乙烯装置离心压缩机干气密封盘螺柱断裂原因

Causes of dry gas sealing disc stud fracture of centrifugal compressor in ethylene plant

某乙烯装置离心压缩机干气密封盘螺柱发生断裂,采用宏观观察、化学成分分析、金相检验、硬度测试、扫描电镜和能谱分析等方法对螺柱断裂原因进行分析。结果表明:304不锈钢螺柱的碳元素含量高,在高温服役过程中材料发生敏化,螺柱的耐腐蚀性降低;含水的腐蚀性介质进入对接法兰之间的缝隙,并接触到发生敏化的双头螺柱中部的光杆位置,造成材料表面局部发生微小腐蚀,在螺柱紧固应力的共同作用下,应力腐蚀裂纹自腐蚀位置起裂并沿径向沿晶扩展,最终导致螺柱断裂。

The dry gas seal disc stud of a centrifugal compressor was broken.The causes of stud fracture were analyzed by means of macroscopic observation,chemical composition analysis,metallographic examination,hardness test,scanning electron microscopy and energy spectrum analysis.The results show that the carbon element content of 304 stainless steel stud was high,the material was sensitized during high temperature service,and the corrosion resistance of the stud decreased.The water-containing corrosive medium entered the gap between the butt flanges and contacted the polished rod position in the middle of the sensitized double-headed stud,causing local micro-corrosion on the surface of the material.Under the combined action of the fastening stress of the stud,the stress corrosion crack initiated from the corrosion position and propagated along the radial intergranular direction,eventually leading to the fracture of the stud.