crane rail installation specification

Crane Rail Complete Installation Technical Specification for Overhead Bridge Cranes

1. Rail Type Selection for Different Capacity Cranes (P Rail / QU Rail / Square Rail)

P-type railway rails are widely applied on trolleys of medium and small overhead travelling cranes. For large-size cranes, QU-type dedicated crane rails or solid square rails are adopted for trolley and end carriage running tracks.
Before formal installation, full inspection must be carried out on all raw materials including crane rails, fastening bolts and connecting splice plates. Any rail or fitting with cracks, severe corrosion or non-standard dimension must be replaced immediately. Worn running surface and side face of rails can be repaired only when the maximum wear depth is within 3mm, and repaired rails can be put into service after qualified rework.
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2. Base Plate (Pad Iron) Installation Requirements & Tolerance Standard
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Rail base plates need full tight contact between rail bottom surface and crane steel main girder. Each stacked layer shall contain no more than 20 pieces of base plates. Each pad iron length shall exceed 100mm, and the width shall be 10–20mm wider than the rail base width. The center-to-center distance between two base plate groups shall not be larger than 200mm.
All base plates shall be fully and firmly welded onto the steel main girder of the crane. The actual contact area between base plate and rail cross-section shall account for no less than 60% of the nominal contact area, and the local clearance between contact surfaces is controlled within 1mm maximum.
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3. Rail Butt Joint Structure, Clearance & Temperature Expansion Gap Rules
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Crane rail joints can be designed as straight butt joints or 45° inclined scarf joints. Inclined diagonal joints ensure smooth wheel rolling transition when the crane wheel passes the joint position. The conventional reserved joint gap is 1mm to 2mm under normal ambient temperature.
For cold northern areas with winter construction, if the installation temperature is more than 20℃ lower than long-term annual operation temperature, extra thermal expansion gap must be reserved from 4mm to 6mm. In addition, the butt joints of two parallel running rails must be staggered more than 500mm to avoid concentrated stress and wheel impact.
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4. Rail Position Deviation, Gradient, Elevation Tolerance & End Stop Protection
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Fixed end stop baffles shall be installed at both track terminals to effectively block the crane from running off the rails. Strict geometric tolerances are specified as below:
  1. Deviation between actual rail centerline and theoretical geometric centerline ≤3mm
  2. Allowable rail gauge tolerance for overhead bridge crane: ±5mm
  3. Maximum longitudinal longitudinal gradient of single rail: 1/1500
  4. Relative elevation height difference between two parallel rails ≤10mm