Temperature controlled Sea Freight
Temperature controlled Sea Freight16.01.2019 | By web3d_coldtruck
There are a number of methods to transport refrigerated goods and commodities overseas.
Sea transport is cheaper, enables larger volume transport, and planning of the supply chain according to the requirements of the customers.
Reefer vessels: These are vessels which specialize in transport of temperature controlled cargo. The storage facilities of the vessel are actually sophisticated cold rooms which are divided into a number of cells which enable to transport different commodities with different temperature controlled specifications. In every cell the variants are controllable: temperature, humidity, ventilation, which are all monitored and amendable in case required throughout the journey to the final destination of the goods. A regular monitoring schedule will also provide the shipper and receiver of the goods with precise indications and monitoring of all required specifications in order to evaluate the quality of the product and to discover any casualties the cargo endured during its journey.
The reefer vessels are usually utilized and operated between countries which transfer large quantities of agricultural goods which require temperature control between them. A good example of adequate commodities is the citrus fruit family.
Reefer containers: Very similar in the dimensions to a “normal” 40’HC container unit, the reefer container units are built from steady and sustainable / insulated materials in order to preserve the atmosphere conditions that are p[re set for the transport of the goods. There are also 20’REEF units available in the market, but due to the limited requirements, these are scarce and difficult to find in specific locations in accordance to the need f the carriers.
The reefer containers are produced from sustainable materials such as stainless steel, fiberglass, and aluminum and double insulated side walls. The floor of the reefer containers, its side walls and closing doors are polygonal shaped in order to enable transfer of cool air or ventilation (depending on product) in order to ensure the unified temperature control of the cargo throughout its journey from stuffing at the supplier’s premises and up to un stuffing at the receiver’s warehouse.
In the front part of the reefer container an electrical cooling / refrigerated of unit is installed. This unit is functional when connected on an electric power transport facility or storage house, but can also be operated with an external power unit (usually an adapted unit called a gen-set or alternative diesel powered means). Next to the power unit a monitoring facility will be facilitated in order to obtain full records of the temperature, humidity, and other relevant measures throughout the voyage of the cargo. These records should be made available to the customer upon demand, depending on the carrier, BUT, are the property of the carrier and may at times be kept internally in order to prevent input which is not in favor of the responsibility of the carrier.
The process of the cooling of the reefer container unit is performed by inserting cold air, usually at the bottom part of the container through the floor ventilation canals, which is then distributed throughout the container space and through the polygonal canals under, above and in between the open spaces left between the packages of the cargo (usually on pallets).
The return, warmer air, which is generated on the top part of the container, is being sucked back into the cooling unit, and this process goes on continuously throughout the journey, as long as the reefer container is connected to a power source.
It is extremely important to acknowledge that the temperature that is being measured is of the air that is being returned to the cooling unit, and not the temperature of the goods themselves.
Each and every temperature controlled reefer container there is a regulatory cycle of self-defrosting that takes place every 6 to 8 hours which prevents generation of ice and plugging of the pipes and ventilation areas. These regular defrosting cycles can be misinterpreted as an increase of the temperature within the container to the unprofessional eye.
Beyond the cooling facility, one can find a controllable ventilation valve in the front of the container. The opening of this valve enables exchange of air between the internal and external space of the container and is used mostly with perishable goods to ensure removal of harmful generated gasses such as Ethylene from the container.
Controlled atmosphere (CA) containers: Some of the reefer containers are equipped with additional technological measures which enable further control of the gases, humidity and other atmosphere influencers inside the container. After the stuffing of the container with produce, and especially in cases of fresh produce (e.g. avocado, citrus and other fruits and vegetables) gases (usually Nitrogen) are inserted into the container area in order push out the available air within the open spaces between the pallets inside the container. A system of sensors monitor the amount of gasses available inside the container. Once the level of carbon dioxide increases to levels beyond the recommended, due to the natural respiratory of the produce, gases are inserted into the container to slow down the natural ripening of the produce which eventually leads to decay. The use of such modern methods enables to increase the shelf life of products beyond the decay of the produce within a “normal” reefer container.