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Journal of Failure Analysis and Prevention

, Volume 4, Issue 6, pp 44–50 | Cite as

Stress-corrosion cracking of a monel 400 tube

  • A. I. Katsamas
  • G. N. Haidemenopoulos
  • A. D. Zervaki
  • I. Melas
Peer Reviewed Articles

Abstract

A bent Ni-Cu Monel 400 alloy tube, which operated as part of a pipeline in a petrochemical distillery installation, failed by through-thickness cracking. The pipeline was used to carry a stream of gaseous hydrocarbons containing hydrochloric acid (HCl) into a reaction tower. The tower provided a caustic solution (NaOH) to remove HCl from the stream, before the latter was directed to a burner. Metallographic examination showed that the cracks were intergranular and were frequently branched. Although nominal chemical composition of the component was found within the specified range, electron dispersive analysis by X-ray (EDXA) indicated significant segregation of sulfur and chlorine on grain boundaries. Failure was attributed to hypochlorous-acid (HClO)-induced stress-corrosion cracking (SCC). The HClO was formed by the reaction of HCl with atmospheric O2, and the oxygen entered the tube during shutdowns/startups of the installation. Residual stresses, originating from the in situ bend forming of the tube during assembly of the line, provided a driving force for crack growth, and the segregation of sulfur on grain boundaries enhanced the susceptibility of the material to cracking.

Keywords

hypochlorous acid Monel 400 petrochemical industry stress-corrosion cracking 

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Copyright information

© ASM International 2004

Authors and Affiliations

  • A. I. Katsamas
    • 1
  • G. N. Haidemenopoulos
    • 1
  • A. D. Zervaki
    • 1
  • I. Melas
    • 1
  1. 1.Laboratory of Materials, Dept. of Mechanical EngineeringUniversity of Thessaly, Pedion AreosVolosGreece

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