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Powder & Bulk Engineering
Powder & Bulk Engineering

Test Lab Simulates Bulk Handling Applications

Test laboratories can take the risk and guesswork out of designing and fabricating custom bulk handling equipment and systems by simulating any variety of field conditions in a controlled environment.

Following a move to new headquarters in Bethlehem, PA, in 2002, Flexicon Corporation unveiled a new test laboratory equipped with full-size flexible screw conveyors, pneumatic conveyors, bulk bag unloaders, bulk bag fillers, manual dumping stations, weigh batching systems and other bulk handling equipment. Each can be tested throughout its full range of sizes and configurations, both individually and as integrated, automated systems incorporating equipment manufactured by Flexicon and by others.

The ability to replicate virtually any bulk handling process its customers may encounter often makes the difference between total success and failure, even with applications as seemingly straight-forward as manual dumping of bulk materials and conveying them for 7 ft at a 30° incline, as the experience of Sunnex, Inc., Springboro, OH, demonstrates.

Move Widely Disparate Materials

Sunnex, a manufacturer of adhesives, sealants and coatings for the auto industry, needed a better way to deposit 10 to 15 ingredients of materials having disparate flow characteristics and bulk densities, into two high-speed dispersers on a 10-ft high mezzanine. The company had been forklifting 50-lb bags to the mezzanine and manually dumping directly into the dispersers.

Ingredients range from fumed silica to calcium carbonate—both notoriously difficult to convey. Fumed silica (synthetic amorphous silicon dioxide) is one of the lightest substances known, with bulk density of 3-lb/cu ft (38 kg/cu m). Handled incorrectly the feather-light particles readily escape as nuisance dust.

Calcium carbonate, with a bulk density of 35 to 58 lb/cu ft (443-734 kg/cu m), is a sluggish adhesive powder that readily packs and cakes and increases in stickiness after being treated by the company.

The company also needed to contain dust from bag dumping, and minimize waste from spent bags.

Grant Hayne, Sunnex senior manager, initially considered installing bag dump stations at both high-speed dispersers but decided to evaluate the addition of flexible screw conveyors for total dust containment.

However, in test laboratory trials conducted at another flexible screw conveyor manufacturer, moving materials having extremely dissimilar flow characteristics using one conveyor, appeared impossible to accomplish.

Before abandoning the idea, despite increased skepticism about flexible screw conveyors, Hayne contacted Flexicon based on a trade publication advertisement.

Laboratory Simulates Sunnex Application

In its test lab, Flexicon engineers simulated Sunnex's application for three of its most difficult materials: fumed silica, treated calcium carbonate and PVC powders. They evaluated hopper and bag dump station design, flexible screw conveyor diameters, lengths, angles, speeds and screw configurations, recommending a self-contained, dust-free mobile bag dump-conveying unit that can be wheeled between the two blenders. The unit integrates a hopper designed specifically around the flow properties of the bulk materials, with a mechanical agitator, and a 6-in UHMW polyethylene outer tube enclosing a specially engineered screw. The design reduces compression of the material on all screw surfaces except the top surface that propels material in the desired direction, enabling the unit to convey products at the required rate, wide-ranging flow characteristics notwithstanding.

To suppress dust during dumping and compacting of bags, a high velocity vacuum fan draws dust onto two cartridge filters cleaned by an automatic reverse-pulse filter system. The integral bag compactor contains dust otherwise released during bag collapse, while reducing the frequency of trash disposal.

Laboratory Verifies Modifications

After using its mobile unit, Sunnex management in Japan decided to discontinue the fork lifting of bags to the mezzanine to reduce material handling. Flexicon application engineers again proved-out a modified bag dump conveyor; a stationary unit mounted at floor level with 25-ft conveyor at a 45° incline and higher horsepower needed to elevate material to the mezzanine. In addition to the modified unit, Flexicon engineered an additional stationary unit to feed the second blender.

"The test lab streamlined the path to a conveying solution that performed correctly the first time," Hayne says. "When we arrived, everything was set up based on Flexicon's initial investigation without even seeing our facility. The trials ran without a hitch. The basic lab layout came pretty close to our final results."

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Flexicon engineers evaluated hopper and bag dump station design, flexible screw conveyor diameters, lengths, angles, speeds and screw configurations in the test lab, ultimately recommending a hopper designed according to the flow properties of Sunnex's bulk materials, with a mechanical agitator and 6-in (150mm) UHMW polyethylene outer tube enclosing a specially engineered screw (shown).

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Operator discards empty sack into integral bag compactor of completed mobile bag dump station as delivered to Sunnex.

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Conversion of the mobile bag dump station with low-incline conveyor to a stationary unit with longer conveyor at higher incline is simulated in the test laboratory prior to modifying Sunnex's equipment.