The Art and Science of Packing a Shipping Container—Part 2

Robert Smith | December 1, 2014
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Shipping_Container_Fail_2Once you've gone through the hard work of getting an export shipment produced and the documentation all in order, some may treat the actual packing of the shipping container to be less critical.

In Part 1 of this series of articles, I described the important things to consider before you even begin loading a shipping container. In this article, I’ll discuss the art and science of readying your container for its voyage.

The Not-So Indestructible Shipping Container

Safety_ApprovalOnce you are ready to ship your freight, there are some important things to watch out for. Let’s start with the container, also known as a cargo transport unit (CTU). Is it seaworthy? Affixed on the back-left door of every container is a stainless steel container safety certificate. This certificate provides information such as the total mass and maximum stacking weight allowed.

It is the responsibility of the owner of the container, which is usually the shipping line, to ensure that each container is maintained and in good order. While containers are inspected at regular intervals, it is still necessary to inspect them before loading to ensure seaworthiness.


Begin by inspecting the outside of the container. This inspection should make sure:

  • There are no holes or cracks in the walls or roof.
  • The doors operate properly.
  • The closing devices operate properly.
  • There are no adhesive labels from the previous cargo, e.g. IMO placards.

Your inspection of the inside of the container should ensure:

  • The container is watertight. To do this, someone under supervision should enter the container, close both doors tightly, and look for any light coming in from any pinholes or small cracks. This is very obvious when you are standing in complete darkness.
  • The container interior is absolutely dry.
  • The container is clean, free of cargo residue, and completely free from any odor.
  • No nails or other protrusions exist that could damage the cargo.

Container_5After inspecting the container, it is critical that is it properly positioned for loading based on the loading facility’s capabilities. Biological contamination is a risk often overlooked. Containers without a trailer chassis must be placed on a paved level surface to prevent soil being lodged in the corner lashing points. When the container is not being loaded, its doors should never be left open to prevent the possibility of insects, rodents or snakes entering the CTU. Caution should always be taken when loading the CTU outside at night. Floodlights might attract moths and other insects, which could enter the container.

If you can load the container from dock height, the trailer chassis must be attached and supported. The average height of most shipping docks is lower than this height so an extended ramp is usually required to allow forklift loading. Check the container’s floor weight restrictions to ensure that it can withstand certain forklift axle weights. If double stacking is performed, the forklift must have a low mast height to function within the CTU.

Before anyone starts loading a container, some calculations are once again required. That means more science! You must calculate the gross mass of the payload to ensure it is within the container’s allowable physical limits. Overloading a container occurs a lot, and it has calamitous results. The shipper must take into consideration all highway transport weight regulations.

Once the total allowable weight is established, the shipper must determine how the packages will be loaded and distributed within the CTU. The general rule of thumb is 60% of the freight’s mass should not occupy more than 50% of the CTU space. In longitudinal direction, the center of gravity of the packed cargo should be within allowed limits. In transverse direction, the center of gravity should be close to the half width of the CTU. In vertical direction, the center of gravity should be below half the height of the cargo space of the unit.

Container_7When planning how to load a container, the shipper should aim at producing either a tight stow, where all cargo packages are placed tightly within the boundaries of the side and front walls of the CTU, or a secured stow, where packages do not fill the entire space and will, therefore, be secured within the boundaries of the CTU by blocking and/or lashing.

The shipper must also take into account the compatibility of all the cargo and the nature (i.e. the type and strength) of any packages or packaging involved. The possibility of cross-contamination by odor or dust, as well as physical or chemical compatibility, should be considered. Incompatible cargo should be segregated.

Container_8Individual packages should be capable of supporting the weight placed above them. Care should be taken so that the strength of packages is appropriate for the stack design. Shippers should also consider any potential problems that may be created for the people unpacking the CTU at its destination. For example, the shipper should avoid the possibility of cargo falling out when the CTU is opened.

As you can see from Part 1 and Part 2 of this series, there are a lot of things to consider when preparing your goods for shipment. In Part 3, I’ll review some of the additional requirements that exist for packing and shipping dangerous goods.