Crane Load Charts and Lift Planning
Core concepts
Load charts define capacity by boom length, radius, and boom angle, and they are specific to configuration-outriggers versus on tires, counterweight, jib stowed or deployed. Candidates must read the chart correctly: find the radius, then the boom length, then apply deductions for the load block, rigging, and any stowed attachments. Net capacity is chart capacity minus all deductions. Planning also includes ground bearing pressure, power line clearance, and a written lift plan for critical lifts.
Traps to watch
Questions often quote gross capacity and ignore deductions, or use radius measured to the boom tip instead of the load's center. Another trap is interpolating between chart values when the chart says not to, or using an on-tire rating while set on outriggers. Watch for capacity at a longer radius being higher than at a shorter radius in some charts-never assume monotonic decrease without reading the chart. Also beware of confusing boom angle with boom length.
Worked example
A chart shows 12,000 lb at a 20 ft radius for a given boom length. The load block and rigging weigh 1,200 lb. Net capacity is 12,000 − 1,200 = 10,800 lb. Rule of thumb: always deduct everything hanging below the boom tip, and measure radius to the center of the load, not the hook.