Before stuffing your Reefer Products
Pre-treatment of products
Above all it is necessary to keep in mind that perishable products must have correct treatment prior stuffing in order to secure cold chain is maintained to preserve quality of cargo. It means that even though relevant shipping factors such as temperature, ventilation and humidity are all optimal during the voyage, products will only arrive in perfect condition if the pre-treatment has been performed correctly.
Pre-cooling of products
Refrigerated containers have been designed to preserve temperature of the products, in that sense it is necessary the products are set with the required shipping temperature prior stuffing. The appropriate pre-cooling of products will have a positive effect on both shelf life and out turn, compared to products that have not been pre-cooled.
Air circulation inside the reefer container
Air circulation is key factor to keep set point temperature of products inside the reefer container.
Reefer containers provide air from the bottom of the unit so cold air circulates inside the container through and around the cargo space to reduce and eliminate heat then that air is conducted to the refrigeration unit which as result will chill it so start cycle again.
During stuffing your reefer products
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. Further, the GENSET should be stopped during stuffing, due to the risk of exhaust gas reaching the fresh cargo.
Optimal stuffing – Top view
Covering the floor in a proper manner will improve the flow of air and hence, refrigeration. In order to force air up and through the cargo and to avoid short-circuiting of the circulating air, the entire floor should be covered. If cargo does not cover the entire floor some type of filler should be used, such as dunnage or cardboard. Do not stuff past the end of the T-floor with cargo or filler.
Optimal stuffing - Side view
The correct stuffing and distribution of cargo inside the container will directly affect the flow of air during voyage.
In the case of chilled cargo, covering the entire floor with cargo forces the cool air to flow through both the cartons as well as the product, throughout the entire load. When frozen cargo is stuffed in this manner, the cold air flows around the cargo – blanketing the cartons and removing any heat that enters the reefer container through the walls.
Blocking and bracing
Wood can be used for blocking and bracing cargo. Floor should be covered with filler between pallets and at the end of the last pallets in order to force air up and through the cartons.
Just make sure you are not blocking off airflow past the end of the T-floor.
Avoiding cargo damage
do not leave any areas open or uncovered on the floor, the front bulkhead or the side walls (if pallets are placed at the front bulkhead, be sure to place cardboard under empty pallets)
do not run unit with rear doors open
do not stuff cargo beyond the end of the T-floor
do not plug channels at the end of the T-floor
do not stuff cargo above the red load line
do not put reefer set point at a temperature below what is required for the cargo (this will not expedite the cooling process)
stop GENSET during stuffing to avoid the risk of exhaust gas reaching fresh cargo.
Packing and stowage
Frozen cargo is usually pre-cooled to the correct transport temperature, so it is only necessary for air to circulate around the load. A block that has no spacing between any of the packages or pallets requires only air can circulate under, over and to each side and end of the stow, but not through the load as it is necessary for chilled products.
Fruit and meat for example require air circulation both around the product and through the load to remove respiratory heat, water vapor and gases such as carbon dioxide and ethylene.
Packing plays a very important role to maintain product quality since it will permit correct respiration of products and airflow circulation, avoiding damage of the products.
Packing material should be able to withstand rough handling (stuffing and un-stuffing), humidity, stacking weight and height, among others. The most used packaging are crated boxes, cartons and bags.
Cartons for fresh fruit and vegetables require symmetrical holes on top and bottom (number and size of the holes depend on the type of product to pack). These holes will permit airflow to easily circulate from bottom allowing fresh air passes through all the cargo.
Cargo must never be stowed above the red load line, otherwise air will no be able to circulate properly.
For palletized cargo, the cartons on the pallets should be placed so that air flows up into the cartons unrestricted. The corners of each carton should be supported directly by the pallet, ventilation holes must be aligned to allow the air to pass freely through the entire load, and if pallets are wrapped in plastic to provide stability, the bottom and top of the pallet/cartons must not be covered.
Proper packaging procedures will help protect frozen cargo during transport. Frozen products do not require air holes in the top and bottom of the cartons. Air flowing around the load is sufficient to remove heat that has penetrated the container.
The cartons should be stacked directly on top of each other to take advantage of their strength in the corners. If palletized, the corners of each carton should be supported directly by the pallet.
The packaging material must be able to support a stacking height of up to 2.4 meters.
The stowage of frozen products is simpler than chilled products. All that is required is solid block stowage, leaving no space between the packages/cartons and no space between the cargo and the walls of the container. However, it is very important that the cargo is stowed below the red load line, as this allows the refrigerated air to circulate evenly around the cargo, thereby keeping the frozen products at the required temperature.
Finally for frozen products transport it is necessary to keep fresh air ventilators closed and the humidity indicator should be in the OFF position.
Cold chain shall be protected during journey to avoid product damage, once temperature deviation happens unfortunately damage can not be reversed, therefore proper and continue control is critical. CSAV Group specialists will not only control temperature and ventilation. Fresh air circulating inside the unit will make possible to remove heat, carbon dioxide and other gases produces by the cargo itself. Excess or poor humidity may result in different kind of damages to the fruit: mold and fungi development and product weight loss respectively.
The temperature is maintained by a thermostat controlling the refrigeration machinery. The temperature sensor measures the air temperature and sends a signal to the controller, which adjusts the refrigeration system. Modern refrigeration systems control the temperature by generally applying three different modes: full capacity, modulation control and on-off control.
The set-point is the temperature at which the controller is set.
The main object of reefer transport is to ensure minimum loss of quality during transport, and therefore precise control at the lowest temperature the cargo can tolerate is necessary. When transporting chilled goods (–9.9°C or warmer), our modern refrigeration units are controlled by a sensor located in the delivery air stream, i.e. the air leaving the unit and about to enter the cargo space. This is called delivery air control. The units retain a sensor in the return air for control when transporting frozen goods (return air control at –10°C or colder).
It must be emphasized that the set-point temperature should not be confused with the product temperature.
The air warms up as it moves through the cargo space, and the temperature of the return air will be higher than the temperature of the delivery air.
Atmosphere control allow us to change air composition of the container atmosphere to improve the effect of refrigeration. Harvested fruits and vegetables continue to live and breathe until they are consumed or destroyed by decay or desiccation. Under normal circumstances, these factors dictate the life span of individual products. The life span can be extended by keeping the products at their optimal temperature, combined with the supply of the most effective blend of oxygen, carbon dioxide and nitrogen.
Cold treatment is the procedure to exterminate insects and larvae in reefer containers by maintaining a sufficiently low temperature for a pre-determined period of time. Time and required temperature are defined in protocols established by phythosanitary authorities of the importing countries. If the temperature rises above the established requirements, the entire Cold Treatment process will fail and must either be extended or started over again depending on the protocol.
Applying Cold Treatment eliminates the need to fumigate cargo using insecticides, such as methyl bromide, which is illegal in many countries.
This procedure is applied to various types of fruits, such as oranges, grapefruit and clementines, kiwi fruit, apples, pears, grapes, among others.
It is required the product has been properly pre-treated, pre-cooled, optimal packaging and stowage to ensure the best results of Cold Treatment to the cargo.
Some type of products require Multi-temperature set point, for those special requirements can be coupled by setting the containers to run a defined temperature program as per the needs of our customers and their individual cargo.