On 24 August 2012 drilling operations were underway on the Stena Clyde Modu drilling rig in the Australia’s Bass Strait when the drill pipe string became stuck in the hole. Three days later instructions were given to rig up for a wire line operation to sever the stuck pipe in the well. The drill crew was preparing for the downhole cutting and removal of the stuck pipe. While attempting to unscrew the top drive from the drill pipe string, to facilitate the wire line operation, two workers were struck by a manual tong that rotated at speed. Shortly afterwards, the two workers died. After the operator, Stena Drilling (Australia) Pty Ltd, notified NOPSEMA, the regulator & they initiated an investigation, commencing mobilisation of its investigation team.
Preliminary considerations would indicate that the rigging arrangement of the break out tong at the time if the incident was a change from the usual arrangement, apparently arising from the combination of circumstances of the stuck pipe, inclement weather and the resulting heaving motion of the rig. There was no risk assessment completed and investigators are suggesting that one may have been required to cover the change associated with the chosen rigging arrangement including snatch blocks and the tugger winch under the meteorological and ocean conditions. The rig was also fitted with a top drive and integral pipe torque connector. The torque connector could not provide the necessary torque to disconnect the pipe, which led to the decision to use the manual break out tong. The continuing investigation will focus on the factors relating to the understanding of the risks related to this situation of change of equipment failure related to the stored energy combined with the equipment design limits and the impact of the external conditions. How confident are you that when plant fails in your workplace that those operating it understand the risks of rectification?
Article by: Julie Armour – www.WorkingArmour.com.au
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