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.
The belt scraper is a thin metal or rubber plate, measuring the width of the conveyor belt, that is used to remove material that has attached to the belt. Belt scrapers are used on top and/or bottom of a belt depending on the type of material being screened.
Coloring is sometimes done to mulch to give the product a richer, longer-lasting color. It is an after market add-on and the most common colors include gold, rich browns, reds or blacks. Customizable colors are sometimes available depending on your provider. Coloring can be done at grinding, but it is usually done with a trommel screen during the drum rotation. This technique creates more consistency and the ability to customize your landscaping.
Compost is organic matter that has been decomposed and may be made from single source material or blended for specific application performance. Green waste materials uses include: garden debris, kitchen scraps, manure, or yard and lawn waste.
Nutrient rich in composition, compost acts as a natural, healthy, organic fertilizer for your plants. It is typically a soil additive mixed prior to planting to provide nutrients and improve soil structure, but can also be used a protective mulch layer or top dressed to planted areas.
Screens are very useful with compost because it helps provide the most consistent end product for consumer use and higher profitability due to reduced waste.
Conveyor lengths on Terra Select Screens vary in size from 6′ 7″ (200 cm) to 23′ 7″ (720 cm), depending on the specific machine being used. The optional extra long conveyor belt extends to 26′ 5″ (806 cm).
A secondary conveyor belt that pivots from horizontal to vertical allowing stones to roll backwards while processed stock is transferred forward via conveyor belt. This feature may be added to any screening/separating machine.
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.
There are multiple discharge belts on Terra Select Screens. Typically there are three different belts moving different sized material away from the machine into a stockpile. The discharge belt length and height determines the stockpile size before needing to remove the machine or reposition the screen.
There are primarily two methods used to change a trommel drum. The first requires you to connect chains to both ends of the drum and lift it out of the trommel machine using an excavator. The second method requires the drum be lifted out of the cradle using a forklift or a loader.
Feed material in screening applications includes Waste Wood, Green Waste, Asphalt Shingles, Compost, Dirt/Soil, Aggregate and other types of materials. Depending on what material is being screened, it may have already been run through a grinder. So the material that is being screened is getting sorted by size to create a consistent finished product.
Hardox is a type of wear-resistant sheet steel. It is manufactured and exported worldwide by the Swedish company SSAB, which developed the first modern wear-resistant sheet in 1974. This steel is used in Terra Select Screens because it wears very slowly, even when under large mechanical load.
The Infeed Hopper includes the hopper, the hopper feed belt and in star screens, a dosing roller. It is the first thing to greet the feedstock as the feed rollers pull the feedstock into the machine for screening.
Lifting bars are used in trommel drums to lift material while the drum turns to help in the material separation process. The lifting bars in a wire mesh drum are part of the drum frame and cannot be removed. Lifting bars in a punch plate drum are not part of the drum frame and can be removed. Removing lifting bars for certain material screening applications, such as aggregate, helps eliminate drum damage.
The optional Magnetic Head Pulley is positioned at the top of the discharge belt and is designed to pull ferrous materials (such as nails) from the ground material. The ferrous metal then travels around the head pulley, is separated, and falls down the metal collection chute into a container below, or onto the ground.
Often made from bark, low value trees (non-merchantable stems) or wood waste, it can be made from a variety of materials, typically organic, but not exclusively. Organic mulches are typically a product that can decompose providing nutrients to the soil over time. Not all mulch materials are available commercially. Materials include:
Polyurethane wear plates are used in areas of a machine, such as the inside of the hopper and conveyor side walls, where material passes and creates abrasion. These wear plates vary in thickness and slow the rate at which the machine parts wear.
Sometimes referred to as a cogged belt, the positive fitting drive belt is a belt that has notches on the bottom. This allows for positive traction with the conveyor belt pulley, eliminating belt slipping.
Sometimes referred to as Reclaimed Asphalt Shingles (RAS); Recycled Asphalt Shingles are the byproduct of Asphalt Shingle Grinding. This is done by processing asphalt roofing shingles down to a smaller spec, usually 3/8”, in an effort to use recycled asphalt material in roadways, resulting in reduced road building costs and can lower amounts of material sent to a landfill. A screen helps filter out any larger pieces that cannot be used in RAS applications.
A side skirt helps prevent spillage of the product and reduce contamination under the conveyor belt. It consists of an aluminium enclosure with a strip of Polyurethane wear plates to reduce the damage done to the machine.
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 star screen attachment is an additional piece of equipment that can be added to a screen for additional separation, such as vacuum system to aide in removing light fraction material (plastic), destoner conveyor to aide in the removal of stones, or a magnetic pulley (roller) to aide in the removal of metal.
Throughput is the amount of material that passes through a machine during a given amount of time. It is often measured in cubic yards per hour. Peterson calculates throughput values using the amount of material put into the machine.
Tier II (Tier 2), is an engine emissions standard. There are several tiers of emissions standards that large diesel engines must adhere to by certain dates.
Tier II engines have more advanced technology than Tier I which reduces the amount of nitrogenous emissions from the engine. Tier II was implemented from 2001-2003 and was the current standard until 2005.
Tier III (Tier 3), is an engine emissions standard. There are several tiers of emissions standards that large diesel engines must adhere to by certain dates.
Tier III engines have more advanced technology than Tier II which reduces the amount of nitrogenous emissions from the engine. Tier III was implemented from 2005-2006 and was the standard until the interim Tier IV was implemented in 2011 and the final Tier IV requirement was implemented in 2014.
Tier IV (Tier 4), is an engine emissions standard. There are several tiers of emissions standards that large diesel engines must adhere to by certain dates.
Tier IV engines have exhaust after treatment systems to reduce emissions of particulate matter (soot) and nitrogenous compounds. This EPA mandate significantly reduces smog and other pollutants from diesel machinery.
Topsoil is the upper, outermost layer of soil, usually the top 2 inches (5.1 cm) to 8 inches (20 cm). It has the highest concentration of organic matter and microorganisms and is where most of the Earth’s biological soil activity occur.
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.
A wire mesh drum is an alternative drum to a punch plate. It consists of woven wire to make the desired screening size. The downfall of a wire mesh drum is that it does not keep its shape as well as a punch plate, which can lead to inconsistent screening.
The Yard Drive is a wheel drive system that aides in the movement of a wheeled machine in an operation yard. The system consists of a steel wheel that applies pressure to a machines wheel and turns it for machine mobility.