General Flange Design.

[SD12]

Hello.

Consider a flanged connection subjected to the internal pressure only. Metal-to-metal contact with the O-ring. No other loads and temperature variations are present. Both flanges are welded to the pipes of the infinite length, i.e. there is no blind flange or dead end in the visinity of the flanged connection.
My question is: Why should we take into account the Hydrostatic End force "Hd" when designing the flanges if there is no dead end in the visinity of the flange?

Thank you in advance.

 

[SnTMan]

So, your system is open to the atmosphere? Then by all means disregard hydrostatic end force, there isn't any.

But every pressure system of any use is not open to atmosphere.

Regards

Mike

 

[SD12]

So, your system is open to the atmosphere? Then by all means disregard hydrostatic end force, there isn't any.

But every pressure system of any use is not open to atmosphere.

Regards

Mike

Hello Mike.

I understand your thought. But, what if we have 3 pipes, two of the them have blind flanges/dead ends at their respective ends. The pipe in the middle doesn't have any. Only flanged connections to pipe 1 and pipe 3. Those flanges (of the middle pipe 2) doesn't support any dead end loads. Do you agree?

Best regards,
Sergey

 

[SnTMan]

No. Pressure acts in all directions. Is the end force not acting to separate the flange pair?

 

[SD12]

No. Pressure acts in all directions. Is the end force not acting to separate the flange pair?

Yes, it does. And I can see it clearly when the dead end or blind flange is in place. When they are not, even in the vicinity of the flange, the doubts arise.

Thanks a lot for your help.

 

[SnTMan]

You're welcome of course.

Maybe this idea is useful to you: Consider a section thru the pipe wall at any arbitrary distance from a capped end.

The end force is acting to separate the wall either side of the section. This force is resisted by the wall itself.

 

[TGS4]

Draw yourself a free body diagram. Properly consider the end conditions. You’ll see horse what SnTMan says is correct.

 

[CuMo]

What are you trying to achieve?
The procedures for flanged joints design have been established so that they cover potentially all loading scenarios.
A flanged joint subjected to internal pressure will experience mostly radial outward stresses which might however translante/transform into bending stresses which act axially & perpendicularly to the flange peripheries.
So the equations in Mandatory Appendix 2 are there to ballance the whole joint and trying to oversimplify it or ignore all other potential loads except for one, will probably lead to nothing good.
There's a paper that I can think of since July 2001: "Modeling of internal pressure an Thrust load on Nozzles using WRC 368" from the COADE Mechanical Engineering News, which might help understand how thrust loads in a pipeline work.
If I am understanding your question correctly.

 

[SD12]

What are you trying to achieve?
The procedures for flanged joints design have been established so that they cover potentially all loading scenarios.
A flanged joint subjected to internal pressure will experience mostly radial outward stresses which might however translante/transform into bending stresses which act axially & perpendicularly to the flange peripheries.
So the equations in Mandatory Appendix 2 are there to ballance the whole joint and trying to oversimplify it or ignore all other potential loads except for one, will probably lead to nothing good.
There's a paper that I can think of since July 2001: "Modeling of internal pressure an Thrust load on Nozzles using WRC 368" from the COADE Mechanical Engineering News, which might help understand how thrust loads in a pipeline work.
If I am understanding your question correctly.

Thank you.