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bar that attaches to the bag’s four corner straps. The bag is
positioned above the hopper.
Powder is discharged from the bulk bag through a patented
Spout-Lock™ clamp ring that creates a dust-tight seal between
the spout and the equipment, and a patented Tele-Tube™
telescoping tube that promotes product flow and complete
discharge by exerting continual downward tension on the bag as
it empties and elongates.
To make the connection, the clamp ring is raised pneumatically
toward the bag spout, with the clamp ring in the open position.
The spout is pulled over the rim of the tube and the ring is
locked in place over it. The bottom end of the telescoping tube
is connected to a collar in the lid of the sealed hopper.
Once the clamp ring is connected, the pneumatic pressure that
raised the tube is released, causing the assembly to exert
downward tension on the spout. The drawstring on the bag spout
ABOVE: The patented Tele-Tube™ telescoping tube promotes
is then untied to allow the powder to discharge through the
product flow and complete discharge by exerting continual
downward tension on the bag as it empties and elongates
spout. Continuous downward tension keeps the spout taut at all
times and helps maintain a steady flow of powder by preventing CO2 cartridge is removed and replaced by a fresh one, then the
excess material in the spout from bulging outward and creating canister cap is unscrewed and the hose nozzle is purged with
dead pockets, or falling inward and restricting the flow. compressed air.
Powder transfer is further enhanced by means of Flexicon’s At this point a canister is ready for refill. The container is fitted
Flow-Flexer™ bag activators. These are two pneumatically driven with a specially designed fill head that creates a vacuum for
plates located opposite each other, that rhythmically raise and powder transfer. This is attached to a venturi-driven fill hose from
lower opposite bottom edges of the bag to direct material into the hopper. Three 2.4 m fill hoses are attached to the hopper -
the outlet spout. As the bag empties, the stroke of the plates one for extinguishers equipped with CO2 cartridges, one for
increases to form the bottom of the bag into a steep V shape those that use stored-pressure nitrogen, and one for wheel-
and promote total evacuation. An adjustable timer controls the mounted units. Extinguishers that use nitrogen are first filled, and
frequency of the strokes. then N2 is injected into the canister through an adapter.
Canisters are refilled from the floor hopper via hoses, using an The major innovation on the conveyor line is the installation of
air-driven venturi system. This is the same method as was used a dust-collection system. Dust generated by the cleaning
before, says field-support foreman Donnie Calhoun, who is in operations is removed via overhead hoods and collected on
charge of the refilling operation. However, a key difference is wide-pleated, spun-bond polyester cartridge filters, which are
that the floor hopper has a capacity of only 90 kg versus 4,350 periodically cleaned by back-flushing.
kg for the hopper that was previously used. In the new The new filling operation started up in May 2005 and the
arrangement, the bulk bag essentially fills the role of the supply results have been “excellent,” says Peddy. “The bulk-bag
hopper, and the floor hopper is a sealed transfer unloading equipment is very efficient and reliable
unit that continually feeds the refill line. and has made our job a whole lot easier by
Besides being dust-free, the new allowing us to move the whole operation
unloading system is more efficient than into one building.” Under the former
the previous one, says Calhoun. “It used arrangement, drums of chemical powder
to take about four hours to fill a hopper were stored in one building, CO2 in
from the drums, using the auger,” he another, and the powder-transfer and
says. “Now, it takes only about five refill operations were partially outside.
minutes to set up a bag on the discharge Moving the refill line indoors had
frame and start feeding powder.” another benefit in that it liberated the
BFTF uses about 13,000 hand-held fire work from the vagaries of the weather.
extinguishers per year, each of 9.2 or Peddy explains that refilling must
13.6 kg, so the refill line’s weekly volume conform to standards set by the National
averages a modest 250 canisters. Most Fire Protection Association, and at times
of the extinguishers use pressurised it was difficult to meet the standards
carbon dioxide (CO2) as a carrier gas for with the outdoor operation. “For
the NaHCO3, but some use nitrogen. The example, we couldn’t fill on days when it
latter include wheel-mounted was raining,” he says, “but now we do
extinguishers, of which about 100 are everything in a building that has a
used annually. humidity-control system.”
Canisters are moved manually along For more information please contact
the roller conveyor from station to station. Flexicon Europe on tel: +44 (0) 1227
First, residual gas and powder are 374710, email: sales@flexicon.co.uk, or
Canister, ready for refill
exhausted from each extinguisher; next, the visit: www.flexicon.co.uk
www.solidsandbulk.co.uk August 2007 • Solids & Bulk Handling 7
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