If the temperature falls below the lower temperature limit, the same product groups are susceptible to expansion due to freezing, so meaning that containers should also be stowed below deck in the winter months.
If ventilated containers are used, e.g. in the winter months to transport green coffee beans (from hot to cold regions), ventilation in the hold should be reduced so as not to supply too much cold air, which may lead to sweat formation as a result of the temperature falling below the dew point.
In the case of crystalline goods etc., e.g sugar, temperature fluctuations during the voyage result in caking (see Section 17.7). Transport in double-layered bags (exterior jute, interior plastic) has therefore proved effective.
To deal with temperature fluctuations e.g. on voyages in the winter months from cold to hot regions, it is recommended to pack particularly cost-intensive goods, e.g. high-quality machines, precision instruments etc., in refrigerated containers which operate independently. The thermally insulated walls of the refrigerated container put an end to the considerable temperature fluctuations, which could result in the temperature falling below the dew point, and sweat formation and corrosion may be prevented.
In the cold season especially, quick unpacking (stripping) of containers at the port of destination is essential, e.g. in the case of green coffee beans and raw cocoa. Coming from the relatively protected environment of the ship's hold, coffee cargos can be expected to retain a core temperature of 18 - 20°C.
If they are then exposed to the substantially lower external temperature, the humidity in the containers rises rapidly. Condensation on the container ceiling and the walls leads to inevitable wetting damage to the cargo.
In summary, it may be stated that the temperature sensitivity of cargoes differs widely. If there is a risk of expansion due to freezing or of chilling for example, temperature-controlled transport must be used. If the consequences of the temperature falling below or exceeding the limits are only slight, an assessment of whether the risk is worth taking may be carried out in each individual case. Help in reaching this decision may be found on the Cargo information pages.