An innovative and inspectable composite solution for FPSO structural hull repair

Oil & Gas industry is built on steel pillars, the latter begin to rust the day they are built. This observation raises several challenges for the asset integrity and life extension of all offshore units. Thereby, for the ageing FPSOs (>10 years), frequent and costly structural maintenance operations in hazardous environment may be required. While a standard ship can go to dry-dock for “crop and renew” maintenance operations through standard hot works techniques, a permanently moored asset has to be maintained in situ. The challenge is to perform these offshore structural maintenance operations with no production disruption while maximizing safety even for the most stressed areas such as a mid-ship deck plating.
CELLULAR hull reinforcement is the result of more than 10 years of R&D and is mainly focused on repair of local spots, up to 10m². It is designed to both stop corrosion and restore hull structural strength. It is adapted for general or local corrosion and pitted areas. By leveraging the latest adhesive bonding techniques, this innovative technology allows for a highly repeatable installation process. Indeed, installation can be performed regardless of the atmospheric conditions and always the same way. Therefore, the resulting structural performances exhibit high values with low scattering. The outstanding encapsulation system of every single cell shows an incomparably high durability for bonded products. In addition, for a sound and simple Nondestructive test, the regulatory capacity of every independent cell can be proof load tested, either just after installation or during its lifetime. The demonstration that every cell holds more than their design capacity can be therefore provided.
This paper will focus on the powerful characteristics linked to the combination of multiple cells. The Physical tests that are presented could demonstrate successfully the unique macroscopic toughness (unlike classic bonded composite reinforcements) specific to cellular assembly through the redundant cells. CELLULAR assembly combines 2 main technological bricks which are both at TRL7 (technology readiness level). The latest development and the work with Class intended to bring the combined system to TRL5 and shortly to the first commercial applications.
This paper presents the general design approach, including the experimental setup witnessed by Class, and the numerical analyses. CELLULAR assembly can be adapted for a structural repair but also to a heavy-duty fastening point, carrying several dozens of tons of mechanical capacity.