A 6 meter (20ft) ISO container is built to the standards set forth in the ISO 668 specification for classification, dimensions, and ratings, along with the standards in ISO 1161 and ISO 1496, which cover technical details about what these containers are made from, how they are to be assembled, and how they are to be made wind and watertight.
How we arrived at 20ft
Malcolm Mclean was the man responsible for standardizing shipping container dimensions and construction, and showing that such standardization would not only improve the speed and efficiency of unloading and reloading seagoing vessels, but greatly improve truck and rail service, too. Between 1968 and 1970, three ISO standards were implemented. The first was ISO 338 in January, 1968. This standard defined terminology, dimensions, and ratings. The second one was ISO 790, which went into effect in July of the same year. This standard defined how containers should be identified. The last standard during this time period went into effect in October of 1970, defining the recognized sizes of containers.
As a result of these standards being agreed upon and put in place, both 6 meter (20ft) and 12 meter (40ft) shipping containers became the recognized standard lengths. The 6 meter (20ft) container was used so heavily that it became the definition of the Twenty foot Equivalent Unit, or TEU. This term is still in use today as a reference to cargo volume, along with a similar term, Forty foot Equivalent Unit, or FEU.
What Makes 20ft Such a Great Size
One of the biggest advantages to this size is its overall strength. Because of its short length, it has a much higher overall structural strength than its longer counterparts. This translates to reduced likelihood of catastrophic failure leading to cargo damage and loss. The average container is generally in service for a minimum of ten years, meaning that these containers last.
6 meter (20ft) containers come in two heights, general purpose, 2.4 meter (8ft 6in), and high-cube, 2.9 meters (9ft 6in), with a wide variety of configurations, making it possible to ship most anything anywhere in the world.
General Purpose Container – Recognized as the most common type of container, the general purpose container is a weather and watertight rectangular steel box with a set of doors on one end. These containers are ideal for transporting cargo that is on pallets, slip sheets, bundled, boxed, or floor loaded.
Open Top Containers – These containers are ideal for over-height loads such as machinery. They also are designed to transport solid bulk materials and loose bulk products that must be loaded from the top. Open top containers have two basic types of tops: a removable metal top and a soft top made up of a tarp and supporting tarp bows. These containers also have the flexibility to be unloaded from the top or using the doors.
Side Opening Doors – This configuration makes for easy loading and unloading of cargo that is long, bundled, and otherwise difficult to load or unload from the ends of the container. Side opening containers are available in a variety of configurations ranging from side doors on one side with rear doors to having doors on both sides and both ends. Some examples of cargo transported in tunnel containers include lumber, glass, high-volume bins, and plastic irrigation tile.
Double Door Containers – Double door containers are a general purpose container with a set of doors at each end, allowing faster, more efficient loading and unloading, whether the load is on pallets, slip sheets, or floor loaded.
Flat Rack Containers – The real heavy haulers of the bunch, these stackable containers are built extra heavy for transporting heavy machinery and equipment. When empty, the ends can be collapsed, allowing for efficient storage and relocation. Metal Pipe and certain other kinds of cargo are often restricted to being transported on flat rack containers, due the inherent difficulty such cargo pose with regard to securing loads.
Refrigerated Containers – These containers have built-in refrigeration units that run on external, 440v 3-phase electricity. They’re used to transport refrigerated and frozen foods, along with other cargo types. When dealing with temperature sensitive cargo, it is important to make sure your outside air supply is adjusted properly for the cargo. Otherwise, cargo damage may occur.
Why 20ft containers are so popular – Size matters. With a 6 meter (20ft) container, there is higher utilization of capacity when loaded with heavier materials. A 12 meter (40ft) container can only hold about 50% more cargo by weight than its 6 meter (20ft) long counterpart. Smaller size also translates to a smaller footprint when staged or stored on land.
Aside from the weight-to-length ratio, this container size is just right for shipping orders of goods. Furthermore, when staged or stored, it takes up about as much room as a regular parking space. This is great news for businesses in cramped, metropolitan areas where properties are small and extra space is at a premium. The flexibility provided by this size continues to make it a popular choice among shippers. For the foreseeable future the 20ft container will continue to be a favourite for shippers all over the world.