Container Handling

Container handling equipment can include side lifters, front-end lifters, reach stackers, straddle carriers (including grappler lifts) and gantry cranes.

Side lifters

They are road-going vehicles with hydraulic powered cranes fitted at each end of their chassis to hoist and transport standard intermodal containers. The cranes are designed to lift containers from or place containers on the ground, as well as to move road vehicles and low stacked containers. Owing to their mobility, side lifters are able to move containers to and from any accessible location in a freight terminal and also to engage in the collection and delivery of containers at sites separated from the terminal. If side lifters are not available at terminals, containers can be moved around with the aid of vertical loading equipment; however, they move at a slower speed. Although side lifters require a special chassis, they are less expensive per twenty-foot-equivalent-unit (TEU) handled than other handling equipment because of their lower capital, infrastructure, maintenance and operating costs, which result from their relative ease of operation, lesser need for strong and smooth pavement service and higher handling speeds. Side lifters require a low level of skill to operate.

Front-end lifters

They operate similarly to reach stackers, but they cannot lift containers from as tall container stacks as reach stackers can. Loading capabilities for front-end lifts are up to 40 tons. Because of poor mass distribution and torsional movements, rigid pavement surfaces are required at terminals that employ front-end container lifting equipment. They are therefore relatively inefficient as far as land utilisation is concerned. Their capital and maintenance costs are comparatively moderate, and in view of their medium level of skills required to operate them, their operational cost is also moderate.

Reach stackers

They are high-capacity container trucks fitted with a lifting arm and a spreader beam at the end of it to lift containers onto and from vehicles. Reach stackers can stack containers up to six high, and can place a container in a rear stack by reaching over a low stack, resulting in high land utilisation The spreader beam of a reach stacker lifts a container with twist-locking devices that attach to its top corners. Like gantry cranes and straddle carriers, reach stackers require a strong pavement foundation and a smooth surface for operation. They have moderate operating and maintenance costs, and require a medium level of skill to operate.

Straddle carriers

They are special types of mobile cranes developed to straddle, lift, move, place and stack containers at intermodal terminals. By straddling the container, this device carries the container within the structure of the crane. The carrier lifts the container using a spreader and twist-locks, and then moves it to another location (it has wheels on each of the four corners of its frame). It is a versatile mover and stacker of containers, and can achieve quick turnaround times owing to its ability to hoist loads while moving. The straddling allows it to move and handle containers at higher speeds than the reach stacker, which has to balance the container against a counterweight while moving.

The limitation of the straddle carrier is that containers need to be stacked in such a way that the frame of the carrier can move over the container stack, making an aisle necessary between every stack. Although the infrastructure cost of straddle carriers is lower than that of gantry cranes, it is higher than that of side lifters because they require stronger pavement structure than other smaller handling equipment. Although straddle carriers have relatively medium capital costs, their maintenance costs are high. The total cost of straddle carriers is substantially higher than that of reach stackers, but as a result of their versatility and swift operational ability, they are therefore only used in large, high-volume container terminals. They require a high level of skill to operate. Grappler lifts are similar to straddle carriers except that they grip the bottom of the container rather than the top.

Gantry cranes

They are used for directly transferring containers either

• between sea-going vessels and rail wagons and, to a lesser extent, road vehicles
• within intermodal rail terminals between rail wagons over a series of rails, or between rail wagons and road vehicles.

Gantry cranes are equipped with a large boom bridging the distance between the ship’s cargo hold and quayside freight vehicles, or bridging the distance between the land vehicles within the intermodal facility. The container-hoisting device moves back and forth along the spanning boom. When direct trans-loading is not possible at a particular time, the space below the crane can be utilised for track-side stacking of containers for later loading by road vehicles or rail wagons. Quayside container gantry cranes are mounted on rails and move parallel to the full length of a container vessel, while gantry cranes that trans-load containers between different rail wagons, or between rail wagons and road vehicles within intermodal rail terminals, are either mounted on rails or are rubber-tyred, moving alongside the full of length of the terminal rail sidings and pathways for road vehicles. Rail-mounted gantries can operate over series of up to ten rails, while rubber-tyred gantries can operate over a series of up to four rail tracks. Both gantry types can stack containers in storage areas up to approximately 1 000 TEUs per hectare.