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Fatal Diver Incident due to uncontrolled differential pressure

Country: NORWAY - Europe

Location: ONSHORE

Incident Date: 26 January 2016   Time: ---

Type of Activity: Diving, subsea, ROV

Cause: Pressure release

Function: Drilling

What happened?:

The diver was preparing to blind off the torpedo pipe on the rig's pontoon. The torpedo pipe is a 0.45 metre diameter pipe running through the pontoon of the rig to allow for wires used when thrusters to be replaced. The length of the pipe is 13 metres, with one lower valve 1 metre up from the bottom, and one upper valve 1.2 metres from the top of the pipe. The valves were partly open to equalise the pipe.

A safety meeting had been conducted before work started, and this pipe was number 7 to be worked on. The diving was carried following the NORSOK U-103 standard for inshore diving.

What Went Wrong?:

When the diver introduced air into the pipe an artificial undiscovered concrete plug on top of the upper valve broke and the diver's head and left arm were sucked into the pipe causing great pain. The standby diver, being fully dressed, entered the water immediately (within 30 seconds) and the wounded diver was brought to the surface within 9 minutes.

At the time he had stopped breathing but his breathing and pulse were regained through CPR. The diver was sent to hospital where he died 2 days later.

This fatal diving incident was due to uncontrolled differential pressure.

Figure 1. Schematic drawing of worksite.

Corrective Actions and Recommendations:

  • Always look for the unexpected through the risk assessment.
  • Be aware of the high potential in an uncontrolled differential pressure release.
  • Notice should be taken for all similar arrangements on drilling rigs.

Safety Alert number: 275
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