A large U.S. plastics compounding manufacturer required a bulk-bag unloading system capable of discharging and conveying calcium carbonate at flow rates up to 9,000 lbs. per hour. The material has a bulk density of 30- to 80-lb. per cubic foot. To meet the company’s challenge, Metso BEST, Inc. designed and manufactured a system that incorporates both standard and custom-made components. The system’s basis is Metso BEST’s Model BBU heavy-duty, 4000-lb.-capacity bulk bag unloader with 1800-RPM ¾-hp vibratory-motor agitation. Standard features include bag-transport frame, upper bag-support frame and heavy-duty rubber hopper isolators. System requirements also included a 20-cubic-foot storage hopper and 12-foot-long screw conveyor. To offset the difficulty of conveying calcium carbonate and ensure optimum system performance, Metso BEST engineers doubled the screw-conveyor motor’s normal horsepower and increased the conveyor’s standard shaft size. A two-ton electric hoist, powered trolley and monorail were added to allow safe, easy bag changes. Finally, an easy-to-use control panel was designed and built in Metso BEST’s in-house UL-listed panel shop.