FIV Assessment of Piping Systems Using Vibration Screening and Advanced Analysis Methodologies

Abstract Structural vibrations of piping systems due to internal fluid flow are common when the system contains flow domain variations, such as elbows, tee-joints, control valves, small bore connections and reducers. In this paper, the applicability of the Likelihood of Failure (LOF) screening methodology, as proposed by the Energy Institute (EI) guidelines, is investigated for a water injection piping system with complex geometry. The system comprises 16″–18″ piping and a manifold that distributes the flow to seven 6″ risers. The system flow rates were checked against the EI guidelines, resulting in a sub-critical LOF (≤ 0.5). A combination of computational fluid dynamics (CFD) and finite element (FE) analyses in ANSYS Workbench software package is also employed for the assessment of the flow-induced vibrations (FIV) of the piping system, considering 1-way fluid-structure interaction (FSI) effects. The resulting pipe vibrations are post-processed to assess their acceptability in the Velocity RMS – Frequency domain, according to the EI methodology. FIV-induced stresses and fatigue damage are also assessed against structural limits. For both models, the flowrates corresponding to sub-critical conditions (LOF ≤ 0.5) cause vibrations that fall into the problematic zone according to the EI Vibration Assessment methodology, and they result in a low fatigue life. Alternative support configurations are analysed, aiming at rectifying the system response in terms of vibrations and fatigue performance. The results presented in this work indicate that even though the LOF screening is widely used for efficiently assessing the flow capacity of piping systems for safe operation, for systems with complex geometries the LOF screening may not be sufficient to ensure no FIV failures will take place. In such cases it is recommended that the assessment should be complemented with more advanced CFD/FE analyses.