OSLO, Norway – Petroleum Safety Authority Norway (PSA) has withdrawn the order it issued recently to COSL Drilling Europe following a fatal accident on the semisubmersible COSLInnovator late last year.
This follows the emergence of new information in the case resulting from dialogue with COSL, and subsequent discussions with the Norwegian Maritime Authority (NMA).
It has become apparent that the regulations have been too vague with regard to the applicable calculation methodology for horizontal wave forces on mobile units.
PSA has therefore 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.
NMA’s requirements for maritime operations normally govern mobile units on the Norwegian continental shelf (NCS), and these refer in turn to the requirements set by a classification society, such as DNV GL.
PSA, NMA, and DNV GL are now working to clarify their requirements to take into account new lessons learnt in connection with the accident. One goal is to develop improved guidelines for calculating the air gap and horizontal wave slamming on semisubmersible facilities.
PSA’s investigation of the fatal accident identified weaknesses in the way calculations of wave forces are applied in the design of mobile units, and these could also impact other facilities on the NCS, it admits.
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