The Mystery of Moisture Problems in Shipping Containers

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Unraveling the Mystery of Moisture Problems in Shipping Containers

Shipping containers are designed to be robust, weather-resistant, and secure. They are built to withstand harsh conditions and protect the goods inside from damage. However, despite these design features, moisture problems can still occur inside shipping containers. This can lead to a range of issues, from mildew and mold growth to corrosion and structural damage.

The question is, why does this happen even when the container is loaded under dry conditions and is tightly sealed? The answer lies in understanding the various factors that contribute to moisture accumulation inside a shipping container.

The Factors Contributing to Moisture Problems

Container Floor

The container floor plays a crucial role in maintaining the integrity of goods during transit. Recent research conducted by our research and development department has revealed that the moisture content of wooden floors in shipping containers is higher than it used to be. This can be attributed to two main factors: the quality of the wood and the cleaning process.

The quality of wood used in the construction of container floors has seen a decline in recent years. The wood used today is often of a lower quality, which can absorb and retain more moisture. This can lead to an increase in the overall humidity levels within the container, which can have detrimental effects on the goods stored within. It’s important to note that not all woods are created equal when it comes to moisture retention. Some woods are more hygroscopic than others, meaning they can absorb and hold moisture from the surrounding environment more readily. This characteristic can significantly contribute to the overall moisture content within the container.

The second factor contributing to the increased moisture content in container floors is the cleaning process. In many cases, the floors of these containers are cleaned with water and are not given enough time to dry out properly before they are used. This residual moisture can evaporate into the container’s atmosphere, increasing the humidity levels and potentially leading to condensation, which can damage the goods inside.

To mitigate these issues, it’s crucial to ensure that the wood used for container floors is of high quality and has a low hygroscopicity. Additionally, proper cleaning procedures should be followed, ensuring that the floors are thoroughly dried before the container is used for shipping. By taking these steps, shippers can help to maintain optimal conditions within their containers, protecting their goods from moisture-related damage.

Packaging

Packaging plays a pivotal role in the safe and efficient transportation of goods. However, it can also be a significant source of moisture, which can lead to a host of problems during transit. Wooden pallets and cartons, two of the most commonly used packaging materials, are particularly prone to this issue.

Wooden pallets, a staple in the shipping industry, are known to contain more than 20% moisture. This high moisture content is inherent to the wood itself, which naturally absorbs water from its surroundings. Regardless of the type of product placed on these pallets, the moisture within the wood can cause problems. It can lead to the formation of mold, mildew, and other fungi, which can damage the goods. Moreover, in certain conditions, the moisture can evaporate, increasing the humidity levels within the shipping container and potentially leading to condensation.

Similarly, cartons, often used for packaging individual items or smaller batches of goods, can also contain a significant amount of moisture. This moisture can either spread into the cargo, potentially damaging it, or vaporize into the air, contributing to the overall humidity within the container.

To mitigate these issues, it’s crucial to consider the moisture content of packaging materials when planning for shipping. Using pallets and cartons with lower moisture content can help reduce the risk of moisture-related damage. Additionally, using desiccants or other moisture-absorbing materials can help maintain optimal humidity levels within the container. It’s also worth considering alternative packaging materials, such as plastic pallets or moisture-resistant cartons, which can offer better protection against moisture.

Products

The products being shipped in a container are often the most significant contributors to the moisture levels within that container. The moisture content (MC) of these products can vary widely, typically ranging from 10% to 35%. This moisture can originate from the product’s natural composition, its manufacturing process, or the conditions under which it was stored prior to shipping.

When the MC of a product reaches or exceeds 25%, it enters what is often referred to as the ‘danger zone’. In this state, the product is at a heightened risk of damage due to the high moisture levels. This can manifest in several ways, depending on the nature of the product. For instance, food items may spoil or develop mold, while metal goods may corrode. Even non-perishable items, such as electronics or furniture, can suffer damage, such as short-circuiting or warping.

Moreover, when the MC is high, the product can release moisture into the air within the container. This can lead to an increase in the overall humidity levels, potentially causing condensation and subsequent ‘container rain‘, a phenomenon where condensation drips from the ceiling of the container onto the products below, causing further damage.

To mitigate these risks, it’s crucial to accurately measure the MC of products before shipping and take appropriate steps to manage it. This could involve using moisture-absorbing materials, such as desiccants, to help maintain optimal humidity levels within the container. In some cases, it might also be necessary to adjust the storage or manufacturing processes to reduce the MC of the products.

Journey and Climate Factors

Journey and climate factors play a significant role in the moisture levels within a shipping container. Even when all other factors, such as the moisture content of the products, packaging, and container floor, are adequately controlled, the conditions during transport can still lead to moisture-related issues.

The duration of the transport is a crucial factor to consider. The longer the journey, the more time the goods spend in potentially varying and extreme climatic conditions. These conditions can significantly affect the internal environment of the container. For instance, a container traveling from a cold region to a hot one can experience drastic changes in temperature, leading to increased relative humidity and potential condensation within the container.

The climate during the shipment and at the final destination also plays a significant role. If a container is shipped through humid regions or is destined for a humid location, the risk of moisture-related issues increases. Similarly, containers shipped through or to regions with large temperature fluctuations are more likely to experience condensation.

Changes in temperature and humidity are the primary causes of condensation within a container. As the temperature fluctuates, the relative humidity inside the container changes, leading to condensation when the air’s moisture-holding capacity is exceeded.

In situations where long transit times are unavoidable, it’s advisable to add more desiccant units to the container. These units can absorb the extra water molecules in the air, helping to maintain a safe humidity level and prevent condensation. This proactive measure can significantly reduce the risk of moisture damage to the goods during their journey.

The Science to Mitigate Moisture Problems in Shipping Containers

Understanding and mitigating moisture problems in shipping containers is a science in itself. The key lies in the use of desiccants, substances that naturally attract and retain water molecules from their immediate environment. By creating a lower vapor pressure within the container, desiccants draw moisture from the air, absorbing it and holding it within their structure. This process effectively reduces the humidity inside the container, preventing the formation of condensation and the potential damage it can cause.

There’s a variety of desiccants used in shipping containers, each with its unique properties and benefits, making them suitable for different applications. These include silica gel, calcium chloride, activated carbon, clay desiccants, molecular sieves, and activated alumina.

Silica gel, a desiccant made from silicon dioxide, is a popular choice due to its high porosity. This characteristic allows it to absorb moisture effectively. One of the standout benefits of silica gel is its ability to maintain its physical shape even when fully saturated with water. This property makes it an excellent choice for protecting delicate items, ensuring no physical damage occurs due to moisture absorption.

Calcium chloride is another powerful desiccant, known for its hygroscopic properties, meaning it readily absorbs moisture from the air. Its ability to absorb up to several times its weight in water makes it one of the most potent desiccants available. Calcium chloride can effectively lower the relative humidity inside a shipping container, preventing the formation of condensation and subsequent moisture damage to the cargo.

In the science of mitigating moisture problems in shipping containers, understanding the properties and benefits of different desiccants is crucial. The right choice of desiccant can make the difference between a successful shipment and one that results in damaged goods.

Choosing the Right Desiccant for Your Cargo

Choosing the right desiccant for your cargo is a crucial decision that can significantly impact the safety and integrity of your goods during transit. This choice is not one-size-fits-all; it requires careful consideration of several factors to ensure optimal protection against moisture damage.

Firstly, the type of cargo you’re shipping plays a significant role in determining the appropriate desiccant. Different goods have varying levels of sensitivity to moisture. For instance, electronics require a high level of protection against humidity, while some types of textiles might be less susceptible. Understanding the specific moisture sensitivity of your cargo is the first step in selecting the right desiccant.

The shipping route and conditions are another critical factor. If your cargo is traveling through regions with high humidity or extreme temperature fluctuations, you’ll need a desiccant with a high absorption capacity. Similarly, the duration of the journey will influence the amount and type of desiccant required. Longer transit times typically necessitate more robust moisture protection.

The required absorption capacity of the desiccant is also a key consideration. This capacity should align with the moisture sensitivity of the cargo, the anticipated environmental conditions during transit, and the journey’s duration.

Lastly, in today’s environmentally conscious world, the ecological impact of the desiccant is an important consideration. Many companies are now prioritizing eco-friendly options that minimize environmental harm while still providing effective moisture control.

In conclusion, choosing the right desiccant for your cargo is a multifaceted decision that requires a thorough understanding of your cargo’s needs, the shipping conditions, and the various desiccant options available. By considering all these factors, you can ensure that your goods arrive at their destination in the best possible condition.

Frequently Asked Questions

Read more

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The Ultimate 2023 Resource for Shipping Container Desiccants: A Comprehensive Collection of Guides and Tips

Tackling Moisture Damage: The Hidden Threat in Shipping

External links

Container Handbook

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