吸附塔焊缝裂纹分析及预防措施

Analysis and preventive measure ofweld cracks in adsorption tower

某石化公司炼油厂在用的吸附塔属于易疲劳容器,年使用压力交变次数达45 000次,在未满设计使用寿命时,容器圆筒体焊缝局部发生穿透性裂纹。经过对该塔焊缝的棱角度检查,筒体和封头的壁厚测试,筒体纵、环焊缝的磁粉和相控阵检测,焊缝TOFD (超声波衍射时差法)检测,对裂纹附近焊缝及母材进行硬度检测,对母材、焊缝、裂纹进行金相组织分析及化学成分分析等,确定焊缝裂纹是由棱角度超标导致的应力集中和疲劳应力共同作用产生的,据此提出压力容器制造过程中棱角度的控制措施。

The adsorption tower used in the refinery of a petrochemical company belongs to fatigable vessel,its operational pressure alternating reaches 45 000 times per year.Local penetrating cracks in the cylinder of the adsorption tower appeared when the adsorption tower working for less than the design life.Through weld edge angle inspection,cylinder and head thickness tests,magnetic particle and phased array detections for longitudinal and girth welds,weld TOFD detection,hardness detection for cracks and nearby base metal,metallographic structure analysis and chemical composition analysis for base metal,welds and cracks,it is concluded that the formation of weld cracks is the joint action of stress concentration and fatigue stress caused by excessive edge angle.Accordingly the edge angle control measure in pressure vessel manufacturing is put forward.