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Technical GuideCrane Rail and Runway Alignment
How is a crane runway selected and aligned? Crane rail types, fixing methods, span and level tolerances, and the damage a bad runway causes.
Why the runway matters this much
A crane has to follow whatever geometry the runway traces. If the runway isn't true, the crane can't compensate — on every pass the wheels press against the rail, rub and strain.
The result on site is always the same: wheel flanges wear on one side, the crane drifts to one side while travelling, the travel gearboxes draw excess current, and torsional strain builds in the girder. The crane gets replaced but the problem doesn't go away — because the problem was never the crane.
What gets measured
A runway inspection measures four quantities:
Span deviation: how much the distance between the two rail centrelines changes along the runway. Level difference: how much the top of one rail differs from the other at the same cross-section. Straightness: the rail's curvature in plan. Rail tilt: how far the rail leans sideways on its own axis.
In addition, rail joints (gap width and level match), the tightness of the fixing elements, and the condition of the shim plates are also checked.
| Symptom | Likely runway cause |
|---|---|
| Wheel flange wearing on one side | Span deviation or the rail not running straight |
| Crane pulls to one side while travelling | Level difference between the two sides, or a wheel-diameter mismatch |
| Impact noise at rail joints | Excess joint gap or a level mismatch at the joints |
| Travel motor drawing excess current | Increased friction — misalignment or binding |
| Torsion / crack marks on the girder | A continuously strained, misaligned runway |
| Fixing elements keep loosening | Inadequate fixing type or a shim problem |
Rail type and fixing method
A crane rail is a wide-base profile designed to spread the load into the supporting beam beneath it. The DIN 536 series A (A45, A55, A65, A75, A100…) is the most common family. Using square bar stock or ordinary railway rail isn't the right solution outside light, low-class cranes.
There are three common fixing methods. Welding looks the cheapest but makes the rail impossible to remove and creates stress in the beam from heat. Bolted fixing is adjustable but prone to loosening. Elastic clips allow both lateral adjustment and thermal expansion of the rail; they're the preferred method for a permanent runway.
How a bad runway is fixed
It starts with measurement: span, level and straightness are recorded at set intervals along the runway. Deviations go into an alignment report.
The fix depends on the source of the deviation. Lateral drift is usually corrected by loosening the fixing elements and shifting the rail; level differences are corrected with shim plates. If the supporting beam itself has settled, the job is no longer about the rail but the steel structure, and needs a structural assessment.
Measuring the runway before installing a new crane is standard practice. A new crane installed on an unmeasured runway repeats all of the old crane's failures within the first few months.
Technical terms
| Term | What it means |
|---|---|
| Crane rail | The wide-base special rail profile crane wheels run on (e.g. the DIN 536 series A). |
| Rail joint | Where two rail sections meet. A defined gap is left for thermal expansion. |
| Shim plate | A thin plate placed between the rail and the supporting beam to correct a level difference. |
| Elastic clip | An adjustable fixing element that holds the rail laterally while allowing thermal expansion. |
| Flange | The rim on a crane wheel that keeps it on the rail. Its wear is the first sign of misalignment. |
| ISO 12488 | A standards family defining the geometric tolerances of crane runways. |
Frequently asked questions
How often should the runway be measured?
Always before a new installation; after that, visually at periodic inspections, and with a full measurement if there's wheel wear or the crane is drifting. On heavy-duty cranes, regular measurement should be part of the maintenance plan.
Why is welding the rail down a problem?
Welding locks the rail to the beam; thermal expansion then loads the structure as stress, and makes realigning the rail later impossible. Welding heat also leaves unwanted stresses in the supporting beam.
Can I fit a new crane without renewing my old runway?
You can, but it needs to be measured first. If the runway is outside tolerance, the new crane will suffer the same wear and drift problems, and it will also raise warranty disputes.