Journal of Applied Reliability (한국신뢰성학회지:신뢰성응용연구)

The Korean Reliability Society (한국신뢰성학회)
권호 표지

The Failure Analysis of Double Pipe for Insulation Used Power Plant by Grooving Corrosion

발전소용 이중보온용 강관의 홈부식(Grooving Corrosion)에 의한 파손 분석

  • Ham, Jong-Oh (Metallic Materials and Mechanical Engineering Team, Korea Testing and Research Institute) ;
  • Park, Ki-Duck (Metallic Materials and Mechanical Engineering Team, Korea Testing and Research Institute) ;
  • Park, Sung-Jin (Metallic Materials and Mechanical Engineering Team, Korea Testing and Research Institute) ;
  • Sun, Il-Sik (Metallic Materials and Mechanical Engineering Team, Korea Testing and Research Institute)
  • 함종오 (한국화학융합시험연구원 금속엔지니어링팀) ;
  • 박기덕 (한국화학융합시험연구원 금속엔지니어링팀) ;
  • 박성진 (한국화학융합시험연구원 금속엔지니어링팀) ;
  • 선일식 (한국화학융합시험연구원 금속엔지니어링팀)
  • Received : 2015.07.21
  • Accepted : 2015.08.30
  • Published : 2015.09.25
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Abstract

Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water ($95{\sim}110^{\circ}C$) for a plant was carried out. The damaged area (${\Phi}5mm$) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.

Keywords

References

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