Alternative Selections of Delayed Coke Drum Materials Based on ASME Material Property Data

Abstract

Severe cyclic thermo-mechanical operating conditions during delayed coking can cause damages in the form of bulging and cracking in coke drums. As a result, the industry has to perform costly repairs and maintenance shutdowns. Therefore, it is important to understand the damage and failure mechanisms of the coke drums and to achieve more reliable coke drum design solutions. This paper explores alternative selections of clad and base material combinations for coke drum applications based on material property data provided in ASME Boiler & Pressure Vessel Code, Section II - Materials. Finite element analyses are carried out by simulating two critical loading scenarios in the coke drum operation cycle, i.e. the heating up and quenching stages. The analysis results show that the major achievement in lowering the stress level in the clad layer is due to matching of the coefficients of thermal expansion between clad and base materials. In addition, the finite element analyses indicate that the differences in Young’s modulus values play an important role in the variation of maximum stress in the coke drum shell during the quenching stage. Among eleven pairs of the clad and base material combinations studied, the combination of SA302-C as the base and nickel alloy N06625 as the cladding material is recommended.