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Transporting a consignment surely needs the container itself to be durable and weatherproof, but when it comes to transporting perishable goods, maintaining conditions like temperature & humidity become non-negotiable aspects of the transport process. To solve this, the global shipping industry uses what are called Reefer containers.
What is a Reefer container?
Reefer container is suitable for cargo that is temperature sensitive and requires refrigeration during the voyage. Considering it, a reefer container can be thought of like a refrigerator that can be taken across the route without spoiling the contents. It is a type of intermodal freight container of a refrigeration system. While being stationed on a land-based site, reefer containers need an external power supply. During transit, they can be powered by diesel generators. Reefer containers can achieve a temperature range of -65℃ to 40℃. In absence of an adequate heat ventilation system, reefers have a water cooling system that helps for venting heat.
Reefers have changed the course of trade significantly as fresh goods can be shared with anyone in the world at any given time of the year. Reefers keep the perishable articles safe and transport them safely without changing the quality or quantity, to meet the demand.
Reefer Container Features and Benefits
- After arriving at the dock or the designated place, the cargo would not require cold storage.
- A wide array of dimensions are available for the container. Thus, they are suitable for all modes of transport.
- We can divide the reefer container to store different articles at different temperatures. This saves cost and allows to store more goods in a single container.
- Durability is high for reefer containers and they can be used even in adverse weather conditions.
- They can carry out a voyage or transit with many carrier vessels. They do not need specific reefer carrier ships. This helps in getting high financial security and faster return on investment.
- Reefer containers can manipulate the ripening of products and help to increase the shelf lives of the articles.
To conclude, reefer containers:
- Have precise temperature control
- Are hygienic and have a low risk of corrosion
- Are highly reliable
- Have low maintenance and operation cost
- Are compatible with all refrigerants. Hence ease of operation.
How do refrigerated (reefer) containers work?
Refrigerated containers have similar functionality as a Refrigerator. The general working remains the same for all the types of reefer containers and the respective methods of cooling used. Their specific T-shaped decking is designed to distribute cool air from the surface. As a result, they are called bottom air delivery units. This type of container design makes, Reefers have a consistent and uniform supply of air and guarantee a good atmosphere with the perfect exchange of air with the cargo.
Even in harsh conditions, refrigerated containers can conserve or lessen the temperature of the shipment. Reefer’s can also maintain a temperature of up to 30℃ for some specific goods when required. The lowering or maintaining of temperature is achieved from a control box usually found near the cooling mechanism.
Reefer Container Temperature Control for Frozen and Chilled Cargo
In Reefer Containers, it is important to maintain the prescribed temperature. This is achieved by circulating temperature-controlled air internally, throughout the cargo space. The type of packaging used and the method of cargo loading affects airflow. Different types of cargo have different temperature, loading, and packaging requirements. Generally, chilled cargo is kept separate from frozen cargo due to different air circulating needs.
For chilled cargo like meat, the packaging used should have ventilation for air to flow through. To remove heat and gases, the air has to flow through the cargo. The main reason for this type of airflow is that the heat is generated by the cargo, in addition to the heat from the outside atmosphere.
For frozen cargo like fresh fruits and vegetables, the respiration process and airflow requirement are different. They require air to flow through the commodity as well as around it to remove gases like Carbon Dioxide and Ethylene (formed due to the respiration of fruits). To achieve this airflow, the cargo is stacked so that there are no gaps between the packages and the walls of the container. As no heat is produced by the cargo, the reefer container fan only needs to remove the outside heat which penetrates through the container walls.
Atmosphere control and fresh air circulation are also extremely important while transporting fruits and vegetables. Carbon Dioxide and Ethylene gases are released because of continuous respiration from this kind of cargo. Excess presence of these gases can lead to product damage, uncontrolled ripening, bad flavor, and aging. Most reefer containers are equipped with Atmosphere Control and proper ventilation to remove these gases and maintain product quality.
How are reefer containers powered?
Reefer Containers are usually powered by a generator that is attached to the container and provides electricity to the Cooling Unit. These generators can be either fuel-powered or electric-powered or both. Some reefer containers have a secondary generator set to act as a backup in case the primary fails.
Reefer Container Stowage Principles
While packing a reefer container, there are a few cargo stowage principles that need to be followed to allow proper airflow and efficient loading.
- Refrigeration/Cooling unit
- Boxes do not extend beyond pallet
- Spacing between deck board allows vertical airﬂow
- Boxes vented for vertical airﬂow
- The pallet load is secured
- Container Rear doors
- Air/free space above the cargo
- Box vents aligned
How much do refrigerated containers cost?
Among the several shipping container types in circulation, the price of reefer containers is the highest. Generally, these are six times that of a general-purpose/ standard container. It also varies based on the cooling mechanism used, size of the container, and additional modifications/ customizations made.
Price of a 40’ Reefer Container is usually between $7,500 (refurbished/ used) to $27,000 (new).
Types of Refrigerated shipping containers
These are the types of Reefer Container available:
Twenty Feet Reefer Containers
The gold standard of the shipping industry, the TEUs (click here to know what TEU stands for) are also available in their reefer versions and it is the most widely used reefer container dimension. Refrigerated versions of FEUs (Forty Foot Containers) are also widely used.
This is the most commonly used Reefer Container. It comes with an integral front wall and an all-electric automatic cooling and heating unit.
Modified/ Controlled Atmosphere (MA/ CA) Reefer Container
This type of reefer container uses insulation to maintain a constant atmosphere. This is achieved by replacing the consumed oxygen using an air exchange system. This helps in controlling the atmosphere at equilibrium with the product’s deterioration rate.
Automatic Fresh Air Management Containers (AFAM)
These are highly advanced reefer containers that use superior technology to regulate the airflow by automatically adjusting the rate of fresh air supply. They work in a way similar to CA Reefer Containers in controlling the composition of Oxygen, Carbon Dioxide, and other gases. The controls for this reefer can be modified to extend the shelf life of the products.
Cryogenic Cooling Reefer Containers
These containers use the Total Loss Refrigeration method to keep the perishable products fresh. Dry Ice or Liquid Nitrogen is used for these containers for cooling. The cryogenically frozen gas evaporates slowly, cools the container, and is then vented out. The average time period for which these containers can maintain their temperature range between 17 days to 30 days.
Redundant Refrigeration Reefer Containers
When transporting highly valuable, temperature-sensitive, or hazardous cargo, system reliability is of utmost importance. Redundant Refrigeration Reefer Containers are used in such cases. These containers have a primary as well as a secondary or back-up refrigeration unit.
Refrigerated or Cool Tank Containers
Designed to transport products like pharmaceuticals, milk, and general-purpose liquids. These tanks are cooled by circulating brine or synthetic oil around the external coils.
Reefer Container - Dimensions
Common Reefer Containers
High Cube Reefer Containers
Offshore Reefer Containers
There are a few other types of Reefer Containers whose dimensions are based on added customizations. These are:
- 20 feet Deep Freezer Container
- 40 feet Ultra Freezer Container
- 20 feet Dual Temperature Reefer Container
- 40 feet Dual Temperature Reefer Container
- 20 feet Triple Temperature Reefer Container
Difference between Reefer container and Dry Container
FAQs on Reefer Containers
1. How much power does a reefer container consume?
Power consumption of a reefer container will depend on the nature of articles stored, outside temperature, and the number of times the container is opened and closed. Hence, consumption can not be definite in all cases. However, newer models would always consume less power compared to older or used models.
2. What is the range of temperature that can be achieved by reefer containers?
Generally, a range of -25℃ to +25℃ is achieved. For newer containers, it is possible to achieve -40℃ to +40℃. And for Superfreezers, they can achieve up to -60℃.
3. What is the volume of a reefer container?
4. What should one make sure of while loading and unloading reefer containers?
The sight of docking the reefer container should be well leveled and firm. The container should at least be placed 1 meter away from any walls so that it can breathe, and in case of any repairs, the technician can get enough space to fix it.
5. Are refrigerated containers airtight?
Yes, Reefer Containers can be made airtight when all the floor drains and ventilation in the cooling unit has been closed.
6. What is a dry reefer container?
A dry reefer container is a modification of a Dry Container fitted with a cooling/refrigeration unit. These types of containers are used to transport temperature-sensitive products that need a dry atmosphere.
7. Why are reefer containers white?
Reefer Containers are white because the color white reflects all wavelengths of light and, thus absorbs the least amount of heat. Resulting in the coolant/refrigerant being used less to cool the container’s air.
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