial mechanism is always placed perpendicular to the axis of the inlet, and the outlet can be rectangular or circular. Most often the outlets of the presented devices are rectangular. This is due to the design of the rotor manifold, which in the standard design has a spiral shape. The rotor of the device has a support disc to which the blades are welded. On the blades on the other side is welded a covering disc with an opening through which air is drawn in. Depending on the application, the described ventilation units are used in various industries, and are characterized by high efficiency of up to 85%. They also have a number of specialized applications. A special variety of radial impellers are transport impellers, where there is no covering disc. Translated with DeepL.com (free version)
The devices are made of ordinary quality steel, acid-resistant steel, plastics. The material of manufacture depends on the working conditions in which it is to operate. Where radial fans have no special requirements we produce them from ordinary quality steel. In the case of contact with acids, the fan is made of acid-resistant steel with the appropriate chemical composition matched to the conditions in which it is to operate. It should be remembered that we have a lot of types of acid-resistant steel that are resistant to various acids. The basic acid-resistant steel is 1.4301 (according to the Polish Standard 0H18N9) we use it where there is no very aggressive chemistry. We use plastic ventilation units made of polypropylene and polyethylene alternatively instead of steel fans. Very often it is a very good alternative. The lifespan of a plastic machine is often much longer than an acid-resistant steel fan. Translated with DeepL.com (free version)
Different models of fans of this type have different blade arrangements and, depending on demand, different numbers of blades.
The blades can be of different shapes:
Radial fans are usually mounted on separate foundations or special frames on shock absorbers. The frame is usually fixed to the ground with specially adapted anchor bolts. Flexible ventilation ducts can be connected to this type of equipment.
Thanks to the use of a frequency converter, the fan speed can be adjusted steplessly. This has a very big advantage because we can easily adjust the performance and pressure of the fan to the current needs. We recommend this solution as an alternative to belt-driven units where there is no need for a belt drive. In the case of belt-driven fans, changing the speed is possible but requires changing the pulleys.
Not everyone realizes that a properly designed fan has a closely coupled manifold and impeller. When designing a fan, we first need to determine what performance and pressure parameters it should have at the operating point.
We assume what speed per minute it should have. Based on these assumptions, we calculate the power of the fan. We select a motor to ensure proper operation of the fan. We calculate the inlet diameter of the impeller as well as its outer diameter. The next step is to design the shape and size of the blade. The impeller blade is the most important part of the impeller. We calculate its width at the outlet as well as the inlet. We determine the number of blades on the rotor. The rotor blade is fixed on a specific outer diameter as well as inner diameter. Depending on the assumed parameters of operation, the blades can be straight, bent on a radius backwards, for example, as in drum rotors, or downwards. The bending of the blade is not random it follows strictly from the calculations. In the calculation of the rotor we take into account the space between the blades. It is also necessary to assume when designing the rotor what the thickness of the blade will be. A well-designed radial rotor works on the entire inter-blade spaces.
The next step is to design a collective collector commonly referred to as a spiral housing. The collector manifold has a significant impact on the operation of the fan. Any properly designed unit has a collector that works closely with the impeller. We design the collector for the radial fan so that the equation of continuity of flow is preserved, which will ensure its proper operation. By changing the shape of the spiral collector, we change the operating characteristics of the device.
UNI-PRO offers modular radial fans to be built-in. In this case, we supply the fan without a collector (spiral housing). The responsibility for the proper distribution of air is taken by the recipient. If we do not have a manifold, it is necessary to provide a sufficiently large space around the impeller so that the air can move freely.
Any properly designed and manufactured fan should not exceed vibrations of more than 4mm/s. We dynamically balance rotors of radial devices in G6.3 class on special balancing machines. After balancing, we mount each such component on a shaft, for example, a motor journal. We assemble the entire ventilation device and submit it for technical inspection. During this inspection we check the quality of the rotor, housing, painting. One of the most important things we do during the inspection is the correctness of its operation. Only after determining that the fan does not have excessive vibration do we consider the product ready.
- Incorrect position
Placing a fan in a development where the walls are flat and very close to the radial impeller will lead to flow disturbance. In this case, we do not have the continuity equation preserved. Air flowing out of the impeller encounters the wall. This causes very strong turbulence outside the radial impeller. From its inter-blade space the air cannot escape properly at this point, encountering the wall there is no room for the ejection of the next amount of air. The result is a very strong vibration of the entire fan. These vibrations lead to damage to the housing motor as well as the impeller. The operation of such a fan looks as if the radial fan is unbalanced. In order to exclude bad balance of the fan, the following test should be carried out.
Remove the radial fan from the chamber where it was mounted. Put it on the floor and start it up. If the fan works properly after startup, then the cause is not a bad balance, but a bad installation of the radial fan. Such an installation must then be redesigned. The distance of the radial impeller from the wall should be increased. It is also recommended to make spiral manifolds in this type of housing or to provide a large space behind the impeller.
- Pumpage
Is a flow phenomenon that occurs during operation at characteristic points to the left of the maximum pressure. During pumping, strong vibrations of gas streams transmitted to the structure are produced, as well as a large noise. All these factors mean that the fan cannot operate in this range of characteristics. The resulting vibrations are so large that they will lead to damage to the motor and further may lead to damage to the entire fan.
- Air supply
Another cause of abnormal operation of the fan may be improperly supplied air. That is, the inflow of air to the radial impeller will not take place over the entire inlet cross section. Perceptible symptoms will be similar to pumping. In this case, the fan impeller is not loaded evenly which causes vibration.
- Fan bearings wear
If the fan is not new, vibration may be caused by worn bearings, which should be replaced . When using the fan you should take care of its cleanliness. This is very important in operation. The impeller on which dust settles loses balance, which causes vibration and damage to other parts of the device.
- Rigidity of the mounting system
It happens that the fan and other components of the structure tremble due to the low rigidity of the entire system to which the fan is attached. Therefore, among other things, the fan should be mounted in such a way that elastic compensators are attached to the inlet to the fan and its outlet. Only after eliminating the above causes can we assume that the impeller is improperly balanced.
