How does load weight relate to the crane's load moment capacity and why is balance important?

• A. The crane's rated capacity is fixed and not affected by load weight or CG.
• B. Only weight matters and CG position is not considered when calculating moment.
• C. Load weight and CG determine the required moment; exceeding capacity or imbalance increases tipping risk; maintain center of gravity within the crane's working envelope and use proper rigging.
• D. Imbalance reduces strain on the crane and is acceptable with proper outriggers.

Answer: (C)

Load weight and the load’s center of gravity location together determine the moment the crane must resist. The moment is essentially the load weight times its horizontal distance from the crane’s base, so a heavier load or a larger offset CG creates a larger lifting moment. The crane’s rated capacity isn’t a single fixed number; it changes with how the crane is set up—boom length and angle, radius, outriggers, and where the load’s CG sits within the crane’s working envelope. If the weight or the CG shift makes the required moment approach or exceed what the crane can safely handle, tipping or overstress of the structure becomes a real risk. Keeping the load’s CG within the crane’s working envelope and using proper rigging helps maintain a safe, balanced lift and ensures the load moment stays within safe limits. Rigging also controls the load’s stability and prevents the CG from wandering, which would otherwise compromise balance and safety.