Designing Frozen Food Conveying Systems from Freezer to Weigher

Frozen food conveyor design demands a comprehensive system approach. Image courtesy of Key Technology.

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

In frozen food packaging, how products move from the freezer to the multihead weigher can make or break line performance. Whether handling frozen french fries, chicken nuggets, vegetables, fruits or shredded cheese, optimizing product flow through this critical conveying section directly impacts production efficiencies, product quality and yield.

Success requires more than reliable conveyors – it demands a comprehensive system approach that addresses every transfer point, control loop and flow variability.

The Frozen Product Journey

A frozen packaging line from the freezer’s exit to weighing typically includes several systems. First, scalping conveyors separate individual pieces from clumps, allowing good product to continue downstream while diverting oversized pieces to be reprocessed or removed. Some processors install optical sorters here to remove foreign material and defective products prior to weighing. Alternatively, manual inspection stations are sometimes used, although most processors are moving toward automated solutions to reduce labor requirements and improve consistency.

Next, product is elevated via conveyor belt to reach the scale deck level, where it’s received by a transfer conveyor. A series of distribution conveyors, each one equipped with an automated gate, then advances product along the scale deck. From here, scale feeders meter precisely controlled portions to each multihead scale.

Equipment designs vary based on capacity and operational requirements. Lines may incorporate merry-go-round configurations, for example, that recirculate excess product back to the beginning of the distribution conveyors, allowing for more efficient product utilization when scales go offline for maintenance or package film changes. Or, modular systems may instead feature individual conveyors between each scale, designed with 30 percent overcapacity to maintain consistent product flow to all scales.

Understanding the Challenges

The conveying path between the freezer’s exit and weighing systems presents challenges that don’t exist in room-temperature applications. Frozen products frequently exit the freezer stuck together in clumps that must be removed by a scalping conveyor and/or optical sorter before reaching the scales. This clumping occurs naturally during the freezing process and can severely impact weighing accuracy if not addressed.

Product flow from the freezer is rarely consistent, so downstream conveyors must handle surges and lulls that would otherwise overwhelm or starve the weighing systems. Temperature differences between the frozen product and the processing environment create condensation issues that lead to ice buildup on conveyor surfaces. When this ice combines with product residues like grease or sugars, it creates “caking” on the conveyor bed that impedes product flow and requires frequent cleaning.

Frozen products also generate significantly more noise than room-temperature products when moved on vibratory conveying equipment, creating a loud drumming effect that can make the work environment uncomfortable for workers.

With these challenges in mind, determining the most effective conveying technology becomes critical.

Designing the Ideal Line

In frozen food packaging, the way products move from the freezer to the multihead weigher can make or break line performance. Image courtesy of Key Technology.

Choosing the right equipment depends on several product-specific factors. Traditional vibratory conveyors using mechanical drives produce high-amplitude, low-frequency movement that works well for products requiring significant energy to move, such as frozen shredded cheese or round products like frozen meatballs. For applications requiring aggressive product movement, these vibratory conveyors may use reduced angles to provide gentler handling while maintaining effectiveness.

Horizontal-motion conveyors offer compelling advantages for many frozen applications. These conveying systems deliver significantly reduced noise levels, gentler product handling that preserves coatings and seasonings and continuous self-cleaning action that prevents buildup. However, horizontal-motion conveyors cannot be hung from ceiling structures, which some processors prefer for easier floor cleaning access.

Material selection plays a crucial role in frozen product conveying. Rigid surfaces with texture, for example, work better than smooth surfaces for preventing ice buildup. Some applications benefit from specialized conveying surface materials with raised patterns that promote better product flow and easier cleaning.

Transfer points between conveyors must also be carefully designed, as these are critical control points where flow problems can develop. Important design factors include appropriate drop heights to prevent product damage, proper gate sizing to prevent product bridging and transfer point geometry that promotes smooth product flow between conveying sections.

Modern control systems tie all the conveying units together, balancing product flow among multiple scales while accommodating different bag sizes and production rates. Starting from scale-mounted sensors that detect product levels, the system works backward through the conveying line, opening gates and starting conveyors as needed. When a scale signals for product, the control system starts the appropriate conveyor, opens the correct gate and initiates upstream equipment in the proper sequence.

Operational Considerations

Successful frozen product conveying requires attention to several operational factors. One crucial design consideration often overlooked is vibration isolation. Multihead scales are extremely sensitive to vibration, requiring physical separation between the distribution conveyor supports and scale foundations. This typically involves gaps in the floor structure to prevent vibration transmission from the conveyors to the weighing equipment.

Frozen product conveying lines require equipment designed for thorough cleaning while accommodating the unique challenges of cold, wet environments. All product contact surfaces should be stainless steel, and conveying equipment should feature designs that drain completely and provide access for cleaning. Many processors rely more on wiping with alcohol rather than extensive water use, since water can create ice buildup on conveying surfaces and extend startup times.

Achieving ROI Through Proper Design

Success in frozen product flow requires understanding the unique challenges of cold environments and implementing integrated conveying solutions that address product characteristics, equipment capabilities and operational requirements. The investment in properly designed flow management and conveying systems pays dividends through improved overall equipment effectiveness and reduced waste.

Partnering with an experienced equipment supplier, who understands the challenges of frozen product handling, helps ensure an optimal packaging line design that meet current needs and accommodate future expansion. The right integrated conveying system can transform this section of the line into a smooth, efficient operation that supports consistent packaging performance and product quality.

About the Author

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