Container Desiccant How does water vapor condense inside containers during ocean transport?

Products basically have two different ways of water vapor condensation during containerized ocean transport:

1. Cargo Sweating:

When goods are transported from cold or temperate climate regions to tropical regions, moisture and water in the air

will form condensation on the surface of the goods or their packaging.

2. Container Rain:

When containers are moved from tropical or temperate climate zones to cold regions, moisture in the air will form water droplets on the inner walls of the container, which is what we commonly refer to as container rain.

Fungi, molds, and mildew will not cause damage to goods when the relative humidity is below 55%.

The occurrence and impact of corrosion depend on various variable factors, including humidity and time. Due to these variable factors, the effects cannot be described under a fixed humidity, but overall, lower humidity is better.

The type of product is also one of the factors to consider when deciding how much moisture to remove. This also determines the amount of container desiccant needed in the container to reduce and maintain humidity, so that the goods in the container are not damaged or spoiled due to excessive humidity.

This depends on:

1.  Weather conditions during ocean transport.

2.  The length of the ocean voyage.

3.  The type of goods, commodities, and packaging materials in the container.

4.  Container condition.

5.  Sensitivity of the goods.

6.  Moisture content of floors, wood, other types of pallets, or packaging materials.

Moisture or water is brought into the container along with the goods.

The humidity/moisture typically present in goods depends on the type of product and the relative humidity of the surrounding air during loading. Obviously, the relative humidity of the air in tropical regions will be much higher than in temperate regions. Therefore, when goods are loaded into a container, moisture or water vapor is also brought in. For example, if a container is loaded with 5 tons of furniture, the furniture itself will contain approximately 8% to 25% humidity, varying depending on the type of wood and the degree of furniture drying treatment. This equates to about 400-1250 liters of water. Some of this moisture will evaporate into the air inside the container, becoming an important source of container water vapor condensation.

Humidity or water vapor in the container air.

A 20-foot container has a volume of approximately 33 cubic meters. One cubic meter of subtropical air at 90% relative humidity contains 33 grams of water at 32°C, totaling 1.3 liters of water. (At the same temperature, one cubic meter of air at 55% relative humidity contains 28 grams of water. Conversely, one cubic meter of European air at 100% relative humidity and 0°C contains only 5 grams of water, or a total of merely 0.2 liters of water. At 55% relative humidity, each cubic meter contains 3 grams of water.) Once the air temperature outside the container drops, 1.2 liters of water will condense on the inner walls of the container or the surface of other items inside the container. At 25°C and 90% relative humidity, the moisture content in the air is relatively high. At approximately 22°C and 50-60% relative humidity, the moisture content in the air is relatively low.