Improvement in Connecting the Structure of Spherical Crown Middle Head

Abstract

In a pressure vessel, a spherical crown head can be used as an end head or a middle head. Without a common tangent to connect the surfaces of the spherical shell and cylindrical shell, the connection between the spherical crown head and shell produces stresses and deformation at the edge of the connection, so the head and shell in use need to be stiffened and a stiffening section needs to be arranged. With a stiffening section, stainless steel equipment includes more welding beads and looks less aesthetically attractive. If the shell is stiffened as a whole, the thickness of the shell needs to be increased to the thickness of the stiffening section, which is closely related to the radius of curvature Ri of the spherical crown head. Therefore, in design, the optimization of the ratio of the radius of curvature of the head to the internal diameter Di of the shell must be considered, to obtain the spherical crown head and stiffening section with the minimum thickness. However, in most cases, the thickness obtained may not be the most economical, because the head may be non-standard, and is usually formed by stamping, requiring a costly die. Furthermore, it is permissible for all thicknesses of the shell to be increased to obtain the entire shell instead of a pieced-together shell, and such design can cause too great an allowance of strength, merely increasing the costs of manufacturing. The design of dual-cavity-tank equipment used for irrigation by a company requires the use of a spherical crown head as the middle head. In the design, the challenge confronted by the authors is to ensure an attractive appearance, as well as an economical and reasonable cost. In the design, the internal volume was slightly reduced, the way of connecting the shell and the stiffening section was changed, and the optimal ratio of the radius of curvature of the head to the internal diameter of the shell was selected, to obtain the most reasonable thicknesses of spherical crown head and stiffening section. Thus, the actual difficulties encountered have been resolved.