An overhead crane in girder truss design from 1912. You would think they only exist in industrial museums and technology memorials. You would be wrong. The Stühlen Hebe- und Fördertechnik GmbH from Niederzier-Krauthausen, in the area of Düren, has recently equipped such a crane with a new hoist from the Mannheim based hoisting specialist SWF Krantechnik GmbH.

The girder truss crane, that authentically even has bullet holes from wartimes in uncritical places, has until recently been used with the original hoist from 1911. The relatively heavy hoist with its 7 tons dead weight only had one hoisting speed. It was leaking due to its age and spare parts were increasingly difficult to organise. Additionally it was impossible to refit the necessary precision hoist. Therefore the operator of the plant, who produces hefty steel tubes for the production of hydraulic cylinders, decided to order a new hoist.

Used was an electric wire rope hoist NOVA NF as double girder trolley with an ultimate load of 40 tons. The dead weight of the complete trolley is only 3.5 tons and in comparison to its predecessor it offers all the advantages of a modern hoist. The crane is now operated via remote control, up to date frequency inverter technology makes a stepless and therefore gentle moving of the loads possible. The monitoring device NovaMaster has all relevant data about the hoist ready on a display at the control switch.

The track gauge of the trolley was custom-built for the project by SWF Krantechnik, says managing director of Stühlen, Graduate Engineer Achim Schmalstieg. The crane specialists also used a derailment protection on the hoist in order to eliminate the risk of levering out the trolley because of the tilting effect when turning the trundle-heads with their 35 tons. But the precision hoist of the electric wire rope hoist NOVA is adjusted so precisely that the forces of the tilting effect are deflected onto the whole structure even when turning at its slowest. Therefore there is now danger when doing the regular maintenance works at the trundle-heads.

Experienced technicians from Stühlen disassembled the old hoist and assembled the new one within a week and were able to give over the new, old crane for production after inspection and acceptance. The name Stühlen not only stands for crane construction and service, the company also has long years of experience in the steel industry and construction of indoor facilities, in control technology and in special purpose machinery engineering.

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