Desiccants should be tested in real-life conditions
In this insights article, we explain the importance of testing the performance of desiccants in real-life conditions. In our previous insight (A guide to test the performance of different desiccants) we go through more aspects to consider. It’s a recommended read if you want a clearer view over what to have in mind when you choose your moisture protection.
What’s real and what’s not
Your shipments will face radically different conditions than those in a climate chamber. For example, the relative humidity in a climate chamber is often set to a constant during the test. This will make more moisture available, leading to the desiccants reaching incredibly high absorption rates. Figures around 400 and even up to 600% are common.
Fantastic, sure. But it’s not real, because those absorption figures are not possible to reach during a real shipment. This causes a problem, which comes down to how these desiccants will actually perform in reality. And you need to know that to make sure your shipments are well protected.
Trusting climate chamber measured absorption rates can cause problems. Let’s dig deeper into why.
Climate chamber test results can mislead you
If a climate chamber result is used for desiccant dimensioning purposes, your cargo may be heavily under-protected. Let’s look at an example to make this clearer:
A company promoted that their desiccants have an absorption rate of 400% in climate chamber conditions. You’re in the market for moisture protection. To find out your moisture absorption needs, you’ve made an audit. It concludes you need 10 liters of water to be absorbed inside your container to keep the moisture at harmless levels.
According to the absorption rate reached in climate chamber conditions, you calculate that 2.5 kg of desiccants will keep your shipment safe.
But the absorption rate in real conditions differs. What you actually need is 5 kg of desiccants in order to keep the moisture at safe levels and your cargo well protected.
If you dimension the amount of desiccants needed based on the absorption rate reached in climate chamber conditions, you will be under-protecting your cargo.
A climate chamber test could be compared to measuring the fuel consumption of a car when driving downhill. The result will be appealing. But it won’t be comparable to normal driving.
Different conditions, different results
Desiccants are often marketed by stating high-performance results reached in climate chamber tests. An issue is that there is no consensus on test parameter values and manufacturers do not always state the circumstances for the test (duration, temperature and relative humidity).
Sometimes the climate tests are made by a third party. Desiccant manufacturers often refer to this as being SGS approved or tested. SGS is one of many independent test institutes. Third-party certification is great, as it makes the results reliable. But the problem with performance differences between real-life and climate chamber conditions remain.
Desiccant performance in a short-term test
When you set up a desiccant test, the duration of the test should be the same as that of your actual shipment. It’s important to measure from loading all the way until unloading. A shorter test period will not give you the true capacity for calcium chloride desiccants.
In fact, different types of desiccants perform differently over time. In 2019 we performed a short-term test of 30 days with different types of desiccants in a climate-chamber.
The following results were obtained:
- Silica gel has a very constant absorption over time.
- Calcium chloride shows an increased amount of absorption over time.
- Clay has combined performance, but closer to the silica gel results.
Absorption capacity over time
(Climate chamber test: 30°C, 90% RH, 30 days)
To sum this up, don’t rely on climate chamber tests to calculate the amount of desiccants you need to protect your shipments. Test in real-life conditions instead and avoid being under-protected, risking exposing your shipments to moisture damage.