How do you read a load chart for a mobile crane to determine allowable load at a given radius and boom length?

• A. Guess the capacity by feel
• B. Use a fixed capacity regardless of radius
• C. The chart is optional
• D. Identify the configuration (boom length and angle), locate the corresponding row/column for the radius, read the rated capacity, and confirm the load weight is within that limit, adjusting for slope or other derating factors as required.

Answer: (D)

Reading a load chart is about matching the crane’s actual setup to the chart’s capacity values. Start with the configuration you’ve chosen: the boom length and the angle that sets your working radius. Locate the intersection on the chart that corresponds to that radius for that boom length, and read the rated capacity shown there. This tells you the maximum safe load under those exact conditions, assuming level ground and standard setup.

Then verify the real load weight against that value. If the ground isn’t level or other factors apply, you must derate the capacity using the chart’s slope/grade and any other applicable derating factors, and only proceed if the load remains within the reduced limit. This approach ensures the lift respects the crane’s stability limits rather than relying on guesswork.