DNV GL Approves Modification for Semi-Submersible Rigs
Following the accident involving COSLInnovator on 30 December 2015, some 100 semi-submersible rigs approved by DNV GL will be reviewed.
Preliminary assessments indicate that a limited number of rigs will be subjected to modifications or operational limitations.
The semi-submersible rig COSLInnovator was drilling for Statoil in the Troll field when it was hit by a large, steep wave. Several windows on the rig's two lower decks were shattered. One person was killed.
“Since the incident, we have made great efforts to identify what happened, understand how this could happen and, most importantly, implement actions to prevent similar incidents from occurring again,” says Ernst Meyer, DNV GL Director for Offshore Classification.
Ernst added: “We have been working with rig owners, designers, operators and authorities towards a common goal; to ensure the safety of all those working on board the rigs.”
The incident investigation report presented by the Norwegian Petroleum Safety Authority in April 2016 concluded that the incident involving COSLInnovator has provided new knowledge that must be utilized in order to prevent similar incidents in the future.
DNV GL therefore published a new technical guideline (OTG-13 – Prediction of air gap for column-stabilised units) as early as in June 2016. This gives a consistent and updated approach for calculating the air gap - the clearance between the highest wave crest and the bottom of the deck box in all relevant sea conditions.
Last week, DNV GL asked all owners of DNV GL-classed semi-submersible rigs to provide updated documentation of each rig's air gap.
