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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InterDry Power Desiccant – Frequently Asked Questions:

1. How does InterDry Power Desiccant help solve moisture problems?

This unique product absorbs moisture by extracting water vapor present in the air, thus preventing the humidity inside the container from reaching dew point and condensing. The desiccant then starts to turn into a gel as it continues to absorb moisture. The water absorbed is retained due to the presence of a special binding agent, thus preventing it from leaking. Lower relative humidity InterDry controls the humidity inside containers by preventing the air from reaching dew point and condensing, thus protecting your precious cargo.

2. What is Relative Humidity (RH)?

Relative humidity measures the amount of moisture in the air. It is expressed in a percentage of how much moisture the air could possibly hold. The wetter or damper the air is, the higher the relative humidity. The drier the air feels, the lower the relative humidity. Thus, 100% humidity is actually rain.

3. What are the most common problems caused by moisture?

Moisture in containers causes problems such as mold, fungus, mildew, rust decay, lumping, caking, agglomeration, and decomposition. Moisture can also cause electronics to malfunction.

4. Is moisture damage always instantly visible when handling the cargo?

Unfortunately not. Though common forms of moisture problems such as corrosion, mold, or fungus are visible on the cartons, surfaces etc there are some kinds of damage that is not visible.
Mostly these damages are internal and visible only when the customer opens the shipments. In the case of devices, they often cease to function the way they should.

5. I fumigate my containers; do I still need to put in desiccants?

Fumigation and using desiccants have two different purposes and are not alternatives to protect your goods against moisture damage. Fumigation is primarily to eliminate insects and eggs in the container and in the goods. It has no influence on the humidity inside a container. Desiccants will not influence the effects of fumigation and can easily be put in before or after fumigation.

6. If I use InterDry, will I have any more moisture problems?

InterDry Prevents Moisture damage by controlling the Relative humidity and indeed prevents those problems. However, the ventilation holes in the container need to be closed and the number of units to be put in a container needs to be adjusted to the situation.

7. I load my container under dry conditions and it is very tightly sealed. How come I still experience moisture problems?

If there are still moisture problems, we can easily say that the number of units per containers currently is not sufficient and it is advisable to increase the units per container. There are many factors for bigger amounts of moisture inside the container.

Examples of those factors are:

  • Container Floor: Recent studies carried out by R&D department, proved that the moisture content of the wooden floors is higher than they used to be. That is partly because of the quality of the wood that is being used nowadays and partly because the floors are being cleaned with water and they are not dried out enough before being used.
  • Packaging: Wooden pallets always contain more than 20 % moisture, which always causes problems whichever products are put on the pallets. The packaging, often being cartons, contains a lot of moisture in itself, which will spread into the cargo or vaporizes into the air.
  • Products: The biggest factor of moisture inside a container is the products itself. The MC varies roughly spoken between 10% and 35%. When the MC reach the 25%, the cargo is in the danger zone.
  • Journey and climate factors: When all the above mentioned factors are controlled and there is still a problem, they surely are the conditions during transport. The first point of consideration is the transport time. It depends on the destination and more importantly the climate during shipment and final destination.
  • Basically, the changes in temperature and automatically the relative humidity is the cause of condensation. If long transits cannot be avoided, again our advice is to add more units to absorb the extra water molecules.

8. I ship consumer goods in tubes/cans/jars etc that contain no moisture, yet I still have problems.

As said before the moisture comes from the container floor, pallets, open ventilations, weather change during journey. And it will condense on the tubes/cans/jars that cause corrosion and labels to fall off.

9. Each container of my cargo of peanuts/coffee/cocoa contains tons of moisture. What difference does it make if InterDry absorbs a few liters moisture during a voyage?

InterDry absorbs the exceeding water molecules in the air and reduces the Relative Humidity inside the container, so that it will not reach the dew point.

10. Does it make a lot of difference that my cocoa beans have a moisture content of 8% instead of 7%?

One percent more or less doesn’t make a difference, especially not when the MC is on the lower side.

11. My cargo of peanuts had suffered damage in the centre even though the outside of the cargo looked fine and there were no signs of condensation. Why?

Condensation on the surface of your cargos can evaporate quickly, but it takes more time for the moisture which gets
trapped deeper. Before it evaporates back to the air, mold and fungus would have already grown.

12. How does Silica gel works?

Silica gel is the most common type of desiccant in use today. It is porous sand and can absorb moisture in the air. However, silica gel absorbs moisture best in small, confined spaces and often ends up getting saturated in a very short time span, making them unsuitable for container shipments. Beware that some silica gel – the blue contains cobalt – is toxic, and cannot be disposed of any which way.

13. Do I still need to use silica gel in my boxes?

It is definitely not a bad idea to use sachets of silica where the air is tight, and moisture is trapped, like in boxes and items packed in plastics.

14. My Cargo was damaged even though I used a lot of silica gel and there was no condensation. Would it help to switch to InterDry?

Perhaps there was not enough Silica Gel put inside the container. You need about 40Kg Silica Gel for a 20″ container. I can assure you a better result with InterDry Power Desiccants. Silica works pretty well in smaller closed spaces, like shoeboxes. It absorbs very quickly and is often already saturated before the container is moved.

15. What is so great about InterDry anyway?

We have superb products that actually reduce the RH inside the container. When it absorbs moisture, the powder base will change into a gel. It is more efficient and safe in use. Even when the product gets damaged, it will not spill any water on the goods. It is easy, safe, and inexpensive solution for the problems with moisture damage.

16. How many units must be put in one container?

That depends on many things. The container size, the cargo, moisture of cargo, moisture of container’s floor, moisture of pallets, length of journey, and weather during journey and so on.
An example: a 20 feet container with KD (Kiln Dried) furniture needs 4 units, while 20″ air dried furniture needs 6 units. We generally offer expert advice regarding optimum usage of the desiccants for best results.

17. Do I need to line my container with Kraft paper?

Sweat or Kraft paper is a commonly used method of containing “rainfall” that occurs inside a container. Normally it is installed under the ceiling to absorb the moisture that may occur due to container rain. It is most useful while shipping goods that have very high moisture condensation, but it cannot replace a desiccant that soaks up the humidity before it even turns into rain.

18. My containers are stuffed till the top. Can InterDry still be useful?

It seems that there is almost no free air in the container, while there is actually a lot of free air between the products, and InterDry absorbs the moisture in that air and prevents condensation.

19. I have problems with mold growth inside my shrink-wrapped pallets. Will InterDry help?

No, unless you make holes so the water molecules won’t get trapped.

20. My shipment of steel/galvanized components, aluminum, machinery etc. arrives corroded, stained or discolored, despite heavy packaging. Will InterDry help?

Yes, as long as you put enough units per containers and do not wrap the items in plastic.

21. Can I re-use my InterDry Power Desiccants?

InterDry Power Desiccants are one-time usable, environmental neutral and disposable as normal waste.

22. My cargoes are outdoor furniture with brass parts on it. When the goods arrive at the destination, the wooden part is in perfect condition but the brass part has slight stains on it. What should I do to avoid this? Should I use more units of InterDry?

In some cases, it can happen. I can suggest adding one or two more units and wrapping it properly with only single face carton.

23. I notice that two kinds of containers available in the market right now, which are steel and aluminum types. If I shipped the same commodity inside of steel and aluminum containers should I used same numbers of InterDry or not?

There is not much difference between those containers, so you don’t have to adjust the number of units.

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About moisture and condensation in shipping containers

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Q: How do Nordic absorbers help to solve moisture problems?

Nordic absorbers contain Calcium chloride that very aggressively grab and absorb moisture from the air. They dry the air. When the air is dry, there are no moisture problems.

Q: Can Nordic absorbers solve all moisture problems?

Well, not all. Some cargoes may be so wet that any reasonable number of Nordic absorbers get overwhelmed. But Nordic absorbers can reliable protect even very difficult cargoes that may contain tons of moisture, such as coffee beans, wood products or paper.

Q: I load my container under dry conditions and it is very tightly sealed. How come I still experience moisture problems?

Your cargo or the packaging, including container floors, pallets and crates, contain moisture that is evaporated into the air during transport. Wet packaging material is the most common cause of unexpected moisture problems.

Q: I have shipped the same cargo for years with Nordic absorbers without any trouble, but now I have a lot of damage. Have you changed the poles?

Check your container and your packaging material. Did you just start to store your pallets outdoors? Does your forklift drive into the container with snow on the wheels? Did you just change supplier of crates? You can’t tell by looking whether wood are carton is dry. The moisture properties of wood and cartons have an exponential character. It makes a huge difference if your pallets moisture content should be 20% instead of 17%, say.

Q: I ship consumer goods in tubes/cans/jars etc that contain no moisture, yet I still have problems.

Consumer goods are often shipped with a lot of cardboard packaging. Even if the boxes seem dry they could literally hold tons of water.

Q: Each container of my cargo of peanuts/coffee/cocoa contains tons of moisture. What difference does it make that Nordic absorbers absorb a few litres during a voyage?

All the important things that happen have an exponential character. That means that a small change in circumstances can have a huge effect on the outcome. Nordic absorbers create circumstances that allow almost all of the moisture to remain in the cargo even while the level of humidity in the air is lowered by a crucial amount, sufficient to prevent damage. It is a question of ”leverage”.

Q: Does it make a lot of difference that my cocoa beans have a moisture content of 8% instead of 7%?

Yes, such a difference could be all the difference between no damage and disaster. The moisture behaviour of most agricultural products have a strong exponential character.

Q: My cargo of peanuts had suffered damage in the centre even though the outside of the cargo looked fine and there was were no signs of condensation?

Lots, if not most, damage to cargoes is caused by prolonged periods of elevated humidity without any condensation (Container rain, Container sweat, Super Saturation Event). It is common that cargoes loaded at cool temperature and then moved into warm condition suffer damage in the centre of the cargo as a result of a difference in temperature between the outside and the centre of the cargo. Warm air from the outside of the cargo becomes humid as it moves into the cooler centre. Nordic absorbers protect against this effect even though the absorbers are mounted on the container walls.

Q: I had damage to my cargo even though I used lots of silica gel and there was no condensation. Would it help to switch to Nordic absorbers?

Calcium chloride absorbs moisture even when the humidity is not very high. This protects the cargo against damage caused by prolonged periods of elevated humidity. Some kinds of steel start to corrode at 70% relative humidity, moulds can grow at 80% relative humidity and at near 90% relative humidity lots of things go wrong. Yet, Nordic absorbers are also at their most efficient protecting against condensation. Most other products, such as silica gels, are really effective only in very humid conditions and in protecting the cargo against condensation damage.

Q: What is so great about Nordic absorbers anyway?

Well, they will not fall off the wall, get punctured during loading and unloading, leave a wet puddle on the cargo or run out after half the voyage. They are installed in seconds without ladders and take up no cargo space. The capacity of each absorber is big, so fewer is required. The cost of an installation is very competitive, even against much inferior alternatives.

Q: How many absorbers do I need?

The number of Nordic absorbers required to protect the cargo depends on the cargo, the temperature conditions during the voyage, the length of the voyage – and just how safe you want to be. For some really dry cargoes e.g.. steel coils or household removals, 2-3 Nordic absorbers are enough. For a lot of ”normal” goods 4-6 Nordic absorbers is about right. Some cargoes with very difficult moisture properties on long voyages may require up to 16 Nordic absorbers.

Q: Do I need to line my container with kraft paper?

Lots of containers are lined with Kraft paper primarily for reasons of hygiene or to simply isolate the cargo from direct contact with the container walls. The liner will act as a kind of sponge, catching and absorbing any droplets of water and then re-evaporating the moisture into the air. If liner is used without Nordic absorbers it could contribute top a kind of pumping effect, drawing moisture out of the cargo. When used together with Nordic absorbers the liner will act as a buffer in extreme conditions, and will prevent any container rain from reaching the cargo. Much the same can be said for so called dew cloths.

Q: My container is absolutely filled with cargo. Will the Nordic absorbers still work?

Moisture diffuses very effectively, even through a seemingly compact cargo. Experience shows that Nordic absorbers will make a difference even to mould growth inside cartons in the cargo. It is, however, necessary that some free space is left in front of each Nordic absorbers. If some Nordic absorbers have collected less water than others inside a container, there may be a problem with air access to those absorbers.

Q: I have problems with mould growth inside my shrink-wrapped pallets. Will Nordic absorbers help?

Yes, so long that there is some access of air through the top and bottom of the pallets. If this is not possible, a spiked roller may be used to tear holes in the shrink wrap.

Q: My shipments of steel/galvanised components/aluminium/machinery etc arrives corroded, stained or discoloured despite heavy packaging. Will Nordic absorbers help?

You can forget about your Tectyl, coatings, oil-paper and plastic wraps that are expensive both to apply and remove. Your container can probably be equipped with a sufficient number of Nordic absorbers to protect against any damage at less cost than your present packaging.

Q: I got some brine on my hands while removing used Nordic absorbers . Is it dangerous?

No it isn’t. Calcium chloride is non-toxic and environmentally safe. It is the second biggest constituent of sea-salt and is liberally sprinkled over icy roads in cold countries. The brine is somewhat similar to very salty seawater, and may cause irritation and rashes if left to dry on the skin. We recommend that you wear gloves and goggles when handling used absorbers, but should you get splashed by brine just wash off immediately with lots of fresh water.

Q: Can I re-cycle my used absorbers?

The absorbers can not be re-used but can be disposed of environmentally friendly. It doesn’t contain any harmful chemicals.

More information on desiccant and moisture

Calcium chloride based container desiccant to prevent moisture problems

 About moisture and condensation in shipping containers

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