Comparing desiccants: Absorption rate isn’t everything

Wow, an absorption rate of 500%! I’m getting these desiccants pronto!

Hang on a sec. As we’ve gone through in this insights series, absorption rate isn’t the only thing to take into account. (This is the third and last article in the series, check the others out to get the whole picture). Sure, absorption rate is important. But so are other factors such as sweating, leakage, re-evaporation and installation accessories. Without taking these into consideration, the actual performance of the desiccants you choose may surprise you. In an unpleasant and costly way.

Let’s go through these factors, we hope it will help you avoid such unwanted surprises.

Sweating

A good desiccant shouldn’t show signs of sweating, because it can contaminate the cargo.

If droplets are found randomly over the breathing surface of the desiccant (the permeable side) it’s an indication that the desiccant materials are of low quality.

Leakage

Leakage can harm your cargo. Droplets found in the welded area on a desiccant indicates the welding equipment may be broken or unreliable. The droplets can also appear due to low quality of the materials welded together. This may lead to severe leaking, with increased moisture levels threatening to damage your shipment.

Re-evaporation

All desiccants will partly re-evaporate over the absorption cycle. It’s a result of changes in temperature and relative humidity during transportation. The fact that the absorption cycle occurs several times from loading to unloading a container is important to take into account. Low quality starch (the component binding moisture into gel in gel-based desiccants) can make the absorbing mix solid after the first absorption cycle. If that happens it will decrease the capacity of the second absorption cycle.

This parameter is especially important to keep in mind when considering climate chamber tests. During these tests, the temperature and humidity is constant. Because of this, you won’t be able to test the drop in performance of low quality calcium chloride desiccants due to re-evaporation.

Installation accessories

Different installation accessories are used by the different manufacturers. Selection of accessories vary because of the desiccant’s installation mode (horizontal or vertical) and the characteristics of the moisture absorber (especially for vertically installed desiccants).

Check that the installation devices are in good shape after the test. They shouldn’t show any signs of mechanical fatigue. The breaking of an installation device can cause the desiccant to drop into the cargo. If that desiccant stores moisture as liquid water, it could have severe consequences for your cargo.

Another thing to consider here is that climate chamber tests don’t expose the desiccants to real conditions. For example, g-forces, bumping and jerking are common for a container shipped by boat, train or truck. These forces can affect the installation devices just the same as a careless loading or unloading process.

Let’s sum it all up

This is the third and last part of our series of insights about desiccant testing. We hope we have given you a better picture of all the factors to take into account when testing and evaluating which desiccants to choose.

If you follow the steps we have gone through in this series, you will be able to reliably evaluate the actual performance of different desiccants.

Of course, performing tests in field conditions may be challenging. Luckily, we’re happy to help with our AbsorTest™ process. During the process, we conduct all steps of the test and monitor the performance with our real time monitoring device AbsorTrack™. Placing your confidence in us, you will have full insight and can participate as you see fit during loading and unloading.

After a complete test, we will summarize the results in a report for you. The desiccants you want to include in the test is entirely up to you.

Don’t hesitate to get in touch with our experts to discuss your needs.

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