As container ship capacity grows, container ports require increasingly efficient port cranes to unload vessels and move containers in terminal yards.
Container ports depend on two primary types of cranes:
• Ship-to-shore gantry cranes, the workhorses of container ports, which reach out over docked ships to pick up and move cargo to the dock. Also referred to as quay cranes, these cranes range in capacity from 60-85 tons. Ship-to-shore gantry cranes can also pick up and move specialized cargo, such as yachts, military equipment and other specialized non-containerized cargo.
• Container yard cranes, employed to move unloaded containers from the dock and stack them in the yard. Container yard cranes come in two primary types, rubber tired gantry cranes and straddle carriers, each built for a specific type of yard. Typically, rubber tired gantry cranes (RTGs) are used in densified yards. That’s because RTGs have the ability to stack containers five-to-seven wide and six high, to conserve space. Meanwhile, straddle carriers serve less densified yards. While they don’t stack containers as high as RTGs and require narrow aisles to move between stacks, some port operations believe that straddle carriers provide faster service, as they don’t require the assistance of trucks to move containers, as RTGs do.
At ports served by RTG yards, the containers are first loaded on truck trailers before the RTGs move them to the yard. At ports that use straddle carriers, the ship-to-shore gantry cranes place containers directly on the dock. The carrier then straddles the boxes, picks them up and takes them to the yard.
An increasing number of port cranes—ship-to-shore and yard cranes—run on electricity, which reduces energy and maintenance costs compared to diesel-powered cranes. In fact, most ship-to-shores today run on electricity. Konecranes’ regenerative braking systems, incorporated into port cranes, convert kinetic energy from load lowering into electricity that can be used later, thereby reducing energy costs even more.
About 85 percent of RTGs run on diesel, but with the cost of fuel and diesel maintenance, electric-powered RTGs are gaining in popularity. Diesel unit maintenance accounts for roughly 40 percent of overall crane maintenance, so the switch to electric results in significant savings.
For RTG yards considering a move to electric, two options are available:
• A conductor bar system, which has gained significant industry interest but does require an upfront infrastructure investment; and,
• A cable reel system, which costs less but makes movement through the yard a little more difficult, as cranes are attached to long extension cords. Combined with auxiliary diesel engines, operators are able to unplug the cranes and move to another part of the yard to reconnect to electricity.
To learn more about port cranes, contact a Konecranes sales representative.