How to Calculate the Ideal Desiccant Quantity for Container Moisture Management?

During the export or transportation of goods across different climatic conditions and humidity levels, the stored goods or products react differently to these changes. Thats why container desiccants are used in the shipping containers or cargo to help fight moisture damage and maintain optimal levels of moisture, humidity, oxygen, etc. inside the shipping container. This helps protect and preserve the quality, shelf life, and effectiveness of the variety of products stored in the cargo. But how does one calculate the right quantity of these useful desiccants that will be required for the storage of your goods, so they maintain their quality and effectiveness throughout the transportation and shelf life? We will help you find that in this blog post.

Understanding the role of desiccants in containers and cargo

Since shipping containers and cargo deal with different weather conditions and humidity levels throughout the journey, they have to deal with many issues such as container rain, container moisture, and the growth of mold and mildew that can greatly affect the quality of the stored goods. To safeguard your goods against damage from moisture and humidity, you should use container desiccants which are effective adsorbent materials that absorb moisture from the surrounding air, helping to keep things dry.

There are many common types of desiccants that are used for humidity and container moisture control, and include silica gel, which comes in little beads form that are packed in desiccant paks and is great at soaking up moisture. Clay desiccants are also used which are a natural material that also absorbs moisture, and molecular sieves, which are tiny crystals that effectively help trap water molecules during container rain. Each of these types of container desiccants is helpful and has different properties and benefits, so you can choose the one according to your storage and transportation needs.

Some of the factors influencing desiccant quantity

Let us now see some of the factors that can greatly influence the quantity of desiccant you may need for your container or cargo so that it efficiently controls and maintains optimal levels of moisture and humidity.

The volume of the container: To find out how much desiccant you may need for your cargo, you need to first measure the inside of your container, and you can do this by using a tape measure to get the length, width, and height. Then you should multiply these three numbers together to find the volume in cubic units, and if you want it in cubic meters, divide by 1,000,000. For cubic feet, divide by 1728.

The relative humidity levels inside the container: The amount of relative humidity shows the air's moisture level that is present in the container or cargo, and understanding the initial and desired humidity is key to maintaining the required levels to protect the goods, as more humidity requires a stronger desiccant to maintain the dry atmosphere inside the container.

The required air exchange rate: This refers to the quantity of air and how much outside air can get into your container. If your container is well-sealed, then very little moisture will enter, but if it has openings or vents, more moisture can come in, making it important to adjust the amount of desiccant you use.

Different methods for calculating your desiccant needs

There are two different ways for calculation of the quantity of desiccant you may need to protect your cargo from the ill effects of moisture and humidity. This will help you understand the required quantity and how to use it for your cargo container.

1. The first way to determine the right desiccant quantity is when you know the volume of your cargo. So, for Volume based calculations, you can use the given formula to understand the quantity of desiccant needed for your packaging and cargo setting.

Required desiccant quantity (g) = Relative humidity (%) × Volume (m³) / Desiccant adsorption rate (g/g)

Let us also understand this with an example calculation.

So if we say your container has a volume of 2 m³, the relative humidity is 70%, and the adsorption rate of your desiccant is 0.2 g/g.

Then, the calculation would be:

Required desiccant = 70 × 2 / 0.2 = 700 grams.

2. Another way to determine the desiccant quantity for your cargo is by surface area calculations. You can also calculate desiccant needs based on the surface area of your cargo, and this method works best when there isn’t much air circulation in the container.

So, you can use the below formula to calculate the required desiccant quantity for your shipping container.

Desiccant quantity (g) = Total surface area (m²) × Desiccant unit conversion factor (g/m²)

For your reference, let us see an example calculation:

If the total surface area of your cargo is 10 m² and the conversion factor is 5 g/m², then:

Desiccant quantity = 10 × 5 = 50 grams.

Considerations when using desiccant for your cargo storage

- The packaging materials you use are important for controlling the moisture levels, as the water vapor transmission rate shows how well moisture can move through packaging. Some materials with low WVTR can help keep humidity steady, which may need less desiccant, so choosing the right packaging makes sure the desiccant does its job well.

- The storage container's temperature and humidity levels can also change how much moisture is there and the desiccant quantity needed. If the container is in a humid or changing temperature area, you might need extra desiccant to keep it dry.

- It is also very important to only choose high quality desiccants for your cargo protection like silica gel or molecular sieves, which are more effective at absorbing moisture effectively and can handle specific storage conditions better than lower-quality options. Always buy container desiccants from trusted and established manufacturers and suppliers like Sorbchem India.