ABSTRACT
To extend the fatigue life of coke drum skirt-to-vessel attachment welds, keyholes have become an important consideration in skirt design. The amount of stress reduction they offer to the weld depends on the geometric specifications of the keyholes, namely the slot dimensions, relief-hole diameter, and the distance between the top relief hole and the top of the skirt. Although the directional impact that varying each keyhole parameter has on stress reduction can be intuited, the exact functional relation ships are not well established. This results in significant computational efforts at the design stage to iteratively rank keyhole designs based on fatigue-life performance. To help mitigate the need for extensive simulations, the current study investigates a large parameter space of keyhole designs for two commonly used skirt designs to identify functional trends between keyhole parameters and stress. The functional relationship in certain cases is found to be not only non-linear, but also non-monotonic. However, the variation in stress reduction is well-predicted through simple linear regression models when the parameter space is constrained to include only keyhole dimensions typically used in coke drum designs for various practical reasons. The resulting regression models have the potential to significantly reduce computational efforts when optimizing coke drum skirt designs.