Failure analysis on abnormal perforation of super large diameter buried gas pipeline nearby metro.

As a part of urban pipeline network, buried gas pipelines are mainly used to transport high-pressure natural gas, artificial gas and liquefied petroleum gas. Since it are exposed to harsh service condition, buried gas pipelines are easy to encounter failures. In this paper, an abnormal perforation failure of super large diameter buried gas pipeline with an outside diameter of exceeding 1000 mm happened nearby metro was investigated systematically. The failed pipeline had transported water gas before transporting natural gas and was welded with iron buttresses which were not treated by anticorrosive insulation treatment. The obtained results indicated that the accumulation of impurities from water gas caused localized corrosion on the lower surface of the inner wall of the pipeline, leading to the formation of the corrosion pits. After that, stray current came from metro flowed into the pipeline through iron buttresses, bringing about stray current corrosion inside the corrosion pits on the lower surface of the inner wall of the pipeline. The compound effect of these two corrosions resulted in the corrosion perforations. Finally, countermeasures were proposed to address corresponding problems. • An abnormal perforation failure of super large diameter buried gas pipeline happened nearby metro was investigated in depth. • The compound effect of localized corrosion and stray current corrosion was the root cause of the failure. • The accumulation of impurities from water gas caused localized corrosion and lead to the formation of pits. • Stray current flowing from metro via iron buttresses caused stray current corrosion inside pits and resulted in perforations. [ABSTRACT FROM AUTHOR]