Numéro : 2703 - Year : 2016
Fatigue strength verification of tanker ships converted into offshore units
Karim BARROU, Bureau Veritas (Paris - France)
The principle of converting tankers into floating units for offshore oil production is common practice in the oil industry. It has advantages in terms of cost and construction time, but also presents certain risks for the operator, in particular for fatigue behavior, since these units are operated without production stoppage and do not be hauled into a drydock during their entire on-site operation, making repairs very complicated and expensive.
This is why the regulations of classification societies for Offshore units impose very extensive fatigue calculations.
Bureau Veritas recently received a request to categorize two tanker vessels converted into offshore floating units used in the production and storage of oil.
The thesis will present a general view of the fatigue calculations carried out on these Offshore units.
The method of calculating fatigue is based on a chain of calculations, including hydrodynamic analyzes of the unit's sea behaviour, navigation (before conversion) and on-site (after conversion), structural studies based on the method Finite elements, with different mesh sizes, and finally a sum calculation.