Non-destructive examination (NDE) plays an essential role on maintenanceprogrammes to assure operation of industrial plants. Life of radiantcatalyst tubes of reformer units exposed to high pressure and temperature islimited by creep damage. Present inspection techniques offer unreliableresults, removing tubes from service in a very conservative manner oroccurring unexpected tube ruptures.Existing ultrasonic methods rely on the analysis of ultrasonic amplitude ofthe received signal[1]. Due to the material coarse structure, this producesqualitative assessment as well as, in occasions, unreliable results. Toovercome these limitations a multi-interrogation ultrasonic technique andcorrelation of several parameters such as attenuation, energy and tubediameter with material features is devised.This paper describes the principles of the ultrasonic method for creepdamage detection as well as details of the inspection system. After that,results of measurements performed on representative damaged specimens arealso shown, including relationships between ultrasonic and metallurgicalparameters.
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