10t, 20t, 32t cranes mean very different girders. Fatigue is the only enemy.
Crane girders endure the harshest duty in any plant: thousands of load cycles daily. The design core is not strength — it's fatigue.
By tonnage: below 10t (light duty), rolled-section girders are simple and economical; 10–20t (medium duty) typically uses welded I-girders with a braking structure for horizontal traction; above 32t (heavy duty), the top flange and brake-plate connections need fatigue verification and Class 1 welds.
Three common mistakes: splicing the girder at midspan where bending peaks; rigidly fixing the rail (use clamp plates or hook bolts that allow adjustment); and ignoring the load path of longitudinal braking into the column bracing.
When inquiring, give the full crane configuration at once: tonnage, number of cranes, rail type and duty class (A5/A6). Late additions almost always mean rework.
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