The risk and reliability based fitness-for-services (FFS) assessment addressed in this paper is a quantitative risk assessment (QRA) based FFS study on subsea oil or gas pipelines. The main purpose of QRA is to determine the target reliabilities for different pipeline segments. And then, a structure reliability analysis (SRA) method is used to calculate the maximum safe operating pressure, which indicates the pipeline retaining pressure capacity. It has been revealed that the target reliability or target safety level should reflect the consequences of failure, inspection and monitoring scheme etc. But, in the traditional FFS assessment (e.g. B31G and DNV RP F101), the identification of pipeline target reliability is merely based on qualitative judgments and experience. In this paper, however, a quantitative risk assessment will be performed based on abundant data from pipeline inspection and monitoring records, pipeline environmental impact assessment (EIA) study report, pipeline corrosion study report, pipeline emergency response scheme and anything else which can affect the pipeline failure consequences. An example of pipeline FFS assessment performed at four levels has revealed that the risk and reliability based FFS results have much better consistency to the reality.

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