Head including the convex head, cone shell, adjustable section, flat lid and tighten the mouth of the design. Convex head includes: hemispherical head, oval head, dished head and the spherical cap-shaped head. The force from the perspective of convex head gradually from the hemispherical head is not good, but difficult to manufacture point of view, good manufacturing gradually. 
 Head is a component of the container according to the different geometry, applied to a variety of container equipment, such as storage tanks, heat exchangers, towers, reactors, boilers, and separation equipment. 
 Stitching should head the distance requirements greater than 3δ, and not less than 100mm (heat affected zone is a high-stress area, and the chemical composition in the area will be burnt. Therefore, to avoid high-stress area, the Regional and thickness. According to practical experience, head of the stress decay length is greater than 3δ, and not less than 100mm). But the refrigeration equipment is difficult to meet this requirement, has its particularity.