Entry procedures

On a semi-submersible drilling unit, the port-aft column was opened up to allow a team to gain entry for visual inspection of an instrument on the cross-tubular section. Access to this section was via one of the ballast tanks. Since the rig was under tow at the time and had become slightly out of trim, the control room operator started to pump seawater into the port ballast tank. On completion of the inspection and when bolting the access hatch back up, one of the team members noticed that the water level was slowly rising. The team evacuated immediately and the control room was told to cease the ballasting operation. Although a permit to work system was in operation, the control room operator was unaware that the inspection team had passed through the tank to gain access to the cross member. The seawater inlet valves were normally remotely operated from the control room but no mechanical or electrical isolations had been carried out. A full risk assessment had not been done although the inspection team had carried out a toolbox talk. Also in place was a tank entry procedure and bolted plate closure procedure.

The incident highlights the importance of the use of risk assessment and of following correct procedures.