A Complete Guide to Reefer Containers

Refrigerated containers, commonly referred to as ‘reefer containers’, are essential for the global transportation of temperature-sensitive cargo.  These specialised units ensure that perishable goods such as food, pharmaceuticals, and high-value agricultural products are maintained under controlled conditions throughout their journey. Keep reading to find out more…

Categories of Reefer Containers

There are five main types of reefer containers. You’ll find more details regarding each type below:

General purpose reefer containers

Also known as GP reefer containers, these are the most widely used units, capable of maintaining internal temperatures between -35°C and +30°C, with adjustable humidity levels ranging from 0% to 100%.  Ventilation settings can also be manually controlled to suit the cargo’s needs; these are commonly used for the transport of vegetables, meat, seafood and certain pharmaceuticals.

Water-cooled GP reefer containers

These units are the same as normal GP reefer containers, but they can connect to a central water-cooling system onboard the vessel when carried in a cargo hold, which is used to reduce the heat generated in the reefer refrigeration plant.  This improves the efficiency of the container and reduces the ambient heat build-up in the cargo hold.  These containers are more expensive to manufacture, require the vessel to be fitted with a water-cooling system, and are not used by all operators. 

Cold treatment containers

Cold Treatment is a technique used to prevent the spread of flies, pests, larvae in fruit and vegetables without chemicals.  This is achieved by lowering the pulp temperature under the specified level for a set period of time.  The containers also have the ability to be programmed to slowly bring the cargo back up to temperature to avoid any stress on the cargo.  There are usually additional probes within the cargo to monitor the temperatures commonly required for cargo to the USA and referred to as USDA Probes.

Controlled-atmosphere containers

These containers can control the amount of oxygen (O2), carbon dioxide (CO2) and nitrogen (N2) within the container – ideally suited to the transport of high value and voyage sensitive cargoes such as avocado, bananas, asparagus, and blueberries.  Some shipping companies offer additional services within their controlled atmosphere container fleets, such as controlled ripening, which allows for bananas to be ripened on a voyage so that they are at the desired stage of ripeness at the time of delivery.

Superfreezer containers

Operating within a temperature range of -20°C to -70°C, superfreezers are used for ultra-sensitive cargo such as pharmaceuticals and high-grade tuna.  These containers ensure that deep-freeze conditions are maintained consistently throughout the voyage.

Onboard cargo operations

Onboard cargo operations in relation to reefer containers involve a critical set of procedures to ensure the safe and effective transport of temperature-sensitive cargoes. Below, we’ve provided more detail on these operations.

Company safety management system (SMS) 

The SMS is an implemented system on board vessels that enables the shipping company to manage and implement the safe operation and organisation of working practices across its vessels. 

With the potential high value of cargo within a reefer container, most companies have a section included within their SMS relating to the safe operation, operating procedures and reporting of malfunctions for reefer containers on board. 

Stowage planning

Reefer containers, like standard general-purpose containers, must be stowed in accordance with the vessel’s cargo securing manual, giving consideration to the container weight, total stack weight of the container stacks, lashing forces and the stability of the vessel.

Stowage is typically coordinated by shore side central planners and verified by the vessel’s Chief Officer.  It is best practice to place reefer containers in designated slots to facilitate safe access for monitoring and maintenance.  To increase reefer capacity, splitter boxes and Y-connectors are sometimes used, although splitter boxes are preferred due to their integrated circuit breakers.

Pre-connection procedures

Once the container is loaded on board, the practice is to check the general condition of the container for any structural damage.  This role is carried out by the vessel’s crew.

Before connecting to the vessel’s power, the cable and plug is checked for damage. 

There are multiple settings listed on the reefer manifest which need to be checked. This includes set point temperatures, relative humidity and ventilation settings; any errors should be corrected as per the manifest. 

If the container is a cold treatment container, then this is to be checked against additional documentation. 

Monitoring during voyage

During the voyage, the cargo should typically be monitored at regular intervals by the vessel’s crew, depending upon the requirements of the cargo - but this is usually at least once every 24 hours.  Specialist and high-value cargo such as chilled meats, superfreezers, cold treatment and controlled atmosphere are usually monitored every 12 hours. 

The manual monitoring of the cargo should include checking and recording of temperatures and any malfunctions or alarms being given by the reefer containers. 

Remote container monitoring is now in use with some shipping companies.  Each company offers their own levels of functionality of remote monitoring, but all allow the customer to monitor the cargo temperatures and settings.  One company allows for the remote change of the container settings.  These are all usually add on services to the customer. 

All container controllers have a downloadable data log file which can be used for the operational history and events within the controller and can provide a valuable insight to the reefer containers operation. 

Maintenance and repairs

Most shipping companies carry a dedicated inventory of spares for their reefer containers covering the different types and manufacturers of equipment.  Companies that share container slots on trades will often supply each other with spares for their containers. 

Many of the malfunctions can be repaired on board if the conditions allow.  In extreme cases, repairs may not always be possible, but the container could be kept running to protect the cargo to the next available port.  This could be because of no suitable spares onboard or where access to the component is not possible.

Operational challenges

Despite technological advancements, several challenges persist in reefer operations:

• Hot ‘stuffed’ containers – this is where the cargo has not been pre-chilled prior to loading into the container, for example, fruit that has been picked and directly packaged into the container.  This can result in malfunctions to the machinery due to the extra strain.  Frequent manual defrosting is also required.
   
• Delays in connecting containers to the ship’s power supply.
   
• Reefer containers taken off power for prolonged periods due to insufficient power availability onboard – i.e., due to vessel manoeuvring or generator malfunction.
   
• Weather conditions preventing alarms on the units being attended to.
   
• Breakdown of reefer containers/time to effect repairs/multiple breakdowns.
   
• Spares may not be available onboard.
   
• Reefer controller ID numbers not matching container ID numbers.
   
• Accessibility due to containers being inadvertently loaded in incorrect slots/or slots blocked preventing repairs.
   
• Human error – container set points wrongly adjusted/set during initial checking at time of loading – this can be from wrong data entered into the BAPLIE (an electronic exchange of stowage files) files and this is used, instead of cross-checking with the manifest when verifying set points and settings.
   
• Reading/recording of set point temperatures instead of return temperature during monitoring.
   
• Overloading of ‘splitter boxes’ can result in damage to the supply plug.
   
• Poorly loaded containers or shifted loads, preventing correct airflow inside the reefer. 

Conclusion

Reefer containers are a basis of modern logistics, enabling the safe and efficient transport of temperature-sensitive goods across vast distances. While technology continues to play an important part in monitoring and control capabilities, the success of reefer operations ultimately depends on meticulous planning, skilled personnel, and adherence to best practices.

Scientific cargo advice from Brookes Bell

If you find yourself involved in a cargo-related dispute, Brookes Bell is here to help.

With scientists trained in physics, chemistry, biology, food science, forensic science, chemical engineering and toxicology, we’ve been offering industry-leading scientific cargo advice for over half a century and have an excellent track record of providing expert evidence for litigation. 

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