Causes of leakage of external manifold of natural gas gathering station

Leakage occurred in the external manifold of a natural gas gathering station. The causes of pipeline leakage were analyzed by means of macroscopic observation, penetration testing,chemical composition analysis, mechanical property test, metallographic examination, scanning electron microscope and energy spectrum analysis. The results showed that the chemical composition, mechanical properties and microstructure of the base metal of the pipeline met the requirements of the standard. The content of Mn and Si elements in the chemical composition of the weld was high, and the tensile properties and hardness were higher than those of the base metal, and the microstructure was lath martensite. The fracture was characterized by intergranular and transgranular mixed cracking morphology. The reason for the leakage of the manifold was the hydrogen embrittlement cracking of the material caused by improper welding process.