Eugenio Ferri is the co-founder and director of EPG Industries. Through a global network of dedicated offices and specialised distributors, he is working with shippers to develop solutions to protect cargo against container rain damage caused by fluctuations in temperature and moisture within the box. www.epgindustries.com
[s2If is_user_logged_in()]It’s no surprise to see so many industry professionals are concerned about shipping container condensation. After all, studies show that as much as 10% of container shipments are affected by moisture damage, which means a clear economic impact in direct losses.
However, the fallout doesn’t end there. There is a ripple effect that negatively impacts insurance premiums and customer relationships, as well as the wasted time spent handling claims and paperwork. There are also the significant environmental consequences of cargo losses and waste.
Simply put, we all have a responsibility to take a step back to analyse our cargo packaging strategies to better protect goods against shipping container condensation.
Causes of container rain
Many shippers are often left scratching their heads when they open their container at unloading to find their cargo soaking wet. They packed the container dry, so where did all this moisture come from?
Well, it might not be obvious, but when you load a shipping container it is full of moisture. This can be found in the air, the cargo, packaging, pallets and wooden flooring.
When the temperature in the container starts to increase this moisture evaporates into the air, increasing the relative humidity within.
Problems arise when the temperature falls. This leads to the moisture in the air condensing on the cooler surfaces of the container ceiling and walls.
The drops of condensation that form on the container ceiling then fall onto the goods below in a phenomenon called container rain.
Because the cycle of evaporation and condensation follows the temperature changes that occur between day and night, the risk of container rain is constant and repeated.
This risk is augmented by the temperatures inside the container often being more pronounced than the ambient conditions outside the container, a result of the metal walls of the container heating up with the warm periods during the day.
Container rain can lead to cargo damage such as mould and fungus, or rust if transporting machinery or automobile parts. Damaged packaging can mean that shipments are rejected as products are unfit for retail.
Needless to say, the complex nature of international transport means that there are an array of hard-to-control risk factors that make shipping container condensation so tough to foresee and mitigate.
I won’t be able to discuss each and every variable here but getting to grips with these factors is an important first step in learning how to prevent condensation in shipping containers.
Firstly, it’s important to understand that the moisture from your cargo is a major contributor to shipping container condensation and will dictate what kind of materials you should use to protect your goods.
As we have seen, condensation in shipping containers is closely related to temperature changes. This means that you need to pay close attention to factors such as the destination, shipping route and conditions at loading.
In the below graph you can see that it is common for containers loaded with the same cargo and shipped on the same vessel to experience dramatically different stresses. There are many reasons why this can be the case, but a frequent explanation is the position of the container on the vessel. A container that is exposed to direct sunlight will experience a greater range of temperature fluctuations, which exacerbates the risk of container rain damage, compared to a container that has been buried below deck.
Choosing a cargo desiccant
Cargo desiccants are a popular way to prevent condensation in the shipping container. They work by removing humidity from the air, thereby reducing the likelihood of container rain damage.
There are a lot of important characteristics you should keep an eye out for when picking a cargo desiccant, and I won’t be able to cover them all here, but I want to take a moment to discuss absorption capacity.
This refers to the volume of humidity that a given cargo desiccant can remove from the air and is directly linked to the composition of the absorbent gel formula.
The most well-known absorbent recipe is silica gel. You’re probably familiar with this having seen little sachets of it when buying new shoes or a computer. While it is ideal in these kinds of short-term, low-intensity scenarios, silica gel absorbs only 40% of its own weight in humidity. This low capacity means that it does little to reduce the risk of condensation damage to cargo, as the complex risk factors of container shipping require a more analytical and rigorous approach. This makes sense, what works inside a shoe box is unlikely to be effective for a shipping container.
At the other end of the scale is calcium chloride. This is a high-performance gel formula that can absorb up to 300% of its own weight in humidity. This capacity not only dwarfs that of silica gel, but also other materials that are commonly used such as clay and makes it the go-to gel formula to protect container shipments.
You should be cautious of cargo desiccants that claim to be calcium chloride-based but contain relatively little calcium chloride. These are manufactured with a mix in which a greater ratio of inferior materials and absorb less, and so represent a greater risk of damage to your goods.
Here I like to make the comparison with alcoholic beverages. Both beer and whisky are alcoholic drinks, but a pint of whisky would make you feel very different to a pint of beer. The same logic applies to desiccants that only contain 10% of calcium chloride compared with those that contain 80%.
Understanding these factors is not only important in reducing cargo losses, but also in overspending on unnecessary desiccant materials. In other words, choosing low-absorption cargo desiccants means you need to use a greater volume to get the same level of protection that superior models would achieve.
While the economic impact of our desiccant choices are clear, there are also a range of ecological consequences that need to be considered. As we all know, reducing waste is one of the most important steps we can take in the fight against climate change. Therefore, we all have a responsibility to analyse our cargo packing in order to reduce cargo losses.
As we touched upon, low-absorption desiccants require a greater volume of materials. Which in turn means a greater environmental impact in regards to handling, warehousing and transportation compared to higher-capacity models.
As popular as cargo desiccants are, they are not infallible. They do not act like a magic sponge that absorbs all the humidity from the air as soon as they are placed in the container. Instead they work gradually, absorbing a little humidity each day over the course of a voyage.
This opens up the risk of condensation in the shipping container as soon as the temperature starts to fall on the first night after loading. The container desiccants have not had the chance to absorb a significant amount of humidity, and condensation will already start to form on the cool container ceiling and walls. This cycle will repeat night after night, meaning your cargo will be constantly exposed to container rain.
Another key stage when goods are at risk of condensation damage is at the end of a voyage when the container desiccants have reached full capacity. However, the condensation cycle will continue to pose a risk to your cargo. This risk is augmented by greater temperature shifts as containers are unloaded and exposed to direct sunlight.
An industry where this problem is a constant headache is coffee. The frequency of these problems stems from a myriad of complex risk factors, such as the high moisture content of the coffee bean, and temperature fluctuations that are associated with shipping from one climatic zone to another. This means that even if they packed their containers with 100kg of high-capacity desiccants, there would still be a risk of container rain.
Because of this many coffee shippers are exploring options to better protect against shipping container condensation. Those that succeed not only see an immediate economic advantage in reducing cargo losses, but also gain a competitive edge in a crowded market in which moisture damage is endemic.
The below graph is taken from a study into how better to protect coffee shipments against container rain damage. As you can see there were excessive peaks and fluctuations and highlighted extended periods of conditions in which condensation forms, even though cargo desiccants had been used.
Despite these challenging conditions there were zero signs of condensation damage to the cargo. The shipper had been saved by packing the container with the Vdry Blanket, an ultra-absorbent blanket that hangs over the cargo and absorbs any drops of condensation that fall from the container ceiling.
These results underline the risk of condensation damage to cargo even when using high-quality container desiccants. It can also be concluded, especially given that the Vdry Blanket was shown to have absorbed 9 litres of condensation when weighed at unloading, that had it not been used that there would have been expensive cargo losses.
Wrapping Up
Well, we’ve covered a lot of ground, and I hope you’re left with a clearer idea of what steps you can take to protect cargo against shipping container condensation. To recap on a couple of key points:
- Container rain damage to cargo is a common and costly occurrence, with a variety of far-reaching economic and ecological consequences.
- This is a complex problem owing to a myriad of hard-to-control risk factors.
- There are a variety of characteristics you should consider for when choosing a cargo desiccant, with those manufactured with calcium chloride having the highest absorption capacity.
- Even when using cargo desiccants there is a risk of shipping container condensation. This means you should explore other solutions to pack your container to work in harmony with cargo desiccants.[/s2If]
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