zachry publications
2024
Optimizing Coke Drum Keyhole Dimensions Using Statistical Modeling
This study developed a novel methodology for sizing keyhole dimensions during the design stage of coke drums. Typically, keyhole sizing is a computational intensive endeavor that involves separate FE models for each of the prospective keyhole designs to rank their performance. The statistical model developed in this research initiative greatly reduces the need for upfront simulations by providing an estimate for keyhole performance with a simple, linear regression equation that can be used for multiple skirt designs.
Key Learnings from Large-Bore Compressor Piping Design of a Carbon Capture System
This paper presented a case study involving the retrofitting of a carbon capture and storage (CCS) as a means to highlight the engineering difficulties that arise when designing large-bore pipe systems. Key lessons learned and best practices developed during the course of the project are summarized, to aid in the design of future systems with similar constraints.
2023
On the Effect of Rising Liquid on Coke Drum Skirt Fatigue Life
This study compares two methodologies for modeling heat transfer in coke drums to estimate the fatigue life at the skirt-to-vessel attachment weld. Findings revealed up to 20% discrepancies between the two methods, suggesting the use of a more complex model incorporating non-uniform thermal fields for higher accuracy, while a simpler method could be used for quick, conservative estimates.
Local Post Weld Heat Treatment of a Pressure Vessel: A Postmortem Evaluation
This research evaluates a process tower that distorted significantly following a local post weld heat treatment (PWHT), testing several analytical techniques using Finite Element Analysis (FEA) to best predict such deformation. The study concludes with findings from these techniques and suggests potential optimization for PWHT design and execution.
2022
Coke Drum Keyhole Optimization with Alloy Weld Overlay
The study investigates a novel design for coke drums involving the use of N06625 overlay at keyhole locations to delay crack initiation and prolong fatigue life. The results reveal that this design, when coupled with increased keyhole fillet radii, significantly improves the fatigue life by an order of magnitude compared to previous designs, offering potentially substantial cost-effectiveness benefits.
Reliability Improvement Concept on Welded Lip-seal Heat Exchanger Flange Joints
This study proposes and evaluates new design features for lip-seal flange joints, commonly used in high-pressure heat exchangers, to improve their reliability and fatigue life. The modifications, which include machined pockets, a self-alignment feature, and strict fabrication tolerances, are assessed through Finite Element Analysis simulations comparing stress distributions in the conventional and redesigned joints.
On the Effect of Hot-Box Size on Coke Drum Skirt Fatigue Life
This study explores the effect of “hot-box” emissivity and height on fatigue life in the weld of coke drum skirts, specifically the influence of design features like “keyholes.” The results indicate that while fatigue life is not significantly affected by hot-box height without keyholes, the presence of keyholes introduces variable fatigue performance, offering guidance for optimizing hot-box size.
2018
Integral Mean of Yield Concept Applied to Thermal Hot Spots: Validation of a Level 2 Damage Assessment Method
The study evaluates the accuracy of Seshadri’s Level 2 assessment for detecting local thermal hot spots in pressure vessels by comparing it with a Level 3 assessment. Findings reveal minor differences between the two methods, with Level 2 providing a more conservative estimate of load capacity reductions due to hot spot damage.
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