How Are Shipping Containers Loaded and Stacked?
All shipping containers are cumbersome, unwieldy beasts, which means transferring them between trucks, trains and ships is no task for amateurs.
An empty 40-foot steel shipping container container weighs in at a hefty 8,600lbs (tare weight) but fully-laden it can reach over 67,000lbs (33 tons) which can create a lot of destruction if dropped from height. Thankfully, most of the world’s cargo terminals are now equipped with all the necessary heavy-lifting gear, plus highly-skilled teams of longshoremen using essential safety equipment.
It’s All in the Planning
Way before even a single shipping container is taken aboard a vessel, a huge amount of activity happens behind the scenes. It’s the ship’s Chief Officer who’s ultimately responsible for safe and secure stowage and he or she needs to run the operation with military precision. There are five main areas to consider when planning stowage:
- Vessel protection
- Cargo protection
- Maximising capacity in holds and on decks
- Fast yet safe loading and unloading of cargo
- Crew and third-party safety
The Right Hardware is Essential
The only way to safely and efficiently load or unload fully-laden shipping containers onto cargo ships is by using dockside gantry cranes, otherwise known as ship-to-shore cranes. These come in two main types: low-profile and high-profile. Their use is dictated largely by local conditions, such as the presence of low-flying aircraft. The cranes shuttle back-and-forth along the quayside on specially laid tracks. Gantry cranes are further classified by their lifting capacity and the size of ship they can service.
Panamax cranes – are able to load ships small enough to pass through the Panama Canal, which is governed by its lock widths and the height of the ‘Bridge of the Americas’. This means vessels can be no taller than 190-feet and no wider than 106-feet (or the width of 13 containers). Such craft can generally handle up to 5,000 TEUs (the equivalent of 5,000 20-foot shipping containers).
Post-Panamax cranes – can service larger cargo ships, unable to pass through the Panama Canal, which are alternatively known as ‘single ocean vessels’.
Super post-Panamax cranes – are demanded for serious heavy-lifting onto the ocean’s largest vessels, including monsters like the Emma Maersk, capable of transporting over 15,000, fully-loaded, 20-foot Conex boxes. Some of the latest super post-Panamax cranes have a huge lifting capacity of 120-tons. These giant hoists can themselves weigh as much as 2,000 tons. The busy Port of Savannah has the highest number of these new gantry cranes, all built by Konecranes of Finland, making it one of the most important links in the chain of ports that service the Atlantic seaboard, along with the Port of New York/New Jersey and Charleston.
Smaller cranes – these are often used in railway siding to transfer shipping containers between trucks and freight trains. Straddle carriers are commonly used in these scenarios to lift and stack Conex boxes. They are large, wheeled vehicles that can handle up to two containers at a time.
Identifying Individual Shipping Containers
Anyone who has visited a large container terminal must wonder how the longshoremen distinguish each individual container. Thankfully, every sea container possesses a unique registration number, which is registered on a ship’s electronic manifest. This allows for easy identification among the many thousands of units. More about this in a later article.
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