Fatigue Analysis Of Coke Tower Under Cyclic Loading

The coke tower is one of the important equipments for the delayed coking device.And it's a thermally and mechanically cyclic loading pressure vessel.This paper regards sensitive parts of the coke tower-the skirt to shell attachment weldment as the research object,using the finite element analysis software and a combination of methods of numerical simulation and measured data, appropriately simplify the actual model and the analysis model,and accomplished the following contents for fatigue under cyclic loading analysis of coke tower:(1)In accordance with the actual status of operator curve,an operation cycle is divided into heating,coking and cooling stages,and make good use of the powerful software ANSYS to calculate the temperature fields and thermal stress fields at different stages in its operation.(2)Makes shakedown analysis of coke tower in accordance with the results of one operation cycle.(3)Analyzing fatigue based on the analysis design and elasto-plastic analysis in accordance with the results of one operation cycle.Using numerical method,in accordance with the new requirements in ASME-â…§-2,making shakedown analysis and fatigue analysis under cyclic loading of the coke tower are the innovations of this paper.The analysis results indicate that radial stress,axial sress and central stress of the drum wall,and the thermal sresses are the essential components of the combined stress on the wall.Comparing the combined stress of mechanical and thermal stress with the shakedown criterion,conclusion is that the structure of coke drum contents the qualification of shakedown. Using S-N fatigue curves and linear cumulative damage theory to evaluate fatigue life,the result is that service life is 39.4 years according to analysis design and 32.5 years to the elasto-plastic analysis method.Latter is clearly more conservative,more secure.