Failure Analysis of Three Spider Lift Boom Arm Fractures

Over the span of 10 months starting in 2020, a three different spider lifts, all of the same manufacturer and type, experienced catastrophic failures of the telescoping boom arms, resulting in serious personal injuries in all three incidents. All three failures occurred at the same location on the boom arm, where the lower end of the uppermost boom arm steel was welded to the connecting boom structure. A number of metallurgical exams were conducted to investigate the condition of the welds and their involvement in the failure. This paper will present analysis of fractures as well as results of metallography, hardness, and alloy testing, as well as other factors related to the root cause analysis.