CHARACTERIZATION OF REFORMER TUBE CREEP DAMAGE BY ULTRASONIC ATTENUATION PATTERN AND MICROSTRUCTURAL CHANGES

Creep damage is a critical degradation mechanism in reformer tubes which experienced prolonged service periods at elevated temperature. Thus, continuous monitoring of creep is vital in ensuring plant integrity. Since creep damage relates to the changes in microstructure, characterization of creep using common ultrasonic attenuation and metallography techniques can be used. This project utilized the attenuation of ultrasonic wave in different tube samples and changes within the microstructure in characterizing the level of creep damage. The study was based on a failed reformer HK-40 catalyst tube by which the tube was cross-sectioned to the thickness corresponding to exposed temperature calculated based on heat transfer formulation. The sample was characterized in terms of ultrasonic wave attenuation, metallography and micro hardness. Results had shown that tube sample which had been exposed to higher temperature produced higher attenuation of ultrasonic wave, significant increase in carbide formation and hardness value while revealing a decrease in grain size than the sample exposed to lower temperature. Based on the results, it is clear that tube sample which had been exposed to higher temperature exhibits the characteristic of creep damage in tertiary stage, while the tube sample exposed to lower temperature are proved to be in secondary stage. In conclusion, creep damage can be evaluated based on ultrasonic wave attenuation and microstructural analysis.