Separation Actions

Sieving plus Air

The sieving separation action is normally based on the aerodynamic properties, dimensions, specific weight, the conditions of the surface, differences in shape, etc.

Figure 1 shows the pneumatic separation in a vertical air stream. If the gravity force (Q) is greater than the vertical force

Based of the air flow rate, four different conditions are described as follows (Tabatabaifar and Persson, 1995):

  • When the vertical force is much smaller than the gravity force (R<<Q), crop material resting on the sieve;

  • When the vertical force increase, crop materials are expanded by the air stream;

  • When the vertical force is equal to the gravity force (R=Q), the entire crop layer will be lifted intact;

  • When the vertical force is greater than the gravity force (R>Q), the crop materials dissolved into each other and move along the air stream.


 Karpenko, A.N. and Zelenev, A.A. (1965) Grain-Cleaning Machines, 266-290, Agricultural Machines . Israel Program for Scientific Translations, Jerusalem 1968.

Tabatabaifar, A., Persson, S.P.E. (1995) Layer Breakup and Particle Movement on A Chaffer Sieve. American Society of Agricultural Engineers . 37(5):1035-1313


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