Selecting the Ideal Conveying System for a Food Packaging Line

Horizontal-motion conveyors offer the gentlest handling and the easiest sanitation of all vibratory conveyor types. Image courtesy of Key Technology.

By Rudy Sanchez, Food Handling Systems Product Development Manager at Key Technology

Many food processors and packers have traditionally relied on belt conveyors as well as personnel to handle products on their packaging lines, in part because the belief that low capital costs make these options seem the most affordable. However, when the total cost of ownership is factored in, the affordability equation shifts in favor of other conveyor types. Add performance requirements, such as throughput and gentle yet sophisticated product handling, into the analysis and each food product and application points to its own ideal conveying solution.

In this article, we will explore the different types of conveyor systems – belt conveyors, vibratory conveyors and horizontal-motion conveyors – that are suitable for various food products on packaging lines and highlight the strengths and weaknesses of each. The goal is to help food processors and packers identify the most effective conveying solutions for their specific packaging line application.

Belt Conveyors

Belt conveyors typically offer the lowest initial capital cost of all the conveying solutions, which helps drive their popularity. But this simple cost analysis is short sighted, as high maintenance and cleaning costs quickly inflate the total cost of ownership of a belt conveyor. Although the initial price tag for vibratory conveyors and horizontal-motion conveyors is often higher, the larger upfront cost is quickly recovered because they can cost so much less to maintain and clean than a belt conveyor.

However, there are food packaging applications that are best served with belt conveyors, warranting their use despite the higher routine costs. These applications include the following:

• When significant changes in elevation are needed, belt conveyors are the ideal. While vibratory conveyors are effective in many applications if the required incline angle is 6 degrees or less, any angle beyond 6 degrees requires a belt conveyor.
• Belt conveyors can be designed to store large volumes of product that can then be slowly fed back into the packaging line. For medium-capacity storage applications, horizontal-motion conveyors are often suitable as well.
• Packaged products can be conveyed effectively with either a belt conveyor or a vibratory conveyor. Since the sanitation benefits provided by a vibratory conveyor are less important when handling packaged products, a belt system is often appropriate for conveying packages.

Belt conveyors can be optimized for many food packaging applications and are available with a range of plastic, fabric and metal belt materials as well as conveyor geometries. However, high maintenance costs and sanitation challenges often make vibratory conveyors and horizontal motion conveyors preferred solutions.

Vibratory Conveyors

High maintenance and cleaning costs can inflate the total cost of ownership of a belt conveyor. Image courtesy of Key Technology.

Vibratory conveyors, sometimes called “shakers,” come in two types – true natural frequency conveyors with mechanical drives and electromagnetic conveyors with electromagnetic drives. Both use frame-mounted drives and spring arm assemblies to distribute energy to the conveyor bed, which produces a diagonal, harmonic motion that moves product forward.

Traditional vibratory conveyors that use mechanical drives produce high-amplitude, low-frequency movement. Electromagnetic shakers allow lower conveying pan amplitudes at higher frequencies to be varied, making them ideal for packaging lines that handle a wide variety of products or lines that require precise metering, spreading, alignment and/or singulation.

Compared to belt conveyors, vibratory conveyors are inherently more sanitary, featuring stainless-steel product zones and no belt to pulley/gear laminations. They also reduce maintenance, which results in a lower total cost of ownership over the life of the conveyor. Some newer shakers further minimize maintenance by utilizing drive systems that eliminate the need to lubricate or change oil.

In addition to these across-the-board benefits, there are specific packaging line applications that do particularly well with vibratory conveying, including:

• Vibratory conveyors are ideal for spreading, as the vibration moves the product forward and across the width of the conveyor, releasing the bond between the product. This spreading application is needed for a wide variety of potato products, fruits and vegetables, snacks, shredded cheese, nuts and pet food.
• Vibratory conveyors work well for product distribution on packaging lines because gates can be easily opened and closed to divert product to multiple points.
• Sizing can also be effectively achieved with vibratory conveyors, depending on the product. A multi-deck shaker is fitted with screens that allow product of a particular size to drop to the lower level.
• Leafy greens are conveyed more effectively with vibratory conveyors than with horizontal-motion conveyors because the product actually absorbs the energy of the vibration. The slight vertical lift of the vibratory conveyor helps move the product forward.
• When manually sorting products like wine grapes, vibratory conveyors offer an adjustable speed control to display product evenly for better visual inspection.
• Electromagnetic shakers, which can start and stop quickly, are often ideal for scale feed applications, where accurate metering to scales greatly enhances scale and bagger performance. Vibratory conveyors with mechanical drives and horizontal-motion conveyors can also be used effectively in many scale feed applications, depending on the product.
• Feeding a cutter or slicer, where product orientation and singulating improves the effectiveness of the operation, is handled best with vibratory conveyors.
• A combination of natural frequency and electromagnetic conveyors working together is ideal when aligning product to feed pick-and-place robots on packaging lines or aligning product for manual packaging.

Horizontal-Motion Conveyors

Vibratory conveyors, sometimes called “shakers,” come in two types – true natural frequency conveyors with mechanical drives and electromagnetic conveyors with electromagnetic drives. Image courtesy of Key Technology.

Horizontal-motion conveyors offer the gentlest handling and the easiest sanitation of all vibratory conveyor types. Additionally, the lower maintenance requirements lead to a lower total cost of ownership than belt conveyors. Some of the ideal applications for horizontal-motion conveyors include:

• Horizontal-motion conveyors are often ideal for most packaging lines handling bulk seasoned and coated products. The gentle handling reduces the loss of seasonings and coatings, while the horizontal motion produces a continuous self-cleaning action that prevents buildup.
• The sliding action of horizontal-motion conveyors prevents mixing and size separation, making this conveyor ideal for premixed blends.
• Horizontal-motion conveyors are perfect for packaging lines handling delicate products. This benefit must be considered on a product-by-product basis however, because many seemingly delicate products such as blueberries and leafy greens are handled well or even better with vibratory conveyors.
• Unlike vibratory conveyors, horizontal-motion conveyors can be designed to reverse product flow, which increases the flexibility of the line and provides some storage capacity.
• Some products such as frozen meat, which would make a loud drumming noise on vibratory conveyors, will run more quietly on horizontal-motion conveyors. That said, electromagnetic drives are the most inherently quiet to operate, so if product drumming is not an issue, an electromagnetic vibratory conveyor will be the quietest solution.
• Because horizontal-motion conveyors can be heavily loaded, they provide some bulk storage capacity on the packaging line when conveying products that are not in danger of being damaged.

Conclusion

To select the ideal conveyor for each situation, food processors and packers should consider a wide variety of factors, from total cost of ownership to performance requirements. The strengths and weaknesses of each conveyor type should be considered, and the benefits of each type must be judged based on the specific application. For help navigating this complicated analysis, processors and packers can work with an experienced equipment supplier to identify the conveying solutions that create competitive advantages by improving the performance on the packaging line.

About the Author

Rudy Sanchez is the Food Handling Systems Product Development Manager at Key Technology. Learn more at https://www.key.net/en/.