The Gentle Way Forward
By Del Williams
Tubular cable conveyors can take care of packaging needs while reducing product damage, energy use, noise and maintenance
In food processing, greater adaptability in packaging is increasingly required these days, as the market continues to shift from share-size bags to single-portion packages.
This change requires advanced packaging machines that provide flexible packaging materials, sizes, high speeds, and lower reject rates.
However, packaging size reduction requires additional adjustment of other parts of processing technology to ensure that the packaging line can cope with the produced amounts efficiently.
For this reason, food processors—particularly of snacks and other high-value products—need to invest in adaptable product transfer systems that can ensure the gentle and sanitary movement of specific amounts through different production stages.
This is particularly true of valuable products susceptible to damage such as nuts, chips, etc., as well as small or individual-sized packages of coffee, cereal, and dry pet food, where material breakage and loss is a costly problem that can harm the bottom line.
Even a difference between one- and five-percent waste can mean the difference between profit and loss.
To convey such delicate food product, packagers and processors should avoid conveyors that may force the fragile material through stressful phases during transport that could impact its integrity, while still meeting high throughput requirements.
Given this need, some packagers are reconsidering conveying fragile, high-value products using high velocity air power through tubes, bends or sweeps before it is unceremoniously dumped 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, process engineer and director of Plus One Percent Engineered Solutions, a consulting firm that works in the food industry and markets food industry conveyor equipment globally.
“When a whole macadamia nut is broken, for example, “its value can drop by half,” Schliebs points out. “Instead of a premium price for whole nuts, damaged nuts are often sold at a substantial discount, often crushed for use in cooking or processing further upstream in the food packaging industry.
“Many high-value food products can be fragile and need very gentle handling,” Schliebs explains.
“Otherwise, whole forms can be broken, crushed to bits, and even turned to powder,” he explains.
“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,” says Schliebs.
“In some cases, more than 10 per cent of delicate product can be damaged by high-velocity air-power systems,” he elaborates.
“The cost to the packaging 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,” adds Schliebs, who frequently consults on food engineering equipment design, plant layouts, and process flows.
Schliebs says food packagers and processors need to be aware that a wide range of fragile high-value value 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 utilize air by creating air pressure above or below the atmospheric level—employing filters that require regular replacement.
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 of typically 3,400 to 5,000 feet per minute.
While the product usually has minimal breakage in straight pathways, most systems have bends and sweeps where it can be forced through constricted areas, quickly change direction and be damaged. In such cases, high-dollar value food can often torun out to be too fragile.
Dense phase pneumatic conveyor systems, where the product is not suspended in air since 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.
While aeromechanical conveyors have a different method of conveyance, 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 materials 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,” Schliebs notes.
“This can be the case with both pneumatic or aeromechanical conveyors.”
According to Schliebs, a gentler alternative to protect sensitive, high-value packaged food products is to utilize 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 (f lights) are attached to the cable, which push the product at low speed through the tube without the use of air—preserving product integrity and minimizing waste.
Located in Oskaloosa, Iowa, conveying systems experts Cablevey Conveyors (www.cablevey.com) has specialized in the design and engineering of cable and disc tube conveyors for almost 50 years, with system installations in more than 60 countries worldwide.
“Food industry manufacturers can decrease product damage down to one to two per cent with a slower process like a Cablevey Conveyors tubular cable system, where the product is gently transferred at low speed, so there is minimal to no damage,” says Schliebs.
In the packaged foods industry, these conveyors are utilized for products such as snacks, nuts, cereal, coffee, pet food, beans and seeds, with the systems capable conveying f lakes, pellets, shavings, crumbles, granules, regrind, chunks, parts, pills and powders—with numerous layouts using multiple inlets and outlets—at speeds of up to 2,000 cubic feet per hour.
Since the material is carried between the f lights, 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 the whole load, as is more typical with conveyors utilizing air.
“To minimize product damage, it is important for food industry manufacturers to not only transfer gently, but also get product in and out of the conveyor safely and gently as well,” Schliebs explains.
“That is more achievable with conveyors like those from Cablevey, which allow the product to slide down, rather than drop out, at the end.”
For packaging lines, 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 with a pneumatic conveying system because it has more components and electrical connections.
Also, another bonus of the Cablevey systems is that the ‘footprint’ can be quite small compared to other conveyor systems, which really helps with tight and compact packaging and manufacturing areas.
“Because of the ‘bespoke’ design of each Cablevey system for customer-specific requirements, we can tailor the design to be very ‘non-intrusive’ 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 f loorspace, which is another cost to manufacturing.”
Whereas pneumatic systems convey product at high velocity—thereby typically requiring larger, power-hungry motors that run fans, blowers and rotary valves on food packaging and processing lines—in a dense phase system, a pressure tank requiring compressed air also consumes additional power.
In terms of noise level, pneumatic conveying systems tend to generate considerable noise volumes, while aeromechanical systems running at high speeds also generate considerable motor and disc noise.
“By using smaller motors to operate, tubular cable systems are quieter overall and utilize much less energy,” according to Schliebs.
“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 utilizes about one-tenth that of pneumatic systems,” Schliebs concludes.
“For dense phase models, the electricity savings by using a tubular conveyor can be sizeable, with one-year ROI (return-on-investment) in some cases.”