Why do both the nozzles and the cylinder of high-pressure vessels need to be flanged? What is the purpose?

Ensure structural continuity and reduce local stress.

Agree with the view from the 2nd floor; furthermore, since the flanged part is welded to the pipe fitting, it is easy to achieve full penetration in terms of welding quality and non-destructive testing.

It seems the original poster didn’t say it’s a mandatory requirement, right? It’s not absolute.

The opinions from the second and third floors, when combined, represent the best option! :lol

It is to connect the joints for better stress distribution.

Agree with the view from floor 5; combine the views from floors 2 and 3

The questions posed by the original poster are problematic in the first place. Who said that the connections between the nozzles of high-pressure containers and the container body must use flanging? Insertion-type, embedding-type, or mounting-type connections can also be used; as for a flanging structure, I’ve never heard of it.

High-pressure vessels have relatively thick shell walls and an inserted fitting structure, resulting in high welding stresses; therefore, as compared to the inserted type, the fixed type is more appropriate.

This post was last edited by Pinocchio on 2017-4-5 at 08:50. The flanged structure mentioned by the original poster is likely the embedded structure specified in GB150.3 Appendix D.3.2. There is no requirement that both the nozzles and the cylinder of high-pressure vessels must be flanged; the choice of structure also depends on factors such as the diameter of the pipe openings, temperature differences, and the intended use. The weld is a weak point, and the joint between the nozzle and the shell is a high-stress area; an embedded structure can help keep the weld away from this high-stress area. Furthermore, the embedded structure allows for RT, UT, and MT to be performed simultaneously in order to improve the reliability of the welds. However, the embedded nozzles on the cylinder are not axially symmetric, which makes it difficult to machine the nozzle components. Therefore, embedded structures are generally used in axially symmetric locations such as the center of spherical or elliptical heads, where the stress concentration caused by small-diameter openings is not significant; in such cases, thick-walled inserted or seated types are more suitable. Welding stress can be addressed through welding processes and post-weld heat treatment.