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When it comes to low-cost, reliable separation of differently
sized particles in a stream of recyclable materials, few solutions
can outperform vibratory screens. Using the combined forces
of gravity and mechanical agitation, many vibratory screeners
move streams of material down horizontal or sloped screening
decks featuring apertures of graduated sizes. Particles then
either fall through the apertures to hoppers or conveyor belts
below or are ejected from the end of the screening deck. In
another approach, circular vibratory screeners use rotary
vibrating action to push particles through screen apertures.
The screens themselves differ as well. Vibratory screeners
may use wire mesh, perforated metal sheets, disc screens or
fingers to segregate particles by size.
Applications for vibrating screens are found in many different
industries. In recycling, they help to separate construction
and demolition debris, divide scrap tire particles, segregate
wood chips, break up municipal solid waste, sort out auto
shredder residue, recover sand from foundry waste and divide
plastic and metal particle streams by size, among other uses.
Vibratory screening equipment selection depends on a number
of factors, including the size and shape of particles, throughput
rate, moisture content and more.
At The Cleveland Vibrator Company in Cleveland, Ohio, screeners
may be air-powered using a reciprocating piston or electromechanical
drives. General sales manager Jack Steinbuch says recycling
applications for Cleveland Vibrators exist at foundries, where
screens are used to recycle sand employed in the metallurgical
process. Plastics recycling operations employ Cleveland Vibrator
screens to filter streams of ground plastic materials. “We
do a lot with the plastics recycling guys,” he says.
For recycling, Cleveland’s EMS electromechanical screeners
are the most popular units. These employ two rotary electric
vibrators, one rotating clockwise and the other rotating counterclockwise.
The vibrating rotors produce a linear vibration force which
is placed at an angle designed to go through the center of
gravity of the screening body, Steinbuch explains. Material
lifts from the screening deck and moves forward propelled
by gravity. “That has proven to be a very reliable motion
to separate material by particle size,” Steinbuch says.
Coarser material is lifted from the screen deck by the vibratory
force and moves forward, while finer material gets closer
to the screen deck and eventually falls through.
Cleveland’s design allows the machines to be installed
in areas with less headroom because there is no need to have
a large hopper under the equipment. “It’s a little
simpler to work with, and very easy to install,” Steinbuch
Plastics recyclers typically employ EMS machines equipped
with 24 by 48 inch screen decks. These vibratory screeners
sell for approximately $10,000. Larger machines, up to 48
by 96 inches, are priced at approximately $20,000. Steinbuch
says one advantage of their approach is that the electric
vibrators employ no belt drives or other mechanical linkage,
so they are reliable and easy to maintain. “The biggest
issue for us has been lower maintenance,” Steinbuch
Action Equipment in Newberg, Oregon, offers its Taper-Slot
and Vibra-Snap screens for a variety of screening applications.
The Taper-Slot is used for materials with particle shapes
and sizes that would tend to plug a conventional screener,
says President Andrew LaVeine. Construction and demolition,
scrap tires and wood waste often incorporate particle sizes
and shapes that are tough for many screens to handle, he says.
Particles that are oblong in shape, for example, tend to plug
Many applications employ multiple screeners, using Taper-Slot
screeners with larger aperture screens for larger particle
sizes and Vibra-Snap screeners for finer material streams.
“That’s a machine that’s suited for screening
very small particle sizes with moisture content,” LaVeine
says of the Vibra-Snap, which can work with particle sizes
down to 1 or 2 millimeters.
patented finger design used on the Taper-Slot makes for a
highly rigid screen deck and provides for more accurate screening
and less catching. The Vibra-Snap takes a different approach,
with a non-rigid screening deck made up of a tensioning and
relaxing polyurethane panel. “It’s like a trampoline,”
LaVeine says. The Vibra-Snap deck moves a few inches, rather
than the much smaller distance typical vibratory screen decks
move. “It’s really a specific machine for nasty,
icky smaller aperture screening, LaVeine says. “There’s
no way to bind a Vibra-Snap screen aperture.”
Vibra-Snap screeners are priced at approximately $50,000
for a model with a 4 by 10 feet deck. Double-deck models may
cost up to $200,000. Taper-Slots are general custom designs
with up to 20-foot screeners and costs vary widely, LaVeine
Recycling is not a major application for vibratory screeners,
but it is significant. According to Steinbuch, “We do
a little in recycling, but not as much as other markets. We
do a lot in the recycling business with our vibratory feeders
to bring material to an eddy current or something taking material
from the shredder. That is primarily in auto-shredding.”