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Nitrogen Gas Flow Calculation To Maintain Tank Pressure

gas flow calculation nitrogen

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#1 jeetu911


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Posted 07 May 2018 - 04:30 PM

Dear All,


I need help to calculate nitrogen gas flow which in used to maintain pressure of 1.5 kg/cm2 of a 10 m3 vessel   

( material filled 9 MT).

Low pressure nitrogen is used (nitrogen tank pressure 2.33 kg/cm2) to maintain 1.5 kg pressure.


please help.






#2 Art Montemayor

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Posted 07 May 2018 - 05:09 PM



Are you intending to inert a fluid stored in a tank by constantly flowing nitrogen into the vessel?  Why are you using this purging method when you could simply maintain a constant vapor space pressure of 1.5 kg/cm2g?   (Note that I do not use your careless and sloppy method of failing to identify the complete pressure units required).   By stating that you intend to use a gas flow into the tank, you are inferring that you are purging the vessel.  Is that what you really mean?


Or are you intending to simply keep the tank contents protected by an inert blanket of nitrogen gas?

#3 Amit J

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Posted 08 May 2018 - 12:34 AM



I assume that you have provided N2 blanket over tank material and you want to calculate peak flow rate of inlet N2 when unloading being done. This N2 flow rate can be used for related control valve sizing, line sizing etc.


Basically this N2 inlet flow depends upon unloading rate out of tank.


But considering worst case scenario, assume that tank is empty at atmospheric pressure (A1 condition). Another B1 condition of tank desired pressure of 1.5 kg/cm2g. Find out N2 density at both these A1 & B1 scenario. you know tank volume i.e. 10m3.  Based on density difference and tank volume, you can calculate how much kg of N2 is required ( density * volume) for makeup within the tank.


Find out time, depending on your operation scenario, in which pressure make up need to be done in that tank.   Thus you can fix N2 flow rate required (i.e. worst case scenario).


Hope my assumption of scenario helps you to arrive at solution.

#4 jeetu911


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Posted 08 May 2018 - 06:35 PM

Thank you Amit Ji.


That will help.

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