Bulk bag handling system keeps compounding line clean
US-based elastomer manufacturer Kirkhill-TA has slashed inventories of carbon black by 90% and prevented carbon black dust from contaminating the plant environment by replacing a large silo storage system with a Flexicon bulk bag discharging system. The overall outcome has been significant cost savings, greater production efficiency and improved competitiveness.
The bulk handling system is the latest upgrade for this company, which manufactures highly engineered silicone parts for commercial and military aircraft, missiles and even the Space Shuttle.
Carbon black is produced by burning heavy oil or tar to form soot-like particles. When airborne, they can penetrate operating equipment. “Carbon black tends to soak up lube oil,” said Larry Pierce, Vice President of Technology at Esterline Technologies, Kirkhill’s parent company. “If it gets into the bearings and rollers, they will wear out prematurely.” It can also cause short circuits.
California classifies it as a hazardous material. Since it is shipped as 1-3 mm diameter pellets, to reduce the likelihood of airborne release, manufacturers must remain vigilant to prevent spills and the cleanup that would follow.
Kirkhill-TA had several priorities for its new materials handling system: the company had to improve inventory efficiency, keeping costs in line; it needed to use as much of the existing infrastructure as possible; and it had to prevent carbon black dust, caused by the friable pellets rubbing against one another, from escaping into the plant or processing equipment.
Kirkhill-TA had a significant infrastructure to handle carbon black, with a rail offloading station incorporating screw conveyors, bucket conveyors and two large storage silos. Carbon black pellets flowed from the silos to the mixers in two ways: by pneumatic conveyor and when weight in the silo fell below 22,675kg by large steel totes that hold approximately 900kg of carbon black. These are moved by forklift, the carbon black gravity fed into a weighing container, with an integrated weigh scale, on a mezzanine above the mixers. When the container and pellets reach the required weight, the container’s chute opens, discharging material into the mixer for compounding with elastomers prior to moulding into finished seals.
Since material delivery to the site by rail is no longer possible, coupled with lower volume requirement, there was no longer a need for silo storage and the associated pneumatic conveyors but the steel totes and weighing system remain as part of the new bulk handling installation.
Bulk bags were a clear choice for receiving carbon black, not least because they are available in 450 and 900kg sizes – large enough to receive bulk discounts.
The Flexicon bulk bag discharger is engineered to fully contain the material being unloaded
The bulk bag discharger also improves site cleanliness since it moves bulk material handling operations inside the facility, so any accidental leaks are contained within the plant. The discharger also uses dust-tight connections to fully contain carbon black until final addition to the mixer.
Trucks deliver 10 to 12 palletised bulk bags at a time. A forklift raises each bag by its straps and delivers it to a storage site on the mezzanine. When carbon black is needed, the forklift operator attaches the bag straps to a detachable bag lifting frame and then lifts the frame into the cradle on the bulk bag discharger.
The Flexicon discharger unloads carbon black pellets from the bulk bag into a purpose-built hopper, from which a 4.5m long model 14.5 flexible screw conveyor transfers the material to a steel tote. A forklift transports the tote along the mezzanine to the container above one of the mixers, where it releases its load.
The Flexicon bulk bag discharger is engineered to fully contain the material being unloaded. The bag spout is attached to a Spout-Lock clamp ring, which forms a sealed connection between the clean side of the bag spout and clean side of a Tele-Tube telescoping tube (through which the material is discharged).
The tube raises the clamp ring pneumatically, allowing the operator to make a dust-tight connection with the bag spout. The tube then lowers, elongating the bag to discharge the pellets fully. Also promoting full discharge, Flow-Flexer bag activators -- two plates located under the bag -- raise and lower opposite bottom edges into a ‘V’ shape, directing material toward the bag spout.
Above the clamp ring, a Power-Cincher flow-control valve encircles the upper portion of the bag spout to allow retying of partially empty bags. When the bag is empty, the operator actuates the Bag-Vac dust collector, which generates vacuum within the sealed system, collapsing the empty bag dust-free for retying and removal.
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