What is a reefer container?
“Reefer container” is yet another industry jargon that refers to refrigerated containers. Simply put, reefer containers are big fridges that are used to transport goods that require temperature controlled while in transit.
Examples of cargo that are usually transported in reefer containers are fruits, meat, fish, seafood, vegetables and dairy. Reefer containers also carry non-food products such as flowers and pharmaceuticals.
We here at MTS are very experienced in handling reefer cargo. In fact, recently we started carrying one of the biggest and most prestigious chocolatiers in the world. For this particular client, we ship chilled/frozen products that require strict temperature control during transport.
When it comes to reefer containers, there is no wiggle room. Temperature setting requirement must be precise as the integrity of the product depends on it. Reefer containers have the ability to maintain the cargo at the required temperatures for the duration of the transit.
How does a reefer container work?
Reefer containers are bottom air delivery units designed to distribute chilled air from the floor, via specific T-shaped decking, with the advantage of producing a consistent and uniform flow of air across the entire shipment, powerful enough to ensure a perfect air exchange with the goods.
Refrigerated units can maintain or lower the temperature of your shipment. Reefer containers are also equipped to ‘warm up’ the goods for those shipments where required, with the ability to maintain temperatures up to 30°C when required, regardless of outside temperatures. Important point to note is that a reefer unit is not designed to reduce the temperature of the cargo but rather to maintain the pre-cooled cargo temperature.
The airflow requirements of each commodity varies and there is no one size fits all in reefer cargo movement.
▪ in the case of chilled cargo, air has to flow through the cargo at all times so that heat and gases are removed, therefore the cartons used should have ventilation
▪ in the case of frozen cargo, air has to flow around the cargo so there should be no gaps between the cargo and the walls and the cargo itself, so the cargo has to be block stowed
Airflow pattern for chilled cargo – Image from http://maersklinereefer.com website
Airflow pattern for frozen cargo – Image from http://maersklinereefer.com website
While in transport, some fruit types have the potential to carry pathogens. In an effort to prevent this, all shipment from importing countries such as China, Japan and Nigeria require cold treatment of the fruit, colloquially known as Steri shipments.
For these kind of shipments, the fruit will be pre-cooled to a lower temperature, and in order to monitor this, steri probes (about 3 per shipment) are inserted into the pulp of the fruit, within the carton.
There is a minimal tolerance allowed in temperature variance. Should the tolerance be exceeded, either additional hours or days will be required to bring it to the required temperature.
Should one of the probes drift above the tolerance, the cargo will be rejected at country of destination, due to the potential of the fruit still retaining pathogens.
All in all, cold-treatment cargoes follow the normal pattern of shipping with one or two additional requirements.
Should the units be packed correctly and cargo post-harvest process followed, barring the unit failing, cargo can be received by the customer on a ready to eat basis or even for further storage.
Checklist for stowage of reefer cargo
Some general tips on stowage of reefer cargo:
▪ Cargo should not be stuffed beyond the end of the T-floor
▪ Cargo should not be stuffed above the red load line
▪ Cargo must be stable on the floor and tightly wedged so it doesn’t shift during passage
▪ Unit must always be set at the proper carrying temperature and this set temperature will vary according to the cargo being loaded
▪ Dehumidification controls must be checked
▪ If pre-cooling is required, it must be the cargo that is pre-cooled and not the container, unless the container is loaded in an airlocked cold tunnel in the cold storage
▪ Ventilation setting is of utmost importance and must be set at the correct level
▪ As air will follow the path of least resistance, there should not be any restrictions for air flow and any gaps between the pallets and the doors must be closed using cardboard or even wood. This will then force the air to circulate correctly and reduce the potential for heat sinks (warm air continuously circulating) near the doors