Leakage failure analysis of sewage pipe used for buried valve in natural gas station

Leakage accident occurred during the operation of a buried valve blowdown pipe in a natural gas station. After the macroscopic morphology, mechanical properties, chemical composition, metallography, scanning electron microscopy and energy spectrum analysis of the leaking blowdown pipe, it was found that the corrosion perforation was located in the outer wall of the pipe, and the damage of the corrosion layer caused the corrosion components in the saline soil to contact the steel pipe to produce oxygen corrosion. In addition, Cl – ions in the soil played a role in accelerating corrosion, which eventually led to the occurrence of perforation accidents.