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

Paper Number: 122531

122531 - T-Slot Design and Fatigue Life Assessment of Coke Drum Skirt to Cone Knuckle Weld Joint 

Coke drums experience failures in through-wall cracking throughout their operating life, resulting from low cycle fatigue at the skirt to cone joint and keyhole slot ends. In some cases, drums built without keyholes have experienced 360° through-wall cracking within five years of operation. Keyholes are added to the skirt to mitigate low-cycle fatigue failures and extend the life of the drums. Typical designs terminate the slots with top and bottom holes, hence, keyhole slots. Once a skirt modification with keyhole slots and the coke drum is put into service, cracks at the top keyholes have been discovered as few as two years later. Depending on the crack size, there is little concern about these cracks breaching the pressure boundary of the drum. However, if unattended, they will continue to grow over time, and a breach of the coke drum’s pressure boundary is more likely.  This paper presents T-Slots as an alternative to conventional keyhole design. An iterative methodology was used to compare changes in keyhole slots and T-Slots using finite element analysis (FEA) to optimize the geometry and placement. Several crotch radii, standard keyhole slot sizes, T-slots are examined to find an optimum design with the most extended service life before fatigue crack initiation.  T-slots were the most effective in extending the operating life of the Coke drum skirt to cone joints and slot ends.

Presenting Author: Anthony Scandroli WSI

Presenting Author Biography: Tony Scandroli currently manages WSI’s Structural Engineering Group at WSI in Suwanee, Georgia. He has been with the company for over 33 years and holds a BS from Georgia Institute of Technology. His experience includes working in the Automotive Industry, Stealth Test Equipment Design and Tracking Devices used by the United States Navy, and Pressure Vessel Design Repairs in the Oil and Gas Industry. Tony has several patents, including a Coke Drum Support Skirt Slot Design.

Authors:

Anthony Scandroli WSI
Omar Nassif WSI