Power handling
The Portalink ship unloader transfers 600 tons of grain – twice its own weight – to the silo every hour.
Today, over 90 per cent of the world’s trade is moved by sea. The logistical task is nowhere near finished when the ship has reached port safely: the big job of unloading the cargo has to commence immediately. Cars, containers, pallets – all routine. But what happens when the ship’s hold is full of grain?
Sayga Flour Mills, Sudan’s largest mill operator, masters this challenge every day. It would take ten men close to 4,000 days to transfer to the company’s grain silo the 70,000 metric tons of freight that a modern freighter can haul. Thanks to the proven technology of the Switzerland-based Buhler company of Uzwil, this massive volume of grain can be offloaded in no more than five days by just a single worker – at the controls of a powerful machine.
Right into the corners
For over ten years now Buhler, a recognized specialist in food production technology, has been enhancing the entire production chain for Sayga Flour Mills. The most recent addition is the Portalink ship unloader, with an offloading capacity of 600 metric tons of grain per hour. Four support cylinders stabilize the Portalink’s 335 tons of operating weight while it digs deep into its work.
The main hydraulic unit is located above the ship unloader’s slewing ring. A diesel power plant delivering 317 kilowatts of power drives the triple axial piston units, ensuring that the grain is extracted gently from the ship’s hold. From the intake nozzle, the grain passes into the vertical conveyor shaft, forming a dense column of grain that moves steadily upward. When it reaches the level of the boom, the grain is transported via a horizontal chain conveyor to a down tube, which discharges it to the waiting trucks. The speeds of the chain conveyors are infinitely adjustable so that they can be matched perfectly to the product.
But the Portalink needs to make an extra effort if it is to unload every last bit of cargo. So a kick cylinder aligns the vertical conveyor in the kick-in or kick-out position, letting it reach into the corners of the holds and efficiently offload all the grain. All movements are effected with proportional valve technology for smooth, even motions. The grain is thus transported gently to the silo, kernel by kernel.
Amazingly maneuverable
Space and time are scarce and expensive in international ports and that makes it important that the Portalink be just as flexible when its work is done. 16 tires the height of a human being are mounted on eight axles, making this powerful mechanical stevedore – 28 meters tall and 54 meters long – not merely mobile, but surprisingly maneuverable as well. Back in Switzerland, Rexroth had installed in this behemoth a powerful hydrostatic drive to achieve maximum speed of 600 meters per hour.
The hydraulic power unit with its threefold axial piston assembly generates the fluid stream to power the four Hydrotrac transmissions with their constant axial piston motors. The Portalink can also be remotely controlled using a joystick – letting it vacate its quayside slot in no time. And so the Portalink is on its way to the next massive challenge while the first ship is still weighing anchor.
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