The development of the shipping container industry threw up some interesting design problems as its own success then began the need of variations in shipping container construction. Customers had different needs and its surprising that the industry managed to keep within its standard design structure with such needs. At the same time more modifications to the standards had to be added as new problems developed that hadn’t been seen with such things as the corner standard fittings you see on the shipping containers, but nobody had assessed maximum payloads and containers began to fail because they hadn’t been tested to high stress levels and needs of customers demands. As these failings became apparent the International Standards Organisation was swift to step up the specifications on the standards and the quality and strength of shipping containers improved.
The next issue involved railroad cars as there needed to be shipping container reinforcements on the end plates as the containers had extra pressure added when the railroad cars hitched and unhitched costing around an extra $100 per shipping container.
The next issue was standardising the lengths of units to fit into all shipping situations and this seen the rise of five initial standard shipping containers develop :-
- 20 ft (6.1m)
- 40 ft (12.2m)
- 45 ft (13.7m)
- 48 ft (14.6m)
- 53 ft (16.2m)
The matrix of shipping containers were designed so that they would fit into most fitting needs and being able to interlock the different sizes within ships without difficulty. The U.S. prefers the larger shipping containers while Europe prefers 40ft containers. Adding to this was the weight restrictions to keep the shipping containers manageable but also within restrictions such as road limits for freight this seen the following standard shipping container weights develop :-
- 20 foot: 52,910 lbs/24,000 kg
- 40 foot: 67,200 lbs/30,480 kg
- 45 foot: 67,200 lbs/30,480 kg
- The net load totals are:
- 20 foot: 48,060 lbs/21,600 kg
- 40 foot: 58,820 lbs/26,500 kg
- 45 foot: 56,620 lbs/25,680 kg
The development of the shipping container has seen two materials mainly in use Aluminium and Steel. Most common being steel as it handles the bashing of shipping container needs as well as still functionally light and a cheap material. Aluminium is a more expensive solution but doesn’t suffer with the obvious rust problems that steel does. In recent years though Corten steel has seen its entry onto the market place which is rust and mould proof making it the most practical solution.