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After the openings are made in the actual container shell, nozzles or flanges must be welded in place, and the stress concentration at these nozzles is different from that resulting from small circular openings in the shell. Under the operating pressure, the membrane displacements at the connection points between the shell and the perforated nozzle are not equal, but the final displacement values must still be consistent with each other. Therefore, mutual restraining forces and bending moments are generated at the connection points; thus, at the perforated fitting, there are not only concentrated stresses and membrane stresses at the edge of the hole, but also edge stresses and welding stresses. Furthermore, factors such as the structural shape of pressure vessels, their loading conditions, and operating environment have a more complex impact on stress concentration at the joints compared to the case of drilled holes. Therefore, the stress concentration at the shell joint is more severe than that at a smooth hole, with the stress concentration factor reaching 3 to 6. However, its attenuation is rapid and it has a distinct local nature; it does not cause any significant deformation of the shell, so stress peaks can exceed the material’s average yield stress. The purpose of reinforcing container openings is to reduce the stress peak at the edge of the opening to an allowable value. To this end, the reinforcement must meet the following basic requirements: ① Select an appropriate reinforcement method and structure based on the operating conditions of the container and the properties of the materials; ② Use sufficient amount of reinforcing metal, ensuring that it is applied directly in the area where stress peaks occur around the openings, and include appropriate transition radii to prevent the formation of new stress concentrations.