jacketed vessel design 2

[arcc]

If you have a jacketed vessel and the internal vessel is operates under full vacuum (15 psi external) and the water jacket has 35 psi internal would the internal vessel be required to have a external design pressure of 50 psi or 35 psi based on the pressure in the water jacket?

 

[desertfox]

Hi arcc

I think its needs a design pressure of 50psi externally as your pulling a vacuum on the inside and pressure from the water jacket is 35psi.

hope this helps

 

[prex]

If you don't want to ask many questions to the process engineer, take 50 psig external, as indicated by desertfox.
However it is not impossible that the internal vacuum is never concurrent with the jacket pressure, so that they are not to be superimposed. Note by the way that I've never met such a condition and that it would need to be clearly specified in the design conditions for the vessel. prex

http://www.xcalcs.com

Online tools for structural design

 

[Shmulik]

Hi,
To my opinion it is absolutely clear that the external design pressure should be of 50 psig, it is NOT unusual condition requirement. However, even though process engineer clearly defines that process requirements never combine internal vacuum and external heating / cooling, your design conditions have to take into account the possibility of control or operating failure.

Good luck.

 

[LSThill]

Hi arcc (Mechanical)

What do the U1 from the National Board say?

Leonard@thill.biz

http://www.thill.biz

 

[dooron]

Correct me if I am wrong but its my understanding that
it may be easier to consider all pressures in terms of absolute. The description mixes absolute pressure and gauge pressure. The Jacket sees 35psig (gauge), and the vessel sees -14.7 psi gauge (i.e 0 pressure absolute). So if all pressures are read as absolute then the jacket vessel sees 35+14.7=50psi on its internal face and (35+14.7)-14.7(due to atmosphere)=35psig on its external face.

 

[kyong]

I think dooron is most correct.
So, in my opinion, the design pressure should be 50 psig on inward faced members and 35psig on outward faced mambers unless process engineer or customer clearly specifies that the vacuum and 35 psig of jacket doesn't concur. It seems to be very unlikely that they would specify so, though.

kyong

 

[JOHNPIA2]

It depends on the type of jacket. If a dimple-jacket is used, there is no need to add the jacket pressure to full vacuum. Vacuum is calculated using the complete vessel dimensions, L/D and D/t; the dimple-jacket acts as a stiffener, but I would still check the vessel for full vacuun only.