Fatigue And Reliability Analysis Of Coke Tower Under Cyclic Loading

The coke tower is one of the main equipments of the delayed coking process. Andit is a typical pressure vessel working under thermally-mechanically cycle load. In theprocess of production, the coke tower-the skirt to shell attachment weldment is causeda lot of structure failure problem by thermal-mechanical coupling stress. So it is veryimportant to calculate the safety and reliability analysis of coke tower.This paper regards key parts of the coke tower-the skirt to shell attachmentweldment as the research object, using Petro China Dushanzi Petrochemical Companya coke tower structure and original operating parameters as the basis, analytic modelsfor the coke tower shell and skirt seat connection parts were set up, based on thetheory of finite element. Using of the software Ansys was made to the calculation ofthe temperature fields and thermal-mechanical coupling stress on the differentoperation of stages. Based on the coupling stress calculation results of the finiteelement software of Workbench, determining the s-n curve of material and calculatingthe fatigue life of coke tower. Using the stress and strength of interference theory inMonte-Carlo method, with immediately taking the load of temperature (Ti) andpressure (Pi) variables as boundary conditions, with determining the maximumcoupling stress of probability density distribution function, the reliability of thestructure are calculated.The analysis results show that the coke tower key support section stress is mainlycomposed of axial temperature changes, and the whole cycle of peak stress appear inthe joints of cylinder body and skirt. The fatigue life of coke tower is about30yearswhich is calculated by the workbench software.Using Monte-Carlo method tocalculate the reliability of the coke tower connection parts which is about0.95076.