Guindaste Pórtico Instalação Guide: Rails, Alignment, and Commissioning
Pórtico cranes are only as good as the track they run on. A 50-ton MG double-girder unidade can be leveled and squared to within a millimeter at the factory, but if the rail foundation is soft or the span is out by 20 mm on site, you will see flange wear, skewed travel, and premature wheel bearing failure within months. This guide covers the practical sequence for installing MH single-girder, MG double-girder, and RMG container pórticos, from rail bed preparation through load testing and commissioning.
1. Prepare the Rail Foundation Before Anything Else
Pórtico grua rails transfer point loads that can exceed 20 tonnes per wheel on an MG 50T unidade. The foundation must be designed for those loads, not for the crane's average weight.
- Concrete grade: Use C30 or higher for rail beams. C25 is acceptable only for light-duty MH cranes under 10T with low duty cycles.
- Embedded plates: Rail clips or welded base plates must be set with anchor bolts at 500–600 mm centers. Verify bolt torque after the concrete has cured for 28 days.
- Drainage: Outdoor RMG and shipbuilding gantry rails need a 1–2% cross fall away from the rail line. Standing water under the rail causes differential settlement within one season.
- Expansion joints: For rail runs over 60 m, leave 4–6 mm gaps at butt joints to allow thermal movement. Welded continuous rail without expansion gaps will buckle in summer heat.
2. Rail Instalação Tolerances That Actually Matter
GB/T 3811 and FEM 1.001 both specify rail tolerances, but the numbers that cause real problems are span, straightness, and elevation difference between the two rails.
Span tolerance
Measure the center-to-center distance between the two rails at five points: both ends, both quarter points, and the middle. For an MG crane with a 20 m span, the allowable deviation is ±10 mm. For spans over 30 m, keep it within ±15 mm. If the span is too wide, the crane will crab; if too narrow, the wheel flanges will bind against the rail head.
Straightness and elevation
- Straightness: Maximum lateral deviation of 10 mm over any 10 m length, and no more than 1/2000 of the total rail length.
- Elevation difference: The two rails must be level with each other within 10 mm over the full travel length. Use a laser level or a water level, not a spirit level on a short straightedge.
- Rail joint steps: Vertical step at a butt joint must not exceed 1 mm. Horizontal step must not exceed 1 mm. File or grind the rail head if needed.
Rail type and fixing
Quenched and tempered rail (QU70, QU80, QU100) is standard for MG and RMG cranes. For light MH cranes, a flat bar rail on a continuous base plate is often sufficient. Use elastic rail clips rather than rigid welds where possible — they absorb shock and simplify future replacement. For RMG container cranes, the rail is usually A75 or A100 with a hardened head.
3. Guindaste Assembly and Wheel Alignment
Assemble the gantry on a flat, hard surface near the rail line. For a double-girder MG crane, bolt the legs to the girder before lifting; do not try to align the legs after the crane is on the rails.
- Wheel alignment: All wheels on one side must be parallel to the rail within 1 mm over the wheel diameter. Use a piano wire or laser to check the wheel centerline against the rail centerline.
- Diagonal measurement: Measure the diagonal distance between opposite wheel centers. The difference between the two diagonals must not exceed 5 mm for a 20 m span. This is the single most important check for preventing skew travel.
- Clearance: Wheel flange clearance to the rail should be 10–20 mm per side for standard rail. Too tight causes friction; too loose causes impact loading.
- Buffer and end stop: Set the end stops so the buffer contacts the stop plate with 20–30 mm of compression remaining. Do not bottom out the buffer.
4. Commissioning: No-Load and Load Tests
Commissioning follows a fixed sequence. Do not skip steps to save time — a skipped no-load test often means a damaged hoist during the load test.
No-load test
- Travel the full length of the rail in both directions at slow speed. Listen for wheel squeal, gearbox noise, or rail joint impact.
- Check that the crane does not skew more than 10 mm from the rail centerline over a 20 m travel.
- Test the hoist up/down limit switches, cross-travel limits, and long-travel limits. Verify the emergency stop.
- Check brake gap and adjust if the brake drags. For Schneider or SEW brake motors, the gap is tipicamente 0.2–0.5 mm.
Load test
- Static test: Lift 125% of rated capacity (e.g., 62.5T for an MG 50T) and hold for 10 minutes. The crane must not drift, and the rail must not deflect permanently.
- Dynamic test: Lift 110% of rated capacity and cycle hoist, cross travel, and long travel for at least 15 minutes. Check motor current against nameplate FLA.
- Deflection: For an MG crane, the maximum deflection under rated load should not exceed 1/800 of the span. For a 20 m span, that is 25 mm.
5. Practical Notes from Export Installations
Most installation problems we see in the field trace back to three things: rail foundation settlement, diagonal misalignment, and brake adjustment. For outdoor RMG cranes in ports, add rail cleaning and anti-corrosion checks to the commissioning checklist. For cold climates, use low-temperature grease in the wheel bearings and gearboxes.
If you are specifying an MH, MG, or RMG gantry crane, confirm the rail span, rail type, and foundation drawing before production. Chunhua Guindaste supplies 81 standard models across overhead, gantry, parking, light lifting, and manipulator categories, with Q345B steel structures and Schneider, Siemens, ABB, or SEW components. We provide CE, EAC, SASO, and SONCAP documentation, a 4-hour quote response, and 30–45 day production. Contato us on WhatsApp at +86 193 9277 7259 or email yuhua0095@gmail.com with your span, capacity, and rail layout for a commissioning-ready package.