On a crane's load chart, what do the numbers below the bold line indicate?

• A. Rated capacities based on the stability of the crane
• B. Rated capacities based on wind conditions
• C. Rated capacities based on operator experience
• D. Rated capacities based on the length of the boom

Answer: (A)

The numbers under the bold line are the crane’s rated capacities that come from stability requirements for the current setup. They represent the maximum load you can lift safely for the given boom length and radius while the crane remains stable with the configured outriggers, ballast, and balance. The bold line marks the boundary: exceeding it would push the crane into an unstable condition.

Wind, operator experience, or other factors don’t define those specific numbers. Wind is a separate adjustment you’d consider in addition to the chart, and operator skill or judgment affects safe operation, not the chart’s numerical limits themselves. The boom length and radius are part of what the chart uses to determine the stability-based capacity, so the numbers change as those factors change.