The flat-head double-opening nozzle structure is widely used in equipment such as plate and shell heat exchangers in the petroleum, chemical and energy industries. There are structural discontinuities in the opening nozzle area of the flat head, resulting in complex stress distribution and local stress concentration in the nozzle area. The external load of the flat head taking over the pipe, such as the coupling of pipe bending moment, axial force, and torque, will also make the stress distribution in the pipe connection area more complicated. Therefore, it is necessary to study the stress distribution law in the nozzle area of the flat head.

　　in conclusion:

　　(1) With the increase of the axial tension of the nozzle, the maximum stress, film stress and primary stress + secondary stress in the connection area of the double-opening nozzle of the flat head continue to increase; with the increase of the axial thrust of the nozzle, the double-opening of the flat head The maximum stress, film stress, and primary stress + secondary stress in the connecting area of the nozzle continue to decrease.

　　(2) Under the combined action of the axial load of the nozzle and the internal pressure, the influence of the axial load of the nozzle on the elastic stress in the connection area of the double-opening nozzle of the flat head is partial. Appropriately increasing the axial thrust load of the nozzle can effectively reduce the flat head The elastic stress concentration effect caused by the discontinuity of the structure in the connecting area of the double-opening nozzle. The influence of internal pressure on the elastic stress in the connection area of the double-opening nozzle of the flat head is global, but the influence on the connection area of the nozzle and the head is more significant.

　　(3) The internal pressure and the axial load of the nozzle have significant effects on the ultimate load of the double-opening nozzle structure of the flat head. The axial thrust of the nozzle can effectively improve the ultimate pressure-bearing capacity of the nozzle area, and with the increase of the axial thrust, the limit internal pressure of the joint area of the flat head double-opening nozzle continues to increase. The axial tension of the nozzle will reduce the ultimate pressure-bearing capacity of the connection area of the double-opening nozzle of the flat head, and with the increase of the axial tension of the nozzle, the limit internal pressure of the connection area of the double-opening nozzle of the flat head will continue to decrease.

　　(4) The linear elastic finite element method can be used to draw the limit load relationship curve of the flat head double-opening nozzle connection area, and the design and safe operation of the flat head double-opening nozzle structure pressure vessel can be guided by this relationship curve.