The paper presents a Probabilistic System Approach for Risk Based Inspection (RBI) of FPSOs. This approach is based on a hierarchical model of the hull and uses Bayesian Probabilistic Networks to propagate probabilities from component level to system level. The system approach makes risk analysis more tractable because consequence analysis, including evaluation of direct and indirect consequences of damages to the constituents of the system, may be developed in an exhaustive and systematic way. This approach is new as consequences of failure and damages are usually considered only in setting crudely acceptable failure probabilities at component level. A model example is given for illustration. The paper gives also some insights regarding the owner and class point of views in terms of RBI. This paper explained also how Risk Based Inspection may be developed within the Class regime.
Floating Production, Storage and Offloading Units (FPSOs) are specific installations regarding their operating conditions and functions in comparison with classic ships. One of these specificities is the lack of opportunity to dry-dock. Operating FPSOs continuously whilst at the same time safely presents therefore a particular challenge which ultimately led to the development of new Inspection, Maintenance and Repair (IMR) procedures to be applied to FPSOs.
This has encouraged major companies and class societies to adopt Risk Based Inspection (RBI) as the most appropriate procedure for IMR planning of FPSOs. As a consequence, the challenge of both parties during the last decade was to develop and implement RBI methodologies which guarantee profitability and competitiveness of FPSOs while ensuring the required structural integrity level throughout the service life.
Bureau Veritas has developed, since the beginning of this period, RBI methodologies which have then been applied to a significant number of offshore units and can also be used within Class regime. Bureau Veritas thus acquired major knowledge and competency in the field of RBI. In parallel, many major' oil companies decided to implement risk based IMR plans to some of their FPSOs.
Advantages and benefits of RBI are first presented. It is shown how RBI may be a key issue to ensure the success of a Structural Integrity Management program for FPSOs. General principles of RBI are then reminded and a new RBI approach based on system considerations is presented: the approach uses a hierarchical representation of the hull and Bayesian Probabilistic Networks (BPNs) to compute at system level the risks associated to any inspection planning. A model example is given as illustration. The last part of the paper reverts on the challenge of the development of system approaches for RBI.
