Debunking Misconceptions About Tubular Drag Conveyors

Tubular drag cable and disc conveyors decrease downtime and increase flexibility and quality control when integrated into food packaging lines. Image courtesy of Cablevey Conveyors.

Cable and Disc Systems Complement Food Packaging Systems for a Wide Range of Materials and Conditions

By Del Williams and Karl Seidel, Marketing Director at Cablevey Conveyors

As food packagers produce increasingly flexible materials and sizes, end-of-the-line packaging equipment must be paired with complementary conveyors on the production floor that can gently convey a variety of delicate product and blends without damage. In conjunction with packaging equipment, the conveyors must fit within available facility space while minimizing cleaning, maintenance, and downtime.

However, at a glance industry packaging veterans can be challenged to distinguish whether the conveyor tubes they see are screw (augur), pneumatic, vacuum, aeromechanical, tubular drag chain and disc or tubular drag cable and disc.  In fact, many lack substantial technical or hands-on experience with such conveyors.

This knowledge gap can result in extreme consequences when delicate materials or precise blends must be reliably conveyed but instead, costly product destruction or inaccurate blends occur.

Misconceptions about tubular drag cable and disc conveyors will be the focus of this assessment, addressing six widely held viewpoints in the industry.

Tubular drag cable conveyors 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.  These conveyors excel in transporting delicate, precise blends for a wide variety of food types in versatile layouts and configurations.

Misconception #1:  Conveyors are not designed to protect blends and mixes

When transporting a blend of product with a conveyor system, maintaining a consistent mix ratio is essential, whether a fine powder, coarse mix, or larger variable-sized amalgams of different weights and shapes.

However, conventional conveyor systems are not specifically designed to precisely transport blends without changing the mix ratio. Various product material weights, sizes, and shapes can shift and disperse in open systems like bucket conveyors, and vibration can cause the blended product to shift throughout transport.  Vacuum and pneumatic systems can cause smaller lightweight particles in a blend to move at different speeds than heavier or larger particulates, resulting in significant blend restructuring when the product reaches its discharge point within packaging equipment.

In contrast, tubular drag cable conveyors are engineered to maintain precise blend ratios, which can be important to quality-focused food packaging industry professionals, particularly the specialty food, coffee, powder, nut, and pet food markets.

As an example, our company’s engineers have resolved the issue with a completely enclosed, compartmentalized tubular conveyor system. Not unlike an endless succession of train cars, each space between solid circular discs holds a predefined volume of product.  Based on the manufacturer’s specifications and requirements, engineers can calculate the optimal speed of the system, the most appropriate tube angles, and the proper construction design to guarantee their blended product remains consistent from input to discharge in packaging, even at high volumes.

Modular systems like tubular drag cable conveyors are an excellent option for complex layouts that could require curves or changes in direction. Image courtesy of Cablevey Conveyors.

Misconception #2:  These conveyors are the same as a screw system

One of the most common misconceptions is that tubular drag cable and screw conveyors are identical, which is far from the case,” says Seidel.

Screw systems, also known as auger conveyors, typically utilize a helical blade that moves granular materials within a tube.  However, augurs can cause product damage and compromise blends.  So, the units tend to be an option when material integrity is not critical, such as when conveying food waste.

The key difference for packaging pros to look for is that augurs convey material with a helical screw. The transfer speed is directly proportional to the rotation speed of the screw.  On the other hand, tubular drag cable conveyors transfer material between two discs pulled by a sealed cable and are designed to protect delicate products and blends.

Misconception #3:  Conveyors cannot carry moist, hot, or frozen material

Tubular drag cable systems can be designed to convey food materials in a wide variety of forms and states including powdered, pureed, chopped, moist, hot, and frozen with throughput rates up to 80,000 pounds per hour.  The systems can convey material with high moisture content such as soaked beans and chickpeas when some water is being conveyed along with the product.

While the tubular conveyors are constructed of plastic components, the standard units are designed to operate at 180° F (82° C) with a high-temperature option up to 230° F (110° C), so can receive the product from ovens, fryers or dryers.  Even frozen products can be conveyed, although it is important that the temperature is controlled along the path, so no melting occurs with water freezing later in the system.

Misconception #4:  Conveyor footprint and expansion limitations

Some in the food packaging industry do not consider tubular conveyors because they believe that the systems cannot fit within their facility’s available space or accommodate its layout, which may include significant inclines or elevation changes.  However, this is not the case.

Modular systems like tubular drag cable conveyors are an excellent option for complex layouts that could require curves or changes in direction. Tubular conveyors do not have to be installed at 90 degrees and can use angles so can go in between, around, above or below existing packaging equipment or other obstacles.  That is important for existing facilities that may not have the flexibility to move equipment out of the way.

In addition, tubular conveyors are quite space efficient. To conserve space, the conveyor turnaround and its inlet can stand on end, so it is only one foot across instead of three.  If conveyor discharge occurs best using gravity, tubing can be run through walls and discharge out of the building roof, which saves interior space.

Misconception #5:  Conveyors are for indoor installation only

It is a misconception that tubular conveyors are only installed indoors.  In fact, it is common to see portions of equipment extending outdoors.  This may occur when conveying product from outside to inside such as when unloading raw material from a truck or railcar or loading finished product into similar transport.  Materials may also travel from a feed mill to a production or packaging room which may be ten feet or even one hundred feet away.

When some equipment is used outdoors, and when a moist product is moved, it can be helpful to wrap the tubes in heat tape to prevent moisture from condensing or freezing in the tubes.  The conveyor manufacturer can also provide a range of accommodations to account for the effects of wind, dust, rain, insects and direct sunlight.

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