Optimized Design of Coke Drum Shell Plate and Weld Seam Arrangement to Minimize Bulging and Cracking: A Comparative Case Study

The present study focuses on the design of coke drums, particularly the arrangement of shell plates and weld seams, to minimize susceptibility to bulging and cracking. Coke drums are historically prone to fatigue-related failures, especially shell bulging, primarily caused by the formation of cold and hot spots due to localized thermal transients during operation. This design offers an optimized combination of vertical and horizontal plate configurations to address these issues. In this improved design, the bottom portion of the cylindrical section, which is more vulnerable to bulging, is constructed using vertically arranged plates. In contrast, the upper portion, less prone to bulging, uses horizontally oriented plates. Additionally, the circumferential seams between adjacent sections are offset by half the plate width. This seam arrangement disrupts the continuity of circumferential weld seams, enhancing the drum’s resistance to severe thermal cycles and reducing the likelihood of bulging and cracking. Fabrication activities are optimized by using vertical plates in the bottom section and horizontal plates in the upper section, with one continuous circumferential seam included to facilitate post-weld heat treatment (PWHT). This configuration enables PWHT in two halves and the final local post-weld heat treatment (LPWHT) at the closing seam. A case study conducted on a typical coke drum demonstrates that this design approach significantly reduces the tendency for shell bulging and cracking compared to conventional designs, while adhering to recognized technical guidance, such as the API 934 technical report [1].