Calculate desiccant requirements
Which factors must be considered?
In order to calculate the correct amount of desiccants required, many different factors play a role. The following list is intended to provide you with an initial overview of the information that is fundamentally necessary for this. A reliable desiccant calculation for your specific application, which is both safely effective and economical, can only be carried out as part of an individual consultation.
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1. Barrier layer
Desiccants protect your goods by reducing humidity. The dried air must not become more humid through the continuous supply of new air. A barrier layer is therefore necessary to limit the exchange of air. Wood and cardboard boxes do not limit air exchange sufficiently and are therefore unpredictable and unsuitable as a barrier layer. Barrier layers made of film around the packaged goods are common. When using overseas containers, the container itself can represent the barrier layer.
- Container: In the case of a container, it is assumed that it cannot be completely airtight. A small amount of air exchange occurs through cracks, holes, and the opening of doors. However, large ventilation openings must be sealed with adhesive tape.
- PE film: A PE film should have a thickness of 0.2 mm (200 my). The thicker the film, the less water vapor diffuses through it.
- Aluminum composite film: Compared to PE film, aluminum composite film has a significantly denser barrier layer and is particularly suitable for long storage periods.
- Size of the packing space: The packing space is the volume of the space enclosed by the barrier layer. While for containers it is necessary to specify whether, for example, a 20 or 40-foot standard container or a 45-foot high cube is being used, when using PE or aluminum composite film, the size of the packing space (length x width x height) must be specified.
2. Climate during packaging
It makes a big difference whether the goods are packed and loaded or stored at around 18°C and 70% relative humidity or at 25°C and 90% relative humidity. We recommend basing the calculation of the required desiccant quantity on the most humid climate possible in order to protect your goods optimally in any case.
3. Moisture content of the goods to be protected
The goods to be protected can also contain moisture that is released into the air. In the event of temperature fluctuations, moisture can condense on the surface of the goods and cause damage. It is therefore necessary to check whether the goods release moisture.
- Weight of the goods
- Do the goods contain no water? This is the case with metal, for example.
- Are the goods air-dry? This assumes a water content of max. 18%. Of this 18%, a maximum of 8% can evaporate, leaving 10% residual moisture in the material. Dry-stored wood and cardboard, for example, reach these values.
- Own moisture measurement: Moisture meters can be used for an accurate check. It is also possible to weigh a sample piece, dry it in an oven at 60°C, and weigh it again. The weight difference corresponds to the moisture content that can evaporate. The calculation is based on the following formula:
4. Packaging (auxiliary) materials
Packaging (auxiliary) materials are intended to secure and protect the goods. However, they can contain too much moisture. In this case, the moisture damages the goods to be protected during temperature fluctuations. It is therefore important to use only the driest possible packaging (auxiliary) materials. What and how much of these are included in the barrier layer envelope besides the goods?
- Type of packaging (auxiliary) materials, e.g., pallets, cardboard, cushioning and securing material
- Quantity / weight of the packaging aids
- Moisture content (air-dry? own moisture measurement using the formula above?)
5. Transport climate / storage climate and duration
This information is approximately necessary to calculate the air exchange through the barrier layer over time.
- From which country to which other country are the goods being transported? Or – in the case of pure storage – in which country are they being stored?
- Transport: Duration (loading to unloading time) including storage time at the starting location before shipping and at the destination after shipping
- Storage: How long are the goods to be stored?
- Desired final humidity: The calculation according to DIN is usually carried out with a desired final humidity of 40%. It is, of course, possible to carry out the calculation for a different target value as well.
Important note
If the moisture content of the goods and/or packaging (auxiliary) materials is too high, the required amount of desiccants increases indefinitely. In this case, supplementary measures are necessary to ensure economical desiccant use. Our team of consultants can also support you with process optimization. Get in contact with us – together we will keep your goods dry!