The primary method of seed cleaning is the air-screen separator. It uses a combination of air, gravity, and screens to separate seed based on size, shape, and density. These widely-use units come in a variety of models with two to eight vibrating screens. In all cases, the cleaning principles are the same. The seed mass drops onto the top screen which scalps and removes large trash and impurities. Seed and smaller trash pass through to the next screen which retains the seed and allows the trash to pass through. Multiple screens provide seed size and density separation. Air streams remove the trash and impurities and the seed moves to bagging or collection units. Numerous types and sizes of screen are available. The rate of feed, airflow, oscillation of the screens, and screen pitch are adjustable. With experience, an operator can set all the variables and achieve excellent results.
References / Additional Information
Desai, B.B.; Kotecha, P.M.; Salunkhe, D.K. 1997. Seeds handbook: Biology, production, processing, and storage. New York, NY: Marcel Dekker, Inc. 640 p.
Harmond, J.E.; Brandenberg, N.R.; Klein, L.M. 1968. Mechanical seed cleaning and handling. USDA Agricultural Handbook No. 354. Washington, DC: U.S. Department of Agriculture, Forest Service. 56 p.
Harmond, J.E.; Klein, L.M.; Brandenburg, N.R. 1961. Seed cleaning and handling. USDA Agricultural Handbook No. 179. Washington, DC: U.S. Department of Agriculture, Agriculture Research Service. 38 p.
Jorgensen, K.R.; Stevens, R. 2004. Chapter 24. Seed collection, cleaning, and storage. In: Monsen, S.B.; Stevens, R.; Shaw, N.L., comps. Restoring western ranges and wildlands, vol. 3. Gen. Tech. Rep. RMRS-GTR-136-vol-3. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 699-716.
Vaughan, C.E.; Gregg, B.R.; Delouche, J.C. 1968. Seed processing and handling. State College, MI: Mississippi State University, Seed Technology Laboratory. 149 p.
Young, J.A.; Young, C.G. 1986. Collecting, processing, and germinating seeds of wildland plants. 3rd ed. Portland, OR: Timber Press. 236 p.