20钢45°热煨弯管失效分析

Investigation of Failure of 45° Hot-bend Elbow in St. G. 20

分析20钢45°热煨弯管在某油田服役48天后发生失效的原因。通过分析该热煨弯管的化学成分、力学性能和金相组织以及爆裂区的能谱图,发现冲刷腐蚀致管壁减薄是弯管爆裂的原因。输送介质中含H_2S、CO_2等腐蚀性介质,加强了冲蚀的作用;冲蚀与腐蚀的交互作用会加速管壁的减薄;当弯管管壁局部位置减薄到一定程度,在钢管内压力作用下,造成弯管局部爆裂。

The cause for failure of the 45° hot-bend elbow in St. G. 20 as just having served in a certain oil field for 48 days is investigated. The chemical composition, the mechanical properties, the metallographic structure and the energy dispersive X-ray spectrum of the bursting area of the said elbow are analyzed. As a result,it is identified that the cause for the failure is that the erosion gets the elbow pipe wall thickness reduced, thus the burst happens. Corrosive medium like H2S, and CO2 contained in the conveyed medium strengthens the erosion effect. And the interactions by erosion and corrosion speed up the reduction of the pipe wall thickness. Finally when some location of the wall thickness of the elbow is reduced to a certain extent,local burst will take place due to the internal pressure of the pipe.