ISO sizing, or to give it its longer sexier name, International Standards Organisation sizing is a globally recognised set of specifications that determine the exact dimensions of products around the world, from cars to clothes to containers. Without it, people would look on as shipping units from different companies failed to stack on top of one another, gracefully sliding into the arms of the sea below.
Having a standard set of sizes that manufactures adhere to helps maintain compatibility in all areas of freight transport. Having an ISO container means that you can be confident that it’ll fit on the back of a truck, train or stack on the deck of a ship, without issue. ISO specifications also determine the strength and durability of units, important when transporting units across extreme environments and loading them with heavy duty cranes. The upshot of all of this is that a level of safety and quality is guaranteed no matter which container you use.
There are actually multiple kinds of ISO container, all designed for different purposes but maintaining the same frame dimensions. This means that any truck can carry any kind of container, saving cost and time for every party involved. The most common types of ISO container are outlined below.
Dry freight containers – The kind of container most people think of when they think of shipping. Totally enclosed, loaded from the front and great for general transport and storage.
Flat racks and platforms – These are most often used for moving heavy machinery, lacking walls and a roof in order to accommodate awkward shapes and sizes. They will often have bulkheads on either end and multiple points for lashing.
Refrigeration containers – Like insulated containers these are great for transporting chilled goods. However, these containers also include a refrigeration unit making them suitable for longer journeys or more precise temperature control.
Open top containers – Similar in appearance to dry freight containers, these containers don’t have a roof, meaning they can be loaded from the top. This makes them ideal for carrying unusually tall items or goods like coal which are otherwise difficult to load.
Tank containers – These containers consist of an ISO sized frame with a large cylindrical tank fixed between. These are perfect for large quantities of a liquid or bulk materials such as grain.
It should be noted that ISO specifications do not mean that all containers are the same size, in fact many lengths of container are widely available. It’s analogous to picking up sheets of paper from your local stationary shop – A3 is bigger than A4, but you can be sure that everything advertised as A3 will share exactly the same dimensions. That said, there are some container sizes which prove to be exceptions:
Normally there is little variation in width, as this is dictated by the width of the vehicles transporting the container. Most units are therefore built to measure 8.0ft across. Any exceptions are clearly marked as such and are mainly used for storage.
Like width, most shipping containers share a standard height – matching up to the cab height of lorries. However, there are a few alternate heights that come in useful for certain goods. Standard ISO containers measure 8.6ft in height, while ‘extended height’ or ‘high cube’ containers allow extra storage and measure a foot higher at 9.6ft. Alternatively ‘half height’ containers, measuring 4.0ft or 4.6ft can be used for moving vehicles or goods such as pipes. Any pedants noticing that neither of these sizes are technically ‘half-sized’ will unfortunately have to accept this term…
This is the dimension with the most variation, allowing great flexibility when it comes to choosing storage capacity. The most popular sizes are 20.0ft and 40.0ft, although a range of other sizes are available. From 5.0ft all the way to 45.0ft (and many discrete sizes in between) the choice is astounding. However, make a note that alternative transport arrangements may be needed for containers measuring 10.0ft and under.
Every shipping container will have a unique 11 character identifier, registered with the BIC (Bureau of International Containers) that shows its ownership and specifications.
The Equipment identifier shows which category container is being transported. In the case above the unit is a standard dry freight container. Other markers used are:
J – Detachable freight container related equipment
R – Refrigerated Containers
Z – Trailers and Chassis
Beneath this code a container will have a 4 digit ISO code, taking the form of two numbers, a letter and a final number (e.g. 20HR). These refer to the exact ISO container and its purpose, making identification easy for all involved. For example, the code 42R9 refers specifically to a refrigerated unit containing no food. The first two digits describe the group, while the latter two show its size.
Although the multitude of markings printed on containers can seem overwhelming, all ISO means is that you can be guaranteed that the container you expect is the container you get, with no need to whip out the tape measure to make sure. At Unit Hire all our shipping units are ISO sized, meaning that you’ll know exactly how much you can store, how much room it’ll take up and just how long it’ll last (a very, very long time since you ask). Get in touch today with our friendly team or come and have a look for yourself, we’d love to help you out!