Understanding the Effects of Hydrogen on SCC of Pipelines

A thesis submitted in Department of Chemical and Materials Engineering University of Alberta, © Zeynab Shirband, 2016.

Near-neutral pH stress corrosion cracks (NNpH SCC) are developed under coating disbondments on the external surface of pipelines where the surface of pipeline is exposed to the soil solution. NNpH SCC initiation and early stage of growth is mainly governed by the dissolution process of steel. …This study aimed at understanding the contribution of these important factors to NNpH SCC. In this study, the role of coating disbondment on hydrogen ingress into pipeline steels and the effects of mill-scale and hydrotesting on NNpH SCC crack initiation are investigated.

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Publicités

Analysis of corroded elbow section of carbon steel piping system of an oil–gas separator vessel

An interessant case study published in « Case Studies in Engineering Failure Analysis« , on 09january 2013.

A pinhole in elbow section of oil piping system is formed by localized corrosion. The corrosion is found to result from sequential chlorination and sulfidation reactions : the chlorination results from hydrolysis of calcium chloride in the crude oil and the sulfidation results from hydrogen sulfide in the crude oil.

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Grooving corrosion of seam welded oil pipelines

A interesting paper in « Case study in Engineering Failure Analysis«  published on ScienceDirect.com.

24″ pipeline carrying oil was failed in the form of longitudinal crack at the 6 O’clock position resulting in oil spill. The failed pipe was investigated to reveal the main cause of its failure. Cracks were originated from weld defected sites, initiated by grooving corrosion, propagated by inertia at the normal designed pressure condition, and stopped when stress relief is attained.

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Corrosion of Welded Joint in Alloy Steel Pipe

2015-11-15_10h33_54An interesting article published on 4 November 2015 in the International Journal of ELECTROCHEMICAL SCIENCE.

In this paper an investigation on corrosion behaviour of welded joints was performed to facilitate determination the causes of preferential degradation by corrosion of the welded metal (WM) and the heat affected zone (HAZ), in a welded pipeline of grade ASTM A355P5, used in a petrochemical plant as transfer line between a thermal cracking heater and a column which are part of an atmospheric distillation and vacuum (DAV) unit. It was found that the corrosion of the weld analyzed in this research has resulted due to its dendritic structure (pearlite, ferrite, complex carbide, bainite and martensite in localized areas), which reveals the lack of post welding heat treatment (PWHT). Read more …..

 

Gas pipeline leakage detection based on acoustic technology

Un nouvel article publié via  ScienceDirect.com dansEngineering Failure Analysis – Gas pipeline leakage detection based on acoustic technology.

Le signal acoustique de fuite d’un pipeline de gaz peut être utilisé pour le diagnostic et la localisation de la fuite sur le pipeline. Dans un pipeline de grande distance, la collecte  du signal acoustique causée par la vibration due à la fuite revêt une grande importance pour sa détection. L’article étudie l’émission acoustique sur le principe de la fuite du pipeline et la caractéristique de la source. D’autre part, la vibration de la paroi du pipeline est analysée avec la technologie d’analyse harmonique du logiciel ANSYS. Enfin, l’expérience sur le terrain montre que cette approche peut améliorer la capacité de détection des petites fuites avec un taux réduit de fausse alarme.

Rupture prématurée de segments d’extension de pipeline

ScienceDirect.com rapporte l’analyse de défaillance de segments d’extension de pipeline qui se sont rompus prématurément. Des dégradations de surface dues à l’expansion diamétrale des segments alliées à la fatigue en service sont à l’origine de ces ruptures.