IMCA released its Safety Flashes for October, summarizing a case where a topsides started swinging during lifting operations.
The incident
During lifting operations, a topsides connected to pre-tensioned rigging became unstable and prematurely lifted off its substructure. Two rope access technicians were on the substructure at the time of the premature lift and some personnel were on the back deck of the crane vessel when the crane tugger weak links parted.
According to IMCA, the incident had a high potential for multiple fatalities.
Findings
- The crane vessel was on hire to an external contractor responsible for the work, including the engineering;
- The engineering assessment did not fully evaluate the effect of pre-tension and crane tip movements on the post-cut stability of the structure;
- How the crane would react to instability was not well understood.
Lessons learned
- This incident shows how important exhaustive expert verifications are to prevent a lift from going wrong and how significant the consequences could be;
- There is a sensitivity to stability inherent in this form of monopod structure, which will need taking into account in future.
