Weld Seam Cracking Failure Analysis Of Outlet Tee Tube Of The External Heat Exchanger Of FCC Unit

The tee is an important component,which is used in many fields of industrial production.However,due to discontinuity of geometric structure's change of tee,serious stress concentration frequently occurs at the intersection line.And due to some of the reasons before and after manufacturing,the tee often contains defects such as porosity and crack,which makes tee more easily damaged in the practical engineering.Therefore,the failure analysis of the three links is of great significance to the long period safe operation of the equipment.Based on the situation of the cracking failure of external heat exchanger inlet and outlet water vapor tube of the catalytic device in the actual project,we studied the tee which occurred weld cracking failure of outlet water vapor tube in the paper and then drew the reason of the cracking failure.Meanwhile,we put forward suggestions and measures for improvement on the basis of this,which play a certain guiding role in preventing the occurrence of such failure.Firstly,in this paper,we used the finite element analysis method to analyze the finite element stress analysis of the tee,as well as studied issue of tee's strength merely under internal pressure and discussed stress concentration of the tee at welded seams.Then through water quality analysis of circulating water in equipment as well as macro analysis and micro analysis of failure three pass specimen's fracture,chemical composition analysis and material micro structure analysis and of tee material we analyzed and studied the crack formation and destruction at welded seams.Finally,in order to discuss the influence of welded cracks on the bearing capacity of the tee structure,according to the basic principle of fracture mechanics we analyzed stress intensity factor of semi elliptical cracks in the tee's welds.Then we obtained the distribution of stress intensity factor of the crack front and compared with the critical stress intensity factor KIC to discuss the circumstances and causes of the crack's growth.At the same time,we studied the influence of different crack lengths and different crack depth on the stress intensity factor.