Pneumatic conveying: pressure mode
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.
Pneumatic conveying: suction mode
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 controlled vacuum pumps.