At a steel plant in North Rhine-Westphalia, HSOS completed a three-week on-site machining campaign on multiple crane runway end girders – with material removal depths up to 50 mm, overhead work positions and fully mechanical machine fixation.
Background
Crane runway girders in heavy industry are subject to high cyclic loads. At a steel plant in NRW, several crane runway end girders were newly fabricated; the bearing surfaces, produced as flame-cut parts, were outside permissible flatness tolerances due to manufacturing inaccuracy. Uneven contact surfaces cause point loads, vibration-induced fatigue and accelerated rail wear. HSOS Industrial Services was commissioned to machine the surfaces to specification on site – without removing the girders from their installed position.
Scope of Work
Over three weeks, the following operations were carried out on multiple end girders:
- Face milling of bearing surfaces with material removal of up to 50 mm – necessitated by the manufacturing inaccuracy of the flame-cut parts
- Milling of a rectangular aperture measuring 330 × 180 × 200 mm with an internal corner radius of 5 mm – the most demanding milling task of the project
- Overhead machining on several girders, placing particular demands on machine rigidity, vibration control and swarf management
Key Technical Challenge: No Welding Allowed
Fixing the milling machine without welding was a defining constraint of this project. Adjacent components had already been finish-coated or were not suitable for thermal loading, ruling out the conventional approach of welding machine rails directly to the structure. The unit was secured entirely by mechanical clamping systems. This method requires careful alignment of the linear guides and ongoing verification of clamping forces, but leaves the parent material thermally unaffected and allows removal without any trace.
Results and Quality Assurance
All bearing surfaces were machined to the specified flatness tolerances and dimensionally verified on completion. The rectangular aperture, measuring 330 × 180 × 200 mm, was produced with the required 5 mm internal corner radius to limit stress concentration in the girder section. Pre- and post-machining measurement records were handed over to the plant operator.
Conclusion
This project demonstrates that on-site milling can handle substantial material removal – up to 50 mm per pass – in challenging geometries including overhead positions, with no need to dismantle or transport the girders. For the operator, the result is a defined, contained shutdown period and a fully documented dimensional restoration.