Causes of Perforation and Leakage of Elbow of a Gas Transmission Pipeline in Western China

After 15 months of service of a buried pipeline in western China, perforation and leakage occurred on the outer arc side of the elbow pipe. The causes of perforation of elbow pipe were studied by means of macroscopic observation, chemical composition analysis, hardness test, metallographic examination, scanning electron microscopy, energy spectrum analysis and phase analysis. The results showed that the corrosion of sulfate-reducing bacteria was the main cause of corrosion perforation at the elbow of the pipeline, the scouring effect of conveying medium on the outer arc side of the elbow pipe accelerated the expansion of corrosion pits to the perforation position, and the CO₂ dissolved in the water phase also promoted the corrosion perforation.