MOISTURE DAMAGE – A CHECKLIST
Sea Containers is an economical and safe way of shipping almost any kind of cargo. But putting cargo into a closed steel box also entails a constant risk of moisture damage for every kind of cargo on every voyage.
- Metals corrode, discolor and loose their shine
- Cargo and packaging get moldy, soft, crumbled and discolored.
- Bad odour
- Physical damage from water, ice, items 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”.
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
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 Absorbopak 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 curse 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 15%.
All pallets and other wooden dunnage must be dry. Preferably the moisture content
should not above 12% and certainly not above 15%. 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.