Vessel collision with fixed structure on wind farm

What happened?

A vessel collided with the working platform on a wind turbine Transition Piece. The incident occurred during worsening weather conditions. The vessel was on DP, when it was decided to pull off. Whilst moving away from the tower, a switch was made from DP to independent joystick control. Once the switch was made, the thrusters returned to zero pitch, effectively leaving the vessel without drive, approximately 120m from the Transition Piece.

The wind was 28 knots. The action of the weather and sea had already started to turn the vessel back towards the Transition Piece. The crew attempted to regain control of the vessel using the joystick. They were ultimately successful in regaining control of the vessel but were unable to prevent two collisions; one between the Transition Piece external working platform and the upper bulkhead of the vessel, and a second between the vessel’s crane platform and the Transition Piece external working platform.

Note: after the incident the vessels DP systems, joystick systems and manual control systems were extensively tested. An additional failure modes and effects analysis (FMEA) test was carried out. All systems were found in good working order without any technical defects.

What went wrong?

The following points were noted:

• The officer of the watch handover procedure was unclear to those involved;
• The decision to change over in a position in close proximity to the Transition Piece was inconsiderate;
• The Master misjudged how the systems would perform during the transition from DP to independent control.

What were the causes?

• Poor judgement of situation by the vessel Master;
• The vessel was already moving against an increasing wind and was still within the wind farm boundary;
• Insufficient awareness of DP system handover procedures and the adverse effects in the actual situation.

What actions were taken?

• Revision of DP operations manual to fully cover changeover procedures;
• Revision of DP familiarisation process to include better verification;
• Introduction of a recordable in field passage planning.

What lessons were learned?

• Full understanding on changeover procedures and relationship between (DP) systems;
• Full understanding of vessels DP systems and verification thereof (no DP system is the same despite naming);
• Bridge resource planning, especially transiting between work areas should be improved.

IMCA seeks to raise awareness of the importance of detailed operational activity planning, both in the offshore renewables sector and in the offshore oil and gas sector. Within an offshore wind farm there are a large number of fixed assets which present a high risk to the navigator. It is considered that detailed planning and care is required to ensure safe operations

Members should refer to Guidance on operational activity planning