Over pressurization of Vessel due to Over pressure in Jacket?

[ImRB]

Hello All,

In a jacketed vessel (SS Jacket on a SS Cylindrical Vessel), if there is a thermal expansion of chilled water in the jacket due to blocked outlet then there will be tremendous pressure rise in jacket & so PSV is required.

My doubt is that when the jacket will have overpressure, it will apply compression at the vessel shell & hence can't the vessel too be over pressurized?

Do we need to consider shell pressurization as well? If no then why? If yes, then which code to refer as I guess API 521 does not say anything about it.

with regards,
ImRB

 

[LittleInch]

Correct.

Excessive differential pressure from outer to inner can buckle / crush the inner vessel very easily if the shell thicknesses are small.

Just need to put the maximum differential pressure into your shell calculations.

This is pretty standard jacketed system design.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RVAmeche]

LI,

Shouldn't the vessel/jacket should be designed such that the vessel wall can withstand the jacket being pressurized to it's MAWP? If OP installs a jacket side PSV that's properly sized I would've expected the vessel wall would be adequate.

 

[LittleInch]

Yes it should. It's not clear from the OP whether this has been foreseen or not. About 10% of the information to do anything useful so bland generalisations is as good as we can offer.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RVAmeche]

Fair point

 

[ImRB]

hello,

thanks to all of you for the replies.

this was my conceptual doubt & hence could not give the actual design problem data along with it.Nevertheless, all have replied fairly well to clear off my doubt.

@RVAmeche (Mechanical): i agree with you that the vessel wall should be designed to withstand the jacket being pressurized to it's MAWP. the concern is that at the time of relieving of the Jacket PSV, the pressure in the Jacket would be 110% of MAWP (because the Set Pressure is kept = MAWP).

So i still dont know whether typically the vessel shell is designed while considering that the external pressure could be upto 110% of the jacket MAWP?

with regards,

ImRB

 

[don1980]

ImRB - A jacketed vessel is two separate pressure vessels that share a common wall. So the answer to your question is yes. The inner pressure vessel's shell is also part of the jacket. Each vessel (jacket and the inner vessel) have their own design T&P. So the strength (thickness) of the shared wall is designed to be sufficient for the design T&P of both vessels. Like any other pressure vessel, the jacket has an MAWP, so the PRD on the jacket is sized using the same accumulation limits that are applied to any other pressure vessel.