Load-Handling Safety and Standards
This domain tests rated capacity, load-chart use, rigging geometry, and stability under real lift conditions.
Load chart basis and deductions
Rated capacity is configuration-specific: boom length, radius, quadrant, counterweight, outrigger spread, and jib state all matter. Read the chart's stated basis. If capacity is gross, deduct the hook block, slings, and any erected jib or attachment; if the chart is net, do not double-deduct. Never interpolate beyond the chart's permitted method, and never use a chart for a different serial number or boom configuration.
Rigging geometry and stability
Sling tension rises as the angle from horizontal decreases. For a two-leg bridle, each leg tension = load divided by (2 times sin of the angle). Use the sling's vertical rating and reduce it for angle and hitch type. Keep the load under the boom tip, check the center of gravity, ground bearing under floats, wind, and power-line clearance. Outrigger floats must be fully extended and blocked per the manufacturer.
Worked example
Chart at 30 ft radius, 60 ft boom: 24,000 lb gross. Deduct 900 lb block, 300 lb rigging, and 1,200 lb erected jib = 21,600 lb allowable load. The pick weighs 18,000 lb, so capacity is acceptable. Two-leg bridle at 60 degrees: each leg tension = 18,000 divided by (2 times 0.866) = 10,393 lb. With 12,000 lb vertical slings, allowable bridle load = 2 times 12,000 times 0.866 = 20,784 lb, so the rigging is also acceptable.
Traps that cost marks
Using boom length instead of radius; ignoring jib and block deductions; assuming a two-leg sling doubles capacity at any angle; checking capacity but not ground pressure or power-line clearance; and accepting a chart that does not match the crane's actual configuration.