A container crane (also container handling gantry crane or ship-to-shore crane) is a type of large dockside gantry crane found at container terminals for loading and unloading intermodal containers from container ships.

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Container cranes consist of a supporting framework that can traverse the length of a quay or yard on a rail track. Instead of a hook, they are equipped with a specialized handling tool called a spreader. The spreader can be lowered on top of a container and locks onto the container's four locking points ("corner castings") using a twistlock mechanism. Cranes normally transport a single container at once, but some newer cranes have the capability to pick up two to four 20-foot containers at once.

Cranes were used in harbors starting in the Middle Ages (see crane: harbor usage and list of historical harbour cranes). Modern inter-modal containerization emerged in the mid-s from transport strategies developed in the Second World War and the Korean War, and the development of specialized cranes paralleled developments in containerization.

The first container crane was built by PACECO Corp. for Matson at the Encinal Terminal in Alameda, California in .[1]

There are two common types of container handling gantry crane: high profile, where the boom is hinged at the waterside of the crane structure and lifted in the air to clear the ships for navigation, and low profile, where the boom is shuttled toward and over the ship to allow the trolley to load and discharge containers. Low-profile cranes are used where they may be in the flight path of aircraft, such as where a container terminal is located close to an airport. The type of crane selected in container terminal design process is determined by the design vessel and local environment.

Container cranes are generally classified by their lifting capacity and the size of the container ships they can load and unload.

Smaller container cranes, such as straddle carriers, are used at railway sidings to transfer containers from flatcars and well cars to semi-trailers or vice versa. Both the rolling stock and the trailers may pass under the base. Smaller container cranes are also used at break-of-gauge transloading facilities.

A Panamax crane can fully load and unload containers from a panamax class container ship capable of passing through the Panama Canal.[2]

A "post-Panamax" crane can load and unload containers from a container ship too large (too wide) to pass through the Panama Canal.

The largest modern container cranes are classified as "super-post-Panamax". A modern container crane capable of lifting two 20-foot (6.1 m) long containers at once (end to end) under the telescopic spreader will generally have a rated lifting capacity of 65 tonnes. Some new cranes have a 120-tonne load capacity, enabling them to lift up to four 20-foot (6.1 m) or two 40-foot (12 m) containers. Cranes capable of lifting six 20-foot containers have also been designed. Post-Panamax cranes weigh approximately 800–900 tonnes, while the newer-generation super-post-Panamax cranes can weigh 1,600–2,000 tonnes. The largest Super-post-Panamax cranes have an outreach of 26 container rows.[3]

The crane is driven by an operator who sits in a cabin suspended from the trolley. The trolley runs along rails located on the top or sides of the boom and girder. The operator runs the trolley over the ship to lift the cargo, usually containers. Once the spreader locks onto the container, the container is lifted, moved over the dock, and placed on a truck chassis (trailer) to be taken to the storage yard. The crane also lifts containers from chassis on the dock to load them onto the ship.

Straddle carriers, sidelifts, reach stackers, or container lorries then manoeuvre underneath the crane base and collect the containers, rapidly moving them away from the dock and to a storage yard. Flatcars or well cars may also be loaded directly beneath the crane base.

A crane can be powered by two types of power supply: a diesel engine–driven generator located on top of the crane or electric power from the dock. The most common is by electric power from the dock (also known as shore power). The voltage required may range from 4,000 to 13,200 volts.

• Gantry crane
• Rubber tyred gantry crane
• Straddle carrier

What are the Main Components of a Gantry Crane for Container Handling?

Gantry cranes are essential equipment in container handling operations at ports, terminals, and logistics centers. They play a critical role in loading, unloading, and stacking containers efficiently and safely. To understand how a gantry crane functions in these demanding environments, it is important to be familiar with its main components. This article will provide an in-depth overview of the key parts that make up a gantry crane for container handling.

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1. Bridge or Girder

The bridge, also known as the girder, is the primary horizontal structure of the container handling gantry crane. It spans across the working area and is supported by legs at either end. The bridge's function is to support the trolley and hoist, allowing them to move back and forth along its length. In container handling operations, the bridge is typically designed as a box girder or truss girder, providing the necessary strength and rigidity to handle heavy loads and withstand the environmental challenges such as wind and saltwater corrosion.

2. Legs or Support Structures

The legs of a gantry crane are vertical structures that support the bridge. These legs are mounted on wheels, which enable the crane to move along the rails installed on the ground (rail-mounted gantry crane) or on rubber tires (rubber-tired gantry crane). The legs are typically made of steel and are designed to withstand the dynamic forces generated during container handling operations. Some gantry cranes have a rigid leg on one side and a hinged or articulated leg on the other to provide flexibility in movement and reduce rail wear.

3. Trolley and Hoist Mechanism

The trolley is a mobile platform that runs along the bridge. It carries the hoist mechanism, which is responsible for lifting and lowering containers. The hoist consists of a motor, drum, wire ropes, and a spreader. The motor powers the drum, which winds or unwinds the wire ropes to raise or lower the load. The spreader is a specialized lifting device that can be adjusted to lock onto the corners of a container, ensuring secure lifting. The trolley's movement along the bridge, combined with the hoist's vertical motion, allows precise positioning of containers.

4. Spreader

The spreader is a critical component in container handling operations. It is a specialized attachment connected to the hoist and is designed to lock onto the corner castings of a container. Spreaders come in different types, such as telescopic spreaders, which can adjust their length to handle containers of varying sizes (20ft, 40ft, etc.), and automatic spreaders, which can lock and unlock automatically. The spreader's design ensures that the container is lifted securely and without damage.

5. Wheels and Bogies

For a gantry crane to move along the designated paths at the port or terminal, it is equipped with wheels or bogies. These are mounted on the legs and provide mobility to the entire crane structure. Aicrane rail mounted gantry cranes (RMG) use steel wheels that run on rails, whereas rubber-tired gantry cranes (RTG) use rubber tires that provide flexibility in movement without the need for rail tracks. The wheels are driven by electric or diesel engines, allowing the crane to move from one container stack to another.

6. Control System

The control system is the nerve center of a gantry crane, responsible for coordinating all its movements and operations. Modern gantry cranes use advanced computerized control systems to enhance precision, safety, and efficiency. Operators can control the crane manually from a cab situated on the crane or remotely from a control center. The control system includes features like anti-sway mechanisms, load positioning systems, and collision avoidance technology to ensure smooth and safe operations.

7. Electrical System

The electrical system powers the various motors, control systems, and lighting components of the gantry crane. The system typically includes a power supply, transformers, switchgear, and distribution panels. For rail-mounted gantry cranes, power is often supplied through a busbar system running along the crane's path. In contrast, rubber-tired gantry cranes may be powered by diesel generators or hybrid systems that combine diesel engines with battery power to reduce emissions and fuel consumption.

8. Cabin and Operator Controls

The operator's cabin is an enclosed space where the crane operator controls and monitors all crane operations. It is usually located on one side of the gantry crane, providing a clear view of the working area and container stacks. The cabin is equipped with ergonomic seats, joysticks, control panels, monitors, and communication systems. The operator uses these controls to maneuver the crane, ensuring precise lifting, lowering, and positioning of containers.

9. Anti-Sway System

One of the critical challenges in container handling is the sway of containers while lifting and moving. The anti-sway system is an essential component designed to reduce the sway of the load, ensuring smoother and more accurate operations. This system utilizes sensors, software algorithms, and mechanical devices to counteract the sway motion caused by wind, inertia, or rapid movements. By minimizing sway, the anti-sway system enhances safety, reduces cycle time, and increases overall productivity.

10. Braking System

The braking system is a safety feature that ensures controlled and safe stopping of the crane and its components. There are multiple types of brakes used in gantry cranes, including mechanical brakes, hydraulic brakes, and electromagnetic brakes. These brakes are installed on the wheels, hoists, and trolleys to control their movements precisely. The braking system is designed to provide immediate response during emergency stops and prevent unwanted motion, thereby enhancing safety.

11. End Trucks

End trucks are located at the ends of the bridge and house the wheels or bogies that run on the rails. These trucks are essential for providing lateral movement of the crane along the rails. End trucks are equipped with motors and drive systems that allow the crane to travel across the working area, making it possible to position the crane accurately over the container stack.

12. Support and Stabilization Systems

To ensure stability and safety during operation, gantry cranes are often equipped with support and stabilization systems. These systems include features like outriggers, which provide additional support when lifting heavy loads, and damping systems, which reduce vibrations and shocks. For rail-mounted gantry cranes, rail clamps and storm brakes are used to secure the crane against high winds or during idle periods.

13. Safety and Monitoring Systems

Safety is paramount in container handling operations. Gantry cranes are equipped with various safety and monitoring systems, including load moment indicators, limit switches, overload protection devices, and emergency stop buttons. Additionally, modern cranes may have cameras and sensors installed to provide real-time data on the crane's operation, enhancing situational awareness and preventing accidents.

Conclusion

Gantry cranes for container handling are complex machines that consist of various components working together to ensure safe, efficient, and precise operations. Understanding the main components—such as the bridge, legs, trolley and hoist, spreader, wheels, control systems, and safety devices—helps in appreciating the technology and engineering behind these essential port and terminal assets. Each component plays a critical role in the crane's overall functionality, and together, they form a robust system capable of handling the rigorous demands of modern container handling operations.

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