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Del Williams

Quality Insider

To Boost Profit, Use Airless Conveyors to Move Valuable Product

Tubular cable conveyors can significantly reduce product damage, energy use, noise, and maintenance

Published: Monday, November 9, 2020 - 12:03

For companies that process high-value products such as nuts, cereal, coffee, snacks, and dry pet food, material breakage and loss is a costly problem that can harm the bottom line. Even the variation between 1-percent waste and 5 percent can mean the difference between profit or loss.

To convey such delicate food products, processors should avoid conveyors that force fragile material through stressful phases during transport that could affect its integrity. This can be problematic when food processors also must maintain high-throughput requirements. To address the transport issue, some fragile-food processors are reconsidering using conveyors that send products through tubes, bends, or sweeps via high-velocity air power before before dumping them into bins or containers.

In the coffee industry, for example, processors go to great expense to roast whole beans. However, the beans can be damaged by high-velocity air conveyance, compromising flavor and aroma, according to Gary Schliebs, a process engineer and director of Plus One Percent… Engineered Solutions, an Australian consulting firm that works in the food industry and markets conveyor equipment globally.

For nut processing, keeping product in one piece is a problem. When a whole macadamia nut is broken, its value can drop by half. Instead of a premium price for whole nuts, damaged nuts are often sold at a substantial discount, and often crushed for use in cooking or processing further downstream in the food industry.

“Many high-value food products can be fragile and need very gentle handling,” says Schliebs. “Otherwise, whole forms can be broken, crushed to bits, and even turned to powder. This significantly lowers the value of the product, and damaged portions may need to be removed or disposed of to prevent perceived quality issues that could prompt customers to turn to other brands.”

Schliebs frequently consults on food engineering equipment design, plant layouts, and process flows. “In some cases, more than 10 percent of delicate product can be damaged by high-velocity air-power systems, he says. “The cost to the industry is compounded because the damage often comes at the end of the process, after considerable value has been added, only to have it degraded by a poor choice in the selection of transfer conveying equipment.”

The limitations of air conveyors

A wide range of fragile, high-dollar food products can be prone to excess breakage when conveyed at high velocity by air power, such as in pneumatic and aeromechanical systems.

Pneumatic conveyor systems create 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, the food product is suspended in the air as it is transported through the conveying pipe at extremely high velocities, typically 3,400 to 5,000 feet per minute. Although the product usually incurs minimal breakage during straight pathways, most systems have bends and sweeps where product can be forced through constricted areas, quickly change direction, and be damaged. In such cases, high-dollar food often can be too fragile.

Dense phase pneumatic conveyor systems, where the product is not suspended in air because it is heavy or abrasive, function at lower velocity than dilute phase. However, with air speeds of about 700 to 1,500 feet per minute, delicate food items are still susceptible to breakage at bends and sweeps.

Aeromechanical conveyors have a different method of conveyance, but these enclosed, high-capacity mechanical systems can also degrade delicate product. With these systems, a wire rope with evenly spaced discs within a tube travels at high speed, running in sprockets at each end of the conveyor. This generates an internal air stream traveling at the same high velocity as the discs that carry product along in the tube. However, these conveyors may also force vulnerable products through stressful phases during transport, which could impair their integrity.

“Any fragile or friable food product conveyed at high velocity is prone to damage, particularly if it changes direction or exits with impact,” says Schliebs. “This can be the case with both pneumatic or aeromechanical conveyors.”

A gentler approach boosts profitability

According to Schliebs, a gentler alternative to protect sensitive, high-value food products is to use tubular cable conveyors. These systems move product through a sealed tube using a coated, flexible stainless-steel drag cable pulled through on a loop. Solid circular discs, called flights, are attached to the cable, and they push the product at low speed through the tube without the use of air, preserving product integrity and minimizing waste.

“Food industry manufacturers can decrease product damage down to 1 to 2 percent with a slower process like a Cablevey Conveyors tubular cable system,” says Schliebs. “With it, product is gently transferred at low speed, so there is minimal to no damage.”

Tubular cable conveyors move product through a sealed tube using a coated, flexible stainless-steel drag cable pulled through on a loop. Solid circular discs are attached to the cable, which push the product at low speed through the tube without the use of air, preserving the product integrity and minimizing waste. Click image to enlarge.

Cablevey Conveyors is an Oskaloosa, Iowa-based premium, specialty-material moving, mechanical conveyor company that has designed, engineered, and serviced enclosed cable and disc tube conveyors for almost 50 years. Its conveyors can be found in more than 66 countries.

In the food industry, the conveyors are used for products such as nuts, cereal, coffee, snacks, pet food, beans, and seeds. The systems can convey up to 2,000 cubic feet per hour (56 m3/hr) of flakes, pellets, shavings, crumbles, granules, regrind, chunks, parts, prills, and powders with numerous layouts using multiple inlets and outlets.

Tubular drag conveyor systems like Cable Conveyors’ adhere to all the safety and quality standards of other freezing and packaging equipment, yet also maximize throughput speed to efficiently transport products and prevent unwanted thawing. Click image to enlarge.

Because the material is carried between the flights, it is also much easier to safely convey some sticky or easily compacted materials in a tubular cable conveyor than in air-powered conveying systems, where such materials can form plugs.

“With pneumatic or aeromechanical conveying systems, any soft or sticky material, like dried fruit, can smear and adhere to surfaces, particularly at bends and sweeps that change direction, which is not an issue with tubular cable conveyors,” says Schliebs.

According to Schliebs, the tubular cable conveyor’s modular construction can also help reduce product damage by enabling it to slide out on a gentler gradient, rather than simply drop out, as is more typical with conveyors that use air.

“To minimize product damage, it is important for food industry manufacturers not only to transfer gently, but also get product in and out of the conveyor safely and gently as well. That is more achievable with a conveyor like Cablevey, which allows product to slide down rather than drop out the end,” says Schliebs.

In fact, most tubular cable conveyors have interchangeable components that allow the conveyor to be easily expanded or reconfigured to change the length, conveying path, and the number of inlets and outlets. These modifications are more complex and time-consuming to do with a pneumatic conveying system because it has more components and electrical connections.

Also, another bonus of these systems is that the “footprint” can be quite small compared to other conveyor systems, and that really helps with tight and compact manufacturing areas.

“Because of the ‘bespoke’ design of each Cablevey system for customer-specific requirements, we can tailor the design to be very nonintrusive in the work area and not hinder access for people and maintenance, as other systems can,” says Schliebs. “This is a real bonus for safety, access, and saving floor space, which is another cost to manufacturing.”

Less energy use, less noise

Because pneumatic systems convey product at high velocity, this typically requires larger, power-hungry motors that run fans, blowers, and rotary valves. In a dense phase system, a pressure tank requiring compressed air consumes additional power.

In terms of noise level, pneumatic conveying systems also generate considerable noise. Aeromechanical systems, running at high speed, generate considerable motor and disc noise as well.

Given that smaller motors are used, tubular cable systems are quieter overall and use much less energy.

“A low-speed tubular cable system is quiet enough to easily have a conversation around it while it is running,” says Schliebs. “In regards to energy, it uses about one-tenth that of pneumatic systems. For dense phase models, the electricity savings by using a tubular conveyor can be sizeable, with one-year ROI in some cases.”


About The Author

Del Williams’s picture

Del Williams

Del Williams is a technical writer based in Torrance, California. He writes about business, technology, health, and educational issues, and has a master’s degree in English from California State University-Dominguez Hills.


Excellent lean example

The cable conveyor reminds me of Archimedes' screw, an invention roughly 2000 years old.

The issue of wasted power in a pneumatic conveyor is meanwhile an example of waste hiding in plain view; if air blows past the product being moved, it represents wasted energy even if the product is not subject to mechanical damage the way some of the food products are.