Prediction Method for Acoustically Induced Vibration of Process Piping Generated by a Restriction Orifice

Abstract Acoustically Induced Vibration (AIV) of the piping system downstream of the restriction orifice (RO) could be a concern when a large amount of gas is released in the blowdown system through an RO. The severity of AIV generated by the pressure reducing devices can be evaluated by utilizing the noise prediction method specified in the IEC standard (IEC 60534-8-3), since it is known that the vibration stress caused by AIV is basically proportional to the sound pressure level at the piping surface. Also, it is expected that the sound pressure level generated by the RO would decrease as the number of holes increases under the same process conditions. However, to the best of the authors’ knowledge, the governing parameter to evaluate the sound pressure reduction effect by a multi-hole orifice plate which is applicable to the IEC standard has not been published. In this study, experimental investigations were conducted to establish a prediction method for acoustic power generated by multi-hole orifices. As a result, the correlation between the number of holes and the valve correction factors for the acoustic efficiency defined in the IEC standard was obtained. It was confirmed that the sound pressure level at the pipe wall could be accurately predicted by using this method. Also, the comparison between the proposed method and the conventional AIV sound power level calculation method by Carucci and Mueller is presented.