Recently, Spiroflow Systems worked with Access Security Products Ltd. to resolve a powder handling problem with a proprietary cement mixture used in its manufacturing process. Access Security Products manufactures and supplies burglary- and fire-resistant safes, vaults, and physical security equipment.
The company uses an expensive proprietary cement mixture in the walls of its 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 -- and also happens to be very difficult to handle. A fine powder, it arrives by container quite compacted, has very poor flow characteristics, bridges easily, is very 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 2,000 lb single trip, single loop, lined bulk bags, which must be emptied into a large outdoor storage silo. The entire load 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. A robust and reliable powder handling solution was needed.
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. Unable to resolve the problem with the vendor, Access Security ultimately had no choice but 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.
Complex Requirements
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 the cement material without material buildup 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 Ontario, Canada. 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 2,000 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 cement mixture and the frustration the customer had previously experienced, Spiroflow Systems experts recommended that it be tested in the company's test lab.
Testing Leads to Success
"Having our cement powder thoroughly tested was a vital step in the process. It gave us confidence that Spiroflow's recommended solution would work as specified," Gauthier commented. Additionally, Spiroflow Systems has long guaranteed any powder handling solution tested in its lab. "The company's performance guarantee also gave us peace of mind."
Based on Access Security's requirements, Spiroflow Systems recommended the T4 Single Trip Bulk Bag Unloader, a combination of Flexible Screw and Aero Mechanical Conveyors, and a control panel.
The T4 Bulk Bag Unloader uses a pneumatic bag-piercing knife to cut open the bottom of each single-trip bulk bag, along with 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 degree angle, are fitted to the bottom of the Bulk Bag Unloader. These conveyors use 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, which is four in. in diameter, 13 ft long, and positioned vertically. A second Aero Mechanical Conveyor, 38 ft long and positioned at a 33 degree 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 end.
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 buildup 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 buildup. 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," reported Gauthier. "Our goal was to empty each 20 ton container in 10 hours and we have cut that time in half!"
