Heads are formed steel plates for pressure vessels and heat exchangers. The heads are usually found at the ends of an equipment, top or bottom for vertical vessels and left right for horizontal vessels. There are only a few shapes used for the heads that have proven to be useful. If the head is cut in half over the diameter of the head, the shapes follow more or less an ellipse, see also the figure below.
The strength calculation of heads are one of the frequently performed calculations since most equipment consist of one or two of them. The Head Thickness page is an example page to calculate the wall thickness of heads, ellipsoidal, torispherical, kloepper and korbbogen heads. Calculation codes are ASME, Dutch Rules and the EN Euronorm.
Below figure gives the an indication of the dimensions used in the calculations. The calculation also require the user to enter a stress value depending the material. The calculation page has a link to a material property page, but the values on the material pages are for reference only and are not to be used in actual calculations.