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Safe, gentle conveyance of delicate food materials: enclosed tubular cable conveyors prevent contamination and ease of cleaning.

Del Williams

July 22, 2020

7 Min Read
Inspection_Tube_CABLEVEY.jpg
Image courtesy of Cablevey Conveyors

Del Williams, technical writer, Cablevey Conveyors

Transporting powder and bulk solids in the food industry often involves mixes and blends of products, as well as raw ingredients such as flour, sugar, salt, and yeast. 

Although processed food conveyor systems are capable of handling many different sizes, weights, and combinations of materials, maintaining proportionate mix blends of batches as they move through the production cycle is essential to success. This presents many issues as ingredients can be of variable densities and granularity, leading to separation issues that can affect proportional accuracy.

Fortunately, cable and tube processed food conveyor systems present a definitive solution to such issues as batch loads are contained in sealed sections that move all batch ingredients without wastage, separation, or damage.

Such an approach toward powdered ingredients is critical because in every step of food processing – from receipt of raw materials through packaging – keeping foreign matter from entering the process stream, maintaining hygiene, and keeping the system free from unwanted allergens are critical objectives. As such, many food processors are reconsidering the use of “open” conveying systems such as bucket elevators and flat-belt conveyors in favor of enclosed systems designed to prevent exposure to ambient conditions and possible contamination.

Since the 2011 enactment of the FDA’s Food Safety Modernization Act, the importance of preventing product contamination has only increased with stringent product track and trace mandates, as well as consumer demands for safety.

Additionally, as food processors seek to increase production uptime and reduce laborious maintenance, the ease of cleaning such equipment is also a major concern.  Traditionally, powders and bulk solids can be difficult to clean from conveyors and can even be dangerous if the dust becomes airborne.

“With increased regulation, the primary focus of food processors has been on preventing contamination and reducing cleaning requirements,” said Mike Judy, an independent food industry sales representative and installer of conveying systems.

In food production, line changeovers have become a focal issue, relative to both cleanliness and changeover speed as companies are increasingly running different product lines within a single shift or day. Despite these changeovers, processing plants are expected to maintain rigorous levels of sanitary, allergen-free operation.

“With smaller margins, food companies are producing a broader range of products, which results in more product changeovers and more attention on efficient cleaning of production equipment,” said Judy.

Also important to food processors’ bottom line is the capability of conveying equipment to reduce any potential product damage, in order to optimize quality and profit. 

While powder does not suffer “breakage” in the way that larger product does (since it is already comprised of particles), rough, high-speed movement through constricted spaces (like pneumatic turns, etc.) can change its physical properties. It can compress, deform, or change some other property, like tendency to agglomerate (especially if exposed to moisture in open containers). This can degrade the powder’s desirability and performance as a food product or ingredient when utilized in combination with other ingredients during processing.

To ensure the safe, clean conveyance of even delicate powder and bulk solid materials with minimal product degradation, a growing number of food processors are turning to enclosed systems such as tubular drag conveyers that help prevent contamination and significantly ease, or even automate, cleaning.

The Disadvantages of Open Conveyor Systems
Traditionally, bucket elevators and flat-belt conveyors have been the predominant systems used to transport powder and bulk solid food products. However, open systems like these have substantial drawbacks in terms of the potential for contamination and ease of cleaning.

Bucket elevators utilize a continuous line of buckets, either attached to each other on a rubber belt, or attached by pins to two endless chains running over tracks and driven by sprockets. Centrifugal force moves the food being conveyed out of the buckets into a discharge spout as the buckets pass. This type of conveyor handles food products gently, but potentially exposes it to contamination from the surrounding environment.  

Flat-belt conveyors have the same issue, and so some are covered. Unfortunately, the covers can collect residue and must be removed and cleaned between runs, a tedious and time-consuming task. 

Open conveyors also allow powder and bulk solid product (if hygroscopic) to absorb moisture. Given that many food processing facilities are not climate controlled, this is a very real possibility. Such moisture absorption can cause product to expand, or clump, which can not only degrade quality but also make conveyor cleanup more difficult. 

The Advantages of Closed Conveyor Systems 
Unlike open systems, closed conveyor systems effectively seal off powder and bulk solid product from the outside environment, and any potential contamination from that source.

Although there are several types of closed systems, one popular example when conveying high value powder and bulk solid food ingredients that are prone to degradation is tubular drag cable conveyors. These systems gently move product through a sealed tube using a coated, flexible stainless steel drag cable pulled through on a loop. Solid circular discs (flights) are attached to the cable, which push the product through the tube without the use of air. The coated cable ensures that no powder and bulk solid debris or residue accumulates within the strands of the cable, as the cable is totally sealed.

The enclosed nature of tubular drag systems ensures no powder and bulk solid dust escapes, which could lead to an unsanitary and potentially dangerous coating of dust on the floor or process equipment. The result is a safer, cleaner, dust-free work environment and reduced risk of dust explosions if the product is in powdered form.

In the food industry, the conveyors are utilized for various product in powder and bulk solid form such as coffee, flour, sugar, salt, yeast, seeds, and beans. The systems can convey up to 2,000 cu ft/hr of powders, granules, regrind, shavings, crumbles, pellets, and fluff with numerous layouts using multiple inlets and outlets.

In addition to avoiding external contamination, food processors also increasingly expect conveyor systems to be designed for easy cleaning when it comes to powders and bulk solids.  

In this regard, bucket elevators are particularly difficult to clean in preparation for production line changeovers. To clean them, each bucket must be removed and cleaned inside and out to remove accumulated residue. 

Every minute spent disassembling a conveyor system for cleaning consumes valuable production time. Yet, if not cleaned properly, the powder or bulk solid food product being conveyed must be discarded due to contamination, which equates to lost profit. Or worse, consumers could be harmed, resulting in costly recalls, damage to brand and reputation, or even potential litigation and liability. 

With closed conveyors, cleaning is also a mixed bag. Pneumatic conveyors are popular, enclosed systems, but cleaning can still be relatively time consuming. Because high-pressure air is used to convey product, it can create excessive degradation as materials get battered through a course of vertical and horizontal tubing, turns, and sweeps.

“When cleaning is factored in, closed-system tubular cable conveyor systems are actually less expensive to own and operate than pneumatic equipment,” says Judy.

In regard to maintaining cleanliness, tubular drag cable conveyor systems also offer more options for dry and wet tube conveyor cleaning. These include brush boxes, urethane wipers, air knives, inline sponges, inline bristle brushes, and multi-step, essentially automated clean-in-place (CIP) wet cleaning.

“Compared to pneumatic conveyors, tubular cable conveyor systems also reduce powder and bulk solid product degradation and use less horsepower, which equates to less electrical use and less noise,” added Judy.

Cleanliness is also a key consideration when selecting between cable and chain tubular drag conveyors, both of which come into contact with the powder and bulk solid food ingredients during operation. Tubular chain conveyors have more surface area and connection points where residue can accumulate compared to a coated cable, which only has 20% of the surface area.

“Once a tubular cable conveyor system is installed, it dramatically reduces the cleaning and maintenance required,” said Judy. He cites an example at a food processing facility when a Cablevey tubular cable conveyor system was installed. “What previously took about 14 man-hours of cleaning (with a different, previous system) was accomplished in two hours.”

Minimizing powder and bulk solid product degradation is another important advantage of enclosed tubular cable conveyors. According to Judy, traditional conveyor systems can damage up to 10% of product, but tubular cable conveyors dramatically reduce any such damage. 

Although there are many conveying options for powders and bulk solids in food processing, few offer the same capability of preventing contamination and easing cleaning as closed system tubular cable conveyors, while also minimizing product degradation. This combination of attributes, along with low energy requirements and design flexibility, make the conveyors worth investigating for food industry professionals looking for a competitive edge.

Del Williams is a technical writer for Cablevey Conveyors (Oskaloosa, IA). Cablevey has designed, engineered, and serviced enclosed cable and disc tube conveyors for almost 50 years. For more information, call 800-247-3344 or visit cablevey.com.

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