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How to Prevent Excessive Cargo Container Condensation and Product Damage With Desiccants
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Companies shipping products via overseas cargo containers, railcars, barges, and truck trailers lose millions of dollars every year to excessive condensation build-up, also known as container rain or container sweat.  Fluctuations in humidity and temperature levels inside a container cause airborne water vapor to return to liquid form, leading to mold, mildew, corrosion, and warping.  This post takes a closer look at the container rain causes as well as strategies to minimize product damage as goods travel through the supply chain.

Temperature conditions inside your container are dictated both by design considerations and the weather.  Containers with good heat transfer properties, a large surface area to volume ratio, and reflective outer surfaces are more apt to fend off some of the moisture problems associated with container sweat.  The effects of solar radiation, external air temperatures and humidity levels, and precipitation–natural elements that are key contributors to container condensation buildup—are more difficult to control.  Although changing shipping routes may reduce some of the effects of the weather, this isn’t always possible or economically feasible.  Lumber or dunnage used to brace loads, wooden pallets, and container flooring material choices may all contribute to increased moisture levels.

The moisture content of your pallets may seem inconsequential, but your pallet choice can have a significant impact on condensation levels inside cargo containers.  For starters, the pallet industry is a just-in-time market sector.  Manufacturers don’t typically sit on huge inventories of lumber or finished pallets; chances are good those new pallets arriving on your loading dock are very green and laden with moisture content ranging from 35-60%.  For those thinking of heat treatment as a means dry pallets, think again.  Heat treating does kill insect larvae in wood, ensuring pallets are free of pests, but contrary to popular opinion, this procedure doesn’t dry out wood.  Heat treating actually brings moisture to the wood’s surface which may cause mold to form.  Additional steps taken to dry green pallet wood simply add to cost, and in our industry, cost is historically the number one factor influencing buying behavior.  All of these considerations underscore why presswood is such a good fit for goods shipped by container.  In addition to being  ISPM 15 Export Ready, presswood pallets have an average moisture content of 4% at the time of manufacture.

With the contributing factors to container condensation in mind, what is the best way to shipments dry?  Desiccant use is one of the best ways to minimize the effects of container rain.  A desiccant is a hygroscopic substance that creates or maintains a state of dryness.  Common desiccants include silica, activated charcoal, calcium sulfate, and calcium chloride.   By removing moisture from ambient air, the dew point or the temperature where the humidity in the air returns to a liquid form is effectively lowered, keeping your valuable cargo safe and dry.

Desiccants and Dew Point Control

Desiccant BagsAlthough highly effective, container size, shipping route, temperature, and humidity levels must be taken into consideration, and care must be taken to use enough desiccant to keep cargo dry.  Litco offers a desiccant called Container Dri II, which comes in adhesive backed strip and bag configurations to meet your specific needs.

Container Dri II-Plus Desiccant comes complete with a hook and strap system that can be hung and suspended inside containers, river barges and rail cars.  Typical usage recommendations are 3-4 bags for a 20-foot container, and 5-6 bags for a 40-foot container.  The actual number of desiccant bags required to keep your cargo dry depends on shipping conditions, length of transit time, and the nature of the product being protected.

Desiccant StripsContainer Dri II-Strip Dessicant comes in adhesive strips for installation onto the walls of shipping containers.  Usage recommendations are 5-6 strips for a 20-foot container, and 10-12 desiccant strips for a 40-foot container.  Again, these recommendations are general guidelines.  Your actual usage requirements will depend on shipping route, transit time, anticipated changes in climate, and the types of products being shipped.

Desiccant use is a highly effective strategy to prevent the product damage associated with condensation buildup in cargo containers, but it is imperative to use enough of the material to achieve best results.   It is also important to take into consideration shipping routes, transit time, humidity and temperature levels, and the nature of your cargo.  If you have questions regarding the proper use of desiccants for a cargo container shipping application, contact the product protection experts at Litco International for additional assistance.  Whether your freight is shipping out-of-state or internationally, taking the appropriate steps to minimize product damage will reduce losses associated with rejected shipments and keep your customers happy too.

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