Karl Seidel | Cablevey Conveyors
Tubular cable conveyors can help reduce material damage, energy use, noise, and maintenance needs in a plant. This article explains how these conveyors work and how they can offer benefits over air-powered conveyors for certain applications.
For food manufacturers processing high-value end-products that are susceptible to damage, such as nuts, cereal, coffee beans, dry pet food, and others, material breakage and loss can be a very costly problem that can harm the bottom line. When a whole macadamia nut is broken during processing, for instance, its value can drop by half. Instead of a premium price for whole nuts, damaged nuts are often sold at a substantial discount or crushed for use in cooking or upstream processing.
Processors can reduce some of that loss by avoiding conveyors that force these fragile materials through stressful phases during transport throughout the plant. In certain applications, up to 10 percent or more of a fragile material can be damaged by high-velocity air-powered conveying, such as via pneumatic and aeromechanical systems. Sometimes the cost is compounded because the damage comes after a value-added process has been completed. For example, manufacturers go to great expense to roast whole coffee beans, but moving those beans via high-velocity air-powered conveying — besides possibly impacting material integrity — can compromise the roasted beans’ flavor and aroma.
Tubular cable conveyors can help avoid some of these problems. In specific applications, tubular conveyors can help move delicate, dry food products with little impact on the material’s integrity while still meeting high-throughput requirements.
Tubular cable conveyor systems work by moving material through a sealed tube using a coated, flexible drag cable that’s connected to a sprocket and pulled through on a loop. Solid circular discs (also called flights) are attached to the cable at regular intervals. These flights physically push the material at low speed through the tube without the use of air.
The conveying tubes may be straight or curved, of varying lengths and diameters, and laid out in various configurations, including vertical, horizontal, angled parallel lines, or others. The assembly is an endless loop that runs from the turnaround unit, through the conveying tube and drive unit, then back through the return tube. Along the way, material can be picked up at one or more inlets and discharged through one or more outlets. A drive unit powers the assembly through the tubes, and a tension mechanism maintains the proper cable tension. Compression couplers and gaskets connect the components, making the system totally enclosed and dust-free. Tubular cable conveyors can transport up to nearly 80,000 pounds of material per hour at low speeds.
Air-powered conveyor limitations
Air-powered conveying methods, such as pneumatic and aeromechanical conveying, work well for many applications, but they also have limitations.
Pneumatic conveying systems use air by creating air pressure above or below the atmospheric level. The two main types of pneumatic conveyors — dilute-phase and dense-phase — differ by speed and pressure, and both can be configured as a pressure or vacuum system.
In dilute-phase conveying, material is suspended in the air and transported through the conveying pipe at velocities of 3,400 to 5,000 fpm. The material usually has minimal breakage over straight paths, but many systems have bends and sweeps where material can be forced through constricted areas or forced to quickly change direction, which can cause material damage. In dense-phase conveying, where the material isn’t suspended in air, systems function at lower velocities (700 to 1,500 fpm), but fragile food materials are still subject to breakage at conveying line bends and sweeps.
Aeromechanical conveyors, although they have a different conveyance method, also can degrade delicate materials. In the enclosed, high-capacity mechanical systems, a wire rope with evenly spaced discs travels within a tube at high speed. This generates an internal airstream traveling at the same high velocity, which can also force friable materials through stressful phases during transport.
With a slower conveying process, such as with a tubular cable system, processors can lessen material damage but still convey up to 2,000 cubic feet per hour of flakes, pellets, shavings, crumbles, granules, regrind, chunks, prills, and powders with numerous layouts using multiple inlets and outlets. Since material is carried between the tubular cable conveyor’s flights, safely conveying soft, sticky, or easily compacted materials also can be easier because the material doesn’t form plugs, which can happen in a pneumatic conveying system.
Configuration, energy use, noise
Many tubular cable conveyors can be designed according to customer-specific requirements. The systems can be tailored to a specific work area and arranged to not hinder staff movement or maintenance access, which isn’t always the case with air-powered conveying systems.
Interchangeable components also allow the tubular systems to be expanded or reconfigured, changing line lengths, conveying paths, or the number of inlets and outlets. These modifications can be more complex and time-consuming with pneumatic conveying systems, which tend to have more components and electrical connections.
In terms of energy use, since pneumatic systems convey materials at high velocities, this typically requires larger motors that run fans, blowers, and rotary valves. In a dense-phase system, a pressure tank requiring compressed air also consumes additional power. Aeromechanical systems, running at high speeds, generate considerable motor and disc noise as well. Tubular cable conveyor systems use smaller motors, so these systems are quieter overall, with some units using about one-tenth the electricity required for certain pneumatic systems.
For further reading
Karl Seidel (641-673-8451) is the marketing director of Cablevey Conveyors, where he leads a small team of professionals that market the company’s services worldwide. He’s been with the company since 2005.
Cablevey Conveyors • Oskaloosa, IA
800-247-3344 • www.cablevey.com
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