By David Gibson, ExxonMobil Manufacturing Principal Engineer
The following was summarized from David Gibson’s presentation at RefComm Galveston 2024. Click the link below to download the full presentation.
In the presentation, David covered an overview of the drum design in question with severe cone/flange distortion issues. The analysis objective was to determine if the flange deformation and leakage was caused primarily by non-uniform circumferential temperature distribution or asymmetric radial stiffness of the BUD valve.
A finite element analysis was performed. Process data and external temperature measurements were used for boundary conditions model calibration, producing a model with all flange attachment components included.
Main conclusions
The root cause of the distortion – thermal gradients created by the dual feed nozzles. The valve stiffness did not appear to be a significant contributor to the ovalization. Insulating the flange neck to the back of the flange produced slightly less flange deformation and gasket stress variation. The flange bolts exceeded yield during coke drum operation. Gasket performance during operation was very sensitive to variation in bold load.
Recommendation
The recommendation was to install a Center Feed Device (CFD) on all four drums to eliminate temperature gradients. Flange replacement was only an interim repair and not recommended.
General Conclusions
The larger diameter drums with dual feed inlet nozzles are susceptible to cone/flange distortion. The root cause of the issue was thermal mal-distribution induced by dual feed nozzles. The condition worsened the distortion over time, accelerating fatigue life consumption. It created a potential for anchor bolt issues. There were several temporary mitigations which could be implemented but the longterm mitigation solution was to convert from dual feed to retractable center feed device prior to cone life consumption.
2 responses to “Coke Drum Dual Feed Issues”
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How do we get admission to refcomm
W.Paul: there are also other solution then just installing Center Feed Devices.