There are basically two different ways of condensing water during the marine transportation of products:
1. Cargo water:
Moisture and moisture in the air when goods are shipped from cold or mild climates to tropical areas
Condensation will form on the surface of the cargo or on its packaging.
2. Container rain:
When a container is transferred from a tropical temperate climate to a cold region, moisture in the air will form water droplets on the inner wall of the container. This is what we often call container rain.
Fungi, mold, and mildew will not cause damage to the goods when the relative humidity is below 55%.The occurrence and impact of corrosion depends on a number of variables, including humidity and time. Due to the variable factors, the effects can not be described at a fixed humidity, but in short, the lower the humidity, the better.
One factor to consider when deciding how much water to remove. This also determines the amount of container desiccant that needs to be placed in the container to reduce and maintain humidity, so that the cargo in the container will not be damaged or deteriorated due to excessive humidity.
it depends on:
Weather conditions on the sea.
The period of the sea voyage.
The type of goods and commodities in the container and the packaging materials.
Container condition.
Cargo sensitivity.
Moisture content of floors, wood, other types of pallets or packaging materials.
This chart clearly illustrates the problem of humidity. If the box is filled with air with a relative humidity of 90% and a temperature of 30 ° C, each cubic meter of air will contain 27 grams of water. If the temperature is as low as 0 ° C, this one cubic meter of air contains only about 5 grams of water. The difference of 22 grams of water will condense from the air and may damage the cargo.
A 20-foot container has a volume of about 33 cubic meters. In a subtropical air with a cubic meter of relative humidity of 90%, it contains 33 grams of water at 32 ° C, which is a total of 1.3 liters of water. (At the same temperature, one cubic meter of air with a relative humidity of 55% contains 28 grams of water. In contrast, a 100 cubic meter of relative humidity at a temperature of 0 ° C in Europe contains only 5 grams of water, or a total of 0.2 liters of water. 3 grams of water per cubic meter at 55% relative humidity.) Once the temperature of the air outside the container decreases, 1.2 liters of water will condense on the inner wall of the container or the surface of other items in the container. At 25 ° C and relative humidity of 90%, the moisture content in the air is relatively high. At about 22 ° C and a relative humidity of 50-60%, the moisture content in the air is relatively low.
