For many end-of-line packaging professionals, the choice of pallet packaging method may not immediately surface as a critical success factor when designing, upgrading or refurbishing a production line or distribution center. There are many aspects that should be considered when choosing a pallet packaging method, as the choice can significantly impact overall profitability and distribution chain performance.

There are three recognized methods available for pallet packaging: conventional spiral stretch-wrapping, heat shrink-hooding, and stretch-hooding. Each method has its advantages and disadvantages depending on the specific application. This is part two of a three-part series in which we examine the different methods. You can read part one here.
Heat shrink-hooding

Introduced in the 1960s, heat shrink-hooding is the oldest form of pallet packaging by means of polyethylene film. Until the advent of stretch-hooding, heat shrink-hooding was the preferred method for optimal stability and pallet load protection. Heat shrink-hooding equipment uses gusseted tubing that is cut and sealed to form a bag. The oversized bag is applied over the pallet load and is then shrunk using heat. The most common heat sources for shrink-hooding are natural or liquid propane gas, but other heating methods, such as infrared or electrical hair dryer-style heaters, are also used. There are various types of heat shrink-hooding equipment available. Most contemporary approaches to heat shrink-hooding are of the ring type, which allows for a much more controlled heat application and provides the all-important bottom shrink that ensures proper pallet and load unitizing.

The heat shrink-hooding method provides very good pallet load stability and protection; it works particularly well with loads that have a substantially smaller footprint than the pallet as the film will shrink tightly around the contours of the pallet and load. In practice, however, such applications are rare.

The operating costs of a heat shrink-hooding system are much higher than those of both spiral stretch-wrapping and stretch-hooding. Because the film bag is shrunk (as opposed to stretched), it must have a larger pre-shrink circumference than the perimeter of the pallet load so that the equipment can apply the bag over the pallet load prior to the application of heat -- requiring substantially more film than stretch-hooding. Using significant energy consumption for heating, the heat shrink-hooding method also carries the risk of fire, which can often mean higher insurance premiums to protect against potential losses. Additionally, heat shrink-hooding equipment can be more maintenance-intensive compared to the other two methods.

The fact that most of the performance advantages offered by heat shrink-hooding (i.e., pallet load stability and protection) are available with the more cost-effective stretch hood technology has all but made obsolete heat shrink-hooding for bagged products.
Stay tuned for Part Three in July!

Uffe Steen Kristiansen, Director of Sales, Palletizing & Packaging, BEUMER Corporation. for more information.