Analytical Solution of the Thermoelasticity Problem in a Coke Drum With Cladding

Abstract

Craze cracking and clad disbonding typically occur in cladding due to thermomechanical cycling and high property mismatch between dissimilar materials in a coke drum. The thermoelasticity problem in a coke drum with cladding is assumed quasi-static and solved analytically in this paper. The transient temperature distribution in both radial and axial directions is derived analytically based on the two-dimensional heat conduction theory. The iteration technique is applied to simulate the dynamic thermal boundary conditions caused by a fluid surface level rising continuously during both heated feed filling and water quench steps. Additionally, the classical laminated thin shell theory is applied to solve the quasi-static structural problem. The analytical results of the quasi-static thermoelasticity problem are compared with the finite element analysis. It is shown that during the water quench step, the maximum axial thermal gradient occurs at the inner surface of the clad, close to the water surface. The tension stresses occur in the clad due to its coefficient of thermal expansion smaller than that of the base metal material. Both the maximal axial stress and hoop stress occur at the cladding surface. These results may be helpful in explaining the formation mechanism of the clad disbonding and the shallow surface cracks at the inner surface of cladding.