Failure analysis of ruptured pipe connected to natural gas pre-heater H.M. Shalaby * , W.T. Riad, A.A. Alhazza, M.H. Behbehani Kuwait Institute for Scientific Research, P.O. Box 24885, 13109-Safat, Kuwait Received 20 January 2005; accepted 20 February 2005 Available online 22 April 2005 Abstract Failure Analysis was made on a ruptured low carbon steel pipe that was connected to a natural gas pre-heater in a chemical plant. The pipe has been in service for about 30 years. The analysis indicated that failure of the pipe was due to thin-lip rupture, resulting from high temperature sulphidation. The rate of sulphidation was much faster at the bend areas where turbulent flow was occurring. The pipe also suffered from graphitization due to decomposition of the pearl- ite phase as a result of long service time at moderately high temperature. It was recommended to replace the pipe with a new one and to regularly monitor the pipe thickness with special emphasis on bend areas. The plant was also advised to minimize the ingress of humidity and oxygen into the piping system during shutdowns. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Heat-exchange failures; Piping; High temperature sulphidation; Carbon steel; Graphitization 1. Introduction The chemical company requested failure investigation on four specimens that were cut from a ruptured low carbon steel pipe that was connected to a natural gas pre-heater. The pipe has been in service for about 30 years. The company engineers provided the following information:  Natural gas quantity = 13,380 Ncbm/h  Gas temperature = 400 °C  Design pressure = 43 kg/cm 2 1350-6307/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.engfailanal.2005.02.005 * Corresponding author. Tel.: +965 398 0499; fax: +965 398 0445. E-mail address: hshalaby@prsc.kisr.edu.kw (H.M. Shalaby). Engineering Failure Analysis 13 (2006) 797–804 www.elsevier.com/locate/engfailanal