Geometric: In the case of the same volume, the surface area of a hemispherical head is small, while the surface area of an elliptical head is basically the same as that of a disk.

Mechanics: Under the same diameter, wall thickness and working pressure conditions, the hemispherical head has small stress, equal bidirectional membrane stress, and is evenly distributed along the meridian. The stress of the elliptical head is not as uniform as that of the hemispherical head, but worse than that of the torispherical head.

From the analysis of the manufacturing process, the deeper the head, the larger the diameter and the thicker the wall, the more difficult it is to manufacture. Especially when using high-strength steel, the integral stamped hemispherical head is not as easy to manufacture as the elliptical head.