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Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant / Z.-G. Yang in Materials and corrosion, Vol. 63 N° 1 (Janvier 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 1 (Janvier 2012) . - pp. 7–17 Titre : Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant : Part I: Electrochemical corrosion Type de document : texte imprimé Auteurs : Z.-G. Yang, Auteur ; Y. Gong, Auteur ; J.-Z. Yuan, Auteur Année de publication : 2012 Article en page(s) : pp. 7–17 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Electrochemical  corrosion  Erosion  Heat  exchanger  Hydrogen-assisted  corrosion  Seawater  Titanium  tube Résumé : Titanium tubes generally exhibit superior resistance against electrochemical corrosions amid seawater for their passive films TiO2. However, hydrogen-assisted corrosion (HAC) is actually the Achilles' heel to titanium materials when the temperature exceeds near 70 °C. In this event, severe degradations like quick thinning and leakage were frequently detected on a large number of titanium tubes exposed to natural seawater environment within heat exchangers in a nuclear power plant, which caused serious safety problems. This paper is the Part I of totally two parts conducted for the whole failure analysis study, mainly focusing on electrochemical aspect of failure causes and their behaviors. By means of over ten kinds of characterization methods, the analysis results identified that the HAC induced by the interaction effects between galvanic corrosion and crevice corrosion led to local bulges of the inner walls of some titanium tubes, and then the bulges were quickly thinned and eventually ruptured under the eddy erosion from the seawater containing sediment particles. Finally, relevant mechanisms were addressed in detail and prevention methods were proposed as well. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106189/abstract [article] Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant : Part I: Electrochemical corrosion [texte imprimé] / Z.-G. Yang, Auteur ; Y. Gong, Auteur ; J.-Z. Yuan, Auteur . - 2012 . - pp. 7–17. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 1 (Janvier 2012) . - pp. 7–17 Mots-clés : Electrochemical  corrosion  Erosion  Heat  exchanger  Hydrogen-assisted  corrosion  Seawater  Titanium  tube Résumé : Titanium tubes generally exhibit superior resistance against electrochemical corrosions amid seawater for their passive films TiO2. However, hydrogen-assisted corrosion (HAC) is actually the Achilles' heel to titanium materials when the temperature exceeds near 70 °C. In this event, severe degradations like quick thinning and leakage were frequently detected on a large number of titanium tubes exposed to natural seawater environment within heat exchangers in a nuclear power plant, which caused serious safety problems. This paper is the Part I of totally two parts conducted for the whole failure analysis study, mainly focusing on electrochemical aspect of failure causes and their behaviors. By means of over ten kinds of characterization methods, the analysis results identified that the HAC induced by the interaction effects between galvanic corrosion and crevice corrosion led to local bulges of the inner walls of some titanium tubes, and then the bulges were quickly thinned and eventually ruptured under the eddy erosion from the seawater containing sediment particles. Finally, relevant mechanisms were addressed in detail and prevention methods were proposed as well. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106189/abstract

Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant / Y. Gong in Materials and corrosion, Vol. 63 N° 1 (Janvier 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 1 (Janvier 2012) . - pp. 18–28 Titre : Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant : Part II: Mechanical degradation Type de document : texte imprimé Auteurs : Y. Gong, Auteur ; Z.-G. Yang, Auteur ; J.-Z. Yuan, Auteur Année de publication : 2012 Article en page(s) : pp. 18–28 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Clogging  Erosion  Heat  exchanger  Recirculating  cooling  water  Seawater  Titanium  tube Résumé : Serious failure incidents like clogging, quick thinning, and leakage frequently occurred on lots of titanium tubes of heat exchangers in a nuclear power plant in China. In the Part I of the whole failure analysis study with totally two parts, factors mainly involving three kinds of electrochemical corrosions were investigated, including galvanic corrosion, crevice corrosion, and hydrogen-assisted corrosion. In the current Part II, through microscopically analyzing the ruptures on the leaked tubes by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), another four causes dominantly lying in the aspect of mechanical degradation were determined – clogging, erosion, mechanical damaging, and fretting. Among them, the erosion effect was the primary one, thus the stresses it exerted on the tube wall were also supplementarily evaluated by finite element method (FEM). Based on the analysis results, the different degradation extents and morphologies by erosion on the tubes when they were clogged by different substances such as seashell, rubber debris, and sediments were compared, and relevant mechanisms were discussed. Finally, countermeasures were put forward as well. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106190/abstract [article] Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant : Part II: Mechanical degradation [texte imprimé] / Y. Gong, Auteur ; Z.-G. Yang, Auteur ; J.-Z. Yuan, Auteur . - 2012 . - pp. 18–28. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 1 (Janvier 2012) . - pp. 18–28 Mots-clés : Clogging  Erosion  Heat  exchanger  Recirculating  cooling  water  Seawater  Titanium  tube Résumé : Serious failure incidents like clogging, quick thinning, and leakage frequently occurred on lots of titanium tubes of heat exchangers in a nuclear power plant in China. In the Part I of the whole failure analysis study with totally two parts, factors mainly involving three kinds of electrochemical corrosions were investigated, including galvanic corrosion, crevice corrosion, and hydrogen-assisted corrosion. In the current Part II, through microscopically analyzing the ruptures on the leaked tubes by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), another four causes dominantly lying in the aspect of mechanical degradation were determined – clogging, erosion, mechanical damaging, and fretting. Among them, the erosion effect was the primary one, thus the stresses it exerted on the tube wall were also supplementarily evaluated by finite element method (FEM). Based on the analysis results, the different degradation extents and morphologies by erosion on the tubes when they were clogged by different substances such as seashell, rubber debris, and sediments were compared, and relevant mechanisms were discussed. Finally, countermeasures were put forward as well. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106190/abstract