This paper describes some of the considerations for evaluating the structural adequacy of a hybrid tank-vessel-stack design where column-type instability must be considered. The equipment is utilized as a flue gas desulphurization (FGD) absorber/stack assembly in a petroleum refinery installation and is comprised of three major structural and geometric sections. The bottom section is considered to be very similar to an API 650 storage tank. The middle section is considered to be comprised of both cylindrical and conical pressure vessels. The third and upper most section is comprised of multiple ring sections of decreasing wall thicknesses as a function of elevation and resembles an ASME STS-1 stack. Because the height of the FGD absorber/stack exceeds 300 feet in combination with tank diameters of approximately 70 feet, wind loads, self-weight, and platform loads become a significant consideration in the design of the entire assembly. While no single nationally recognized code or standard fully addresses the buckling implications in the design and analysis of such a structure, a conglomeration of codes and standards, including ASME Code Case 2286-1 is reviewed and addressed in the following paragraphs with respect to the applicability and usefulness of the subject code case. Not withstanding, the interfaces and design considerations with respect to the other pertinent codes including, but not limited to, API Standard 650; ASME Section VIII, Divisions 1 and 2; and ASME STS-1 in combination with the suggestions contained within Code Case 2286-1 are also addressed herein. Finally, a consideration of the ultimate design factors of safety associated with each of the aforementioned codes is also discussed and revealed for the designer and owner in order to make an educated decision regarding the use of Code Case 2286-1.

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