Within several common withstand the pressure head oval, conical, spherical cap, conical head, do the following description for the following four head shape and structure of the relevant circumstances:
1. Elliptical Head circumferential (hoop) stress and meridional (axial) stress points are changes in the housing, the hoop stress and axial stress vertices are equal, while at the equator stress. Elliptical head to withstand the internal pressure even when the axial stress constant tensile stress (positive), and the maximum to the equator decreases gradually to a minimum at the vertex; the ring to stress, head pressure transition zone will begin to appear stress, if the minor axis ratio continues to increase, compressive stress head edge transition zone will rapidly increase, the more light that is head, the higher the compressive stress head edge, so that the head and minor axes ratio is limited to 2.6 less is more reasonable. In addition to head thickness should meet the strength requirements of large-diameter thin-walled oval head, but also put up due to the compressive stress head the transition zone, resulting in the reduction of elastic instability, therefore should head thickness meet the stiffness requirements.
2. dished head by a spherical section, straight section and a transition zone of three parts. Transition zone connecting the spherical portion and the straight section, the radius of curvature of the warp at both ends of the transition zone has a mutation will produce edge stress. The ratio of the radius of the spherical radius of the size of the transition zone and dished head edge stress related, the smaller the ratio, the more severe curvature of the border mutations, the greater edge stress, when the ratio of the radius of the transition zone limit ie 0:00, dished head turned into a spherical cap head and body straight, this time to the maximum edge stress. So dished head of the transition zone is to reduce the edge stress, and straight side edge portion in order to avoid stress in the weld head and the cylinder connection.
3. The spherical cap shaped head occur in the spherical radius of curvature of the cylindrical junction mutation, but because of two housing exists no common tangent lateral thrust, so considerable discontinuity stress, so this is generally only head pressure is not high for the occasion, and the fillet weld head and cylinder connection must be full penetration structure. When the ball crown-shaped head design, should pay attention to the thickness of the cylinder head and the connection should not be less than the thickness of the head, or should be set up to strengthen the connection between the transition section and the cylinder head. The thickness of the cylindrical segment should strengthen and seal top thick, the length should not be less than the purpose of edge stress reduction.
4. The conical head what time zone folding angle restrictions refer GB150 relevant chapters argument. Here to talk about the internal pressure that is no hemming conical head.
The main body portion cone under the action of the internal pressure, the maximum stress occurs at the big end of the film. Cone and cylindrical portion junction, due to the geometric discontinuity, the radius of curvature mutation, so there will have a greater lateral thrust, causing the larger edge stress, prone to bending, so be strengthened.
