Ultrainnova - Steel structures - design, construction - sandwich panel


















Sea container with no secrets

The endless ocean, sailing ships, pirates ... sea voyages have fascinated mankind for centuries. And the seas and rivers are the routes of movement of goods that have been used by man for thousands of years. The means of shipping have evolved and are still changing. It is worth getting to know its most popular form today: container transport. Why containers have gained such popularity? How are they built and what are their types and purpose? Is it really the key freight route in the world? According to the EMTER'2021 report of the European Environment Agency and the European Maritime Safety Agency, 77% of European external trade and 35% of all trade between EU Member States is carried out by sea. Sea transport is therefore a key element of a modern supply chain. Interestingly, it is estimated that around 90% of goods in the world are transported by sea, of which more than are container loads. Sea container without secrets | Ultramodula

Find out about the types and purpose of sea transport containers

Looking at the percentage value of goods transported by sea, it is easy to guess that practically every thing in the world is packed in containers. Therefore, there are many types adapted to the specificity of the goods being shipped. The basic types of containers have been specified in the ISO standard and are:

  • general purpose container,
  • dry bulk containers (bulk container, dry bulk container),
  • thermal containers,
  • plate (platform) and plate-type (flatrack) containers,
  • tank containers,
  • air containers,
  • specialized containers (named cargo container).

Each type of container is used for and adapted to different purposes. 

Thank you containers general purpose well suited for the so-called general cargo, and at the same time they are the most universal. The most popular in this category are 20 or 40-foot containers with a door located on one of the front walls, a plywood floor, and vents that allow gravity ventilation. Interestingly, this type of containers can be - after minor modifications - used to transport loose / loose goods. For this purpose, the so-called big bags completely filling the interior container and pneumatically loaded. It is worth remembering, however, that a container tipper semi-trailer or a specialized pneumatic device is required for unloading. Another type are dry bulk containers with a structure that is more resistant to loads arising during filling, transport and emptying. They are additionally equipped with filling and emptying openings, making them ideal for the transport of solids in bulk without packaging.

Special requirements

Isothermal containers, in turn, are an essential part of food supply chains as well as other temperature-sensitive goods, such as medicines. They owe their insulating properties to polyurethane walls. Moreover, such containers can be cooled with the use of a refrigeration unit. What is extremely important when packing such container, always leave an air gap of about 75 mm at the top. The so-called flatrack and plate containers, because they have no roof or walls or only end walls. They are intended for the transport of bulky and heavy loads. Their floor is usually raised compared to standard containers and lined with boards for greater strength. The last popular type of sea containers are tank structures. They are used to transport liquids or gases and are constructed in a simple way: a tank is placed in a frame with the dimensions of a standard container. This solution also enables the transport of dangerous, explosive, flammable or poisonous goods.

Containers with an opening roof

Finally, it is worth mentioning an important variant of containers, i.e. versions with an opening roof. They appear as the so-called hard top, where the folding roof is made of steel or, in the option without a roof, only with an overlay tarpaulin (secured for transport with a customs rope). Such containers are used for packing loads that cannot be placed in a standard container, e.g. due to their dimensions.

The size of the container matters

We also divide containers due to their dimensions. This parameter is particularly important because it is the unification of container sizes that allows for the optimization of transport and made this type of transport so popular. The basic division is this one containers 20 and 40 feet, as well as those of standard height and HC versions, i.e. high cube. The table below presents a summary of the basic sizes. It is worth noting that the length of the 40ft container has been selected in such a way that it is possible to place two 20ft containers on it (or under it) while maintaining the appropriate spacing (3 inches).




Name Length x Width x Height Volume
20ft (20ft) 20ft x 8ft x ft 8,6 in 6,1m x 2,4m x 2,6m ~ 33 m3
40 ft (40 ft) 40ft x 8ft x ft 8,6 in 12,2m x 2,4m x 2,6m ~ 66,9 m3
40 ft HC (40 ft high cube) 40ft x 8ft x ft 9,6 in 12,2m x 2,4m x 2,9m ~ 76 m3


How are sea containers built?

Container construction only on the surface it seems simple. In fact, it is a demanding structure, which requires specialist knowledge and properly selected materials to design and manufacture. Each sea container must be built in accordance with the strict safety criteria contained in the International Convention for Safe Containers (CSC). It must also meet ISO standards specifying minimum strength requirements.

Durable frame

The base element is always a steel frame that consists of corner posts as well as transverse and longitudinal beams. The structure must be so durable that it allows stacking as many as 9 fully loaded containers. Therefore, in addition to the lower longitudinal beams, the so-called transverse ribs forming the basis of the floor. Long containers (40 ft) also have a tunnel in the floor, the so-called gooseneck. It allows to reduce the overall height of the trailer and the container.

Tight walls, roof and floor

All walls of the container are made of trapezoidal sheet metal, and the roof is made of its profiled version, about 2 mm thick. The structure is welded and undergoes demanding tightness tests consisting in directing a stream of water at a pressure of 1 bar directly onto the roof and walls. Then it is checked that all interior surfaces are completely dry. An important element of the container is the floor - remember that during loading / unloading, forklifts move on it. It is made of special container plywood (minimum thickness 25 mm) or boards.

Container doors

The most popular version of containers are those with doors located on the front wall, although it is not uncommon to find versions with gates on a long wall. Usually, the door structure is based on four or five crossbeams, and their structure is double-leaf. The tightness is guaranteed by rubber gaskets mounted around each door. The standard set of container closures consists of bars, bolts (bolt sockets are welded to the container frame), handles, clamps and, of course, a customs seal.

Sea container price - what does it depend on?

Although the requirements for the construction of containers are clearly defined and specified, their quality, and thus the price, depends on many factors. The first are the materials used by the manufacturer: steel, sheet metal, plywood, and, importantly, varnishes and anti-corrosion coatings. Remember that containers spend most of the time in very unfavorable weather conditions. Another element that affects the price of a sea container is the contractor's warranty. It is worth betting on Polish producers who provide reliable and professional after-sales service. Companies with modern machinery will provide containers with better parameters and can guarantee compliance with standards, which is the basis in international transport.

Recent entries