A fatal accident on COSLInnovator cast a long shadow over 2016. The response has aimed to apply lessons learnt in order to prevent similar incidents in the future.
Boosting rig safety
One person was killed and four others injured when a wave hit the semi-submersible on 30 December 2015. A number of windows on the lowest two decks of the living quarters were smashed.
This incident was the first fatal accident in the PSA’s area of responsibility since 2009.
The PSA launched an investigation immediately after the event to identify its causes. This work aimed primarily at learning lessons and thereby avoiding a recurrence.
Weaknesses were identified in the way the industry had calculated wave forces. This meant the superstructure with windows was not dimensioned to withstand horizontal wave loads.
Classification society DNV GL subsequently started work in cooperation with the PSA and the Norwegian Maritime Authority (NMA) on clarifying the way such calculations should be performed.
DNV GL issued two new guidelines in October – one on how to calculate wave heights for semi-submersibles, and the other on the design loads for such units in relation to these heights.
All owners with rigs classed by the society are required to submit new wave-height analyses. If these show that a 100-year wave could strike the topsides, compensatory measures must be taken – such as welding windows and openings shut.
The PSA has sent an identically worded letter to the industry which urges the companies to apply the new guidelines regardless of flag state and classification society.
Both the NMA (as the flag state regulator) and the PSA have authority over Norwegian-registered mobile units on the NCS.
In practice, the NMA follows up design and maritime systems on rigs flying the Norwegian flag, while the PSA handles units registered in other countries. This work is based on the NMA’s regulations and the DNV GL guidelines.