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56 / July 2021 powderbulk.com Equipment suppliers are a valuable source of information about equipment and processes. In light of this, each month we ask suppliers a question of concern to our readers. Answers reflect the suppliers' general expertise and don't promote the suppliers' equipment. If you have a question you'd like suppliers to answer, send it to Kayla Carrigan, Associate Editor, Powder and Bulk Engineering, 1155 Northland Drive, St. Paul, MN 55120; fax 651-287-5650 (kcarrigan@cscpub.com). PBE W hen selecting a mechanical conveyor for cohesive materials, there are a number of factors to consider, but one of the most crit- ical is the amount of shear force that will be imparted on the material being conveyed. Mechanical conveyors that push or pull the material through a housing, such as a screw or drag conveyor, generate high shear forces between the material and conveyor surfaces, which can result in excessive smearing or material buildup. These forces may also cause significant undesirable material degradation. Belt-type conveyors can be a good solu- tion to minimize shear forces, but they may not offer other features required in many applications such as a totally enclosed conveying environment or ease of conveyor cleaning. An aeromechanical conveyor minimizes shear forces, encloses the material, and allows for easy con- veyor cleaning. At first glance, this type of conveyor may be mistaken for a tubular drag conveyor, as it consists of a cable and discs that are pulled through a tube; however, the method of conveying is very dif- ferent. In an aeromechanical conveyor, the discs move through the tube at speeds of around 1,000 fpm, which creates pockets of air between each pair of discs. A low-pressure area is generated behind each leading disc and the material is drawn along in the slipstream that's created, with the particles being suspended in the air pocket and having minimal contact with the conveyor surfaces. The resulting shear forces imparted on the material are extremely low, minimizing mate- rial buildup and degradation. This style of conveyor also offers a totally enclosed, dust-free environment and is extremely energy efficient, with high transfer rates being possible at very low power consumption. Andy Forrester, vice president of sales (Americas), Spiroflow, 704-246-0900 A n aeromechanical conveyor is the most effi- cient mechanical conveying method for a cohesive material. This conveyor type achieves fluidization for this material type, allowing the material to completely empty out of the conveyor with minimal leftover material or residue. All other mechanical conveyors run in a full condition, whereby the cohesive material adheres to the conveyor's walls, causing significant leftover material and blockages for future batches within the conveyor. By fluidizing the cohesive material without creating pressure or vacuum, the aeromechanical conveyor operates in an empty condition and all material exits the conveyor. No other conveyor can achieve such conditions for a cohesive material. Larry Blitz, president, FloAero, 818-789-0546 SUPPLIERS' TIPS What's the most efficient mechanical conveying method for a cohesive material? In an aeromechanical conveyor, the discs move through the tube at speeds of around 1,000 fpm, which creates pockets of air between each pair of discs. A low-pressure area is generated behind each leading disc and the material is drawn along in the slipstream that's created, with the particles being suspended in the air pocket and having minimal contact with the conveyor surfaces. – Andy Forrester, Spiroflow