ASME B30.10: Any hook distortion causing an increase in throat opening of 5 percent , not to exceed 4 inches, shall be?

• A. Repaired
• B. Replaced
• C. Retired
• D. Reused after inspection

Answer: (B)

In ASME B30.10, a hook that is distorted enough to increase its throat opening by 5 percent (up to a maximum of 4 inches) must be replaced. This rule exists because even a small change in the hook’s geometry can significantly affect how the load sits in the throat, how the hook bears the load, and where cracks or residual stresses may concentrate. Once the throat opening has grown beyond this tolerance, the hook’s strength and safety are no longer guaranteed, and repairing or reusing it would not reliably restore its original safety margins.

That’s why replacement is required—repaired or reused hooks cannot be trusted to perform safely, and simply inspecting them after distortion does not make them acceptable for service. Retiring a hook from service without replacing it would also avoid the risk, but the standard prescribes replacement as the proper corrective action for this condition.