Piping design according to international codes to prevent acoustically induced vibration fatigue failures

摘要

Since the issue of pipe fatigue failures caused by acoustically induced vibrations (AIV) was formerly recognized, analyzed and widely documented by Carucci and Muller in 1982, on the basis of their experiences on operating industrial plants, progresses have been made both in the elaboration of more reliable methodologies for risk assessment and in the optimisation of preventive measures. At present, there are two majorly recognised methodologies for AIV risk assessment. First one employs the criteria of Sound Power Level "Limit Curve" versus pipe geometrical parameters and the latter is based on the "Likelihood Of Failure"' criterion, with or without the support of FEM analysis at pipe discontinuity. Other assessment methodologies have been developed taking into account the piping dynamic local stress or the overall piping system modal response and are proficiently practised by various acknowledged companies. Above methodologies are customarily applied by Tecnimont in AIV risk assessment. Additionally this contribution discusses how the combined use of dedicated international codes such as ASME Sec. VIII, enables to carry out piping design, in terms of stress, number of cycles to fatigue failure and appropriate stress concentration factors, both for connections and for supports.