Session: DA-15-01 8th International Symposium on Coke Drum Life Cycle Management 1-Coke Drum Skirt Integrity

Paper Number: 122838

122838 - Optimizing Coke Drum Keyhole Dimensions Using Statistical Modeling 

To provide stress relief to the welded joint that attaches coke drum vessels to the supporting skirt, which is one of the most common failure locations, keyholes have become an important consideration in skirt design. The amount of stress reduction depends on the geometric specifications of the keyhole, namely the slot dimensions (width, height, and circumferential spacing), relief-hole diameter, and the distance from the top relief hole to the skirt-to-vessel attachment weld. Although the directional impact that varying each keyhole parameter has on stress reduction is known (i.e. which dimensional variations have direct vs inverse relationships with stress reduction), the exact functional relationships are not well established. This results in the need for time-consuming numerical simulations at the design stage to evaluate the inherent trade-off in fatigue-life improvement relative to cost of material removal and reduction in buckling resistance. In an attempt to circumvent the need for extensive numerical simulations, the current study investigates a large parameter space of keyhole designs for two commonly used skirt designs to identify functional trends in each dimensional parameter. Although the functional relationship with a number of parameters is not only non-linear, but also non-monotonic, the variance in stress reduction is well-predicted through a simple linear regression analysis. The resulting regression formulae have the potential to significantly reduce computational time when optimizing skirt/vessel design.

Presenting Author: John Fernando Zachry Integrity Engineering Ltd

Presenting Author Biography: John Fernando currently serves as a Stress Analyst for Zachry Integrity Engineering Ltd located in Calgary, Alberta, Canada. Zachry Integrity Engineering Ltd is a Canadian owned engineering and consulting firm with over 40 years of experience. John’s career this far has focused on the analysis and investigation of piping and pressure vessels in the oil and gas industry.

Authors:

John Fernando Zachry Integrity Engineering Ltd
Henry Kwok Zachry Integrity Engineering Ltd
Luke Chan Zachry Integrity Engineering Ltd
Jorge Penso Shell Global Solutions (US) Inc