Conical head

The conical head is a head with a conical surface on the shell surface. It is characterized by uniformly changing the velocity of the medium as it passes through, facilitating the removal of viscous liquids and solid particulate materials. However, its mechanical properties are poor, and the discontinuous stress at the connection with the cylinder or nozzle due to the sudden change of shape is large. In order to reduce the discontinuous stress, a folded structure with arc transition or a local thickening structure can be adopted at the large or small ends of the conical shell. The design code of pressure vessel in China requires that the large end of conical shell should be folded when the half-cone angle is greater than 30 degrees, and the small end of conical shell should be folded when the half-cone angle is greater than 45 degrees. Because of the large wall thickness of conical head, it is inconvenient to manufacture, so it should be adopted only when the process needs.
The material for manufacturing conical head can be carbon steel, low alloy steel, clad plate, stainless steel and non-ferrous metals such as copper, aluminium, titanium, etc. The implementation standard is GB/T 25198-2010.
Under internal pressure, the maximum film stress occurs at the large end of the cone body of the conical head. Because of the discontinuity of geometry and the sudden change of curvature radius at the junction of cone and cylinder, a large lateral thrust will be generated at the junction, which will lead to larger edge stress and easy to bend, so it needs to be strengthened. For the large end, the axial bending stress is the main controlling factor and belongs to the secondary stress, so the stress intensity is controlled in it; for the small end, the stress state at the connection between the small end and the cylinder is mainly the average circumferential tensile stress and the average radial compressive stress, which belongs to the local film stress, so the stress intensity can be controlled, but because of this, the stress intensity can be controlled in the small end. Local film stress may exceed the distribution range of edge effect. For safety, the stress intensity should be controlled within. For the large end, the thickness of the reinforcing section should not be less than that of the conical shell connected under any circumstances, and the length of the reinforcing section should not be less than or equal to that of the cylindrical reinforcing section. For the small end, under any circumstances, the thickness of the reinforcing section shall not be less than that of the connected conical shell, and the length of the reinforcing section of the conical shell shall not be less than or equal to that of the reinforcing section of the cylinder.