Site planning, setup, and load charts
Domain 6: Site planning, setup, and load charts
This domain tests crane siting, foundation and clearance planning, and accurate load-chart use. Expect questions on radius, gross load, configuration deductions, and why a chart does not apply.
Core rules
- Site plan: locate the crane to cover the work with the shortest jib and fewest blind lifts; check overhead power lines, underground services, adjacent structures, other cranes, assembly/dismantling space, access, and emergency egress. Define exclusion zones and tie-in locations.
- Foundation: use a geotechnical report and an engineered design. Verify bearing capacity, concrete strength, anchor bolts, ballast, drainage, and that no excavation or trenching occurs near the foundation. The crane base must be level and plumb within tolerance.
- Setup: torque anchor bolts, ground the crane, install lighting and anemometer, test limits, and post the correct load chart. Barricade the base and swing area.
- Load chart: capacity depends on radius, jib length, counterweight, number of falls, hook block, and free-standing/tied condition. Radius is measured from the slewing centre to the centre of gravity of the load. Gross load includes the load, slings, shackles, hook block, and any below-hook device.
- Structural versus stability: the chart is the lower of the two limits. Never interpolate beyond the chart's notes or use a chart for a different configuration.
- Clearances: maintain the limit of approach to power lines and the manufacturer's clearance to structures.
Worked example
A chart for a 60 m jib, two falls, tied configuration shows 2,700 kg at 42 m radius. The load is 2,400 kg, rigging 150 kg, hook block 120 kg: gross = 2,670 kg, so it appears acceptable. But the actual radius is 44 m, where the chart shows 2,550 kg. At 44 m the gross load of 2,670 kg exceeds capacity. Reasoning: radius must be measured to the load CoG at the final position, and gross load must include all attachments. The lift must be re-planned with a shorter radius, lower weight, or different configuration.
Traps that cost marks
- Reading radius from the wrong point or using the hook position.
- Ignoring hook block, slings, and below-hook devices.
- Using a free-standing chart for a tied crane, or vice versa.
- Forgetting that jib length and counterweight change capacity.
- Planning a crane position without checking underground utilities or power-line limits.