crane rails & wheels
Rails and Wheels of Lifting Machinery: Installation Standards, Selection and Scrapping Guide
1. Crane Rails
A crane rail is a running track paved with steel rails. It mainly provides a specified travelling path for the crane and transmits wheel pressure to the foundation. The rail shall be installed firmly without horizontal or longitudinal displacement and allow easy adjustment.
Core requirements: All metal fasteners shall be free of cracks, loosening and corrosion. Any cracked components must be replaced immediately, and other defects shall be rectified in a timely manner.
1.1 Rail Selection and Technical Parameters
- P-type Rail: Commonly used for the trolley and crab rails of small- and medium-tonnage cranes and is one of the mainstream options at present.
- QU-type Rail: Special heavy-duty rail dedicated for cranes, mainly applied to heavy-load working conditions such as large-tonnage gantry cranes and container gantry cranes. Common models include QU70, QU80, QU100 and QU120.
| Model | Theoretical Weight (kg/m) | Typical Application |
|---|---|---|
| QU70 | 52.77 | Medium to large cranes |
| QU80 | 64.41 | Large gantry cranes |
| QU100 | 89.05 | Heavy-duty & large-tonnage cranes |
| QU120 | 118.50 | Extra-heavy duty cranes |
- Standard length: Normally 9m to 12.5m, customized lengths are available on request.
- Material and performance: Common steel grades include U71Mn, U75V, etc. Alloy elements such as Manganese (Mn), Chromium (Cr) and Vanadium (V) are added to improve strength, toughness and wear resistance. For example, the tensile strength of U75V is no less than 980 N/mm².
- Marking: Raised marks are stamped on the rail web every about 4 meters, including manufacturer, model, steel grade, production date and other information for traceability and management.
1.2 Allowable Installation Deviations of Rails
Concrete Structure Rail
- Center line position deviation: within ±5mm
- Top elevation deviation: within ±5mm
- Center distance deviation between two rails:
- Crane span ≤ 10m: ±5mm
- Crane span ＞ 10m: ±[5 + 0.25 × (Span S – 10)] mm (S in meters)
- Elevation difference between two rails at the same cross section: ≤ 10mm
Steel Beam Structure Rail
- Center line deviation of crane beam relative to design axis: ≤ 5mm
- Rail center line offset: ≤ 1/2 of the crane beam web thickness
- Center distance deviation between two rails: ≤ 3mm
- Top elevation difference:
- At support points: ≤ 10mm
- At other positions: ≤ 15mm
- Lateral displacement and height difference of adjacent rail ends: both ≤ 1mm
2. Crane Wheels
2.1 Wheel Scrapping Standards
- Surface cracks or other defects that affect service performance.
- Flange thickness wear reaches 50% of the original thickness.
- Flange bending deformation reaches 20% of the original thickness.
- Tread thickness wear reaches 15% of the original thickness.
- Out-of-roundness exceeds the limit:
- Operating speed ＜ 50m/min: roundness ≥ 1mm
- Operating speed ≥ 50m/min: roundness ≥ 0.1mm
2.2 Characteristics and Causes of Wheel Rail Biting
Characteristics of Rail Biting
- Bright friction marks on the rail side, with burrs in severe cases.
- Bright wear spots appear on the inner side of the wheel flange and the rail top surface.
- Obvious gap variation between wheel flange and rail within a short traveling distance.
- Crane deflection and twisting during operation, especially when starting and stopping.
Main Causes
- Substandard rail installation accuracy.
- Inconsistent motor speed and unsynchronized startup of separately driven mechanisms.
- Inconsistent diameter of driving wheels or excessive wheel installation deviation.
- Deformation of the metal structure.
3. Summary of Parameters for Typical Crane Rails
Proper rail selection (QU-type rail for heavy load), precise installation and regular wheel inspection form the three key elements to ensure the safe and efficient operation of lifting machinery.
It is necessary to control installation deviations in accordance with relevant standards, select suitable rails according to working conditions, strictly implement wheel scrapping regulations, and timely troubleshoot abnormal phenomena such as rail biting. This can effectively prevent accidents and ensure safe and stable operation.
