Research on creep damage detection in reformer tubes by ultrasonic testing

Non-destructive examination plays an essential role in maintenance programm es to assure operation of industrial plants. Life of radiant catalyst tubes of reformer units exposed to high pressure and temperature is limited by c reep damage. Present inspection techniques offer unreliable results, removi ng tubes from service in a very conservative manner or occurring unexpected tube ruptures. Existing ultrasonic methods rely on the analysis of ultraso nic amplitude of the received signal((1)). Due to the material coarse struc ture, this produces qualitative assessment as well as, on occasions, unreli able results. To overcome these limitations, a multi-interrogation ultrason ic technique and correlation of several parameters such as attenuation, ene rgy and tube diameter with material features is devised. This paper describ es the principles of the ultrasonic method for creep, damage detection as w ell as details of the inspection system. Results of measurements performed on representative damaged specimens are also shown, including relationships between ultrasonic and metallurgical parameters.