DIN 15022 Trolley Rail Dimensions & Design Principles
Standard Overview: DIN 15022 — "Cranes — Design Principles for Trolley Rail Dimensions" — specifies the rail section selection, track gauge tolerance, joint treatment, and installation acceptance requirements for trolley rails on bridge and gantry cranes. This standard works in conjunction with DIN 15070 (crane wheel and rail matching) to ensure smooth trolley travel and keep wheel-to-rail contact stress within permissible limits.
The dimensional accuracy of the trolley rail on an overhead crane directly affects travel smoothness and wheel service life — a track gauge deviation of just 5 mm can cause continuous wheel flange rubbing against the rail side (rail gnawing), reducing wheel life by more than 50%. DIN 15022 establishes a complete set of design criteria across four dimensions: rail section selection, straightness, elevation difference, and joint treatment.
Rail Section Selection
Trolley rails use crane-specific square steel sections (A55, A65, A75, A100, A120) or light rails (15 kg/m, 22 kg/m). The rail model is selected based on the maximum wheel load Pmax: Pmax ≤ 50 kN → A55, ≤ 100 kN → A65, ≤ 160 kN → A75, ≤ 250 kN → A100, ≤ 400 kN → A120. The wheel load Pmax must be calculated under the most severe operating condition — the loaded trolley positioned at mid-span during the hoisting instant — where the trolley dead weight, lifting capacity, and the hoisting dynamic load factor φ₂ act together on the wheels to produce the maximum wheel load.
Track Gauge Tolerance and Straightness
DIN 15022 defines track gauge tolerance based on the span S: ±3 mm for S ≤ 15 m, and ±5 mm for S > 15 m. Gauge measurements must be taken with the main girder unloaded (dead weight condition). Over the full rail length, the side straightness (horizontal direction) must be ≤ L/1500, and the top surface straightness (vertical direction) ≤ L/2000. At adjacent rail joints, the top surface elevation difference must be ≤ 1 mm and the lateral offset ≤ 1 mm. Rail joints use a 45° miter cut rather than a square butt joint — the angled joint allows the wheel to transition from an "impact-style crossing" to a "gradual transition," reducing joint impact load by over 70%.
Rail Fixing and Clamping Plates
Trolley rails are secured to the top flange plate of the main girder using clamping plates. DIN 15022 specifies clamping plate spacing: ≤ 700 mm for QU70–QU100 rails, and ≤ 600 mm for QU120 rails. Clamping plate bolts are Grade 8.8 (tensile strength 800 MPa, yield ratio 0.8), with pre-tightening torques of 120 N·m for M16 and 240 N·m for M20. The contact surface between the clamping plate and the rail base must be flat — any unevenness can create localized stress concentrations severe enough to cause fatigue cracking in the rail weld seam. Clamping plate bolts must be re-tightened once 30 days after initial installation to compensate for initial relaxation, and checked every six months thereafter.
| Crane Rail Model | Section Width×Height(mm) | Allowable Wheel load(k N) | clamping plate Spacing(mm) | Track Gauge Tolerance ±3mm(mm) | applicable span |
|---|---|---|---|---|---|
| A55 | 55×55 | ≤50 | 600 | ±3 | ≤15m |
| A75 | 75×75 | ≤160 | 700 | ±3/±5 | Full Range |
| A100 | 100×100 | ≤250 | 700 | ±5 | Full Range |
| A120 | 120×120 | ≤400 | 600 | ±5 | Full Range |
FAQ: Crane Rail Installation, Wear & Maintenance
Q: Should rail joints be welded?
A: DIN 15022 recommends a 45° scarf joint with welding and grinding. Before welding, preheat the joint to 150–200°C and use low-hydrogen electrodes (E5016). After welding, insulate and cool slowly, then grind flush with the rail surface (hardness check: ground surface hardness ≥ 90% of the parent rail material). Welded joints offer 2–3 times the fatigue life of bolted fishplate joints, making them the preferred choice for trolley rails subjected to frequent alternating wheel loads. For expansion joints (spaced every 30–40m on long-span main girders), use a bridging copper busbar connection rather than welding—this allows the rail to expand and contract freely with the main girder during thermal cycling.
Q: When should worn rails be replaced?
A: Replace the rail when vertical wear on the running surface (reduction in rail height) reaches 10% of the original dimension—at this point the section modulus has dropped by roughly 20%, increasing bending stress accordingly. Side wear on the rail head (caused by wheel flange friction) reaching 15% of the head width is also a replacement criterion—this type of wear enlarges the clearance between wheel flanges and the rail, reducing trolley travel stability. For surface indentations or spalling deeper than 2mm on the rail head, build-up welding followed by grinding can restore the profile (repaired hardness must be ≥ HB260). Each repair patch should not exceed 200mm in length, and the total repaired length on a single rail must stay within 5% of the overall rail length.
Q: Is a base plate required under the rail?
A: DIN 15022 specifies that a rubber or steel base plate (3–6mm thick) must be installed between the rail base and the top flange of the main girder. The base plate distributes contact stress evenly and absorbs high-frequency vibrations during trolley travel, preventing fretting corrosion between the rail base and the flange plate. Rubber base plates must be oil-resistant nitrile rubber (NBR) with a Shore A hardness of 70–80. Stagger base plate joints and rail joints by at least 200mm to avoid overlapping stress concentrations.
Q: What if the trolley rail gauge and wheel base don't match?
A: The distance between the inner faces of the wheel flanges should be 8–12mm wider than the rail gauge (rail head width), providing adequate side clearance when the wheels pass through curved rail sections. Insufficient clearance (less than 5mm) causes continuous flange-to-rail contact—commonly known as "rail gnawing." Excessive clearance (over 15mm) leads to excessive lateral sway during trolley travel, compromising positioning accuracy. The most cost-effective adjustment is adding or removing shims between the wheel bearing housing and the end carriage—each 1mm of shim change adjusts the flange clearance by approximately 0.8mm (lever effect). After adjustment, verify the gauge at a minimum of five points along the full rail length (both ends plus the 1/4, 1/2, and 3/4 span positions) using a track gauge before acceptance.
