The container is used for storing and transporting cargo. It is used most often in sea and rail transport. Usually it is in the form of a metal box, adapted to the movement of general cargo. The use of such a container accelerates the load process and the protection of this type of goods. Each container, and in particular a sea container, must be made in compliance with safety rules. These guidelines are set out in the International Convention on Safe Containers and ISO standards. In this way, among others, strength requirements.
The container can be made of various materials. Currently, steel containers are the most popular due to the low production costs and compliance with all strength standards. The construction of sea containers differs in the purpose of the crate. The components of a standard tank are shown below.
The frame, made of steel profiles, is the basis for the construction of each container. It must be particularly durable, as up to nine heavily loaded containers can rest on it. The components are:
- corner posts,
- lower and upper longitudinal beams,
- lower and upper crossbeams.
As the base of the container floor, transverse ribs are installed, perpendicular to the lower longitudinal beams. In the largest reservoirs, i.e. over 40 feet, there is a tunnel. It is responsible for lowering the height of the container semi-trailer with the container on it. Such a part is called by specialists the “gooseneck”.
Such parts are located at the corners of the frame. They are permanently attached with welds. The four upper corner pieces facilitate the processes of loading and unloading the container. The lower corners are responsible for fixing and securing the container on the means of transport. They must be strong, therefore they are made of specially reinforced steel. Perfectly fitting corners should protrude slightly from the frame of the tank. Usually they stand out by less than 2 centimeters.
Smaller containers have additional facilities for transporting them from one center. These are the so-called pockets into which you can insert the forks of a forklift truck and thus transport the container. It is assumed that this equipment may only be used for lifting empty containers. In order not to damage the floor, use forks with a length corresponding to the width of the tank. The spacing and size of pockets are defined by ISO standards.
Due to various weather conditions, the container must fulfill the protective function of the goods transported in it. The best leak test is to release a stream of water with a pressure of one bar on individual walls. A container with a high degree of protection does not allow such a stream to pass inside. The roof and walls are made of 1.5 mm trapezoidal sheet metal, and in the corners of longer walls, ventilation grates are mounted, thanks to which the air can be exchanged. This solution prevents the formation of water vapor that can damage the goods. The ventilation works in such a way that water does not flood the inside of the tank.
Due to the fact that the entire load takes on the frame, the roof is designed in such a way as to resist loads of up to 300 kg for 0.18 m 2 . This load is sufficient for two people to come out on top to secure the container or perform a service. The floor is made of container plywood, usually at least 25 mm thick. The second way to make the bottom is formwork.
Each sea container is equipped with a double-leaf door, usually located instead of a shorter wall, so that it can be freely entered. Some types have an extra pair of doors on the other short side or on the long side wall. The gates of the container consist of the following parts: the gates are secured by rubber gaskets that ensure tightness. The opening and closing operations are made possible by container closures. They consist of bolts, handles, rods, clamps and customs seals. Other elements without which the door will not function are hinges or bolt sockets. They are very heavy and manipulation with the use of special safety rules.
The door also has an information function. This is where the plates or stickers are located. This is also where the destination of the container or the type of goods transported is located.
The other structural elements that secure the cargo inside the box are the hooks at the corner posts. Further fixings are at the top and bottom of the frame.
The specificity of the construction of sea containers may vary. Not every container is equipped with elements such as:
- handling grooves that are located on the side walls; they facilitate the work of the gantry crane,
- grooves for forceps grips.