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Resolving a Powder Handling Problem

March 25, 2014
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Spiroflow Systems, a leader in the powder handling and conveying industries, recently worked with Access Security Products Ltd to resolve a powder handling problem with a proprietary cement mixture used in its manufacturing process.
    Access Security is a leading manufacturer and supplier of burglary and fire resistant safes, vaults, and physical security equipment. The company uses an expensive proprietary cement mixture in the walls of their safes and vaults rendering them almost impenetrable to thieves and fire. This castable material has an extremely high compressive strength and provides maximum burglary resistance. It also happens to be a very difficult product to handle. The material is a fine powder that arrives by container quite compacted, has poor flow characteristics, bridges easily, is abrasive, and readily absorbs moisture.
    About once each month a single container holding 20 tons of cement arrives from Europe. The cement is packaged in twenty 2000-lb single-trip, single-loop, lined bulk bags that must be emptied into a large outdoor storage silo. The entire load of material must be emptied into the silo as quickly as possible to minimize moisture absorption. The company’s goal was to empty a single bulk bag in 30 minutes and all 20 bulk bags within 10 hours. It needed a robust and reliable powder handling solution to accomplish the task.
    Access Security had initially purchased a $40,000 pneumatic conveying system from another supplier but the cement material accumulated within the conveying tube rendering the conveyor completely inoperable. After working with the vendor for some time without resolution, Access Security ultimately had to scrap the equipment and find an alternative conveying solution. The company was without a powder handling system for about a year, and was emptying the bulk bags directly into the storage silo with a crane - an expensive and labor intensive process.
     President, Peter Gauthier, considered his options and turned to Spiroflow Systems. The requirements for a new system were:

•    Provide a completely closed robust system that could reliably convey cement material without material build up and excessive wear on equipment
•    Accommodate bulk bag unloading inside the company’s warehouse but convey the product through the roof, outside the building, and into a large outdoor storage silo approximately 40 ft away
•    Operate reliably and consistently in temperature and weather extremes typical in the Ontario Canada region
•    Provide a dust-free solution to minimize exposure to moisture in the environment and to provide a clean and safe work environment for employees
•    Successfully unload the 2000-lb single-loop, lined, single-trip bulk bags within 30 minutes or less
•    Incorporate appropriate discharge aids (side massage, bottom massage, and agitation) to encourage material flow
•    Minimize product loss
•    Offer proof that the recommended solution will work before purchase
•    Provide a solution guarantee

    Due to the characteristics of the particular cement mixture and the frustration the customer had previously experienced, Spiroflow Systems experts recommended that it be tested in the company’s test lab. “Having our cement powder thoroughly tested was a vital step in the process,” said Gauthier. “It gave us confidence that Spiroflow’s recommended solution would work as specified.”
    Additionally, Spiroflow Systems has long guaranteed any powder handling solution tested in their lab. “The company’s performance guarantee also gave us piece of mind,” added Gauthier.
    Based on Access Security’s requirements, Spiroflow Systems recommended its T4 single trip bulk bag unloader, a combination of flexible screw and aero mechanical conveyors, and a control panel.
    The T4 bulk bag unloader has a pneumatic bag piercing knife to cut open the bottom of each single trip bulk bag. It also has a dust evacuation frame supplied with a rubber dust seal membrane located inside the support dish for optimal dust control. The unloader was supplied with four corner massage and vibration to encourage material flow. Additionally the pneumatic bag piercing knife serves to encourage material flow by breaking up compacted material in the bottom of the bulk bag.
    Dual flexible screw conveyors, only three feet in length and positioned at a 45° angle, are fitted to the bottom of the bulk bag unloader. These conveyors utilize Proscrews to move the material out of the discharge hopper. Proscrews have a beveled profile ideal for conveying poor flowing material and their semi-rigid construction enables steep conveying angles without bends.
    The dual flexible screw conveyors deliver the fine cement powder out of the bulk bag unloader into a vertical aero mechanical conveyor that is 4 in. in diameter, 13 ft long, and positioned vertically. a second aeromechanical conveyor, 38 ft long and positioned at a 33° incline, moves the cement material from the vertical conveyor, through the roof, and outside the building into the outdoor storage silo.
    A NEMA 4 Certified control panel was provided and operates the entire system. Specific controls include:
•    VFDs for the flexible screw conveyors
•    Motor starters for the agitators and aero mechanical conveyors
•    A low-level probe in the hopper of the bulk bag unloader
•    Four-corner massage
•    Vibration

    Given the physical properties of the cement powder Spiroflow engineers recommended that the company completely clean the equipment after each container of material is conveyed into the outdoor storage silo. This prevents any potential material build up from interfering with equipment operation.
    Once installed and commissioned, operators at Access Security report that the new powder handling system works beautifully. The system is reliable, operates just as promised, and performs at twice the required rate - all without material build up. The closed system keeps the cement powder dry and contained resulting in minimal product waste and a clean, safe environment for employees.
“Spiroflow’s equipment handles our cement powder quite well and actually empties each bulk bag in only 15 minutes,” reports Gauthier. “Our goal was to empty each 20-ton container in 10 hours, and we have cut that time in half!”
    Spiroflow Systems, Monroe, NC www.access-safe.com

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