Journal of Nondestructive Evaluation

, Volume 31, Issue 4, pp 349–356 | Cite as

Development of an Eddy Current Inspection Technique with Surface Magnetization to Evaluate the Carburization Thickness of Ethylene Pyrolysis Furnace Tubes

  • Katsunobu Hasegawa
  • Toshiyuki Oikawa
  • Naoya Kasai


An eddy current inspection system that incorporates a C-core probe and a direct current magnetizer for HP-grade ethylene pyrolysis tubes was developed to estimate the degree of carburization of the tubes. Through the development process, the characteristics of the BH curves and the electric conductivities of service-aged tubes were clarified, and a method of counteracting the external magnetism of the tube, which disturbs the accurate detection of the degree of tube carburization, by installing a direct current magnetizer was validated. The influence of tube external magnetism in the oxide/nitride layer was properly canceled by installing a magnetizer with a magnetizing current of 0.5 A on the external surface of the tube. In addition, a calibration curve correlating the carburization depth from the external surface of the tube with the normalized inductance was obtained by finite element analysis simulation. The calibration curve revealed that the degree of carburization could be quantitatively evaluated from the detected normalized inductance of service-aged tubes using the developed inspection system.


Eddy current inspection Ethylene pyrolysis tube Carburization C-core probe Finite element analysis 


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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • Katsunobu Hasegawa
    • 1
  • Toshiyuki Oikawa
    • 2
  • Naoya Kasai
    • 2
  1. 1.Idemitsu Engineering Co., Ltd.Makuhari Techno Garden B23FChibaJapan
  2. 2.Graduate School of Environment and Information SciencesYokohama National UniversityYokohamaJapan

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