According to this chart, when must there must be at least a 4,500 pound block used when the boom angle is above 80 degrees? Why?

According to this chart, when must there must be at least a 4,500 pound block used when the boom angle is above 80 degrees? Why?

• A. In all conditions due to stability
• B. To counterbalance operator weight
• C. Wind speeds above 30 mph. The boom can be blown over backwards.
• D. Only during rain

Answer: (C)

Wind loading on a tall crane boom is a major factor in stability, especially when the boom is nearly vertical. As the boom angle climbs above 80 degrees, the boom projects farther from the base and the wind’s push creates a larger overturning moment. To counter that risk, the chart requires adding a substantial ballast—4,500 pounds—when wind speeds reach a level (above 30 mph) that would otherwise push the crane toward tipping. This ballast increases the resisting moment at the base, helping keep the crane stable under windy conditions. It’s not about operator weight, nor is it something you apply for rain alone; it’s a specific safety adjustment tied to wind speed and high boom angles to prevent overturning.