Australia's safety regulator has published details of an incident which saw a dive vessel lose position while diving was active near a platform.
The vessel drifted off location by about 40m and was initially noticed by the diver when his umbilical - connecting him to the vessel and supplying him with breathing air and communications - started to become taut.
The vessel was involved in construction activity and had an "unplanned movement" about 130m from the platform, according to a National Offshore Petroleum Safety and Environmental Management Authority (NOPESMA) report. "The loss of position was caused by a deactivation of the forward/aft automatic positioning function by unintentionally deselecting the 'surge' button on the DP console on the bridge, which then deactivated the 'auto position' mode. The deselection was thought to have occurred by the placement of a notepad on the side of the console."
Once auto position was reactivated the vessel stopped moving and remained in position. The diver had followed his umbilical, moved clear of any obstacles, and walked with the vessel.
An investigation found that the locations of the button was too close to desk space used for completing DP related checklists and logs and were therefore susceptible to accidental activation. Therefore the design of the DP system allowed human error to escalate. Further, because no positive confirmation had been required to confirm deactivation of auto position mode, no alarm to acknowledge deactivation was sounded. Displays showing the DP position and track had also been deactivated, adding to the issues.
The incident report, which doesn't divulge which platform or dive vessel was involved, was published at the same time as an International Marine Contractors Association report on DP incidents.
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