Head (vessel)

A head is one of the end caps on a cylindrically shaped pressure vessel.

These ends, which in upright vessels are the bottom and the top, use less space than a hemisphere (which is the ideal form for pressure containments) while requiring only a slightly thicker wall.

Vessel dished ends can also be welded together from smaller pieces.

Its radius varies between the major and minor axis; usually the ratio is 2:1.

The greater depth results in the head being more difficult to form, and this makes them more expensive to manufacture.

However, the cost is offset by a potential reduction in the specified thickness due to the dished head having greater overall strength and resistance to pressure.

[3] The transition between the cylinder and the dish is called the knuckle.

The most common types of torispherical heads are: Commonly used for ASME pressure vessels, these torispherical heads have a crown radius equal to the outside diameter of the head (

The ASME design code does not allow the knuckle radius to be any less than 6% of the outside diameter.

The dish has a radius that equals the diameter of the cylinder it is attached to (

The knuckle has a radius that equals a tenth of the diameter of the cylinder (

This is a head consisting of a toroidal knuckle connecting to a flat plate.

This type of head is typically used for the bottom of cookware.

This type of head is often found on the bottom of aerosol spray cans.