All about REEFERS

Reefers or refrigerated containers are used to carry mainly chilled or fresh produce and frozen foods. Warm cargo like pharmaceuticals , wine , biscuits etc are also carried by Reefers. Reefer traffic is growing together with increase in standard of living. Due to the global village concept and the free trade , we get all kinds of fruits & vegetables in India which we have seen only in pictures few years back. However, before shipping refrigerated cargo always verify that it can withstand the transit time.

Reefer containers are fabricated out of steel frame to with stand the rigors of the long transit , very heavy poly urethane foam insulation for thermal efficiency , white exterior walls for better temperature management and aluminium / steel T-bar floors to allow air flow under and around the cargo inside. Thermoking, Diakin and Carrier are the top 3 makers of the refrigeration units. All units are equipped with vents to create a more suitable atmosphere for vegetables and fruits. Fresh air can be removed and replaced at the rate of 0-260m3 / hr. For frozen foods ventilation should be closed. Humidity also can be reduced up to 55% and controlled at this level. Reefers are available in 3 major classifications, Classic( +35 to -5 ), Magnum ( -5 to -30) and Deep frozen(-30 to -35).

Most of the Reefer containers are equipped with a data recorder. All information & problems during the trip are recorded and the recorder can store about 9 months data . Data Extraction can be done with a handheld PC or Logman with compatible software (Carrier /TK / Daikin) .

Pre Cooling of Reefer Container.

The container should not be pre cooled if proper loading bay, where the temperature in the cold storage and the container is identical, is not available. If warm humid air enters the container during stuffing condensation on the evaporator coil results in the formation of ice. This condition demands frequent de-frosting and eventually affects the cooling capacity required for the cargo.

Also, high condensation occurs on the interior surface of a reefer container if hot air enters during stuffing this eventually results in ice building up for frozen cargo and causes damage on packages for perishable cargo. Ice build up on frozen cargo is one of the reasons for overweight and also restrict the air circulation inside the container.

Pre Cooling of Cargo

Proper pre-cooling of the products is crucial as it rapidly removes heat from commodities before shipping , storage and processing. Reefers’ capacity to absorb heat produced by the cargo is limited. These containers are built to maintain the temperature of the product , not to decrease it. For eg, With a reefer container , it takes more than 5 days to decrease the cargo temperature from 5°C to -18°C and during these 5 days, the cargo continue to develop some bacteria until the temperature reaches -11°C . Whereas With a Cold storage, it takes just a few hours to decrease the temperature of 20 tons of meat from 3°C to -20°C . Also proper product pre-cooling reduces the water loss and spoilage for many perishables and helps maintaining freshness and quality.

Airflow inside Reefers

Air always takes the path of least resistance. In the case of fruits and vegetables, which represent a large percentage of chilled cargo, air has to be forced through vents in the boxes, inorder to remove the heat generated by respiration. In the case of frozen cargo , there is no respiration, so airflow around the cargo is sufficient to maintain the cargo temperature.

Cargo stowage in the container

Cargo can be palletized or bulk , but in both cases solid block stowage is recommended, leaving no space between the cartons and between the cartons and container walls. Be careful to select the correct packing material and correct stowage procedures. Also should be careful to spread the cargo over the entire floor space so as air flow from floor could force up through the cargo.

Why controlled atmosphere ?

For some chilled products such as avocados and asparagus, shelf life can be extended by applying new reefer technologies. By using a natural process to adjust the composition of the air inside the container can increase the shelf life & quality of product and decrease dehydration.