With the use of a Star screen, or a Trommel screen, 2-Fraction Screening is the process of screening material to create 2 product sizes. Product sizes are “Fines” fraction, and “Overs” fraction and creates a consistent product consumers prefer.
Direct drive means that the mechanical parts in a machine are driven directly by a motor, without a belt or other device to transmit power. This feature is commonly found on hybrid (engine and generator) star screens.
Star Screens can perform 2-fraction screening or 3-fraction screening.
For 2-fraction screening, material flows on top of the stars, that have a predetermined fines size. If the material meets those fines requirements, it will fall between the stars while the larger pieces will stay on top flowing to a discharge conveyor.
3-fraction screening requires two star decks. As the material flows on top of the first deck of stars, mid-size pieces of material fall between the first deck of stars onto a secondary deck with smaller stars. The smaller stars separate the middle fraction material from the fines fraction material. The fines will fall through the smaller stars while the middle fraction material flows to a discharge conveyor.
A trommel screen is a rotating cylindrical sieve or screen that is powered either hydraulically or electrically via a chain and sprocket used for sorting, coloring, washing a variety of materials. Drum changes are easy, due to the user friendly design. Terra Select has a wide variety of drums to suit your specific product sizing needs.
The machine is fed using a wide, flat belt conveyor at the bottom of the hopper, into a chamber (via a metering bar) where a strong air stream aerates the material. Light material (such as plastic) is pulled out of the material stream, and sorted material is then dropped onto two discharge conveyors. The first conveyor has a magnetic head pulley to remove any ferrous materials and the final discharge conveyor has a stone separator to remove stones from the compost or biomass. The waste material is collected into a separate waste collection bin.