The various heads can be combined as Thorispherical and spherical heads, which are used as covers of cylindrical pressure vessels or other process engineering vessels. Due to the flattened "hemispherical shape" they take up less space than the ideal hemispherical shape with only slightly thicker walls. The terms dished thorispherical and spherical head with the associated radius ratios are standardized.
Calculation bases for the wall thickness calculation of dished heads under internal pressure loading are available in Germany in the relevant codes for the manufacture of pressure vessels according to the Pressure Equipment Directive AD 2000-Merkblatt as well as in the harmonized standard DIN EN 13445-3. Due to the internal pressure, the greatest stresses are in the area of the brim. For this reason, notches and other deformations should be avoided in this area and this area should usually be made thicker.