ASTEC KDS 710 - Page 29

Astec Mobile Screens Setup 21 KDS 710
710
KDS
Screening Theory
The process of screening consists of two operations:
Stratication - the process of large particles rising to the top of the vibrating material bed, while the
smaller size particles sift through the voids and nd their way to the bottom of the bed.
Separation - the process of particles presenting themselves to apertures (openings in the screen
cloth) and being rejected if larger than the opening or passing through if if smaller than the
opening.
With this in mind, it becomes obvious that without stratication, separation could not take place.
Stratication is affected more by the depth of the bed of material, than any other factor. Without the
proper bed depth, stratication can not efciently occur. By controlling the depth of the bed, you can
optimize stratication thereby making your screening more efcient.
Some factors affecting the bed depth include:
Rate of feed
Stroke
Material depth should not exceed 4 times the cloth opening.
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