Screening & Classifying
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.
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 CAEís 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.
An Optimil Company
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.
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
Nicholsonís 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 screenís 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.
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.
& 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
& Mís 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
& Mís chip classifier has the same gyrating action as the
companyís 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 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.
WSMís 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.
North America Inc
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. IMALPALís
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.
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.
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
Handling Systemsí 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.
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).
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
Kone Brunette Ltd
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.
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.
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.
This page and all contents
©1996-2007 Logging and Sawmilling
Journal (L&S J) and TimberWest Journal.
last modified on Tuesday, February 17, 2004