Inspection of carburization and ovalness in ethylene cracking tubes by using a semi-robot

Carburization and creep are the main causes of failure in the heat resistant tubes of ethylene cracking furnaces leading to a decrease in ductility and embrittlement of the cracking tubes. The aim of present study was to develop a semi-robot for inspection and classification of the carburized zones in heat resistant tubes. Regarding the magnetic characteristics of the formed matrix in carburized zones, the carburization sensors were successfully employed for examination of the carburized layers. The comparison between data acquired via this sensor-based method and those obtained from chemical etching implied a high enough compatibility and appropriate accuracy of the sensor-based measurements. This feasible analyzing method was effectively utilized in a semi-robot that moves on surface of the tubes and establishes a carburization profile. Finally, these carburization profiles together with ovalness graphs were employed for assessment of the points susceptible to embrittlement and failure in petrochemical industries.

► Developing a semi-robot for inspection of carburization/ovalness in cracking tubes.
► A linear correlation between carburized percent and sensor voltage.
► Appropriate reproducibility and comparability of carburization sensors.
► Low tolerance of ovalness sensors with an error less than 1%.