Welding repair technology for coke drum in delayed coking unit
During the operation of delayed coking unit,the B6 circumferential weld on the wall of coke drum cracked.Multiple detection methods were used to analyze the cause of the cracking.According to the results of macroscopic inspection,nondestruc-tive testing,metallographic analysis,hardness test,and chemical composition analysis,it was concluded that the B6 circumfer-ential weld was located at the tower wall with non-uniform thickness,and fatigue cracking occurred due to the drastic change of operating temperature.In order to eliminate the circumferential weld defects at the inner and outer walls of the coke tower,the defects were fixed by repair welding,dehydrogenation heat treatment,and post weld heat treatment.The application of welding repair technology showed that the cracks can be avoided and the residual stress can be reduced effectively by developing reasona-ble welding processes,selecting appropriate welding methods,picking corresponding welding materials,adopting preventive measures such as post weld dehydrogenation treatment and stress relief heat treatment,so that the repaired welding joints can achieve good comprehensive mechanical properties.By using effective welding repair measures,a good foundation was laid for the long-term stable operation of the coke drum.
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