Stowage

In order to maintain the required airflow for desired temperatures, proper stowing is essential. Critical factors to maximize post-harvest life include having a clear stowage plan and understanding how stowage patterns affect airflow in the container. For all stowage and cargo loading, it is important to cover the entire floor with pallets, boxes, or other materials, and load them below the red line.

Chilled Cargo such as fruits and vegetables generates heat as it respires. As a result, it is essential to ensure that large proportions of circulating air pass through (and not just around) the stow to provide good contact with all parts of the load. Chilled produce needs to be block stowed or stacked as a solid block, without leaving any space between the cargo -- preferably with vent holes aligned to facilitate the reefer container’s bottom air (vertical flow) delivery of airflow passing through the cargo. Occasionally, it may be necessary to brace a chilled load to stabilize it in transit. In such cases, APL recommends a refrigerated container equipped with cargo tie-down rings and restraining devices.

Frozen Cargo should always be stacked as a solid block, leaving no space between packages or pallets. In addition, air must be able to circulate around the periphery of the load. It is necessary to ensure air can circulate under, over and to each side and end of the stow. For stowage of produce in containers with flat-sided walls, slightly loose stowage is necessary for air circulation, because cartons that are fit too tightly across the space may give rise to hot spots and cause problems. This stowage pattern allows refrigerated air to circulate evenly around the cargo and ensures that any heat penetrating the container does not come into contact with the load.

Hand stowed cargo stowage in bottom-air delivery containers

Stowage in Corrugated Containers with Scuff Liner

Block Stowing: Hand-Stowed Cargo

• Stack cargo as a solid block. There should be little or no separation between the packages.
• Do not leave any space between cartons. Since air takes the path with least resistance in returning to the refrigeration unit, a gap between cartons can cause the cold air to short-cycle through the gap. When short-cycling occurs, part of the load may not benefit from the cold air, which may result in it being carried at less desirable temperatures.
• To facilitate air circulation for flat-wall containers, it is necessary to ensure cartons are not stowed too tightly against the side walls to ensure sufficient air circulation.
• Cover the entire floor with cargo.
• Leave enough space above and beneath the load for air to properly circulate.
• Do not stow cargo above the red line on the interior container wall.
• Do not use clipsheets with chilled cargo.

Unitized cargo stowage in bottom-air delivery containers

Block Stowing: Unitized Cargo

• Follow all of the instructions for hand-stowed cargo (listed above). In addition, follow the remaining three steps listed below.
• Stack cartons squarely, one on top of the other, so that the weight of each carton is evenly distributed on its four corners.
• Align the top and bottom carton vents, so that air can flow properly through the load.
• Do not use shrink-wrap or other material that may block package vents and obstruct airflow.

Summary of correct loading and stowage requirements:

• Cargo is block stowed – since air takes the path with least resistance.
• There are no gaps between items in the load, and the whole T-floor is covered -- because air should not be short-cycled.
• Cargo level is below the red line with minimum space at the back of the container – since lower airflow could cause hot spots.
• Cargo is not stowed too tightly against the side walls especially on flat (smooth) -wall containers, because air must be able to circulate around the periphery of the cartons.