STUDY ON VIBRATION EVALUTION METHOD FOR PIPING STRUCTURE CAUSED BY FLUID FLOW

In the flare piping system, it is known that piping vibrations occur caused by Acoustically Induced Vibration (AIV) and Flow Induced Vibration (FIV) corresponding to high flow rate, high pressure drop and relatively thin pipe wall thickness. For FIV, turbulence generated at combining tee with high fluid velocity results in low frequency piping vibration. For AIV, large noise produced through a component with large pressure drop results in high frequency piping vibration. In this study, an experiment was executed in order to obtain the basic characteristics of flow induced vibration at tee connection downstream. The experiment results showed the dominated vibration is circumferential direction and the dominated vibration source is the turbulence generated at tee connection. In order to evaluate the integrity of the piping system for the tee connection downstream against flow induced vibration, a new evaluation index is investigated based on the experimental results and random vibration theory. As a result, it was confirmed that the new evaluation index tends to be proportional to the shell mode stress of the random vibration. This new evaluation index was also applied to AIV in order to investigate the dominant physical parameter of AIV theoretically. As a result, it was confirmed the pipe diameter would be the dominant physical parameter of AIV in addition to PWL and D/t which are widely known as the dominant parameter of AIV