Issue link: https://www.e-digitaleditions.com/i/1263839
48 / July 2020 powderbulk.com PBE SUPPLIERS' TIPS "What mechanical conveyor will work best for my fragile material?" T o select the most appropriate conveyor for your fragile material, determine the following mate- rial characteristics: bulk density, volume or units to be conveyed, drop testing data, angle of repose, angle of slide, particle distribution analysis, particle shape, moisture content, temperature and humidity sensitivity, and ambient operating temperature. Also consider equipment-related application requirements: conveying capacity, conveyor layout and route, site con- straints, power requirements, sanitary requirements, cleanability, construction materials, wear properties, enclosed- versus open-conveyor design, and budget. Here are a few conveyors that may be suitable for your fragile material. Tubular cable drag conveyor. This conveyor is among the gentlest available for applications requiring complex circuits and multiple inlets and outlets. This conveyor type is also able to transition grades, both up and down, in a controlled and enclosed fashion. A single cable drag conveyor can operate in three planes, often making it the low-cost choice for many fragile conveying applications. Intelligent design of these complex circuits keeps fragile materials from passing through drive or idler housings and controlling cable and disk speed can prevent material degradation. Wrap conveyor. In this hybrid belt conveyor, mate- rial is initially fed onto a flat belt that is then rolled into a tube by forming rollers to create a totally enclosed moving tube. This conveyor type can curve and nego- tiate shallow inclines and declines without discharg- ing to another conveyor. The wrap conveyor is fairly easy to clean and is a gentle option, but it can't be completely enclosed. Vibratory conveyor. A vibratory conveyor is one of the simplest to operate and maintain and is also incredibly gentle on material. A vibratory conveyor can have a totally enclosed design and disassembles for easy cleaning. Limiting factors are typically distance and changes in direction, which often require addi- tional conveyors and elevation transitions. Belt conveyor. The old standard workhorse in the mining and minerals industry is also a very gentle conveying option. A belt conveyor can easily move fragile materials because material remains stationary as the belt tracks its course. Custom options such as cleated belts allow for traversing steep inclines and declines. Changes in direction or layouts with multiple discharge points are difficult to accomplish using a belt conveyor because special transitions to limit material free fall between conveyors are required to prevent material damage. A standard belt conveyor is often open to the environment, leaving material vulnerable to contamination, which is a major concern for any hygienic application. Andy Forrester, vice president of sales, Spiroflow, 704-246-0953 C onveying material is a critical step in all produc- tion processes and can potentially damage fragile bulk materials like food products, extruded mate- rials, flakes, or pelletized bulk materials. The initial step to designing a system for a fragile material is to conduct a material test to determine which technology is best suited for the bulk material. This is based on the required feedrates, distances, and other considerations. Mechanical conveying can be an effective option for difficult-to-convey bulk materials by incorporating screw conveying with a low load factor. Flexible screw conveyors gently handle fragile materials; however, the conveyor's speed, auger type, conveying distance, and clearance need to be accurately addressed to avoid material degradation. Aeromechanical conveying allows for certain clear- ances while the discs are moving, offering some pro- tection for fragile bulk material handling that may require several inlets and outlets. However, this con- veyor can damage fragile materials in instances where bends are needed, potentially trapping materials between moving parts or against each other. Tubular drag chain conveyors are also an option consisting of a tubular steel casing that contains a flighted chain that catches material and pulls the mate- rial in along the conveyor. Tubular drag chain convey- ors operate best at a low to medium volume and work with dry, fragile, or wet material, offering minimal material degradation. Other options include a bucket elevator, vibrating conveyor, or belt conveyor. Doan Pendleton, vice president, Vac-U-Max, 973-759-4600