The pneumatic conveying system is based on the transportation of fibrous and loose materials through pipelines using air flow. An integral part of the pneumatic conveying system is a fan.
Fan selection
Māris Puzurs, project manager for the magazine “Baltic Tree”
The first pneumatic transport systems were manufactured in England in the 1890s for unloading grain from ships. In 1906, pneumatic transport also began to be used in woodworking. Today, pneumatic transport is used in a wide range of industries: in woodworking, construction, agriculture, the food industry, and for transporting tobacco, tea, flour, various powders, cellulose, grain, hay, straw, cement, sand, lime, and wood chips.
Types of fans
To ensure the air volume and pressure required for transporting materials, various air supply machines are used: turbo air blowers, various types of compressors, twin-rotor rotary air blowers, vacuum pumps and fans. Medium or high pressure centrifugal fans are usually used in woodworking. Fans used in pneumatic transport systems can be divided into three types: dust, transport and clean air fans.
The most widely used in woodworking are VP type dust fans, the design of these fans allows for the transport of loose, non-sticky materials, including chips. Typically, the fan impeller consists of 6-8 blades. The efficiency coefficient does not exceed 67%.
If you pay attention to the blade configuration, you can see that some fans have straight blades, others have forward-curved blades, and others have backward-curved blades. Forward-curved impeller blades provide higher pressure, but lower air output. Backward-curved blades have slightly lower pressure, but this is usually compensated for by increasing the number of rotor blades; this type of rotor blade curvature has more effective self-cleaning and less wear. The VP type fan is universal; it can transport both dust and dry and wet chips; a small lump may “fly out” at a time.
A transport fan usually has backward curved blades and a V-belt drive. Visually, the fan housing looks narrow. Fans with a V-belt drive are recommended for use in systems where there is an uneven supply of the transported material. This is to avoid excessive load on the motor bearings. This fan is able to provide high pressure and transport a large amount of material with a smaller amount of air. The permissible concentration of material in the air is up to 0.5 kg/m³. Transport fans are usually used for extracting chips from filters, feeding them to chip storages, granulators, briquette machines and transporting chips over long distances.
We offer the following for chip transportation:
The VP-G type fan has a belt drive. This fan, thanks to the bearing housing, can withstand a higher load and by changing the rotor speed with the help of pulleys, the fan can be more accurately matched to the performance of each specific system. The VP-E type direct drive fan, the rotor of which is placed directly on the shaft of the electric motor. This rotor arrangement is 5% more economical than a fan with a belt drive.
Clean air fans are usually used in pneumatic conveying in vacuum extraction systems. In this case, the material is not transported through the fan. These fans have a wide variety of rotor configurations; this depends on the application of the fan and the required power. These fans usually have a higher efficiency factor than dust fans, which in some cases allows for savings of up to 25% of electricity with a properly designed pneumatic conveying system.
We produce three models of clean air fans:
The VGZ – type fan is a low, medium pressure centrifugal fan. Thanks to the many modifications of this model, this fan can be very accurately matched to the required indicators. A fan with a very high efficiency coefficient, up to 83%. The VGV – type fan is considered a medium pressure fan. Thanks to the compact arrangement of the rotor blades, the fan has a relatively small size. Efficiency coefficient up to 73%. The VGA – type high-pressure fan is equipped with a more durable housing and more powerful motors. VGV type fans are usually used in vacuum systems, smoke pumps and other technological systems where rarefaction or pressure above 3000 Pa is required. Efficiency coefficient 0.86%.
For economical dust transportation, as a compromise, VGP type fans with an efficiency coefficient of up to 80% are used. The VGP fan has backward-curved, straight blades. The proportions of the transported material are 0.1kg/m3 of air. The recommended material size is up to 20x20x30 mm. But, for example, for a container line with circular saws, VGP would not be recommended.
Choose the most suitable fan
To choose a fan, it is important to know the amount of air to be extracted and the pressure that the fan should develop. Once these indicators have been determined, you should definitely look at the fan performance chart. According to the chart, you will be able to choose the fan that best suits your indicators and is the most economical in terms of electricity. Each chart indicates the percentage efficiency of the fan's performance, or efficiency coefficient. If we look at the curve of the chart, the efficiency is lower on the sides of the curve than in the middle of the curve. The differences between the side of the chart and the middle can be up to 20%, so the conclusion is that the more accurately you choose the fan, the more you will save.