Pick-and-Carry Overload on a Grade and Soft Patch
A 70 t crawler crane is using a 24 m boom to carry a 7.8 t steel coil from the laydown yard to the fabrication shop, a 55 m travel. The static load chart at 12 m radius allows 7.2 t; the pick-and-carry chart for the same boom at 12 m allows 5.4 t. The operator plans to keep the coil 1.2 m above ground, boom at 65°, and swing while travelling to avoid a parked truck. The route crosses a 7% grade for 8 m and a soft patch where the track ruts 150 mm. Wind is 10 m/s gusting 14 m/s; the coil has a 2.2 m2 sail area. A rigger walks beside the load holding a tag line, and a signal person is at the shop door, 20 m away and not in sight of the operator for the last 8 m. The supervisor wants the move done before the 14:00 shift change.
1. Do the load charts support the move? Explain the capacity decision.
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Neither chart supports the move. The static chart allows 7.2 t at 12 m, already below the 7.8 t coil; the pick-and-carry chart is the governing one and allows only 5.4 t. Add rigging and the overload is worse. Travelling with a suspended load is a separate duty with lower ratings, and the 7% grade, soft patch, and swing while travelling are outside the assumptions of a pick-and-carry chart.
Do not 'travel slowly and watch it.' The load is 2.4 t over the pick-and-carry rating, about 44% over. Use a larger crane with a verified pick-and-carry chart, split the coil, or transport it on a trailer or roller. If a pick-and-carry is still planned, get the manufacturer's chart for the actual boom length, counterweight, and track configuration, and have the route surveyed and prepared.
2. Identify the operational hazards and the controls needed if the move were otherwise permitted.
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Hazards:
- Swing while travelling: can side-load the boom and move the centre of gravity outside the track; avoid swing during travel unless the manual permits it.
- 7% grade and 150 mm ruts: exceed typical crawler travel limits and can tip or shift the load.
- Wind 10 m/s gusting 14 m/s with a 2.2 m2 sail: the load may rotate or drift; check the manufacturer's wind limit and load chart notes.
- Signal person out of sight for the last 8 m: loss of signal must stop the move.
- Rigger walking beside the load: struck-by and pinch hazard; use a tag line from outside the track path.
Controls: prepare a level route with mats over the soft patch, remove the parked truck, keep the load as low as practical and restrained with tag lines, use a dedicated signal person with radio and clear view, stop if signal is lost or wind increases, barricade the route, and use a spotter for the grade. If any limit is exceeded, stop.
3. Management insists the move must proceed. What is your response and what safe alternative would you propose?
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Stop and escalate. Tell the supervisor the pick-and-carry chart is exceeded and the route and signal arrangement are not safe. Document the chart values, load weight, and route defects.
Safe alternatives:
- Use a 100 t or larger crane with a verified pick-and-carry capacity above 7.8 t plus rigging at the actual radius.
- Move the coil on a flatbed or roller, then lift at the shop with a crane at a short radius.
- Reduce the coil size or split the lift.
If a crane move is approved, require: manufacturer's pick-and-carry chart, route survey and ground bearing check, grades within the manual, mats over soft spots, no swing while travelling, load low and tagged, dedicated signal person in continuous view, radios, exclusion zone, pre-lift meeting, and a permit. The operator signs the lift plan and stops if conditions change.