scope:

The frangible joint is the primary design feature which assures the functional integrity of the cylindrical shell and bottom joint to contain the liquid in the event of an unexpected over-pressurization of a tank. API 650 (API, 1993) provides design criteria for fluid storage tanks with frangible roof joints. The rules are intended for fluid storage tanks used to store flammable liquids which could be subjected to sudden over-pressurization. Over-pressurization can occur due to the ignition of flammable vapors and can exceed the capability of the pressure relief vents specified in storage tank design. This report describes research that evaluated the ability of the present design criteria to ensure the desired frangible joint behavior. Particular questions include: Evaluation of the area inequality as a method to predict the buckling response of the compression ring. Effect of roof slope, tank diameter, and weld size on the frangible joint. Effect of the relative strength of the roof-to-shell joint compared to the shell-to-bottom joint. Publication of this document - WRC Bulletin No. 410 was sponsored by the Committee on Dynamic Analysis and Testing and the Committee on Shells and Ligaments of the Pressure Vessel Research Council with considerable financial support from the American Petroleum Institute