Spherical Head(end) is formed in the crown part of the spherical shell. and can be divided into two classes :Hemispherical head and spherical head without folded edge£¬Hemispherical heads are usually used as end head in pressure vessels. That has the following advantage £ºthe minimum surface area under the same volume,  and the required thickness is thinnest under the same pressure conditions. It is the most reasonable choice in terms of saving material and strength. Using the corner weld to connect the spherical head without folded edge and cylindrical shell are commonly used as middle head of two independent pressure chambers in pressure vessel ,It is also used as end head.