Premature Failure of 200T Crane Hook From a Weld Deposit

Abstract

A crane hook of 200T rated capacity failed suddenly at an indicated load of 143T, while the crane was undergoing a load test. Fracture took place through the intrados of the hook at the region of maximum stress. The jib and other portions suffered subsequent damage following the sudden release of the load. Fracture was wholly of the brittle cleavage type except for a small crescent shaped lip at the top right-hand side. In this zone, fracture occurred at an angle of 45 deg to the general plane of fracture, indicative of failure in shear. Failure of the hook had taken place where a deposit of weld metal had been made, probably to eliminate a surface defect but apparently, without complete removal of the defect down to sound metal prior to welding. On many occasions it is preferable to blend out surface defects by local dressing. The effect of the resulting loss of strength is insignificant compared with the increased chance of failure associated with a weld repair.