Brittle fracture assessment of API 12F shop-welded tanks with a new roof-to-shell junction detail

Abstract

Temporary production storage is largely needed in the oil and gas industry, thus, storage tanks that have the capability to sustain the normal operation condition are needed. The American Petroleum Institute (API) specification 12F provides twelve shop-welded tank designs that can accommodate storage and operational pressure needs of the facility requires temporary production storage. The nominal capacity of these twelve designs ranges from 90 bbl. (14.3 m3) to 1000 bbl. (158.99 m3). These API 12F tanks are typically fabricated in shop and transported to facilities of needs, they are relatively smaller than tank designs provided in API 12D, which is the specification of field-welded storage tanks for production liquids. The brittle fracture assessment is conducted following FAD technique adopted by API 579, with updated operational pressure in the API 12F standard published in 2019. The specific gravity of the stored liquid is assumed to be 1.2 and more component thickness combinations are under consideration in this study, thus, effects of internal pressure, hydrostatic pressure, and component thickness to brittle fracture behavior are investigated. The stresses at roof-shell joint (top junction), shell-bottom plate (bottom junction), and cleanout junction are obtained using finite element analysis approach. The top junction and bottom junction are studied under axisymmetric idealization; thus, the axisymmetric models are generated. The cleanout junction is studied by using sub-modeling technique. Stress classification is performed after performing elastic stress analysis, the results are then used to evaluate brittle fracture behavior with assuming operating at a location with one-day mean temperature of −55 °F (−48.3 °C). The report presents the results and discussion obtained from the brittle fracture assessment of the twelve API 12F tank designs.