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Ellipsoidal, hemispherical, and torispherical heads are the three primary types of ASME pressure vessel dished heads, each designed to meet specific pressure and performance requirements. Ellipsoidal heads, commonly known as 2:1 elliptical heads, are widely used due to their cost-effective design, with a head height equal to one-quarter of the diameter, offering a good balance between strength and economy. Hemispherical heads provide the highest strength and pressure resistance, as their shape allows uniform distribution of internal pressure across the surface, making them ideal for high-pressure applications. Torispherical heads feature a combination of a spherical dish and a toroidal knuckle, enabling smooth stress distribution between the head and the cylindrical shell. Each type offers unique advantages, allowing engineers to select the most suitable design based on pressure conditions, cost considerations, and application requirements.
Also known as 2:1 elliptical heads, these are widely used because of their cost-effective geometry. The height of the head is one-quarter of its diameter, making it more economical while still offering good pressure resistance. The radius of curvature varies between the major and minor axes.
A hemispherical head is the ideal form for pressure containment as internal pressure is distributed evenly across its surface. The radius of the head (R) is equal to the radius of the cylindrical shell, providing superior strength and pressure-holding capability.
Torispherical heads consist of a dish with a fixed crown radius (CR), which varies depending on the specific type of torispherical design. The transition area between the dish and the cylindrical shell is known as the knuckle, which has a toroidal shape that helps distribute stress smoothly.
