Coke drums are used in oil refineries to convert the heaviest cuts of crude oil into industrial coke and light gasses such as propane. Fatigue cracks develop in coke drums due to the thermal cycling inherent to the process. As is typical with thermal stress problems, the challenge of designing a support skirt for a coke drum is in providing a skirt which is strong enough to support the vessel under the design loads while being as flexible as possible in the radial direction to minimize thermal stresses. This paper examines two skirt configurations for two coke drums. First, a standard design of a single thickness skirt designed to handle all loads is analyzed, then an alternative design is studied. The alternative is to provide guides to restrain horizontal forces due to wind or seismic events near the center of gravity of the drum. This allows the skirt to be thinner due to the minimal bending moment it will now carry. Thermal stresses resulting from the conventional and the alternate designs are evaluated for fatigue life.
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