The freight container was invented in the 1960s by Malcom (or Malcolm) McLean. Containers are, for the most part, owned by ocean carriers, which means the return of containers has to be organized: if the container consignee has no merchandise to ship back in the container, the ocean carrier will have to take it elsewhere to fill it again and so avoid empty journeys.
A container carries several markings, in particular a 4-letter owner’s code plus a six-digit serial number, giving an owner the ability to register 1 million containers. This code is obtained by registering the container with Bureau International des Containers et du Transport Intermodal (BIC).
Loaded containers are stackable up to nine high but only if weight loadings permit. Most of them have corrugated walls and are characterised by their corner fittings whose position and dimensions are standardised internationally. These allow the container to be both stowed and handled by spreaders using a twist lock.
The ISO container reference size is the twenty foot equivalent unit or TEU (20 ft = 6,058 mm). Less common but also found is the FEU or forty foot equivalent unit (40 ft = 12,192 mm. The last International Containerisation, World Container Census report (2008) gives the following figures for the world container fleet:
Container floors can support forklift trucks with a maximum axle load of 5,460 kg if the contact area per wheel is at least 142 sq. cm, in accordance with the ISO 1496 standard.
Special attention must be given to loads concentrating large weights on a single point: these must not exceed what a container floor structure can support. The maximum floor loading must not exceed:
The dimensions given below are a general guide only. Actually, container dimensions vary with owners and manufacturers. They are standardised to ISO 668 as regards their external dimensions and ISO 1496 for their internal dimensions but there are many containers with characteristics in excess of these norms. Most Hapag Lloyd 20′ containers, for example, exceed these standards. When you are arranging a shipment, you are recommended to contact the ocean carrier or your forwarder to find out the exact dimensions of the container(s) that will be sent to you. This aspect is however secondary in the case of a 45′ palletwide container because it will present the same advantages as a road transport semi-trailer.
|20 ft||40 ft||40 ft HC||45 ft HC palletwide|
|Length||20′ (6.058 mm)||40′ (12.192 mm)||40′ (12.192 mm)||45′ (13.716 mm)|
|Width||8′ (2.438 mm)||8′ (2.438 mm)||8′ (2.438 mm)||Approx. 8’4″ (2.550 mm)|
|Height||8’6″ (2.591 mm)||8’6″ (2.591 mm)||9’6″ (2.896 mm)||9’6″ (2.896 mm)|
There are other types of freight container with, for example, a length of 30 ft or even a « super highcube » going from 48 to 53 ft. These require the use of special equipment: for example low loader « Multifret » wagons for transport by rail.
Internal dimensions and doors
The internal dimensions are less than the outside dimensions, but whereas the former are standardised, internal dimensions vary according to the material used for the inside of the container (plywood or steel walls, etc.). For the same reasons, the weight also varies considerably. Special containers like refrigerated containers have reduced internal dimensions since their walls include thermal insulation. It is also necessary to pay special attention to the dimensions of the doors because these can get in the way of loading, especially if the dimensions of the goods are close to the maximum internal width dimension. You are therefore recommended to contact your broker or transport company to find out the exact dimensions of the container(s) that will be sent to you.
Total weight: in general, the total weight varies between 28 and 32 tonnes, depending on the equipment. It is appropriate to pay special attention to the Gross Combined Weight Rating (GCWR) of road vehicles used for pre and post shipping. Around 15 tonnes can usually be reckoned on for this.
Maximum load: this usually varies between 20 and 28 tonnes.
The volumes varies according to the internal dimensions and is usually approximately 33 m³ (1,170 cu.ft.) for a 20 ft container, 67 m³ (2,380 cu.ft.) for a 40 ft, 76 m³ (2,690 cu.ft) for a 40 ft highcube and 90 m³ (3,178) for a 45 ft palletwide highcube.