Refrigerated containers are often also referred to as reefers, and are one of the main types of shipping containers used in transporting goods.
Reefer containers are used for the shipment of temperature sensitive, perishable cargo such as meats, fruits and vegetables. This container type relies on external power to keep the internal temperature regulated. A genset, or generator set, is a unit that is usually attached to a reefer to cool the container. Reefers generally come in 20ft and 40ft, and are commonly made from a weathering steel known as ‘cor-ten’ steel.
It is important to note that reefers are intended not to cool the product, but to maintain the temperature of the product. The process of refrigeration is thus not the addition of cold air, but the removal of heat from the air inside the trailer.
Reefer containers are bottom air delivery units designed to distribute chilled air from the floor, via a T-shaped decking.
The three main components of the refrigeration unit are the:
Variations in air pressure create air flow. As air from inside the reefer passes over the evaporator coil, it removes heat and redistributes the now colder air back throughout the reefer.
There are two different ways to run the refrigeration unit — cycle or continuous. Running the refrigeration unit in cycles reduces diesel consumption, but also creates more temperature variance.
Many products require continuous cooling. Ripening produce, for instance, generates heat, and requires a steady stream of cool air to maintain a consistent temperature.
Some frozen loads are less temperature sensitive and can withstand slight temperature variances — in these scenarios, cycling may be okay.
Understanding the commodity specifications is thus crucial for truckers as they are responsible for the product from the moment it is loaded onto their trailer until it is unloaded.
When the reefers arrive at the port, they will be unloaded from the vessel and plugged in at the yard to ensure that the internal temperatures are maintained.
When your driver has collected the container and is transporting it to the destination, the reefer will be unplugged from the electricity source. Not to worry though! In Singapore, the maximum travel duration is 1.5 hour. As the reefers are designed to be heavily insulated to preserve the cold temperatures, the internal temperature of the cargo will not change drastically.
However, once your reefer has reached its destination, your driver needs to ensure that the reefer is plugged in and that the genset is running during unstuffing.
When importing reefer containers, you should also take note of the various tariffs imposed at the port.
Below are the additional port charges relevant for reefers in Singapore:
Do also take note of the free storage period (FSP) and the port storage charges if the reefers are stored beyond the FSP. Reefers have a free storage period of 72 hours in Singapore.
For export, empty reefers can be collected from depots/yards to be transported to your warehouse for stuffing.
Depending on your cargo requirements, you will need to inform the depot whether you need to pre-cool or pre-set your reefer:
However, do note that it is generally not necessary to pre-cool your reefer. Especially in a tropical climate like Singapore’s, a large quantity of water droplets may form on the interior surface when the doors of a pre-cooled container are open in a warm ambient environment. Furthermore, the condensates may drip from the roof of the container and cause stains or weaken the structure of the cargo. Although these condensates will subsequently be removed through the evaporator coils of the genset, ice may be formed when the condensate passes through the evaporator coils, causing it to go into a short defrost mode. The more heat and humidity the refrigeration unit must remove, the lesser the cooling capacity available for the main objective of cooling the cargo itself.
It is thus recommended for products to be pre-cooled to the required carriage temperature before being packed into the container, unless the container is loaded in an airlocked cold tunnel in cold storage.
The stuffing and placement of cargo will directly affect the flow of air within the reefer. It is thus essential for you to stuff your cargo correctly.
In the case of chilled cargo, the cargo should be placed throughout the floor with spaces in between, to force the cool air to flow through both the cartons as well as the product, throughout the entire load.
In the case of frozen cargo, if the cargo is pre-cooled to the correct carrying temperature, it is only necessary for air to circulate around the periphery of the load. A block stow (i.e., one that has no deliberate spacing between any of the packages or pallets) is all that is required. However, it is necessary to ensure that air can circulate under, over and to each side and end of the stow.
Some general tips on stuffing a reefer:
When the ambient temperature is warmer than the cargo, operating the reefer with the rear doors open will not cool down the cargo. Rather, the introduction of hot ambient air will heat up the cargo.
When hot humid air enters the reefer, moisture condenses on the cold cooling coil and turns to ice. Cooled air escapes through the rear door, and the cycle continues. Once stuffing is complete and the doors are closed, the reefer could run for hours with a partially iced-up cooling coil. This would reduce its cooling effect and put the cargo in danger until the unit completes a defrost cycle.
As reefers are usually used to transport fresh groceries or temperature-sensitive cargo, it is essential to ensure the cleanliness of the reefer prior to its usage.
The Pre-Trip Inspection (PTI) is an extensive inspection done on empty reefer containers to ensure that the reefer machinery is running properly at the correct settings and that the container is clean and in sound condition. The PTI is usually conducted at depots, prior to the collection of the container by the customer for stuffing.
Here is a general checklist to inspecting your reefers:
Note: The guidelines below should not replace or override PTI procedures recommended by the manufacturer of the reefer container or the procedures set up by the shipping company.
Booking a reefer? Use the checklist below to see what you check the information needed for you to book one:
Note: The guidelines below should not replace or override procedures set up by the shipping company.
Get in touch via the form below and we’ll get back to you shortly!
Please wait while you are redirected to the right page...