There are substantial design differences between refrigerated containers and refrigerated trucks used for domestic transport of refrigerated cargo, which results in significant differences in airflows. It is very important that refrigerated cargo is packed in reefer containers, giving consideration to these differences. The increase in transit times should also be borne in mind.

Consideration must be given prior to vanning of the container to the manufacturer’s mass rating (maximum payload) and the legislatively specified mass limitations. These must not be exceeded. The person consigning a container for transport must make an accurate complying weight declaration.

Packing and securing of cargo in the container must be carried out giving due consideration to sea voyage, which may be undertaken in a variety of weather conditions, which is likely to exert a combination of forces upon the ship and its cargo over a prolonged period of time. Such forces may arise from pitching, rolling, heaving, surging, yawing or a combination of two or more. It must not be assumed that securing methods used for land transport will always be adequate at sea. At the same time, the method of securing must not itself cause any damage or deterioration either to the cargo or the container.

Before Stowage

The container must be inspected for cleanliness, contaminants, residues, pests, odours and bowing, and rejected if it is unfit. If the container ceiling is bowed to such an extent that the necessary roof clearance cannot be attained with properly packed cartons, then the shipping line should be advised before stowing is commenced. If practical the container should be replaced. If the container is being held for more than 24 hours at the packing facility or transport yard, ensure that the machinery is not facing a westerly direction, during hot days the heat on the compressor could cause a malfunction.

The refrigeration unit on integral containers fitted with Partlow charts should be checked for a current pre-trip sticker with current validity and for a chart in the temperature recorder. If the validity date is more than 30 days old, please refer to the shipping line. Details entered on the temperature chart should be checked as correct eg. Container number, commodity, set temperature, intended vessel, Port of Discharge (P.O.D) etc.

The set-point on the unit should be checked to ensure it is near the desired fresh produce temperature. If the set-point is below -2°C or more than 2°C above the desired fresh produce temperature, then a message to check the setting should be sent with the documentation accompanying the container. If the refrigeration unit is to be operated at the packing shed or during transit from the packing shed to the marine terminal, then the setting should be adjusted after consultation with the shipping company.

Ideally, the loading of a container should take place in a temperature-controlled storage area or docked to an anti-chamber. Otherwise, the container should be placed so that stowing can take place under cover in the shade. Handling of produce in a non-temperature controlled environment would likely result in moisture being formed on the surface of the commodity, resulting in ‘cargo sweat’, which could accelerate its deterioration. Condensation may also form on the packaging, which could weaken any fibreboard packaging.

The refrigeration units should never be run with the container’s doors open, except where the container is to be sealed to an anti-chamber. Pre-cooling the container before loading is of no benefit as the condensation produced will deposit as ice on the evaporator coils after the unit has been re-started, resulting in additional defrosts, thereby delaying adequate cooling of the cargo.

Where possible, the container should be placed so that the door end is slightly higher than the unit end. This will result in easier stowing with less likelihood of the tiers of produce leaning out towards the doors.

Determine the stowage pattern before stowing is commenced. If necessary, lay a row of cartons across and lengthways down the container floor.

The best stowage pattern should permit air to move freely through the packing and the cargo, whilst preventing any shifting/movement of the cargo. The ‘respiratory’ heat, carbon dioxide, water vapour and other gases generated by the produce is expelled by air circulation. Any ‘broken stowage’ should be packed with some material, to reduce the possibility of the air ‘short-circuiting’.

The produce should be within 1°C of the desired carriage temperature before loading into the container. In Australia, local or federal AQIS DPI offices can provide advice on export requirements and other relevant matters in regard to shipping temperatures and acceptance conditions at overseas destinations.

During Stowage

The temperature of produce inside cartons selected at random should be measured prior to removal from the cool store. Only produce cooled to within 1°C of the desired transport temperature should be loaded into the container.

Pallets of produce should be brought out of the cool room only as required. Produce should not be left unnecessarily in ambient conditions while waiting to be stowed.

Stowing should be completed without delays and within one hour. If a break in stowing of more than 20 minutes is to occur, then the container doors should be closed and any unstowed produce returned to the cool room.

Cargo must not be loaded higher than the ‘red load line’ marked inside the container or exceed the end of the floor grills at the door, otherwise correct airflow will be impeded. The load also should not exceed the declared cargo weight as shown on the container door. In addition, ensure that the cargo weight is acceptable at the port of discharge, for example some East Malaysian destinations have weight restrictions.

Except to meet the importing country’s quarantine requirements, dunnage battens are no longer required to be placed between cartons in containers. Instead, cartons should be block stowed with vertical dunnage placed in the door gap to prevent gaps opening up through the stow; this dunnage must not prevent airflow up the door gap. If dunnage battens are used, they should be placed between every second tier of cartons and vertical dunnage should also be placed in any remaining gap at the doors. The stow should finish as close as possible to the end of the floor grills, but not so that the door battens indent into the cartons when the doors are closed.

To meet the importing country’s quarantine requirements for produce undergoing in-transit disinfestation, dunnage battens (wooden wedges) must be placed and taped between every second tier of cartons with an additional set of battens between the last and second last tiers.

The lids of cartons in the top layer must be taped to the base to prevent the lids lifting and restricting the ceiling gap (there should not be any dunnage or plastic on the top of the stow, which could become loose and impede or block the flow of air or the return air vent).

For non-palletised stows, cartons should be block stowed, square on top of each other (without space between the load and the walls of the containers), to facilitate the passage of air through them. If they are interlocked (like bricks in a wall), the airflow is impaired unless the cartons are specifically designed with ventilation holes to achieve vertical airflow. Effective carriage of chilled cargo depends on a full container load with minimum air-bagging, where the stow itself requires the cool air to pass through the cartons, thereby avoiding the possibility of air short-circuiting. Space between the cartons could result in air short-circuiting through the gaps, which would result in some of the cargo not being maintained at the carriage temperature.

Loading of pallets – Cartons must be stacked squarely and evenly on top of each other so that the weight is taken by the sidewalls of the carton. The ventilation holes on the top and bottom of the cartons must be aligned to enable air to flow freely through the stow. Any space between the pallets and the door must be covered by a heavy fibreboard to ensure efficient air circulation.

There should be no obstructions in the floor grill that would affect efficient air circulation.

After Stowage

The container doors should be closed immediately when stowage is completed.

All receival terminal documentation should be completed for dispatch with the container.

If the container is not being transported immediately, the unit should be connected to power and switched on to expel the ambient air that has accumulated during loading. Where it is not possible to keep the unit on power, the unit should be off power no longer than 1 hour (for chilled cargo), kept as cool as possible and definitely away from direct sunlight.

Should a shipper or packer place a reefer container on power the following must be checked:

Check Set point temperature setting and place to correct setting.
Fresh air exchange vents are set at the required setting. (The Fresh air exchange vents must remain closed when transporting by rail or truck).

Each link/carrier in the transport chain must notify the exporter and shipping company immediately if any out of specification conditions of the cargo is noticed/ascertained (for example hot-packed containers, equipment malfunction etc).