While transferring materials from the pipe deck to the drill floor on the Statoil-operated installation in the North Sea, the boom dropped 10 metres without warning to the pipe deck after a steel rope failed. The boom weighed about 14.4 tonnes.
The horizontal to vertical (HTV) Eagle crane is used, as its designation suggests, to lift drill pipe from a horizontal position on the pipe deck catwalk to a vertical position on the drill floor.
Two people had adjusted the gripper on the crane’s gripper yoke down on the pipe deck immediately before the incident.
Actual and potential consequences
The actual consequence of the crane boom falling onto the pipe deck was substantial material damage to the crane and to the cable tray for the traverse crane on this deck. In addition, the incident caused a halt to activity on Gullfaks B.
No personnel were injured in the incident.
Under slightly different circumstances, the incident could have caused serious personal injuries or loss of human life. In other circumstances, it could have given rise to even greater material damage.
Direct and underlying causes
The direct cause of the boom falling to the pipe deck was fatigue in the steel rope. The underlying cause was weaknesses in the design of the crane’s hoisting system, which gave rise to wear and fatigue in the rope over time. Fatigue in the steel rope was not assessed as a relevant problem for this design.
Nonconformities from the regulations
The investigation has identified several nonconformities from the regulations.
- Risk assessment of equipment – inadequate identification of risk.
- Investigation of and improvement measures following earlier incidents – inadequate identification, investigation and follow-up of previous hazards and accidents.
- Utilisation of expertise – insufficient use of mechanical handling expertise when specifying crane requirements.
- Responsibility for acceptance and operation of equipment – inadequate follow-up and checks when taking delivery of and operating machinery and equipment.
- Maintenance – deficiencies in the maintenance programme for the steel rope.
Statoil has been asked to explain to the PSA by 20 September 2017 how it intends to deal with these nonconformities.