Causes Analysis of moisture problems in container international transportation

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Causes Analysis of moisture problems in container transportation

1. The problem of moisture in container international transportation is very common

As a safe and economical way of transporting goods, container shipping is a favorite way for many foreign trade customers, but it often encounters the problem of moisture!
As one China freight forwarder company,each year our customers export big volume goods through containers from China ports to worldwide, and the problems with goods are various and common. The most common problem is the damage caused by moisture, mainly as follows:
1) The outer packaging is deformed and collapsed.
2) The product is damp, moldy, rusted, and deteriorated in quality.

 2. Causes Analysis of moisture in container transportation

Many people wonder why the goods in a tightly sealed container will get wet. Where did the water come from?Through research, we found that the following conditions are the main cause of container cargo moisture loss.
The occurrence of moisture loss during container transportation and logistics is caused by significant changes in the ambient temperature and humidity of the container. Such as the change of day and night temperature in the long-distance transportation of goods, the difference in humidity in the logistics area, etc. The biggest cause of moisture damage during transport is due to temperature changes.
   In fact, in the ocean environment, the container is like a big steamer. When the temperature inside the container is more than 10 degrees higher than the outside temperature after sealing, the temperature and humidity difference between the day and night of the ocean changes drastically.
When the goods are transported from low temperature areas to high temperature areas(for example:shipping container from China north ports to West Africa), or when the storage environment of the goods suddenly changes from cold to hot, the moisture in the trays, wooden boxes, etc. will also be evaporated, and the moisture in the air will be condensed into water on the surface of the goods or on its packaging. And the cargo itself will also effluent.

When the container enters the low temperature area from the high temperature area(example:shipping container from China south ports to Canada ports), the internal environmental temperature drops from the high temperature to the dew point temperature, and the water vapor will condense into water droplets, which will condense on the top and inner walls of the container and eventually drip onto the cargo. This is why the goods are wet. The following pictures shows very clear :

moisture problem reason from cold to hot area


moisture problem reason from hot to cold 

3. The specific situations of moisture in container transportation:

1) Condensation
Condensation
When the water vapor content in the air does not change, the humidity of the air gradually increases as the ambient temperature decreases. When the temperature drops to a certain level, the water vapor in the air can reach saturation, that is, the air humidity is 100%. If the ambient temperature continues to drop, supersaturated water vapor in the air begins to appear. The phenomenon of condensed water precipitation is called condensation. The temperature at which “condensation” occurs is called the condensation temperature, which is simply referred to as the “dew point.”

 2) Container foggy rain
Container foggy rain
The most obvious moisture problem occurs when the temperature outside the container drops. When the temperature drops, the container wall and the top become colder than the air inside the container, and condensed water appears on the surface. In severe cases, water droplets drip or flow down the wall. This phenomenon is called container fog.

3) cargo sweat
cargo sweat
When the water-containing goods or packaging materials experience an increase in temperature, the water content will vaporize, and the generated water vapor will liquefy when it encounters a cold surface such as an outer package. This phenomenon is called cargo sweat.

During the transportation of products from high temperature areas to low temperature areas, the ambient temperature will gradually decrease. The heat loss of the whole commodity system is realized by the transfer of moisture from the products to the environment, and the goods will also be sweaty.

The movement of water vapor in the environment of the container is concentrated from the bottom to the top, encountering the low temperature of the top of the container, transferring heat to the top of the container, and the water vapor is condensed into liquid water, that is, the dew is hung on the top of the container. When the water droplets are condensed to a certain size or the vibration of the container body, the water drops are separated from the top of the container and dripped down, or a channel flow is formed along the container inside wall. If it falls on the surface of the product, it causes moisture loss. Once the water vapor condenses into liquid water and falls on the surface or inside of the product, it will bring irreversible damage to the product. Even if the product heats up again, re-vaporizing the absorbed liquid water will not return to the state before the damage.

4. Prevention measures against moisture in container

Based on our many years experience in freight forwarder industry, hereby we suggest our clients considering the following measures to avoid moisture problems

(1)An important way is to use a desiccant. The use of desiccant can effectively absorb water and greatly reduce the possibility of moisture in the cargo. 

(2)Another important way is to package the product with moisture-proof materials taking into account the moisture factor.

(3) The last important way is to buy insurance when you have containers shipping from China  to reduce your losses as much as we can when it happens.

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