Pneumatic Conveying

In the pioneering age of pneumatic conveyance, demand was largely for transporting foodstuffs such as grain and flour. Today, such installations are constructed for a wide variety of uses, such as transporting

  • goods in dust particle form (flour, cement)
  • grain-type goods (dragées, granulate, pellets)
  • piece goods (pneumatic tube conveying systems) and
  • mixed goods.

Special requirements must be observed in these areas. Mixed goods, for example, may not be mixed with different size grains during transport. In addition, the goods should not rub together, which would cause abrasion. This is just as important for explosive granulate as it is for avoiding static electricity.

Pourable goods can generally be transported with vacuum or pressurized air conveyance systems.


Pressure Conveyance Installation

A blower brings air sucked from the atmosphere to the required pressure level. As a result of the excess pressure, air flows into the conveyance conduit. A rotary air lock directs the goods being transported into the conveyance conduit. Air and goods flow through the conveyance conduit into the separator, which separates the goods from the air. The air flows through the clean air conduit back to the outside. The goods being transported leave the separator and are then stored, conveyed or processed. The movement of the goods depends on the means of conveyance and the construction of the conveyance installation.

Due to the low pressure difference available to suction conveyance systems, pneumatic suction conveyance installations have a larger conduit diameter than pressure conveyance systems, yet the volume of goods transported remains the same.

Suction transport systems

The suctioned air creates a mixture of air and transported goods in the conveyance conduit. The conveyance apparatus extracts the granulate from the sieve filter. Operating data: Operating pressure is between –200 mbar and –500 mbar. The air velocity in the conveyance conduits determines the principle of operation. Depending on the goods being transported, this speed is about 20 m/s to 23 m/s.

The vacuum pump must be designed so that the air velocity in the conveyance conduits does not drop below the minimum rate, even at the machine located the farthest away, and that no plugs build up. This requires a higher air velocity at the pump. High conveyance velocities, however, lead to increased wear of the conduits and to abrasion of the goods. Therefore, selecting the optimal air velocity or blower is of utmost importance. Optimal air volumes can be achieved in modern conveyance installations with frequency regulated vacuum pumps.