The premature failure of an onshore underground well fluid line led to a fatal fire incident. Though there is no reduction in overall thickness localized internal corrosion were noticed at both 6 O’ clock and 12 O’ clock position. In some localized area near the weld there is heavy metal loss leading to formation of holes at 6 O’ clock position

Results of various laboratory investigations confirm that the corrosion and premature failure of pipeline sample was caused by localised corrosion attack. The calculation of flow regime confirms that the flow is stratified and software analysis shows that deposition of water is throughout the whole length of the pipeline thereby creating an ideal condition for deposition and growth of bacteria colony. Two different corrosion mechanisms namely microbial induced corrosion and localized corrosion of chloride have acted together and resulted in the severe attack at 6 O’ clock position. With MIC being the most pronounced. The condensed water and acid gases have caused localized corrosion often called top line corrosion at 12 O’ clock position. Therefore the flow condition, presence of high concentration of chloride and bacterial activity has acted in synergy to cause this failure of the pipeline.

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