According to this chart, under which wind speeds must there be a 4,500 lb block when the boom angle is above 80 degrees?

• A. Wind speeds above 50 mph
• B. Wind speeds above 30 mph
• C. Any wind
• D. Only during rain

Answer: (B)

When the boom is very high, the load creates a large vertical line of action, and wind adds a sideways push that increases the tipping and swaying tendency. The chart sets a threshold: if wind speeds exceed 30 miles per hour, a 4,500-pound counterweight block must be used to offset that additional lateral moment and keep the crane stable. This counterweight helps balance the forces so the crane remains within safe operating limits, especially with the boom above 80 degrees where the risk is greatest. Winds below 30 mph don’t reach the required instability level, so the block isn’t mandated. The other options don’t fit because they either set the threshold too high, imply the rule applies in all wind conditions, or confuse wind with rain.