ATM pressure for Pressure vessel

[ZaxMin]

Hi guys, I quite new in pressure vessel this field. I got 1 question about the atmospheric pressure (atm pressure) actually is equal to 0 or 1 when using atm pressure to design a vessel??

 

[racookpe1978]

Hint; What is the gage pressure of the fluid in your pressure vessel?

 

[LittleInch]

Keep the same units as your other pressures - if its bara then its 1, if its barg then its zero

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[ZaxMin]

Thanks for the info...really appreciate...

 

[dineshakabari]

In case of ATM pressure case, there will be pressure at bottom parts of vessel due to the liquid head based on the height of liquid above it. If liquid is heavier than water then specific gravity needs to be considered for static pressure of liquid. Also make there is not a possibility of vacuum during the emptying/pumping out liquid. This may lead to external pressure consideration also.

 

[MechD]

An atmospheric vessel would be e.g. 1.034 BarG internal and 1.034 BarG external at the same time. Be careful when designing as these values are only acceptable when both internal & external pressures are the same, i.e. the pressure in the tank is equal to the pressure in the atmosphere. For instance if you run a vessel calc in PV Elite software, it will calculate internal & external min. required thickness separately. So if I apply 1.034 BarG int. and 1.034 BarG ext. to my PVElite calc, the software assumes there is a potential case of 1.034 BarG ext. and 0 BarG internal, so the vessel would need to be designed for Full vacuum. This will drive up your shell thickness unnecessarily if you are designing an atmospheric vessel. You are better off applying a minimal pressure of e.g. something around 40 mBar (0.04 Bar) internal and external instead of the full 1.034 BarG.

Also note Dineshakabari's comment regarding potential vacuum case - even if you don't envisage a vacuum it could still potentially happen!