The Analysis Of Stress And Fatigue Life Prediction Of Coke Drum Based On The Failure Modes

The coke drum is one of the important equipments for the delayed coking device. And it is a thermally and mechanically cyclic loading pressure vessel. Typically, after some years of operating, coke drums are subject to the following failure modes: spheroidization, bulging of cylinder, cracking of cylinder. Once occurring failure will result in the serious consequence such as personal casualty and economic losses. It’s important to analysis security for improving the economic benefit and preventing safety accident. This paper regards china petroleum & chemical corporation qilu branch number C601/2 coke drum as research object, mainly carried out the following tasks:(1)Testing the coke drum and understanding its safety operating condition by modern testing technology. Analysis of the common defects and defect of coke drum approach, determine the typical failure mode, evaluate the safety level through recent years inspection.(2)Researching the coke drum material speroidizing problem. Observed the 15 CrMo R sample microstructure change under different temperature and holding time through metallographic experiment. Studying the influence law of temperature and time on the sample speroidizing, finally measuring the hardness of sample, analyzing the relationship between the sample nodulizing grade and hardness.(3)Studying the coke drum body deformation and partial cracking problem. Using the finite element analysis software simulate the temperature fields, thermal stress fields and body deformation of one operation cycle. Analyzing fatigue based on the analysis design and elasto-plastic analysis in accordance with the results of one operation cycle.The analysis results indicate that security level 3, the longer the time, the higher the temperature, coke tower material pearlite spheroidization degree is higher, that radial stress, axial stress and central stress of the drum wall, and the thermal stresses are the essential components of the combined stress on the wall. The maximum thermal stress appears in the region of the cylinder and the skirt connection, stress value is 399.28 MPa, which exceed the material yield strength limit. Using S-N fatigue curves and linear cumulative damage theory to evaluate fatigue life, the result is that service life is 38.8 years.