A cylindrical or spherical shell structure capable of withstanding internal pressure and external loadings at nozzles, supports, and attachments. The pressure vessel is designed with consideration for all possible modes of failures (such as fatigue, fracture, or collapse) and with provision of rational margins of safety against each type of failure. The Boiler and Pressure Vessel Code has been developed by the American Society of Mechanical Engineers (ASME), and the Code has been widely accepted as a standard for designing pressure vessels.