pressure vessel interanl pressure

[Adam001]

In Asme division 1 , for calculating required thickness for internal pressure , the rule has a term " P " which is internal pressure . now I have a general grawing of pressure vessel with internal pressure 3.5 bar gauge , so shall I use bar gauge ( barg) or absolute (bara) as they will give different answers ??

 

[XL83NL]

Which answer is the correct one do you think? Apart from the obvious answer, have you read the code to find out the answer?

 

[Stephen Max]

Use gage pressure, since it is the differential between internal and external pressure that creates stress.

 

[david339933]

gauge + static head.....not atmospheric.

 

[Adam001]

Stephan max , or I can use bara and subtract it from external pressue the same right ?

 

[Adam001]

XL83NL , I read the code and " P " is the internal design pressure in UG-27 , some one told me that I use the pressure difference so it will not vary if it is bara or barg is that right ?

 

[TylerM]

david339933 is correct. use your gauge pressure (barg) along with any static head pressured created by your fluid (assuming liquid service) that'll give you your internal pressure to be used in your calculations.

 

[david339933]

Adam...You may have read the Code, but not enough.....UG-27 definition of 'P' directs you to UG-21....which explains what design pressure is.

 

[AK23Static]

Dear Adam
For understanding , Let me create one design scenario.
We transfer your designed (3.5 bar g) Vessel thickness corresponding to this to moon will it survive? Considering Moon does not have atmosphere you need to design it for Absolute pressure and not gauge pressure.
Earth atmosphere (gauge pr) actually gives you leverage of @ 1.01325 bar (1atm pr) from outside so you can design for less pressure Gauge which is numerically less than Absolute.

Hope it clears the doubt.

cheers
AK
Beginning of every success is desire

 

[Stephen Max]

Gauge pressure is the same as absolute pressure on the moon, so you can still design according to gauge pressure.

 

[AK23Static]

Stephen,
Vessel will not sustain the design requirements.
Absolute pressure for process in our case is 3.5+1.01325 = 4.01325 bar A
When we transfer to moon
Gauge Pressure = 4.01325 (Bar A) - Atm pr (0 on moon) = 4.01325 bar G (moon)
So you need to design at higher value design pressure which will further increase the thickness.

cheers
AK
Beginning of every success is desire