For a bolt type shackle, as the sling angle changes from in-line to 90° perpendicular to the shackle pin, the rated working load

• A. Increases 50%
• B. Decreases 50%
• C. Remains the same
• D. Increases 100%

Answer: (B)

Shackles are designed to carry load most efficiently when the load is in line with the shackle pin. When the sling is inline, the load path goes straight through the pin and body with minimal bending. As the sling angle moves toward 90 degrees relative to the pin, the load path is no longer straight; this creates a bending moment on the pin and increases the effective stress on the shackle. That extra stress reduces the safe working capacity of the shackle. At a 90-degree angle, this detrimental effect is greatest, so the rated working load is reduced accordingly—about half of what it is when the sling is inline. In practical terms, if you must lift with a 90° angle, you should use a larger shackle or reconfigure the rigging to keep the load more in line to maintain safety.