case study | Materials handling The flexibility
of conveyor line routing allowed the second bulk bag discharger to be posi- tioned in a restricted space
regulates flow through the bag spout. This prevents material leakage and permits the spout to be closed and retied if a bag is partially unloaded. Due to the diversity of these additives and their
inherent properties, the dischargers are also equipped with pneumatic Flow-Flexer agitation plates. These raise and lower the bottom of a bag to maintain positive flow and achieve full discharge. Each bulk bag discharger empties additives into a hopper, which uses a pneumatic turbine vibrator and mechanical agitator to promote material flow into the flexible screw conveyor intake. The first of the two flexible screw conveyors has a 6 inch (150 mm) diameter and is installed at a 35o
angle,
transporting material 17 ft (5.2 m) to the feeder hopper. As the flexible screw turns, it self-centres within the polymer outer tube, providing efficient delivery. The second flexible screw conveyor is 4.5 inch (115 mm) diameter and runs 27.5 ft (8.4 m) at a shallow angle to empty material into the feeder. The flexibility of the conveyor line routing has allowed the bulk bag dis- chargers to be positioned in restricted spaces. “Material must be transported to the additive feeder
lower-maintenance solution for transferring additives. Delaney also believes that the setup is more efficient
and safer than having workers manually open and empty smaller bags of additives into the feeder hopper from a platform. This process could introduce bag scraps and other contaminants into the compounding operation, take up floor space for bag storage and create a costly waste-disposal problem with the empty bags. Additives arrive at the TPG plant in bags typically
weighing from 1,000 to 3,000 lbs (450 to 1,400 kg), so the Flexicon BFC Bulk Bag Discharger frames have a safety load rating of 4,000 lbs (1,800 kg). Each bag is attached to a four-cornered low-profile lifting cradle and raised into position by an electric trolley hoist on a cantilevered I-beam. A pneumatic Power-Cincher valve
fast enough to maintain accurate metering,” Delaney says. A 100 lb (45 kg) additive load, for example, has to be conveyed to the feeder from the discharger hopper in 10 seconds. A loss-in-weight control system starts and stops the flexible screw conveyor. TPG carries out a materials change one or two times a day on average and a typical run lasts 18 hours. With each line capable of compounding 70,000 lb/h (32,000 kg/h), the reliability of the discharger and flexible screw conveyor system is critical. “If either of these systems goes down, there’s no backup,” explains Delaney, adding that the BFC dischargers and flexible screw conveyors have worked almost flawlessly. “We’ve only had to do normal maintenance,” he says. ❙
www.plasticsgroup.com ❙
www.flexicon.com
AMI Strategy Seminars
These one-day seminars are given by an AMI director and provide invaluable insights into market trends and industry strategies. They are held in small groups and provide ample opportunities for questions and discussions.
17 May 2012 : Hamburg, Germany 19 June 2012: Vienna, Austria 25 June 2012: Chicago, USA
16 October 2012: Cologne, Germany 5 November 2012: Philadelphia, USA More dates to be confirmed
Click here to download our 2012 brochure
www2.amiplastics.com/Seminars
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