Acoustic induced vibration assessment on process piping using coupled acoustical/mechanical finite element approach: improvement of existing method on branch

Abstract

Acoustic-Induced Vibration (AIV) refers to the high acoustic energy generated by pressure-reducing devices that excite pipe shell vibration modes, producing excessive dynamic stress. Analysis of this risk is an important part of Asset Integrity Management systems as AIV can cause catastrophic piping failure. Existing guidelines address this risk through an analytical assessment. However, these methodologies are not fully known and input parameters are limited. Some limits to the guidelines are pointed out with recommendations to improve them. The numerical approach presented for under-standing main phenomena that may lead to a fatigue failure due to AIV is based on a dynamic stress evaluation at pipe discontinuities (welded connections). This evaluation is performed through a one-way fluid-structure coupling Finite Element Analysis. Pressure fluctuations inside the pipe are predicted and coupled with a pipe structural analysis in order to determine the dynamic stress levels. Considering a random fatigue analysis, fatigue damage can be computed and several configurations were compared. This method was used to highlight the influence of branch thickness on branch connection fatigue integrity. In fact, this parameter is not taken into account in existing assessment methodology but may have an unneglectable influence on fatigue life of the connection. The results are in accordance with the fact that a failure is likely to occur within few minutes in a high sound power level area. This first result gives confidence in the fact that this finite element approach is consistent with energy institute guidelines and can be used to compare different geometries or mitigations