A finite element modal analysis approach to assess piping failures due to Acoustically Induced Vibration

摘要

Undertaking a screening study to identify the susceptibility of piping to failures due to Acoustically Induced Vibration (AIV) is a well established approach; however, for existing plant or where the design is mature, making significant changes can be prohibitively expensive. This paper describes a finite element approach to provide a fatigue life assessment for piping identified as being at risk from AIV. Due to the computational restrictions of assessing pipework over a large frequency range, a modal analysis method coupled with a stress-life approach has been adopted. The paper describes the finite element based approach including key assumptions and limitations. It also presents two case studies, the first which shows a good correlation between the actual and predicted life of a reported fatigue failure of a small bore branch on a flare header, and the second defining suitable remedial modifications to an existing flare header that had been identified as having a high likelihood of failure (LOF) by a retrospective screening study.