Failure Reason of 20^# Steel Elbow in Oilfield

On the basis of the service environment, the reasons of 20^# elbow 3 times failure in a short period were investigated by means of physical and chemical property testing, microstructure analysis, corrosion scale analysis, flow rate and erosion corrosion simulated results. The results indicated that CO₂ corrosion occurred at the elbow during the process of CO₂ huffing and puffing, and the loose and porous FeCO₃ corrosion scale formed. Meanwhile, the solid particles in the medium caused erosion corrosion on the outer arc side of the elbow. Under the synergistic effect of CO₂ corrosion and erosion corrosion, the FeCO₃ scale was destroyed, and metal was exposed on the outer arc side of the elbow, resulting in a rapid thinning of the outer arc sidewall and finally perforation. Finally, suggestions were given to avoid or slow down the rapid failure of such elbows.