Issue link: https://www.e-digitaleditions.com/i/1355344
28 / April 2021 powderbulk.com Engineering solution | Making bulk bag unloading systems portable PBE A water utility adds a portable system to unload fluoride powder into its silos. A public water utility in Col- orado needed to change the way it had been handling sodium fluorosilicate, also known as fluoride. The powder is often added to municipal drinking water for the purpose of maintaining good dental health. The additive enhances tooth strength by forming fluorapatite, a naturally occurring component of tooth enamel. The US Department of Health and Human Services sets optimum fluoride lev- els for preventing tooth decay at 0.7 parts per million, or 0.7 milligrams, in every liter of water. At the Colorado utility, fluoride powder had been being deliv- ered in self-unloading, pressure- differential trucks, which delivered the material directly into the util- ity's silos. That option, however, became unavailable, so the utility had to make a change. The alter- natives were receiving the powder in bulk bags or in 50-pound paper sacks. The plant temporarily opted for the individual 50-pound sacks, but that method made for a messy, difficult, and potentially danger- ous unloading task. While fluoride powder can safely be consumed in drinking water, the material is con- sidered a HAZMAT Class 6 Toxic Substance if inhaled. Employees dealing with the sacks needed per- sonal protective gear, and trying to physically handle the bags was a cumbersome, potentially injury- causing task. Eventually, the utility found an overseas fluoride source that would ship the powder in bulk bags, but this would require a new method to transfer the shipped powder from the 2,200-pound bags into exist- ing storage silos at the utility's two water treatment facilities. To inquire about designing a new transfer method, the utility con- tacted Greg Black, owner of Golden Eagle Technologies in Golden, CO, and a local representative for Vibra Screw, a Totawa, NJ-based bulk solids handling equipment supplier. He visited the utility's two loca- tions to assess the existing bins and pneumatic conveying lines. Work- ing on behalf of Vibra Screw, Black proposed a portable skid-mounted bulk bag unloader that discharged into a venturi eductor to convey the fluoride powder into silos through the existing truck delivery lines. He sent the design concept, along with details on the bin sizes, existing con- veying line lengths, and number of pneumatic conveying line fittings, to the supplier for development. "The system needed to be porta- ble for placement on a flatbed work truck for transport between two locations," explains Ed Giacobbe, Vibra Screw regional sales manager. "The equipment also needed to be stored in the facility garage with a door that had 12 feet of headroom." In operation, the system needed to be able to quickly — within 45 minutes — and efficiently dis- charge the material from the bulk bags, whose contents could possibly have compacted during overseas In operation, the system needed to be able to quickly — within 45 minutes — and efficiently discharge the material from the bulk bags, whose contents could possibly have compacted during overseas shipment.