Rig contractor COSL has been ordered to improve its safety measures after a 25-tonne lifting frame was dropped on its Pioneer vessel.
The Health and Safety Executive (HSE) said the lifting operation was not properly planned or supervised, resulting in the failure of a lifting sling.
HSE’s inspector also said the permit used for the job “did not accurately describe the work actually being undertaken”.
COSL Pioneer was damaged during the incident.
HSE has set COSL a revised compliance date of September 30.
COSL’s website shows that the semi-submersible rig has been on contract with Nexen Petroleum UK in the North Sea from the first quarter of this year.
It was booked to carry out plugging and abandonment work at the Ettrick and Blackbird fields.
COSL has been contacted for comment.