Methods to move a container
Shipping containers are ideal for transporting cargo around the world. Through their journeys, they are frequently moved from carrier to carrier and from different secondary modes of transport (train, truck and ship). Seen below are some of the different methods used to move a container, and the comparative costs involved.
Static cranes ($$$$$)
A variety of cranes can be used to move a container from trucks, trains and vessels. Large-scale static cranes are usually located in container terminals and ports where there is a high volume of containers to unload/load. They function by suspending what is known as a 'spreader', a specialized handling tool, which connects and locks to the upper corner casting of a container. They are efficient at handling a high quantity of containers but are hindered by their significant cost, space requirements and lack of mobility.
Straddle carriers ($$$$)
Straddle carriers are, simply put, a form of mobile container crane. The carrier has a wide open space between its wheels, allowing the vehicle to drive over and 'straddle' a container. The spreader is then connected to the container, the container is raised up in the space between the supporting legs, and the carrier can the transport the container elsewhere. Suspending a load of up to 60 tonnes, they can travel up to 18.6 mph. They are therefore useful to move a container around a port or terminal, but ineffective to move a container any significant distance.
A sideloader is a specialized truck chassis which has two small hydraulic powered cranes at the front and back, used to move a container. They are also known as self loading trucks (SLT), sidelifters or container pickers. Before a container is un/loaded to the chassis, four supporting legs are extended to ensure that the chassis does not roll over. They are useful for transporting single containers over large distances. They do however require the space to the side of the chassis as containers can only be unloaded/loaded sideways. They are also restrictive with the size of the container that can be loaded, for example, a sideloader with just over 20 foot of space between the two cranes can clearly not transport a 40-foot container.
Reach stackers are vehicles with an arm which extends over the driver cabin. The arm suspends a spreader which can move a container. Reachstackers are quick and efficient at stacking containers on top of each other in small ports and terminals, but the height of the potential stack is limited by the length of the arm. The 'skystacker' variation is more adept at stacking containers by incorporating some of the design features of a forkllift.
Some truck trailers are able to tilt backwards, allowing a container to be carefully and gradually slid onto the ground. The containers movement is driven by the combination of a winch and the truck pulling forward. It is an effective method of unloading a lightly loaded 20ft container onto the ground, but it is not suitable for unloading heavily loaded containers, or 40 foot plus containers. The container will also be left at ground height, therefore it is not suitable for loading bays and will require a different method should it be moved in the future.
ConFoot legs ($)
By a significant amount, the most flexible and cost-effective method to move a container from a truck can be by using ConFoot legs. The legs are inserted into the lower corner castings of a container mounted on an air suspension equipped chassis. The chassis is then lowered, allowing the legs to take the weight of the container. The actions can be performed in reverse to replace the container onto a chassis. The container is held at loading bay height, giving a multitude of possibilities for the container to be unloaded at a rate which suits the customer. Find out more info at confoot.fi.