Description of Incident
During pulling of the Lower Marine Riser Package (LMRP) assembly, crewmen were working on the spider platform removing the eight riser flange bolts from the telescopic joint (“TJ”) when the incident occurred. The process involved the use of a hydraulically operated riser torque wrench (“wrench”) to break the bolts and raise them up to the retaining insert. The 330lb wrench is suspended via a spring compensator from an overhead utility winch assembly controlled by a wireless remote unit at the drill floor. The winch is used to position the wrench in proximity of the bolts, and the compensator then allows the crewman to manually manipulate the wrench on and off the bolts.
While raising the sixth bolt, one of four on an inner bolt circle, the bolt was unscrewed until the upper section of the wrench motor contacted the larger diameter portion of the TJ. This caused the wrench to become stuck against the body of the TJ, where its diameter increases to accommodate the inner barrel. When the wrench operator and assistant were unable to manually remove the wrench, they gave signals to the nearby winch operator to raise up on the winch, in an attempt to free the wrench from its stuck position. As the wrench operator continued manual attempts to release the stuck wrench and while leaning over it, the wrench suddenly became free, elevating the wrench and the operator rapidly as stored tension in the winch rig-up was released.
This resulted in fatal injuries to the wrench operator.
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