Extremely mobile — a crane for loads up to 500 tons

The development and production program of Kranbau Köthen GmbH has been described as “anything but standard”. The company, engaged in crane manufacturing since 1934, specialises in sophisticated process cranes that are closely integrated into production systems. Example applications of these cranes are in the steel industry, for which Kranbau Köthen builds slab, charging and foundry cranes.

The cranes often work under adverse environmental conditions such as heat, dirt and high mechanical stresses. A recently built process crane does not have these requirements, but the needs are really unusual and extreme in many respects. It is used in an ABB plant in Sweden that manufactures large transformers — and by ‘large’ they mean really massive: the new transformers, being built at the plant weigh up to 500 tons.

This weight increase from previous transformers weighing up to 300 tons required the investment in a new process crane, and the Kranbau Köthen GmbH was commissioned for its development and production. A special feature had to be taken into account: the centre of gravity of the transformers is distributed very unequally. The crane must adapt accordingly and always ensure a smooth and sensitive lifting and lowering of the heavy load.

Based on these specifications, the Kranbau Köthen engineers developed a process crane with the required lifting capacity and a special heavy-duty shaft end support. It consists of two carriers whose spacing is changed by lead screws. The two attachment points on each carrier are also adjustable so that each of the four winches can be positioned separately. The transformer can therefore always be attached in such a way that the large weight is evenly distributed over all four attachment points. In addition, the entire shaft end support is rotatable, and is suspended on a load-measuring bolt of impressive dimensions.

In addition to its extremely high load-bearing capacity, the crane itself also has some special features. These include three auxiliary strokes, each with a loading capacity of 20 tons, and an extraction system on the trolley travelling winch. The reason for this is that if impurities get into the large transformer during the assembly process, this can have serious consequences for its function. For this reason, ABB produces these plants in a very clean environment and demands that the crane does not generate any abrasion during operation.

Cable must be guided on the crane girder to the 30 m-wide bridge; here a standard energy chain from igus, the E4 4040HD series, has been used. Due to the special design of the chain links with undercut design, the chain is able to absorb high push-pull forces and also provides very good strength to absorb lateral forces. The material the energy chain is made of ensures optimised sliding properties and a very long service life with low abrasion, meeting ABB’s requirements.

The design of energy chains follows a standard process at Kranbau Köthen. “We use a form that contains all the necessary information such as specifications, installation situation and options. This allows igus to design the chain quickly and reliably,” said Tom Kuhnt, the engineer in charge of electrical projects. “In this case, the extras included a double strain relief and a floating moving end, which compensates for any lateral misalignment and wheel clearance in the trolley drive. Kranbau Köthen has already had good experience with this system in other projects.

The company has a well-established relationship with igus. “From our point of view, we have been able to order a complete system that is designed precisely for the individual conditions,” Kuhnt said. The chainflex cables were developed specifically for use in mobile systems, and due to the favourable environmental conditions (normal climate window, no high travel speed), cables with a PVC outer jacket can be used in the ABB process crane. They are more cost-effective than TPE cables and also generate less abrasion than PUR jackets, ensuring the required cleanliness.

The energy chain for the crane trolley is equipped with a floating moving end, which compensates for misalignment over long travels.

The electrical connection between the two shaft end supports, which can be moved towards each other, is also built with energy chains and chainflex cables from igus. The E4 series e-chains are also used here, since the undercut design provides firm grip in lateral acceleration and inclination of the shaft end support. An integrated brake offers very smooth running.

At the rotating joint of the shaft end support, an enclosed triflex R energy chain with twistable cables from the igus chainflex range ensures mobility in the rotary axis. This chain was originally developed by igus for robotics. In the process crane, it protects the cables reliably in the required rotary movement.

Before a crane leaves the site of Kranbau Köthen, a factory acceptance test takes place. Here, the crane is fully evaluated and tested jointly with the customer. This elaborate test is a standard procedure at Köthen and shortens the commissioning time of the crane system for the customer.

Subsequently, the crane was distributed over several flat bed vehicles and transported to Sweden. Part of the route was by sea, so ferry loading of the fragile cargo was inevitable.

The test and final inspection of the process crane at ABB also posed special challenges to those in charge; 625 tons of test weight (corresponding to 125% of the maximum nominal load) had to be provided for the acceptance test. Tests of the emergency stop device at full speed were also part of the test series. At the customer’s plant, the acceptance was carried out thoroughly. “After all, as a globally leading technology company, ABB is also a specialist in the field of crane technology and therefore also a critical and competent customer,” said Maik Stern, Head of Production at Kranbau Köthen.

Image: Still on the ground, the 500-ton process crane in Kranbau Köthen's production facility.