连续重整装置中三通管开裂分析

采用宏观形貌分析、扫描电镜观察、电子探针能谱分析、电极电位测定和电偶电流测定等手段,分析了某石化公司连续重整装置中氢气与石脑油混合的三通管的开裂原因。结果表明:开裂邻近三通管与变径管的焊接焊缝处,导致三通管开裂的主要原因是叠加在气蚀、氯和硫腐蚀基础上的电偶腐蚀;开裂三通管材料为Cr5Mo钢,而焊缝材料为铬镍不锈钢,两者之间的电位差高达60 mV,形成了电偶腐蚀,其中三通管因其电极电位比焊缝的更负,成为电偶对中的阳极而被加速腐蚀,从而使三通管在邻近焊缝处的壁厚不断减薄并最终开裂。

Cracking Analysis on Three-way Pipe of Continuous Catalytic Reforming Unit

Cracking reasons of the three-way pipe mixing hydrogen and naphtha of continuous catalytic reforming unit were analyzed by macroscopic appearance observation, scanning electronic microscope observation, energy spectrum analysis, determination of electrode potential and galvanic current. The results indicate that the cracking was near welding joint connecting three-way pipe and adapter bonnet, and the main reason for cracking was galvanic corrosion on the basis of cavitation erosion and corrosion of Cl and S. The potential difference between the cracking three-way pipe made of Cr5Mo steel and the welding seam made of chromium nickel stainless steel reached up to 60 mV, which formed galvanic corrosion. The three-way pipe near welding joint became constantly thinning and finally cracking, because it was the anode of galvanic couple that could be accelerated corrosion because of its more negative potential.