Making light work of heavy loads |
Demag cranes handle large rollers and paper rolls
Regardless of whether they are used for handling rollers or rolls of paper, the cranes supplied by Demag Cranes & Components also make light work of heavy loads at W. Hamburger AG. The Austrian paper manufacturer uses the fast cranes around the clock for maintenance purposes as well as for transporting and storing product.
W. Hamburger AG manufactures high-quality corrugated cardboard base papers using recycled paper. The company invested some Euros 70 million in the conversion of Paper Machine No. 4 (PM4) at its plant at Pitten in Lower Austria, above all to improve quality and increase productivity. Since the new PM4, which entered service at the beginning of February 2004, operates with heavy production rollers and presses and is used to produce larger and heavier master rolls, a transport and handling system was needed with higher load capacities than ever before.
In the production area, Hamburger decided in favour of three double-girder overhead travelling cranes from Demag Cranes & Components. One of them, fitted with three open-winch crabs each with a load capacity of 45 tonnes, is only used for repairs. With its three hoists, it assists in removal of the rollers weighing up to 41 tonnes from the PM4. Due the various steps necessary to complete these operations, in which the crane also has to turn rollers, Hamburger occasionally needs all three open winches and sometimes only one of the crabs.
The second double-girder overhead travelling crane operating in the production line has two open winch crabs that feature infinitely variable lifting and lowering motions with load capacities of 37 and 12.5 tonnes. It is used around the clock in three-shift operation, 350 days per year at intervals of some 30 minutes. Hamburger uses its main hoist unit for handling the master rolls, the auxiliary hoist for maintenance work. The third crane is responsible for handling operations in the roller store. It is fitted with two rope hoists for handling loads weighing 45 and 6.3 tonnes. All three cranes have a span of 18.3 metres, travel on the same runway and are fitted with radio remote control systems.
The 37/12.5-tonne crane picks up the master roll coming from the paper machine and transports it to the roll cutting machine. Here, the paper is cut into several smaller rolls with various diameters for specific customer orders. The rolls are then transported to the roll storage bay on a conveyor system. Both double-girder overhead travelling cranes operating in the store pick up the paper rolls automatically using their vacuum lifting devices and store them vertically as specified by the warehouse management system, which was also supplied by Demag. The vacuum lifting devices are fitted with a guide pin that enters the sleeve of the relevant roll and centres the suction head on it. The air is then evacuated from the roll, enabling it to be lifted by the vacuum lifting device. A mechanical gripper would have needed more space. Rolls requested for retrieval are removed by the cranes and placed on a retrieval belt.
The roll store was planned as an automatic crane store from the very beginning. This was helped by the fact that Hamburger saw the efficiency of this solution when the company visited reference sites. The crane store, in comparison to its storage capacity, requires only a small footprint area. This enables Hamburger to achieve a storage capacity of 16,000 tonnes of paper in an area measuring 3,000 square metres. Sorted by diameters, the rolls are stacked up to a height of 14 metres.
In this area, Hamburger decided in favour of two automatic double-girder overhead travelling cranes, which each have a load capacity of five tonnes and a span of 30.5 metres. If the company had used forklifts, the stacks would have to be much lower in height. In contrast to forklifts, the cranes also always have fast access to all paper rolls, despite the fact that they are stored in dense blocks. The system achieves the required figure of 35 combined storage and retrieval operations per hour, and even 70 at peak periods. And whereas the cranes save space by being installed above the storage area, forklifts need clear lanes to operate in. Forklift truck operation would also risk damaging the edges of the rolls. By way of contrast, the cranes pick them up gently using the vacuum lifting devices. Furthermore, load guidance without any sway facilitates exact positioning. This satisfies one of the requirements for the stability of the stacked rolls.
Planning of the automatic paper roll store was conducted direct between Hamburger and the head office of Demag Cranes & Components in Wetter/Ruhr. Hamburger decided in favour of this supplier since it satisfies the demanding requirements to be met for the cranes and because it was able to offer a complete logistics solution from one source, including the control system. High availability of the cranes was also very important. Above all due to the 30-minute cycle time for the production crane, 99.9 per cent availability is required around the clock, 365 per year. For this reason, a full-service and an on-call standby agreement was concluded for all cranes.
