Hemispherical Head ASME Code

The hemispherical head made by Dalian Dingjin as per ASME code refers to the hemispherical head composed of half a spherical shell and a straight edge (cylinder short section) fabricated as per ASME code. The radius of curvature of the spherical shell is equal everywhere, and the force is uniform. Compared with other heads, the hemispherical head requires the smallest wall thickness when subjected to the same internal pressure. At the connection between the spherical shell and the cylinder of the same thickness, the edge stress caused by the change in the radius of curvature is only 3.1% of the overall film stress of the cylinder, which can be ignored. Therefore, the hemispherical head has good mechanical properties and saves materials.

The axial section of the hemispherical head shell is a semicircle. Dingjin formed the ASME code hemispherical head with a smaller diameter can be pressed as a whole, but the hemispherical head with a larger diameter is difficult to press as a whole due to its greater depth. Therefore, it is necessary to weld several trapezoidal spherical petals of the same size and a circular spherical panel (spherical crown) at the top center. The hemispherical head is very uniformly stressed. However, due to the difficulty in manufacturing, it is generally used for pressure vessels with higher pressure and larger diameter, and is rarely used in other containers.

1. Carbon steel hemispherical head will crack in the environment of ammonia, alkaline sodium, etc., and residual stress should be eliminated when ordering the hemispherical heads.

2. Austenitic stainless steel will cause stress corrosion cracking in a specific environment with chloride ions, so choose the appropriate material when designing the hemispherical head.

3. Carbon steel pressure vessels that need hot-dip galvanizing or aluminizing should be heat treated prior to remove residual stress.