PVElite Steam Jacket

[wfn217]

The vessel shell has a steam jacket with 150 psig steam. If I remove the jacket and apply 150 psig external pressure to the shell, I get a different result than with the jacket pressure on. Why?

 

[GenB]

I do not understand what you are trying to explain.
what's your question?

 

[gr2vessels]

wfn217,

I seems to me that you are in the trouble of understanding the reason for full vacuum design of the vessel...Yes, if you remove the external jacket, you can/should design the vessel for the externally applied pressure, which in your case is the equivalent of full vacuum applied to the vessel. Please check the ASME code requirements for the vessel calculations subjected to internal and external pressure. It will instantly clarify why do you get different results applying the same pressure internally and externally.

Cheers,

gr2vessels

 

[wfn217]

I mean that it seems like applying 150 psig steam pressure to the outside of the shell should give the same results as applying 150 psig external pressure to the outside of the shell.

 

[SnTMan]

wfn217, required thickness for external pressure for cylinders is a function of length. So for example, if your jacket extends only a small portion of the total vessel length, the thickness required for jacket pressure is smaller than if the jacket pressure is applied to the entire vessel length. Is this maybe whats going on?

Regards,

Mike

 

[wfn217]

SnTMan,

No. The jacket is on the entire cylinder.

 

[SnTMan]

wfn217, what do you mean by "results"?

 

[wfn217]

SnTMan,

I mean the required shell thickness is greater when I apply the external pressure than with the steam jacket on.