Cranes for Containers Erected Everywhere

Posted : 12/20/12 9:17 AM

Container cranes have become such a critical component for handling cargo that a port’s capacity for moving freight is often measured by the number of cranes it has available for use. They must be housed within a metal framework that allows the crane to move the length of the yard where it will be hoisting cargo. A platform known as a spreader descends from the crane onto a container. There it locks onto the corners through links called corner castings. Normally, cranes lift only one container at a time, though some will lift two, and a few can carry up to four at once. These cranes are classified by size according to the sort of vessels that they can accommodate. A Panamax can unload a ship small enough in size to pass through the Panama Canal. This is about a dozen containers wide. Post Panamax units can reach the width of 18 containers. There is also a Super Post Panamax that can reach across 22 containers. The load capacity for these is generally around 65 tons which permits the lifting of a single 40 foot container or two 20 foot containers. Some models have double this capacity. The entire assemblages can weigh from 800 to 2,000 tons. The crane operator sits in a cab that is set in a trolley unit that rides on rails along the top or the side of the superstructure. Some cranes are powered by diesel engines located on the top of the structure, but most are run electrically in what is known as shore based power. This is considered a more efficient way to operate. The engines often require more than ten thousand volts to operate, and a diesel equivalent is a massive unit to load atop a crane. Cranes have been used since ancient times to help unload ships. The modern cranes we speak of here developed in the 1950’s as containers came into use for carrying cargo. They grew in size as the size of the ships carrying containers grew. They are found wherever container ships dock which means they now are encountered all over the world. Special side lift cranes are sometimes used to arrange the containers along a dock. Often these cranes load containers directly from ships onto waiting trucks or complete this procedure in reverse to load the ship. Without these devices, world trade would drop to a fraction of what it is today.