Multiple leaks occurred in a carbon steel pipe carrying hot condensate water (149 °C and 10.5 bara). All leaks were located downstream of elbows immediately following the circumferential weld. An extensive root cause analysis was performed that included visual and metallographic examination of failed samples, chemical analysis of weld metal and base metal, and chemical analysis of water samples. The results showed that flow accelerated corrosion (FAC) was clearly the responsible mechanism leading to the failures. Other mechanisms, including organic acid corrosion and erosion-corrosion, were ruled out since the sampled water pH was alkaline and the water flow velocity was relatively low. The failed pipe was replaced with 316 stainless steel pipe to prevent FAC.

Subject
Films, Pipe surfaces, Corrosion failures, Water, Piping, Metal surfaces, Flow velocity, Solids, Leaks, Acidity, Organic acids, Erosion corrosion, Samples
Keywords:
flow accelerated corrosion, weld, carbon steel, erosion-corrosion, chemical plant
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2016
Association for Materials Protection and Performance (AMPP)
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