The Petroleum Safety Authority Norway (PSA) has withdrawn a safety order for COSL in the aftermath of a fatal accident, based on new information.
The initial investigation found the COSLInnovator did not have an air gap of 1.5 m between the underside of the lowest deck and the highest wave top. The facility’s superstructure was not sized to withstand horizontal wave loads. It also found the head count system during mustering “did not work satisfactorily”.
It initially ordered COSL to model tests and verify that the COSLInnovator, COSLPromoter and COSLPioneer facilities, following modifications implemented after the incident, comply with the Framework Regulation. It also ordered COSL to get its findings verified by an independent third-party.
COSL said they were unable to detect a design fault and the “type of forces applied from waves are extremely rare and are not reflected in the current regulations for floating rigs”.
However, PSA today repealed the order, because new information “makes it clear that the regulations have been too vague with regard to the applicable calculation methodology for horizontal wave forces on mobile units”.
A company spokesperson said: “The PSA has amended its investigation report to reflect the fact that conditions related to the air gap and horizontal wave slamming did not represent breaches of the regulations at the time of the incident.”
Rune Morten Narvag, 53, was killed when 100ft high waves hit the Troll field on December 30th last year.
The spokesperson added: “The main goal for the PSA’s follow-up of the fatal accident on COSLInnovator has been to establish what happened and why so that the industry and the authorities can learn from the incident and prevent such an accident from recurring.
“Its investigation has identified weaknesses in the way calculations of wave forces are utilised when designing mobile units. These could also apply to other facilities on the NCS. COSL and other companies are working to utilise the new lessons learnt.”