蜡油加氢装置循环氢导凝管开裂失效分析

FAILURE ANALYSIS OF RECYCLE HYDROGEN DRAIN IN WAX OIL HYDROGENATION UNIT

蜡油加氢装置循环氢管道反飞动控制阀上游导凝管焊缝泄漏,其材质为ASTM A106GRB。经过材质复测、硬度检测、微观检测,判断裂纹从管内壁焊缝的亚表面开始,以脆性疲劳的方式由内向外延伸到外壁,最后引起泄漏。起源处恰在焊缝内壁的未满焊处,存在一个缺口,即应力集中的地方,同时焊后又没有进行消除应力处理,在氢和高应力的交变载荷共同作用下,发生氢致开裂。

Welding seam leakage occurred in the drain of anti-surge control valve on the recycle hydrogen in wax oil hydrogenation unit and it is made of ASTM A106 GRB.Through material retest,hardness test and microscopic examination,it is determined that the crack began from the weld joint subsurface on the welding seam of the pipe inner wall and extended to the outer wall from the inner wall in the way of brittle fatigue and finally caused leakage.The crack began at a point which was not fully welded in the weld joint of the inner wall and there existed a gap which was a stress concentration point.Meanwhile,no stress relieving treatment was done after welding.Under the interaction of alternateload between hydrogen and high stress,hydrogen induced cracking occurred.