Although shipping containers may look like a simple steel box for storage, their initial reason for manufacture is to be stacked several units on high on a container vessel whilst being loaded with tonnes of goods of a wide variety. Therefore, there is much more to their design and manufacture than you may initially think!
The walls of shipping containers are manufactured from (usually) 2mm thick Cor-Ten steel, this may seem immensely thin, however, the corrugations of the shipping container walls and the properties of Cor-Ten steel make the walls immensely strong. The walls are joined at each corner by a formed corner post which is met at the top and bottom by a heavy block called a corner casting, these corner castings are what allow the containers to be lifted by vehicle chains from the top or bottom and to be stacked on vessels.
The floors of shipping containers consist of steel bearers at 12-18” intervals which provide the strength to the flooring – if evenly distributed along the bearers, a 20ft shipping container can hold up to 30T!! The bearers are then overlaid with a 27mm bitumen sealed marine grade ply-wood flooring.
Shipping container doors consist of two door leaves, the right leaf being the dominant opening, both are hinged to the corner posts and ‘lock’ into the top and bottom of the container using cams and keepers manufactured from cast iron. Handles are used to engage and disengage the cams and keepers which allow the doors to open and close with ease. Shipping container doors are surrounded by rubber seal to avoid water and material ingress.
Most new containers are also fitted with a lockbox to the container doors, this is a steel shroud which covers a lock lug providing increased security once the container is ultimately used for storage. Many new models of shipping containers also have the added benefit of three locking bars as oppose to four, and longer handles – this makes opening and closing the container doors much easier and is advisable for more regular access.
Often customers may comment that used containers have rust patches, whilst we may be used to this being a problem with used car sales and the like, it is important to remember that in the case of shipping containers this is to be expected! Cor-Ten steel is actually designed to rust – otherwise known as weathering steel, Cor-Ten is designed to create a rust barrier over time therefore negating the need for painting. This makes sense when you understand that many shipping companies can hold on to their shipping containers on contract for many years, up to fifteen in some cases, without any maintenance or painting programmes to further protect their containers.