Flow-induced vibrations (FIV) of subsea piping due to external flow (e.g., vortex-induced vibrations ofpipeline spans) or internal flow (e.g., high velocity multiphase flow in subsea piping) may pose structuralintegrity concerns due to cyclic stressing at critical welds and, over time, a threat of fatigue failure. Assetsin the design stage or in the operating stage which fail a screening based on published guidelines, mayundergo a comprehensive screening based on numerical simulation. This paper gives an overview of sucha screening methodology, based on computational fluid dynamics (CFD), structural finite element analysis(FEA), and associated fluid-structure interaction (FSI).In the context of pipeline span VIV, seabed proximity effects and flow blockage effects may have asignificant effect on the pipeline span response. High-level screenings based on DNV-RP-F105 may notaccount for these effects appropriately and result in overly conservative fatigue life estimates. We presenta couple of application cases where the comprehensive screening makes evident these conservatisms.In the context of FIV (due to internal flow) a high-level screening approach exists as part of the EnergyInstitute (EI) Guidelines on the Avoidance of Vibration Induced Fatigue Failure (AVIFF). However, theEI AVIFF guideline does not provide a framework for the direct estimation of vibration levels, stresslevels, or fatigue life. The comprehensive screening methodology addresses this gap and is illustrated withan application case.Vibration measurements and piping remediation are much more costly subsea than they are on topsides.Hence, advanced simulation techniques are valuable tools in determining the integrity status as well as thesafe operating limits of subsea piping.
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