Alert 09 – 13 Dropped Drawworks Platform
WHAT HAPPENED:
During the process of lowering the draw-works and support structure to the ground, one of two 35 ton sheaves used in the pulley system failed, causing one side of the draw works structure to fall 3 to 4 meters (10 to 13 feet) to the rig sub base. When the structure collapsed, five employees fell, resulting in major injuries (fractured bones and dislocated shoulder) and first aid cases. Potential was for multiple fatalities. The incident also caused major damage to the substructure and draw-works resulting in the rig being unserviceable. A second shackle had been added to the pulley system sheave used to lower the draw-works. This additional shackle caused misalignment of the sheave with the direction of the load. While lowering the platform, the tension in the pulley system increased forcing the sheave plates apart, releasing the sheave pin and resulting in immediate release of the cable and draw-works.