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Ziaei S.M.R.,Sharif University of Technology | Kokabi A.H.,Sharif University of Technology | Mostowfi J.,East Oil and Gas Production Company
Journal of Failure Analysis and Prevention | Year: 2014

The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results indicate that flow control valve body failed due to combination of hydrogen-induced corrosion cracking and sulfide stress corrosion cracking. According to HIC and SSC laboratory tests and also with regard to cost of engineering materials, it was evident that the best alternative for the valve body alloy is A217-WC9 cast Cr-Mo steel. © 2014 ASM International.


Ziaei S.M.R.,East Oil and Gas Production Company | Mostowfi J.,East Oil and Gas Production Company | Golestani pour M.,East Oil and Gas Production Company | Ziaei S.A.R.,East Oil and Gas Production Company
Engineering Failure Analysis | Year: 2013

The downhole pressure memory gauge cover which is the focal point of this failure case study was hung in the production tubing of a sour gas well at a depth of 3200. m during a multiple rate productivity index test. Approximately 140. h after start up, the tool cover failed. The memory gauge cover experienced repeated premature failures. One failed sample was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The gauge cover alloy was type AISI 316 stainless steel. During investigation many branched cracks were observed on the external surface of the gauge cover grown from the pits perpendicular to the cylinder axis. The results indicate that pressure memory gauge cover failed due to chloride stress corrosion cracking (CLSCC). Also according to slow strain rate test, it was evident that the best alternative for the downhole pressure memory gauge cover alloy is Nitronic 50 and the second option is 17-4 PH stainless steel. © 2013 Elsevier Ltd.

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