A very specialised trade, one which overlaps with the energy market. Cargo is very volatile, expensive, and expensive to carry. The environmental image of these carriers and cargo is extremely negative but the truth of the matter is more pollutants are poured down household sinks compared with accidents relating to this type of cargo.
Each commodity has its own particular requirements, but in respect to all reefer shipments a common failure is hot stuffing. This is the process of not sufficiently cooling down the unit to within a few degrees of the actual carrying requirements and assuming the unit will act the same when fully ladened. A reefer maintains an environment and does not act as a refrigerator like in the home. Ensure the reefer is collected well in advance before stuffing to ensure it has been cooled properly, and never allow cargo to be loaded until ready.
Double check temperature and ventilation
This may sound obvious but probably a quarter of all claims arise from this. Commonly people still mix Celsius and Fahrenheit or block ventilation holes. Prior to loading its always best to receive a once over by experienced personnel.
Loading boxes on pallets
Cardboard boxes should never sit directly on a naked metal floor and there should be a separation to avoid moisture migration. Condensation will damage the cardboard and in turn collapse the stow.
Do not run the unit with the doors open
Not only this is a waste of energy, but you will find cooling the unit to the required temperature quite difficult. This is one of the reasons that leads to hot stuffing.
Do not stuff the cargo beyond the T-Floor or red load line
Shippers naturally wish to maximise loads, but a common mistake is to over stuff. Reefer units usually come with markings, but it is surprising the number of times this is ignored.
Turn off unit during stuffing/unloading
One reason is to avoid exhaust gasses interacting with the cargo but also in very hot climates this can cause excessive condensation to form.
Load mobile temperature recorder
Whilst these days all reefers have their own internal data recorders, but if you suspect there has been any deviation, obtaining this from the carrier may not be so easy. For a small price you are not relying on the information they provide, and this can be essential to support any claim later.
Carrying fresh cargo is normally much more complex because typically the cargo still contains life signs. Fresh fruit and vegetables emit respiration, transpiration and ethylene.
Respiration: The conversion of start into energy which results in the absorption of oxygen and release carbon dioxide. This leads to water vapour and heating. Respiration increases with temperature and vice versa so whilst they are shipped in a controlled environment but the offset between time, sweetening and quality plays an important part.
Transpiration: The loss of water through evaporation. Once fruit and vegetables are picked they no longer have a water supply and inevitably will lose water. To reduce the loss requires low humidity, low temperature, and plenty of air flow. You may also notice some fruit and vegetables arrive in the supermarket with special covers/bags and this is to prevent transpiration in transit.
Ethylene: All plants will emit ethylene and will speed up the ripening process. It is not always necessary to reduce because it can improve the quality, but uniformed control is what is needed. Bananas, avocados and other fruits produce high levels and should be kept away from sensitive cargo such as green vegetables and flowers. To control production careful attention is needed on the temperature, oxygen and carbon dioxide levels, and also removal of exhaust gases from motors or forklifts during loading.
Carrying frozen cargo is much easier because there are less requirements on maintaining a certain atmosphere. Of course ventilation is still required, but rather than worrying about ventilation for each pallet or spacing, the main concern is avoid short circuit. This requires the air does maintains a rotation within the unit to avoid hot pockets or disturbance. Cargo should normally be pre-frozen before loading and the fresh air vent is closed. Frozen cargo can last several days even during a breakdown or power failure.
Cargo insurance for reefer cargo carries different requirements so the coverage generally varies. Often for breakdown of the unit, for any loss of damage to be covered it must be longer than 24 hours. This is in consideration with the time it takes to damage cargo, but in case where the shipment is very sensitive and/or for human consumption a shorter period is something you may wish to discuss with your insurance provider.