CONEX Containers – History, Dimensions, Features And Uses

CONEX containers are one of the most iconic developments in the history of transportation and logistics, as they revolutionized the shipping industry.

These containers gave rise to the industrial intermodal standard containers known today as TEU and FEU.

Intermodal containers can be transported using the road, rail and maritime methods. In certain cases, they can also be transported by air, when the airplane stowage systems are modified to accommodate their specific dimensions.

The term CONEX is an abbreviation of Container Express, indicating that transport times were cut short by having a single container that was compatible with multiple means of transport.

History of CONEX Containers

During the wars in Korea and Vietnam, US troops were in need of quick methods of ferrying supplies to the soldiers at the front lines.

The issue was that goods loaded on container vessels had to be reloaded on to trailers for road transportation. This presented a logistical challenge, as valuable time was spent in the transfer process.

conex containers

To overcome this, a unique design known as the CONEX box was developed. This box was compatible with the trailers on which they could be carried.

In addition, they had locking mechanisms that could connect adjacent boxes to prevent toppling over during transport. The first model of these intermodal containers was the “Transporter” used in deployment during World War II, to ferry supplies to the war front.

The basic design had a 4,000 kg weight limit and was made of corrugated steel, to serve as protection.

Related reading: How are shipping containers made?

Further advances in technology allowed skids and lifting mechanisms to be attached to the early designs. These ensured that the containers snugly fit during transport and that they could be easily picked up by cranes and loaded onto trailers.

During the Korean war, containers were modified so that they could store larger quantities of goods without compromising on structural integrity. The Vietnam war witnessed larger size CONEX boxes being developed, that could double up as living quarters during harsh conditions.

During transport, they could be stacked 3 containers high and were lashed together to prevent accidents.

The modern intermodal containers were developed from the rudimentary CONEX boxes by American trucking magnate and businessman Malcolm McLean, who revolutionized the transport industry.

CONEX containers are still in use by the US military but have been renamed BICON, TRICON and QUADCON containers. These containers are unique to military usage and vary in dimensions from the standard intermodal containers.

Dimensions of CONEX Containers

The generic sizes of the CONEX containers have varied over time, to suit the various types of cargo that it has been used to accommodate. During the wars, the early model known as the “Transporter” used for moving supplies,  was 8 ft 6 in long, 6 ft 3 in wide and 6 ft 10 in tall.

Conex Container Dimension

Half units of smaller dimensions 6 ft 3 in long, 4 ft 3 in wide and 6 ft 10 in tall were used in shipping where space constraints were present.

Small shipping Container

The modern CONEX containers have standard sizes in terms of Twenty-foot Equivalent Unit (TEU) and the Forty-foot Equivalent Unit (FEU).

Related Reading: Different types of shipping containers

As the names suggest, these containers are respectively 20 and 40 foot long and are intermodal in nature. To ensure compatibility and even spacing on ships and trains, the width and height are fixed at 8 ft and 8 ft 6 in respectively.

For larger space requirements, high cube or hi-cube dimensions are used. These are of the same length and width but are taller than conventional containers at a height of 9 ft 6 in.

High Cube Container

Along with these standards, there are more unusual sizes also in circulation, such as the 10 ft, 25 ft, 45 ft, 48 ft and 53 ft long containers.

Certain types of cargo require compact or larger storage spaces, so they utilize these types of shipping. The volume loading capacity of these containers can vary as 33,000 litres for the TEU containers, 67,500 litres for the FEU containers or 75,300 for the FEU hi-cube variant.

The maximum gross weight that is permissible on board these containers are 30,000 kg for the TEU and FEU sizes, while it goes slightly up to 31,000 kg for the FEU hi-cube size.

On average, the weight of the empty containers range between 2,200 for the TEU and 3,800 kg for the FEU.

Features of CONEX Containers

The distinguishing features of the CONEX containers that set them apart from the older variants of the container industry were their superior safety, strength and compatibility.

Built out of corrugated steel sheets, these containers could withstand sufficient forces and strains before crumpling. In addition, specialized locking mechanism was in place that prevented theft of the goods inside.

Certain containers required windows and additional entryways. In such cases, a double locking mechanism that is common on modern day containers was put in place to secure the doors.

Also, steel bars and bullet-proof glass were used on windows to prevent theft. The strength of these containers came from the corrugated shape, that increased the maximum bending stress along the axis perpendicular to the shape distortions.

A key feature of the CONEX containers was the interlocking mechanisms present on the exterior. For instance, the early designs had skids on the bottom, that could fit perfectly over containers below it.

With advances in manufacturing, the containers could also be locked to the adjacent storage units.

For this purpose, a specialized mechanism was used to connect the bottom of two adjacent units, which could be released as and when needed.

In addition to all these features, safety and administrative laws could now be easily applied, as there was a uniform standard that was applied to all the containers that were shipped across the world.

Uses of CONEX Containers

CONEX containers can be used for a variety of purposes, differing based on the type of goods that it houses within itself.

General purpose dry containers can be used to ship cartons, pallets, drums and boxes. They are apt for transferring similar type dry goods.

They can include special mechanisms that are built for particular goods that can be difficult to load into the container. For instance, garments that cannot be folded and transported are stored on hangers and shipped using garmentainers.

Along with garments, the storage of heavy pallets is difficult, since cranes can often not be used to directly place the goods within the allocated location in the container.

To solve this issue, rollers on the floor of the container are used to easily shift the goods. Large cartons and pallets can be loaded in this manner, using only limited personnel to load goods into the container.

For transporting liquids, powders and gases, tank containers are commonly used. These consist of multiple pressurized tanks stored in the container, such that large quantities of fluids or powders can be shipped.

For cargo such as noxious gases, or poisonous liquids, special signs are installed at the doors and on individual tanks to prevent accidents and mishaps from occurring. Along with pressure regulation, certain gases have to be maintained at specific temperature and humidity ranges.

Here, temperature-controlled containers can be put to use. These include insulated containers that are maintained at a constant temperature, either through refrigeration or heating. These are also ideal for perishable goods such as fresh foods, and especially meat.

CONEX Containers

For dry goods that have to be kept at a specific storage conditions, thermally insulated containers can also be used with the same features. In addition, ventilated containers are also available. These have special mechanisms for active ventilation (using a pump system) or passive ventilation (using air drafts through ventilation holes in the container) that ensure goods reach their final destination in the right condition.

Another common method of transporting goods, especially loosely stored items or powders, are using bulk containers. Similar in logic to bulk carrier vessels, these containers are rigid on all four sides and at the bottom. However, the top is sometimes made separately, or with specialized gaps for the loading of loose items. This includes large scale shipping of powders, grains, loose material such as ores and rocks.

Containers Arrangement (Image Credits: Paromita M)

For fine matter that can easily be lost if not stored properly, movable bins are used to collect the material. Once filled, the individual bins are loaded on to the containers, and stacked along the entire length. These bins are extremely useful, as they allow companies to directly roll-on and roll-off goods during loading and unloading operations.

It removes the need for specialized pumps or motorized mechanisms to unload the goods at the destination. For such containers, the top is often removable, or made of a flexible material with a slit, that allows factories to directly load material without the danger of spilling.

Another type of container similar to the one previously discussed is the open-top container, that can be used to store large objects that would have otherwise required the container itself to be dismantled. This is ideal for large machinery that must be loaded through the top.

The difference between the open-top and bulk containers are that while bulk containers can have removable lids, the open-top ones often do not have roofs for the containers. The benefit with this is that for extremely large objects, multiple containers can be stacked and used for transport with minimum modifications.

To stack these containers, the bottoms are also removed for certain ones, and the object is placed in the stack using specialized cranes present at dockyards. Open-side containers can be used to slide objects into the container without having any issue in loading. In addition, having open-sides can aid in ventilating the goods stored within. This is ideal for perishable foodstuff such as potatoes and apples that will be able to withstand the journey without extra protection.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

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