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Screening & Classifying

Raute Wood

The OSB flaking process generates three types of furnish: acceptable flakes for the face; intermediates for the core; and fines, which constitute 10 to 15 per cent of all dry material.  Due to recent innovations developed by Raute Wood, OSB producers can now utilize fines for core material, rather than as dry fuel, and realize significant savings with their recovery.  A new type of rotary screen is equipped with a classifying section for separating the dry furnish into face, core and fines.  The three different types of furnish are then discharged through gated chutes by way of discharge screws.  A standard 14foot by 30foot long rotary screen can process 40,000 lbs of dry furnish per hour. 


CAE Machinery

CAE Machinery has designed a new suspended chip screen with flat rotary motion.  Fabricated out of strong, rigid steel, the high capacity, efficient screens are suspended by heavy-duty Ujoint suspenders.  Designed for simplified maintenance, easy belt changes and screen removal, the four models have capacities ranging from 25 to 60 units per hour.  The bottom screen has CAE�s chip waterfall, which allows the chips to tumble as they travel and greatly improves fines removal, the company says.  The chip screen can be mounted overhead or on its own integral frame.  Efficiencies are achieved through its drive configuration, which maximizes the throw and rpm and causes minimum obstruction of the screen fall-through area.  The CAE/SRC optical chip sorter uses machine vision to remove undesirable material such as bark, rot and stain from wood chips.  The sorter allows good chips to be recovered from low grade material such as chipped tree limbs, tops, chipped log yard waste and chipped commercial thinnings without debarking.  Chips enter the sorter where two scan cameras view each chip for differences in contrast.  A computer processes the data from the cameras and determines which chips are accepted or rejected.  Rejected chips are removed by a precisely directed short blast of air. 


Edem, An Optimil Company

Edem�s high-speed, high-volume vibratory conveyor handles wafers gently while transporting them at 60 fpm and smoothes out the wafer flow from batch at the loading end to continuous at the exit allowing for uniform delivery to the green bin.  The eight-feet by 60 feet conveyor weighs 60,000 lbs and is balanced to transmit no vibration to the surrounding structure and is resonantly tuned for minimum power input.  The soft spring drive system prevents overload during start up and under stall conditions, while the self-cleaning screening system removes fines from wafers in green condition.  Edem�s double action and ring screens are optional.  The conveyors are also used as cleanup conveyors for bark, trim ends, lily pads, small logs and sawdust and also for trim block alignment, feeding chippers and hogs, surge control and screening.  They can also incorporate metal detectors.  The Edem 1/4inch finger screen screens sawdust from chips produced by a chipping edger, alleviating the problems of pins becoming trapped and plugging perforated plate and woven wire screens. 


Acrowood Corp

The DiamondRoll fines screen from Acrowood offers a variable inter-roll opening (VIRO) feature that allows the spacing between the shafts to be independently adjusted at any point along the screen, increasing selectivity.  The DiamondRoll VIRO fines screen separates more than 90 per cent of fines from usable pin chips at high production rates, saving 70 to 90 per cent of the fibre rejected by other screening methods, the company says.  All the shafts in the entire screen are identical and varied roll spacing is achieved simply by changing the shims between adjacent bearing blocks.  The ability to change roll spacing also allows the mill to screen consistently despite variances in fibre supply.  The dust-tight frame completely encloses the chips and fines.  Steel dust covers are set into the frame above, while the chutework connects solidly below, making the entire system dust-proof.  The Particleboard Diamond Roll screen has different diameter shafts than the typical fines screening version, resulting in better screening of small particles.  Effective screening of the green end materials before milling and refining allows much material to bypass this damaging step.  Fibre destined for both face and core fractions remains intact and not shortened or weakened. 


Forano International  

Forano�s super chip screen offers an increased rotary speed up to 50 per cent faster, with maximum fines removal through greater agitation.  Installation costs are minimal and, with few moving parts, maintenance costs are also low, the company says.  Two eccentric weights mounted on a shaft induce full-length flat rotary movement.  Replacement of the plastic, wire or steel screen plates is simple and the lower screen can be replaced without disturbing the upper screen.  Screen plates made of 10gauge steel are standard.  With a speed of 300 rpm and a throw of up to two-inches in diameter, the machine has a main bearing consisting of double row taper roller bearings, housed in solid steel.  The full-length flat rotary screen has a slope angle of seven degrees. 



Nicholson�s high-speed full-flow chip screen offers superior pins and fines removal, fully balanced operation at speeds up to 330 rpm and simplified maintenance and installation.  Chips that pass through the overs-screen are sent back to the top of the fines screen, utilizing its full length and resulting in improved pins and fines removal for each size of screen.  A balanced flat rotary screening action is generated by locating the rotating eccentric at the centre of the screen�s mass, allowing it to operate smoothly and quietly at high rpm while transmitting only minimal lateral forces to the supporting structure. 

The fines pans are fully enclosed, eliminating the need to clean the area around the screen, and can be removed if a bottom fines discharge is desired.  The screens have a capacity of 17 to 156 units per hour.  Any size of woven wire and round or square punched plate may be used Installation is on a freestanding base or overhead hangers.  An optional package provides remote lubrication of the hanger joints and the eccentric bearings during operation. 


Milltec Products 

Liwell fines screens, sold and serviced by Milltec Products, efficiently separate fines and/or pins from wood chips, maximizing recovery and resulting in fast paybacks for new screen rooms and retrofits, the company says.  Unaffected by snow and ice, they also remove wood flour from sawdust, and sand and grit.  Individual flexible mats are easily replaced and allow the adjustment of the screening characteristics to be tailored to particular digesters, maximizing fibre usage with minimal losses.  Available in single or double deck configurations, Liwell screens are simply-designed, reliable and low maintenance, the company says. 


BM & M

BM & M recently introduced its new line of multi-deck sawdust cleaners, offering high capacity due to the 400 square feet of screening area and high-speed rotation.  The totally balanced, patented drive design ensures reliability while the available multiple product separations make it suited for the panel board industry and its fibre suppliers.  BM & M�s Super Screen is a low-cost fibre recovery device for fibre lost through inadequate equipment capacity and high chip quality specifications.  The pin chip reclaim machine is suitable for disc screens and chips screens with larger than 1/4inch woven wire.  BM & M�s chip classifier has the same gyrating action as the company�s full-size chip screens and provides quality and maintenance feedback.  Also, it can be used to optimize the chipper knife sharpening schedule and the screener hole size for maximum recovery, says the company.  The lightweight, portable unit comes with exact screen size or thickness and appropriate trays. 


West Salem Machinery 

West Salem Machinery offers efficient, cost-effective disc screens for high-volume course screening applications from hog fuel to wood chips and bark to board finish.  Material slides down the infeed chute to a series of r o t a t i n g shaft assemblies, each featuring a set of discs and spacers arranged at p r e c i s e openings for the desired product sepa r a t i o n s .  Fines fall t h r o u g h , while overs are conveyed to the end of the screen and discharged into a hog, hammermill, re-chipper, bunker or reject conveyor. 

Available in a full range of sizes and with processing capacities of up to 600 tons per hour, the WSM disc screens are self-cleaning, space saving and low maintenance.  WSM�s flat oscillating screens provide efficient classification from high volume chip screening to precise classification of particleboard furnish.  Features include an adjustable tilt basket assembly, enclosed hanger assemblies, heavy-duty drive with spherical roller bearings, readily accessible drive components and production capacities ranging up to 80 units per hour.   


IMALPAL North America Inc

The Dynascreen from IMALPAL North America offers high performance based on interlocking V profiled rollers that offer continuous cutting and material channeling.  The zigzag movement aligns the flow along the V gaps and facilitates the screening of longer and thinner particles.  IMALPAL�s Superscreens 1316 high-performance oscillating screen has four elastic suspension systems for support and a pyramid base to house the eccentric oscillating kinematic system, the motor and the drive transmission.  Along with the Superscreen 212632, it offers perfect balancing, resistance to extensive oscillation and guarantees stability.  The Multicross 4152 offers up to a five-fraction standard.  The core layer particle flow crosses the length of the machine three times, interrupting or breaking twice.  The Knife Ring Flaker makes large, thin flakes from clean macro-chips and refines wood chips and sawdust.  Easily replaceable sieves allow convenient grading of particle size and shape.  The Dry Chip Cleaner removes all kinds of heavy pollutants from chips and reduces the cost of knives for ring flakers by up to 50 per cent, the company says.  The Airgrader is a high-efficiency gravimetric selector-cleaner for wet sawdust and dry particles. 


Redwood Plastics

The advantages of SynSteel chip screens from Redwood Plastics are a faster flow over screen, fewer problems with pitch buildup and freeze-up and fewer hang-up problems.  Most often with a thickness of 1/4inch or 3/8inch plate, the top screens are usually installed in two or three sections.  The fine screens, with 3/8inch or 5/16inch holes, are usually installed in the same manner.  Longer wear can be expected, in the range of 30 to 50 per cent more, the company says, with 100 per cent more, or double the life, on cedar.  Due to a larger web, there is a smaller percentage of open surface.  An increase in plugup on fines, due to material thickness, can be alleviated by counter sinking the back of the holes. 


Rotex Inc

The Gradex 6S chip classifier from Rotex automatically classifies and weighs up to six size and/or thickness fractions quickly and accurately, the company says.  Employing a hexagonal drum containing testing decks or plates, the five sides of the drum are equipped with either rod decks for thickness determination or round hole perforated plates for size classification.  The sixth side is open, permitting overs discharge.  Any combination of size and thickness decks or plates can be used for testing.  Decks and plates are bolted to the drum for ease of replacement, if needed.  The AutoDischarge feature automatically unloads the sample at the completion of each analysis, permitting both AutoFeed and online sampling options.  AutoFeed permits loading of up to six samples at once.  Rotex and Megatex wood chip screeners use a ball mesh cleaning system . 


Bulk Handling Systems

Bulk Handling Systems� patented Debris Roll Screen design combats the jamming commonly associated with disc screens.  A unique disc configuration produces a wavelike, bouncing action that is imparted to the material as it moves across the screening surface, reducing vibration and shaking.  Also, the pinch points created by overlapping daisy or star discs are eliminated.  The Debris Roll Screen can be designed to release fractions as small as 1/2inch and less. 


Duraquip Inc

Duraquip introduces its Portable Trommel Screening Plant with a six-foot diameter by 26foot long trommel screen with two screening sections.  The system incorporates a large hopper/conveyor, trommel screen and three folding stacking conveyors for three different products.  Portable in less than 10 minutes, the system is self-contained and designed for 16hour processing days.  Other screening systems from Duraquip include disc and vibrating screens and its Rotary Air Separator (RAS).    



The SyncroCoil vibrating conveyor from Vibrotech is ideal as the main conveyor for transporting logs or other material to chippers at speeds ranging from 40 to 100 fpm.  The vibrating movement allows conveyor material to be evenly spread, preventing chipper infeed blockage.  Both the SyncroCoil and the SyncroFlex conveyors come with a counterpoise system, which can reduce equipment vibration by up to 95 per cent.  The conveyors are cost-efficient and lowmaintenance, the company says, with only the drive roller bearings requiring occasional lubrication.    


Valon Kone Brunette Ltd

A totally portable pre-screener and classifier from Continental Biomass Industries (CBI) has a capacity of more than 150 tons per hour.  With a picking station for up to four people, the screener is designed to screen log yard and land-clearing debris and removes metal contaminants.  Working in tandem with a CBI grinder, the screener features a totally enclosed chain guard, a retractable bumper to allow container placement under the picking station, a heavy-duty, fluted 12yard hopper for handling ease and heavy-duty belt scraper to keep the unit running clean. 


Testing Machines Inc 

The Chip Class chip classification system from Testing Machines Inc offers fast, accurate results.  With its lightweight, interchangeable trays and simple tray stacking, the system is easy to use and each testing step is completed more quickly, the company says.  With two sets of trays, more than 40 samples can be tested per shift.  The tray locks hold the trays in a stack and eliminate noise caused by metal-to-metal impact.  Other features include easy-to-read labels, easily aligned tray interlocks, tray alignment guides, low maintenance shaker platform, a compact, sturdy base and convenient controls. 



Mektek disc screens remove oversized material from chip or bark flow and separate stones, metal, branches and stringy bark without binding or plugging.  These non-vibrating screens operate with low horsepower and maintenance is minimal.  An ideal application, says the company, is for removal of acceptable sized material from the flow to a bark hog, resulting in smaller hog requirements and lower maintenance.  Standard screens use 3/8inch plate discs with either a chip or bark profile.  Extra large diameter discs slip onto heavy gauge shafts. 

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This page last modified on Tuesday, February 17, 2004