Issues regarding the short sections of long-neck flanges
Thread Content
When selecting long-neck flanges in accordance with standard NB/T47023-2012, standard NB/T 47020-2012 stipulates that \"the cylinder connected to the long-neck flange... shall have a section length of not less than sqrt(DN·δ)\""； On page p14 of GB/T 151-2014, the diagram of the kettle-type reboiler shows a cone that is directly connected to a long-neck flange. I would like to ask everyone: in the design of such kettle-type reboilers, is it necessary to add a short section of approximately 150 mm between the cone and the long-neck flange?
Generally, no additional short section is needed; welding directly is sufficient.
It specifies the minimum length of a cylinder segment. It didn’t mention the cone tube. This sentence does not apply to welding conical cylinders. As long as the calculation sheet is satisfactory, it’s fine.
There’s no need; a cone-shaped tube is also a type of tube
I have doubts about this issue as well; someone previously said that it is necessary to meet the condition of max{length of the reinforced section at the smaller end of the cone-shaped shell, sqrt(DN·δ)}
There’s no need to add it; as long as the strength calculation is satisfactory, there’s no problem. Moreover, adding short sections will affect feeding, as the space at the feed inlet is too small and the flow area is insufficient
This post was last edited by Forgetting = Forgetting on 2020-5-11 at 14:11. When flanges and butt joints are subjected to torque, due to the stiffness of the flanges, the stress concentration point moves gradually toward the axial end as the neck height increases. Even if the strength calculations for the components are satisfactory, torque still causes the stress concentration point to end up at the weld site; if I remember correctly, this is done to avoid such a situation. I’ll take another look at the original manual later
It’s not clear; I’ve seen devices that are welded directly as well as those with short sections added.
The stress conditions here are complex, and conventional design methods cannot take into account the effect of bending moments; therefore, it is not sufficient to rely solely on the SW6 results. In cases where the operating conditions are severe and the hazard level posed by the medium is high, it is advisable to use splices, with their length having to be sufficient to ensure stress attenuation.