28 • ROCK products • July 2017 www.rockproducts.com
Efficient Fines Management
Bennington stressed that many operations stockpile material
to be washed, and sometimes those stockpiles simply collect
over time. When necessary, that material is hauled over to a
separate screen/screw wash plant, meaning that the oper-
ation is handling the material multiple times. "This method
typically incurs three 'touches' to the material, at a cost of an
additional $1.50 per ton to wash the sand," he said.
To avoid washing altogether, Bennington said that some
operations will employ a common shortcut by trying to dry
feed a sand screw. "That method doesn't work very well,
particularly in limestone. Ultimately, they find that they can
only lower the minus-200 mesh by about 3 percent, which is
almost nothing," he said.
The new low-water washer, said Bennington is a far more
economical and efficient method. Its agitator section is posi-
tioned at the front end of the screen where water is added to
the dry feed and mixed, producing a thick slurry. The agitator
is equipped with a spray bar along the length of the blade mill
for thorough cleaning.
The slurry is fed to a robust dewatering screen that is outfit-
ted with a series of spray bars that help to push the material
down through the screen. "Using a sand screw requires
'lifting the silt over the weirs of the screw with much water
usage. Alternatively, when the new washer pushes the mate-
rial down through the screen, much less water is needed,"
Bennington said.
Conventional wash methods, high water use, and multiple
material handling is much like the cliché of "throwing the
baby out with the bath water." New low-water washing
systems ensure efficient crusher fines management, high-
er-quality products and lower operating costs per ton.
Carol Wasson is a Fort Wayne, Ind.-based freelancer.
WATER WASHING
After washing, the operation is achieving under a
6-percent minus-200 mesh.
Aerial view of the water-saving equipment.