According to ASME B30.9, if the angle of choke is less than 30 degrees, the reduction in wire rope sling strength could be as much as:

• A. 25%
• B. 49%
• C. 60%
• D. 75%

Answer: (B)

When a load is lifted with a wire rope sling that has two legs, the angle between those legs (the choke angle) determines how much each leg has to work to hold the load. The smaller that angle, the more load each leg must carry, and the overall capacity of the sling is reduced. ASME B30.9 provides a chart that shows this effect, and for a choke angle under 30 degrees, the reduction in sling strength can be as much as 49%. In other words, the effective capacity can drop by about half compared with a straight vertical lift. Because of this significant reduction, you’d want to rework the rigging—use a larger sling, add a spreader bar to increase the angle, or choose a different lifting method—to stay within safe limits.