Tower Crane Operation and Load Handling
Operation and Load Handling
This domain tests safe control of the crane under load: pre-use checks, load chart use, radius control, speed and braking, limit devices, wind, communication, and parking. The exam wants the chart method, not a guessed capacity.
Core rules
- Read the chart for the exact configuration: mast length, jib length, counterweight or ballast, trolley position, and any special capacity. Capacity changes with radius; the jib tip is not the rating point.
- Deduct everything below the hook: slings, shackles, spreader beam, and attached devices. Net load plus rigging must not exceed chart capacity at the actual radius.
- Measure radius from the slew center to the load's center of gravity, plumb. If the load swings outward, effective radius increases.
- Use smooth starts and stops. Avoid side pulls, dragging, and shock loading; these produce forces the chart does not cover.
- Test limit switches and brakes before the shift. Never bypass a limit or use a limit as a routine stop.
- Stop for wind, lightning, poor visibility, or loss of communication. Park per manufacturer: trolley position, hook height, brakes, and power isolation.
Worked example
Chart capacity at 40 m radius is 8,000 kg. Load is 7,500 kg; slings and shackles are 300 kg; total is 7,800 kg. That is under 8,000 kg, but the load's center is 41.5 m from the slew center because the hook is not plumb. At 42 m the chart drops to 7,600 kg. Reasoning: the lift is over capacity at the actual radius. Lower the load, reduce radius, or use a larger crane. Do not subtract rigging from the chart; subtract it from capacity.
Traps
- Reading capacity at the jib tip instead of the trolley radius.
- Ignoring rigging weight.
- Using a higher chart for a shorter jib without confirming configuration.
- Treating the anemometer as advisory when the manual sets a stop limit.
- Leaving the crane with the hook near the jib.