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Home → Publications → National Nursery Proceedings → 1978 → Principles of gravity separation

Principles of gravity separation

All gravity separators utilize the same principles to effect a separation. Once these principles are understood, it is usually a simple step to adjust a gravity separator to produce optimum separation. The term "Gravity Separator" is a contraction of the proper name "Specific Gravity Separator" which means, a separator of particles differing in their specific gravities. About 250 B.C., Archimedes discovered the law of specific gravity which is ALL BODIES FLOATING IN OR SUB4E1ED IN A LIQUID ARE BUOYED UP BY A FORCE EXACTLY EQUAL TO THE WEIGHT OF THE LIQUID THEY DISPLACE. The specific gravity of a particle is the ratio of its density to some standard substance, the standard usually employed being water with a unit of 1. Particles having a specific gravity of less than 1 will float and particles with a specific gravity greater than 1 will sink. Gravity separators use air as a standard rather than water. Since air is lighter than water, the relative difference between particles of differing weights is widened. For this reason, the gravity separator is a very sensitive machine and when operated correctly can produce a very precise separation.


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Author(s): Jim Thomas

Publication: National Nursery Proceedings - 1978

Event: Nurseryman's conference and seed processing workshop
1978 - Eureka, CA