The scope

Our client had discovered an integrity problem during a routine inspection of their platform jacket.

After performing a visual ROV inspection, the client’s jacket was found to be covered in a very large quantity of marine growth (over half a meter in some locations). We were asked to perform an analysis of the structure, including extreme wave and wave induced fatigue analyses.

The solution

A model of the jacket was built using survey data, with the appropriate thickness of marine growth on each member modelled individually.  Over 300 different member and coating combinations were analysed in total.

Extreme wave and current load cases were applied to the model and member stresses extracted. The stress utilisation factors of the jacket were calculated to ISO 19902. A wave induced fatigue analysis was also performed using the FEA model with wave occurrence data for the platform. By performing the analysis with and without marine growth, we could find the members whose utilisation and fatigue life were most affected by the marine growth, and determine whether any immediate remedial action was required.

Subsequent analysis was performed assuming continued growth of the marine growth to assess the point in the future at which the levels of marine growth would become dangerous.

The benefits

Our responsive service, with a dedicated lead engineer on the project, ensured the analyses were completed quickly and ahead of schedule.

Our expertise allowed for the application of FEA software which enabled cases to be run efficiently, with a variety of different scenarios investigated. This enabled us to explore several different options for removal of the marine growth, as well as identify suitable timescales for the cleaning operation in order to continue the safe operation of the facility.

This gave the client confidence that the jacket was not under immediate threat, and the client was able to perform cleaning during scheduled maintenance, saving them the cost of mobilising an extra vessel to assist with cleaning operations.

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