Failure analysis of a natural gas pipeline

• The reason on pipeline burst is SCC generated in the mechanical damage zone.
• The SCC was induced by Cl− and HCO3− in near neutral corrosive medium of pH value.
• The stress concentration was induced by the groove damage under inner pressure.

A L390 natural gas pipeline exploded in 2011 in China. Macrofracture examination, thickness measurement, chemical composition analysis, metallographic inspection, mechanical property testing, fracture scan electronic microscopy examination and environment analysis were conducted to the burst pipeline. The results showed that Stress Corrosion Cracking (SCC) generated in the mechanical damaged zone of the pipeline was the reason of the failure. This kind of cracking was induced by Cl− and HCO3− in near neutral corrosive medium of pH value. The stress concentration was induced by the groove damage under inner pressure.