A guide to test the performance of different desiccants
Are you getting the moisture protection you pay for? Today, it’s difficult to answer that question. The reason is the current lack of a common standard to test the performance of different desiccants. This is problematic, because it makes it impossible to accurately compare the various desiccants available on the market.
With this guide, you will get a clear view of why this is an issue, and what you can do in order to make sure you get what you pay for.
The more moisture, the better result
An example of the importance of similar conditions during testing is the amount of moisture available in the test. If there is a lot of moisture available inside a container or a climate chamber during testing, the result will be higher absorption than if there was less moisture available.
This is true regardless of the type of desiccant tested – be it calcium chloride, silica gel, clay or desiccants from different brands. Some manufacturers claim their product’s absorption rate is 500% and beyond. That’s fantastic, but is it comparable to real conditions?
Make an informed choice
This mix-up in numbers can lead to decisions based on incomplete test data. The consequences may be severe if the desiccants you choose don’t perform accordingly when it matters. If you are in the process of choosing a new desiccant supplier, we hope this article will help you choose the optimal solution for your needs.
The multi-million dollar question
The cost of moisture damage can be substantial. Therefore it’s vital your goods are well protected and that you actually get what you pay for. The question we aim to answer below is:
How to test different desiccants to collect objective and fact-based data?
To answer it, we will take you through the following topics:
- Test the desiccants in the same environment
- Buy samples in the open market
- Considerations about loading conditions
- Compare desiccants with the same mode of installations
Test the different desiccants in the same environment
Tests should preferably be made under field conditions to truly reflect reality. Whether you test in real-life or in a climate chamber, make sure test samples are tested in the same environment, either in the same container or in the same chamber.
But what are the differences between climate chamber test and a real-life test?
Climate chamber test
A climate chamber test is an artificial way of testing the desiccant absorption performance. The advantage is that this test easily can be made in a short amount of time to a relatively low cost. However, the results generated leaves an array of important parameters out.
A climate chamber test often has a duration of 30 days. Both temperature and humidity are set to constants, often 30°C and 90% RH (relative humidity). As a result, moisture inside the climate chamber is always present – it is added automatically and set to be constant – and the desiccants will have unlimited amounts of moisture to absorb.
Consequently, the absorption levels reached in climate chambers can be very high (500-600%).
A real-life test is a test performed inside a container being shipped from origin to destination. In a real life test, the amount of moisture will be reduced over time as the desiccants will absorb moisture inside a container or polybag. That is what they are designed to do.
Moreover, the temperature will vary when passing through different climate zones and changes during night and day. The relative humidity will also vary, in comparison to the constant relative humidity in climate chamber tests.
In a real-life test the availability of moisture will be much less compared to a climate chamber test. Consequently, the absorption capacity in a real-life test will look inferior to absorption capacities in a climate chamber. But the reality is:
- Climate chamber and real-life absorption are two completely different things. Desiccant performance during climate chamber conditions can be boosted artificially to reach high and appealing absorption rates. How? Increasing the test duration, the temperature, or the relative humidity.
- Climate chamber absorption levels will never occur in real conditions.
- 400% absorption in a climate chamber could be equivalent to 200% or even less in real life, due to lack of moisture to absorb.
- The absorption in a real-life test could be very low. Simply because there is very little moisture to absorb.
This is similar to the measuring of the fuel consumption of a car. If measured during downhill cruising, the results will be fantastic. However, we are all aware the consumption will be much higher when driving normally.
To underline the headline of this Insight – make a comparison based on the same test method. And never mix the two.
Buy several samples in the open market
This can sound a bit tricky, but in our experience performing tests and comparing our desiccants to the competition, we have found that some samples have been altered to perform better in tests.
To avoid this, the test samples should be acquired from the open market. By doing so, you make sure that the samples in the test are the same quality as those that will be delivered in future serial deliveries.
The test should also be made of several desiccants (not only one) from each of the respective brands tested, to improve the reliability of the test results.
Why? Often the absorbing agents in desiccants, like calcium chloride and starch, are bulk mixed before they’re fed into the desiccant. This mix is not coherent, meaning different ratios of calcium chloride and starch can be filled in the desiccants, although they are all produced in the same batch*.
High calcium chloride amounts will improve absorption capacity, but the desiccant will also become more liquidized with an enhanced risk for leaking and sweating. By running several samples in the test, a bad or good quality mix will not determine the results, instead an average result.
* AbsorGel® Type-X is produced in a controlled dual mixing process, which safeguards that the calcium chloride and starch mix are exactly the same. Desiccant after desiccant.
The importance of like-for-like loading conditions
To be able to compare on a like-for-like basis, all desiccant samples for a test should be placed in the same climate chamber or container when tested. Even a climate chamber may behave differently from one test to another. This condition variation will not exist if they are all in the same test cubicle, either a shipping container or a climate chamber.
Like-for-like conditions in real-life tests
If real life testing, make sure to place all desiccants (one from each manufacturer) in the same container. For real life testing we recommend including several containers in the test. If different desiccants are placed in different containers, some parameters could disrupt the results of the tests:
- The amount of moisture at loading: one container may contain very wet pallets and/or a wet container floor, whereas another could be drier. Variations in moisture quantity at loading can heavily impact the amount of moisture to absorb and the absorption capacity as well.
- The condition of the container: a broken container with holes or with bad quality seals breathe more air and bring more moisture inside the container during the test. This is reason enough to test all desiccant samples in the same container. If you are performing a real-life test, make sure all the containers have their ventilation holes either sealed or open.
- The container placing on the vessel: a container placed below deck inside the ’stack’, compared to one placed above deck (and exposed to harsh environments), means a big difference in terms of how much moisture enters the container during the test.
Compare desiccants with the same mode of installation
The same types of desiccants should be tested together. What do we mean?
Never mix desiccants for horizontal installation (often called blankets or sheets) with desiccants for vertical installation (often called hanging).
Even if you test two identical desiccants from the same manufacturer with the same blend of desiccant absorber, the horizontally installed desiccant will outperform the vertical.
In a vertical desiccant, the absorbing agent moves to the bottom of the desiccant. In the horizontally installed desiccant, the absorbing agent will spread out. This is a phenomenon similar to how a sugar cube in brine will resolve slower than sugar in powdered form.