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The Lift Plan That Grew a Load

CSCS Slinger/Signaller · Put your knowledge to work in context.

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The Lift Plan That Grew a Load

You are the signaller on a planned lift of a 4.5 t air-handling unit onto a roof. The lift plan specifies a 30 m radius, a 12 t crane, and a two-leg sling at 60° included angle. On the day, the unit has been fitted with additional ductwork and now weighs 5.6 t, and the crane has had to move 4 m further back because a delivery lorry is parked in the planned position. The new radius gives an SWL of 6.5 t. The wind has risen and the roof edge has no edge protection. The crane driver asks you to 'just get it up there' before the wind gets worse.

1. Assess the changed conditions against the original lift plan and decide whether to proceed.

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What has changed:

  1. Load mass: 4.5 t → 5.6 t (+24%). The sling and rigging were selected for 4.5 t.
  2. Radius: +4 m. The crane's SWL at the new radius is 6.5 t.
  3. Wind: rising, with an unguarded roof edge.

Capacity check: 5.6 t against 6.5 t SWL = 86% of capacity, leaving only 0.9 t margin for dynamic effects, wind, and the offset/sling angle. That is not adequate margin for a roof lift in rising wind.

Sling check: At 60° included angle, leg tension = (5.6/2)/cos30° = 2.8/0.866 = 3.23 t per leg. If the slings were rated for the original 4.5 t (leg tension 2.6 t), they may now be overloaded - the rating must be rechecked against 3.23 t.

Conclusion: The lift plan is invalid. Every one of the three variables that govern safety has moved in the wrong direction. Do not proceed.

2. Explain the planning and coordination failures and set out the correct sequence to resume.

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Failures:

  • The lift plan was not revisited when the load changed - a material change to the load requires re-planning by the competent/appointed person.
  • Site coordination failed: a lorry was allowed to occupy the planned crane position, forcing a radius change without re-assessment.
  • Wind and edge protection were not addressed; an unguarded roof edge is a fall and dropped-object hazard.
  • Pressure to 'just get it up' is exactly the condition in which lift plans are abandoned - the signaller's role is to hold the line.

Correct sequence to resume:

  1. Stop - no lift until re-planned.
  2. Confirm the true mass of the modified unit (weigh or obtain verified figure).
  3. Re-plan for the actual radius and mass: possibly a larger crane, a closer position (move the lorry), or a reduced load.
  4. Re-select rigging for the new load and angle; verify SWL of slings and shackles.
  5. Install edge protection and control the roof edge; exclude people below.
  6. Check wind against the crane's and load's limits; wait if marginal.
  7. Re-brief the whole team and the driver; only then lift, with tag lines and a single signaller.