Ocean Container Temperature and Humidity Study

By: Pakarada Premtitikul
General Manager
InterDry (Thailand) Co., Ltd.

A study on a few typical shipments and the effect on Temperature and Relative Humidity.

Let’s have a look at three commonly used shipping routes and what this does to the temperature and humidity inside the shipping container.

We’ve chosen three routes, namely Japan – Netherlands, Japan – Memphis and Japan – Portland.

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Typical Conditions

A normal shipment consists of three distinct stages. The first stage includes the time from container filling until the container is loaded onto a ship. This includes road transportation and brief periods of storage. Daily cycles of temperature and humidity are common. For example, figure 2 includes temperature swings of 40° F [22°C] during the first stage of a shipment from Japan to The Netherlands.

The second stage is the actual time at sea or aboard a ship. This may or may not be the longest stage during the container’s journey. During this stage, daily cycles of temperature and humidity are usually very minor or completely non-existent. Temperature changes are gradual, often occurring over days rather than hours. Occasionally, a single temperature/ humidity cycle occurs as the ship makes stops along the route, however extreme conditions are rare. Figure 3 includes a slow temperature rise and fall as a winter route takes the ship near the equator and then north to The Netherlands.

The final stage begins when the container is removed from the ship and continues until the recorder is removed during the freight unloading process. This may include varying periods of time spent in customs, on trains, on trucks, and in storage. Daily temperature and humidity cycles are common and may be extreme.

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Typical summer shipment – Japan to the Netherlands

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Typical winter shipment – Japan to the Netherlands


Extreme Conditions:

Some of the most interesting recordings are the extreme conditions. The highest recorded temperature occurred on July 25, 2005 during a shipment from Japan to Memphis. The temperature reached 135° F [57° C] during the third stage of this shipment (figure 7).

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Hottest shipment 135°F (57°C) – Japan to Memphis (USA).

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Coldest shipment -21°F (-29° C) – Japan to Memphis (USA).

The lowest recorded temperature occurred on January 15, 2005 also along the Japan to Memphis route (figure 8). The temperature dropped to -21° F [-29° C], which is slightly beyond the recorder’s published temperature range.

The shipment with the highest relative humidity occurred during a trip from Japan to Portland. The relative humidity was recorded at 96% on August 5, 2005 while the container was on land. Figure 6 shows the detailed temperature and humidity profile. The most extreme humidity conditions are seen during periods of large daily temperature changes. In this example, as the temperature slowly drops from 88° F [31° C] to 67° F [19° C] over 9 days, the humidity increases to 88% before returning to 79%. However, starting on August 4 as the temperature dropped from 121° F [49° C] to 68° F [20° C] over a 16 hour period, the relative humidity rose from 32% to 96%. The corrugated boxes seem to absorb moisture fast enough to temper humidity during slow changes in temperature while at sea. However, rapid temperature changes seen on land seem to exceed the rate at which the corrugated boxes can absorb moisture.

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Highest relative humidity 96% – Japan to Portland (USA).


 Ocean Container Temperature and Humidity Study

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Moisture Damage can be Prevented

Sea Containers are an economical and safe way of shipping almost any kind of cargo. But putting a cargo into a closed strong box also entails a constant risk of moisture damage for every kind of cargo on every voyage.

  • Metals corrode, discolour and loose their shine
  • Cargo and packaging get mouldy, soft, crumbled and discoloured.
  • Bad smell
  • Physical damage from water, ice, things gluing together, caking etc

Such damage may result in substantial losses and costs. Yet obviously not every shipment suffers moisture damage, and most of those that do, suffer only limited damage. In fact, lots of moisture damage remains unrecognized, because it is considered “normal”. Very few shippers have a good system of feedback from the receivers of their goods. There may be lots of things they don’t know.

The pattern of moisture damage may seem random. The moisture processes are examples of strongly non-linear physics. That means that very small differences in the cargo and voyage conditions can have a huge effect of the outcome. That is why you may have 4 perfectly safe shipments and the 5th may be a disaster. This means that there is always a risk of moisture damage in the next shipment, even if the last one was ok.

Moisture Damage can be Prevented

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Water damage in a container

All containers contain moisture from the time of loading and in the cargo. No container is airtight. Moisture will move in and out of the container during the course of the voyage – “Container Breathing”.

The objective of a moisture protection program is to prevent the build up of moisture in the air to levels where it may cause damage. This is done by reducing the amount of the moisture entering the container and by using “Absorbers” to remove moisture from the air.

We like to present the Nordic Power Desiccant moisture protection program as a kind of checklist of things that should be arranged as well as possible. And it is to be noted that many of the items on the list can be influenced only to a degree. Yet even small changes can result in big improvements. In some cases a few tens of grams of water in the wrong place is enough to cause significant damage.

Storing pallets inside or outside is often enough to make the difference between no
damage and “disaster”. Simply adjusting the temperature of the cargo at loading can prevent damage. Thus it is well worth to make what improvements are at all practical, and the balance will then have to be taken up by the packaging and the absorbers.

Is the Container Tight?

A minimum requirement is of course that the container is watertight against rain and spray. That is usually the case, but especially the bottom side and the doors are vulnerable to damage that may not be noticed.

Check the seals. Certainly no container is airtight, but a container in good condition
allows air (and moisture) to move in and out of the container only slowly, over hours
perhaps. That significantly reduces the amount of moisture moving into the container under common circumstances. (Container Breathing)

Tape the vent holes if you are shipping a dry cargo. For a moist cargo, such as
agricultural commodities, it is usually better to leave the vent holes open.

Is the Container Dry?

A container that has been washed before loading, brought in from outside into a warm loading area or stored in a humid place, may contain lots of water. In particular, attention must be paid to the container floor. The humidity of the wood should not be above 18%.

All pallets and other wooden dunnage must be dry. Preferably the moisture content
should not above 18% and certainly not above 20%. It is easy to check the humidity with a small handheld device commonly used in the construction industry and costing a couple of hundred Euros.

For more information check us out at http://www.interdrythailand.com

 Moisture Damage can be Prevented

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