Automated powder unloading system speeds blending

April 16, 2003
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Bulk bag discharger hits the sweet spot for chocolate powder producer.

This automated bulk bag weigh batching system from Flexicon consists of an 18’4” high discharger frame and 5-foot long flexible screw conveyor. Under loss-of-weight control, the system discharges precise amounts of powder into an auger conveyor that feeds three ribbon blenders at Forbes Chocolate. Source: Flexicon.

A new automated bulk bag discharger from Flexicon is providing sweet results for Cleveland-based Forbes Chocolate’s blending process. The discharger, feeding a flexible screw conveyor, introduces one-quarter to one-third more main ingredient per shift than previous manual dumping of 50-pound bags.

In addition to increasing throughput by 1,500 pounds per hour, plant workers no longer have to cut open, lift and empty bags into a bag dump station. The work area is now free of dust, as the powder stays enclosed throughout the process.

“Instead of previously manually weighing, say, 500 pounds of main ingredient, we just push a button,” says Keith Geringer, Forbes vice president of manufacturing. “Unloading goes 50 percent faster.”

The automated cocoa powder unloading system consists of an 18’4” high bulk bag discharger frame. Beneath the discharger frame, a 1 cubic foot capacity high-flow hopper connects to a 5-foot long flexible screw conveyor that discharges to the auger conveyor through a transition adapter and 12-inch long bellows.

The exact amount of powder flowing from the bulk bag is metered by loss-of-weight control. As the bag discharges, load cells under each leg of the unloader frame transmit weight-loss signals to a controller mounted on the side of the frame. The controller shuts off the flexible screw conveyor once the batch weight has been discharged. The conveyor runs at high speed, then at dribble speed before it stops when the target batch weight has been reached.

The system had to fit into a tight space, so Flexicon supplied a “push” type flexible screw conveyor that locates the 5-hp drive at the intake rather than at the normal discharge end. The motor pushes rather than pulls the powder through. The drive helps the loss-of-weight control function more effectively by concentrating frame and conveyor weight directly on the load cells.

In operation, the hoist and trolley position the 87-inch long bulk bag on the unloader frame. Pneumatically activated Flow-Flexer plates at the bottom of the bag promote flow of the non-free flowing powders by massaging the lower side walls of the bag at pre-set intervals. As the bag empties, the stroke of the plates increases, raising the side walls in a “V” shape, promoting complete product discharge.

Dust is suppressed by a 15-inch diameter iris flow control valve with a flexible, impermeable diaphragm that allows the operator to pull the tied bulk bag spout into the spout access compartment and close the valve around the spout. The spout is then untied, the compartment’s access door closed, and the notched valve released slowly, controlling the rate at which the powder discharges into the hopper to prevent dust from escaping.

For more information:
David Boger, Flexicon, 1-888-353-9426,,

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