Friday, August 20, 2010

Rail Container Gantry Cranes

Rail container gantry cranes are a form of gantry cranes mounted on rails to aid movement while hoisting heavy items from one position to another. The other form of movement can be on rubber tyres. The first design of a rail container gantry crane appeared in the year 1960. It was designed by Paceco Corporation and referred to as a “Portainer”, coined from the words “port” and “container”. The major loads hoisted by this type of cranes are cargo containers, usually from ship to shore or vice-versa. Thus, they are also referred to as ship to shore cranes.

Operation Of Rail Container Gantry Cranes

Using either electrical AC or diesel engine powered DC as the power source, the trolley in rail container gantry cranes run along rails wile hoisting loads. These rails are located on the top of the boom and girder or at their sides and serve as the support end for moving the hoisted load.

Rail container gantry cranes are best suited for inter-modal container terminals where multiple containers need to be moved from one holding area to another. This can include ship to shore, truck to train, ship to truck, ship to train and vice versa. For these operations, the most important consideration is movement of the container to its desired location effectively and not the speed at which it is moved. One big advantage of rail container gantry cranes is that it allows for better land usage at a shipyard or port and also reduces possibility of ground accidents. This is so since movements by multiple mobile cranes has been eliminated. Also, it increases available stacking area for containers. When offloading containers from ships, the rail container gantry cranes usually straddle the ship, allowing for lifting and moving massive objects over the ship without problems.

For maximum effectiveness at a container terminal, rail container gantry cranes are built with a supporting framework that can manoeuvre across the length of the quay. This framework supports a platform, also known as a “spreader”, allowing the spreader to be lowered to latch onto a container and move it to and from a specific location at the quay. Containers are usually picked one at a time, but some newer rail container gantry cranes have the capacity to pick up four (4) containers at a go.

Two major types of rail container gantry cranes in operation today are the high profile and low profile variants. The low profile variants are most suitable for use when container terminals are situated close to airports, where the high profile type may obstruct the flight path of a plane. In terms of size, rail container gantry cranes are rated with reference to the Panama Canal, especially when the cranes are welded on to and travel with the ship.

We can have a “Panamax”, “Post Panamax” and “Super Post Panamax”. In this light, a “Panamax” crane is one capable of fully loading and off-loading a container ship that can pass through the Panama Canal, while the “Post Panamax” does same for ships too wide to pass through the Panama Canal. The largest, which is the “Super Post Panamax”, is about twice the size and weight of the “Post Panamax.”

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