The Sutton Steele and Steele Specific Gravity Separator (or Fluidized Bed Separators) grade dry, granular material according to particle size, shape, or specific gravity.
The material is introduced onto the narrow side of a flat porous trapezoidal deck, sloped in two directions, and vibrated with a straight-line reciprocating motion. Low-pressure air, blown
upward through the deck, fluidizes and stratifies the material according to differences in the terminal velocity.
Heavy particles sink to the bottom of the stratified bed and are conveyed toward the high, or heavy, side by the deck's vibration. Light particles, lifted by the fluidizing air, flow
downward toward the light-end discharge. Particles with intermediate characteristics form a mixture between the light and heavy fractions, called the middlings, which may be drawn off for
re-treatment.