Diver injured during subsea lifting operations

The incident occurred when two divers were assisting in the installation of an external bell mouth on to its protruding J-tube mounting points at an offshore wind turbine base pile in 23 metres of water. Shortly after the start of the dive it was decided to send down a two tonne dead man anchor (DMA) and a lever hoist. These were required to pull the bell mouth into the correct alignment for fitting. Before the DMA was deployed, the diving supervisor instructed both divers to move in a specific direction to a safe location away from the bell mouth. The divers were also told to look upwards to observe the DMA deployment. Diver 1 initially followed these instructions but he later moved back into the danger zone without direction from the supervisor. Diver 1 was subsequently struck by the DMA as it was lowered by the vessel crane from the surface. Diver 1may also have been pinned to the seabed by the weight of the anchor for a few seconds until it was lifted off him by the crane. The injured diver was treated on-board the vessel and subsequently evacuated to hospital by helicopter. The diver was released from the hospital later the same day and sent home on temporary sick leave.

The incident demonstrates that divers keen to complete their work may be tempted to move into danger zones during the course of subsea lifting operations.

• Immediate causes:
  • Lack of knowledge of the whereabouts and depth of the subsea load during its deployment through the water column.
  • Over-rapid lowering of the load.
  • The subsea load was lowered all the way to the seabed with no appropriate mid-water stop point.
  • The diver was directly below the load as it was being lowered.
  • Poor communication and co-operation between the diving supervisor and the divers.
  • Owing to misunderstanding, diver 1 failed to follow the instructions of the diving supervisor.
  • The diving supervisor failed to realise or notice that the diver had moved back into the danger zone.
• Root causes:
• Inadequate hazard identification and risk assessment.
• No common toolbox talk held before the start of the operation.
• No lift plan or safe working procedure for deploying the load whilst divers were in the water.
• Reliance on the diver following instructions; failure to take sufficient account of human factors leading to errors (mistakes and violations).
• Complacency – the operation was perceived as being a simple, familiar and repetitive task, and personnel may have been operating within a ‘comfort zone’.