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EFI Global was hired to investigate the cause of a collapse of a water drill rig derrick, and using metallurgical analysis, determine if the cause was due to a manufacturing defect of the derrick structure components.
EFI Global was hired to investigate the cause of a collapse of a water drill rig derrick, and using metallurgical analysis, determine if the cause was due to a manufacturing defect of the derrick structure components. The derrick itself was built by the insured and the derrick structure was reportedly designed by another company. After investigating the collapsed drill rig mast and trailer, our experts also reviewed the events in the field immediately preceding the collapse and the demobilization procedures for the drill rig. From the visual nondestructive examination, it appeared that the failure initiated within the left shoe and tubing interface materials, with the fracture face indicating a sudden failure. The failure in the material can be associated with the weld process or the joining preparation of the shoe and tubing. The joining process was more suspect because of the gap present at one corner of the internal tubing and shoe interface that existed prior to failure. The tubing sits at an angle against the shoe base. The welding process also could not be eliminated as causation without performing destructive testing. The steel tubing material can be compromised due to the welding process. The properties of the steel in the heat affected zone (HAZ) could be altered, leading to reduced tensile properties. Laboratory analysis of the shoes from the broken mast, the feet from the hydraulic cylinders and the hydraulic cylinders indicated that failure occurred due to insufficient weld quality. Our experts’ conclusions ultimately lead the client to perform inspections throughout its rig fleet on similar models.