Vibrating screen
A perforated deck set into vibration. The product travels along the deck; what is smaller than the opening falls through, what is larger is carried to the end.
What it does
A vibrating screen separates a product stream by size. The deck is a stainless steel panel with openings chosen for the product. As the vibration carries the product along, pieces smaller than the opening pass through; larger pieces stay on top and leave at the end of the deck. The screen can be used to grade the product into size fractions, to remove coarse trash, or to drain water after washing.
Single and double deck
A single-deck screen gives two streams: oversize and undersize. A double-deck screen stacks a coarser deck above a finer one and gives three streams. In dried-fruit lines the double-deck version is used for sizing apricots and figs while taking out coarse trash on the top deck in the same pass. Each fraction leaves through its own wide outlet so the product does not bridge at the chute.
Versions by task
Trash-removal screen
Removes coarse foreign material that arrives with the product. A double-deck layout is common; the panels are made for the product group.
Sizing screen
Grades the product into required sizes. The number of decks and the openings are set from the sizes needed at the outlets.
Dewatering screen
Placed after a washer. Water drains through the deck into a tray; the tray also holds back large particles so the drain does not block. A fan-assisted version removes surface water faster. Driven by two vibration motors. See the article on dewatering after washing.
Screen with aspiration unit
Stones and soil are removed by the deck; leaves, stalks and dust are drawn off by an air stream above the deck. Used on raisins, dates, beans, chickpeas and seeds. Panels are quick-release; a version with air blown from below the deck is available. See aspiration for light foreign material.
Build
The frame and all product-contact surfaces are AISI 304 stainless steel, with AISI 316 as an option where the process requires it. Panels are removable for cleaning and for changing the opening size. Dimensions are made to the line; capacity is set per project from the product and the required throughput.
What affects the result
Screening performance depends on the opening, the layer thickness on the deck, the deck angle, the stroke and frequency, and the condition of the product (wet or sticky product screens less readily). These relationships are described on the screening efficiency page.