Gravity separators are used to sort materials according to density or specific gravity. This is important when seed and/or impurities are similar in size but different in density. The separator uses a vibrating perforated deck that can be tilted in two directions at various pitches. Air moving through the perforated deck separates the seed and any impurities by weight as the deck oscillates. As the materials are separated, they move into appropriate slots or containers. Scalping or other pre-treatments are helpful in removing excessive impurities before gravity separation. Seed of the same species can be separated into various size-weight classes, and many species can be cleaned to 98 or better percent purity with a gravity separator. They are also effective for removing stones.


A.T. Ferrell

Bluffton, IN 46714

Bouldin & Lawson

McMinnville, TN 37111

Carter Day International

Minneapolis, MN 55432

Crippen Manufacturing Company

St. Louis, MI 48880

Forsbergs, Inc

Thief River Falls, MN 56701

Seedburo Equipment Co

Chicago, IL 60607


Plano, TX 75054


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. 38 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. 56 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.