Seed Production of Vegetable, Tuber and Spice Crops (2+1)

1. Air screen cleaner

• This is the most important machine of every cleaning plant.
  
• It uses screens and aspiration (air blow) for two separations (Fig.1).
  
• A coarse upper screen removes larger material, a lower fine screen stops the seeds and lets through fine matter and then the seed fraction passes through a transverse or nearly vertical air stream which can separate light impurities such as empty or partly filled seeds, husks and glumes from the seed.
  
• In most cases a number of sieves with different sized perforations are used and the cleaning is a process of gradually shifting out smaller particles.
  
• Factors which determine the quality and quantity of seed cleaned include
  
1. size of the perforations,
2. the precision of the perforation,
3. the angle at which the sieves operate,
4. the amplitude and speed of movement of the sieves and
5. correct cleaning and maintenance of the equipment.



Figure 1: Working principle of the air screen cleaner