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13 www.spirofl ow.com www.spirofl ow.com QUESTION & ANSWER: Mechanical conveyors Mechanical conveyors are available in an enormous variety of types, including belt conveyors, bucket ele- vators, tubular conveyors using chains or cables and discs, drag (en masse) conveyors, screw and fl exible screw conveyors, vibratory and reciprocating convey- ors, and others. Different types can be stationary or portable and can serve purposes in addition to convey- ing, such as heating or cooling, screening, and accu- mulating. This article sheds light on frequently asked questions about mechanical conveyors by using infor- mation from past Powder and Bulk Engineering articles. All referenced articles can be found in the Article Index or Tips section on PBE's website, www.powderbulk. com. Also see "Conveyor Selection Charts" under Tools & Resources at www.powderbulk.com. Selecting a mechanical conveyor Q: We're going to be starting a new process and will need to convey materials between various parts of our plant. How do we decide what type of conveyor to purchase? A: A huge variety of conveying equipment is available from bulk solids handling equipment suppliers, and this can make the prospect of choosing the right con- veyor for your application a bit daunting. A good place to start is to consider these basic selection factors: • Your material's characteristics. Consider whether your material is dry or moist, extremely hot or cold, hygroscopic, abrasive, likely to segregate, or has oth- er properties that limit which conveying methods can reliably handle it. • The conveyor's required function and performance. Will your conveyor require multiple inlets or outlets? Must it elevate material or move it through multiple planes? Must the conveyor provide a variable con- veying rate? Will it need to provide gentle handling? Must the conveyor be enclosed to contain dust or prevent material contamination, and will it require a dust collection system? • The conveyor's operating features. Can the conveyor handle your required conveying distance? Can it han- dle your required conveying volume? Does the con- veyor have high installation costs? Can it be installed in your existing operation? • The conveyor's required service life. What's the pro- jected duration of the operation or process this con- veyor will serve? Some conveyors are light-duty units suitable for intermittent or short-term operation, while others are heavy-duty machines designed for continuous long-term operation. Consider what ser- vice life your conveyor must provide to ensure that it can handle your application. • The conveyor's long-term energy requirements. Con- sider how the conveyor's energy use will affect its operating costs over the long term. When you're selecting a conveyor, it's best to work with a supplier who offers several conveyor types. Such a supplier has the experience to satisfy your conveying performance needs and to ensure that the convey- or you select will withstand your process's duty level throughout the life of the process. This supplier can of- fer selection advice based on which unit can not only successfully handle your material, but provide the best combination of low purchase price, low operating cost, and high effi ciency. Ideally, the supplier will also have a test lab with convey- ors of various types to help you determine which con- veyor can best handle your material and operating con- ditions. Ask the supplier for references to check whether previous customers with applications like yours are sat- isfi ed with the conveyors they've purchased. Finally, make sure that your supplier provides assur- ances that the conveyor will successfully transfer your material and perform reliably and cost-effectively for the long run.