What are the differences Between Elliptical Head and Torispherical Heads?

Elliptical and torispherical heads, being distinct product types, inherently differ in their geometry and design. The manufacturing processes also present contrasts, with torispherical heads generally being simpler to produce. Elliptical Heads, when subjected to pressure, tend to deform and create opposing radial displacement at their joints. In contrast, torispherical heads are typically formed through stamping, a process that is considered relatively straightforward.

Elliptical heads exhibit a continuous bending radius, eliminating stress concentrations, making them suitable for higher-pressure vessel applications. Torispherical heads, however, feature a discontinuity at the joint, resulting in stress points and favoring their use in lower-pressure vessels. While elliptical heads offer superior stress distribution, torispherical heads are more economical in terms of material usage.

Typical Applications:

1. As end caps: When a pipeline needs termination without immediate extension, a head can be welded to the pipe, serving as a sealed end.

2. Pressure vessel components: Heads are commonly used as the top and bottom closures of cylindrical pressure vessels, effectively forming storage tanks.

Standard elliptical heads, often referred to as such, have a long-to-short axis ratio of 2.0. Their mechanical properties rank second only to hemispherical heads, surpassing those of torispherical heads. The depth of an elliptical head falls between that of hemispherical and torispherical designs, placing the manufacturing difficulty and tooling requirements in a similar middle ground. Spinning techniques have recently simplified the production of large-diameter elliptical heads. Due to their favorable overall performance, elliptical heads find extensive use in medium and low-pressure vessel applications.

Modern advancements in manufacturing technology have improved the stress performance and ease of producing large elliptical heads. This has led to their widespread adoption in low and medium-pressure vessels, benefiting from their improved quality and usability.

Key Differences Between Elliptical and Torispherical Heads:

1. Shape Discrepancies:

• Elliptical Head: Also known as an oval head, it comprises a semi-ellipsoidal section seamlessly joined to a cylindrical straight flange. This design combines the favorable force distribution of hemispherical heads with the shallower depth of torispherical heads. The smooth and continuous curvature of the elliptical section promotes even stress distribution throughout the head.

• Torispherical Head: Also referred to as a dished head, it consists of a spherical cap, a cylindrical straight flange, and a toroidal knuckle region connecting the cap and flange. The knuckle region, with a smaller radius of curvature, facilitates the transition between the spherical cap and the cylindrical flange.

2. Force Characteristics:

   Elliptical heads possess greater strength compared to torispherical heads. However, for a given diameter, an elliptical head will be deeper, and slightly more complex to manufacture. This comes with a higher material consumption and production cost, although the volume difference remains minimal.

1. Standards and Material Selection:

   When selecting heads that comply with the JB4746 "Head for Steel Pressure Vessel" standard, elliptical heads are generally preferred. Using GB150 calculations, the required wall thickness for an elliptical head, for the same pressure, temperature and diameter, is less than that of a torispherical head. This indicates a more efficient use of material for the elliptical design.