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Processes at a Container Terminal – The How’s and the Why’s

Nowadays, container ships are unloaded and loaded at massive container terminals.

Pavel Iovik, First Container Terminal, CC BY-SA 4.0

Nowadays, container ships are unloaded and loaded at massive container terminals. Container terminals can be defined as the intermediate destination facilities that facilitate container ships to switch their methods of transport. This process can be divided into several sub-processes that are explained below.

Unloading and loading of the ship

When unloading ships in container terminals such as South Asia Gateway Terminals, which can be observed at the Colombo Port, both manned and automated terminals are known to use quay cranes. Primarily, they are manned due to the practical problems encountered during the process such as the inability to position the containers in the required manner. The quay cranes can move trolleys along their arms to transport a container from a ship to the transport vehicle and vice versa. A pick-up device identified as a spreader picks the containers, after which the quay crane moves on rails to place the container on the deck. The loading and unloading plan should be made at the operational level as the number of import containers is only known just before the arrival of a ship. This plan would provide information on where the containers that should be unloaded are located on a ship. The time it takes to unload the containers will depend upon their position within the vessel. Although the unloading process may be flexible, it isn't the case in the loading process. It is vital to ensure that the containers are placed in a good distribution.

Transport of containers

Forklift trucks, reach stackers, yard trucks, and straddle carriers are used to transport containers at a manned terminal. A crane is employed to place a container on a yard truck. Multi-trailer systems are used in order to transport multiple containers at once. Automated Guided Vehicles or AGVs are employed to transport containers at an automated container terminal. These are robot-like vehicles that trail along pre-defined paths. These road systems include electrical wires on the ground that control the AGVs accurately. An AGV has the capacity to handle 60 tonnes at once.

Stacking of containers

There are two ways of storing or stacking containers – storing on a chassis and stacking on the ground. A chassis system makes each container accessible in an individual manner; however, with the stacking system, the containers would be piled up in a way that each container cannot be directly accessed. Due to the restrictions in storage, stacking on the ground is utilized more commonly at container terminals. The stack may be divided into multiple lanes, each of which consists of several rows. Depending on the terminal, the height of a stack may vary between two and eight containers high. At the transfer point at the end of each lane, cranes may take the container off the container-transport vehicle – and vice versa. Here, a material handling equipment will have to be chosen that would serve the purpose of storage and retrieval of the containers from the stack. Yard cranes usually can provide high-density storage and can be automated. These automated cranes are identified as Automated Stacking Cranes or ASCs.

Inter-terminal transport

Containers have to be transported from the stack to various other modes of transportation including rail, barges, and road. It is predicted that inter-terminal transport would have a significant role to play in the industry in the future; thus, new technologies may have to be developed in order to meet the growing demand. Multi-trailers and other automated vehicles will carry out the inter-terminal transport. In some terminals, it would be possible to place containers directly on trains and trucks without the employment of container-transport vehicles.

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