Millions of tonnes of goods are stored and transported in shipping containers. Out of these, massive amounts end up damaged or spoilt as a result of moisture build-up and condensation in shipping containers that causes “rain” or “sweating”.
Condensation in a shipping container occurs when its walls are cooled to temperatures below the dew point of the air inside the container. Since a shipping container is a metal box, it keeps changing internal temperatures relative to the weather outside and time of day. It is these changes in container temperature that cause moisture inside the container or its contents to collect and condense on the cool walls and roof causing damage to the goods stored inside as well as the container’s interior.
Moisture can come from a number of sources inside the shipping container such as cardboard, paper, mattresses, books and wood.
Moisture could come from the cargo’s packaging materials or the cargo itself.
How do you prevent shipping container condensation?
Before you put the goods inside the shipping container, you should ensure that the container is dry. Inspect the container’s interior and wipe dry all the excess moisture on the floor and walls. To reduce condensation further, you should use:
1. The right pallets. The moisture content of pallets may seem inconsequential, but in reality, could contribute significantly to condensation levels. Since the pallet industry uses a just-in-time supply approach, pallets are usually constructed moments before delivery to avoid keeping inventory. The lumber used is usually fresh and laden with moisture content that could be anywhere between 35-60%. Heat treatment only adds to the problem as it brings moisture closer to the surface.
To avoid moisture from pallets, plastic pallets that cannot hold moisture should be used for goods shipped by container. If wood pallets are to be used, make sure that their moisture content is low by allowing them to dry first.
2. Desiccants to absorb moisture inside the container. Desiccants maintain a state of dryness in enclosed spaces by absorbing moisture from the air. Common desiccants include calcium sulphate, silica, calcium chloride and charcoal. When excess moisture is absorbed from the air, the dew point – the temperature at which moisture turns into liquid – is reduced. This, in turn, reduces condensation.
Desiccants come in different forms. They could be in the form of poles installed on walls, bags placed on the floor or special paint applied to the interior roof and walls.
3. Air Conditioning and dehumidifiers. This option is ideal for containers being used for long-term storage which have access to power. These devices work continuously to ensure that the moisture content inside the container remains at pre-set levels.
4. Insulation. This helps keep the internal temperatures of the shipping container relatively stable and warmer than the dew point and thus reducing condensation. It also creates a barrier between the container walls and the air inside whose temperature drop faster causing moisture to condense on them.
5. Vents. Ventilation prevents condensation by equalising the exterior and interior air temperature. Warm, moist air goes out and is replaced by air with the same ambient temperature as outside. This solution might however not the best for moist or humid climates as it will bring in the moist air causing an increase in moisture content.
At Tiger Containers, we’ll help you make modifications to your shipping container to ensure that your goods remain safe from moisture during the storage or transit period. Contact Us today to find out more.