SIZING CRITERIA FOR N2 RECEIVERS

[IR56]

Hello everyone,

could any body tell me what is the sizing criteria for a Nitrogen receiver? It provides blanketing gas for tanks in a production unit.

 

[irishal]

How quick can you generate new N2? and how fast do you intend using up what you have? This will help determine how much storage you need to keep as a buffer.

 

[sshep]

IR56,

The same methodology for sizing conservation vents per API2000 when summed over all your tanks will give you the instantanious demand to use for sizing your distribution system. Because API2000 does not address duration, you need to know is how much N2 will be required to meet the total demand so as to set a basis for how much N2 must be stored.

To get a basis for reciever volume, I suggest:
1) Take the volume of all tanks and apply the idea gas law to some reasonable temperature change (maybe 20 or 30F) which might be expected during a rainstorm, etc. The difference in starting and ending volume will be the amount of blanket N2 required for thermal changes in the worst case thermal in-breathing situation of all tanks being almost empty.
2) Add to this requirement any working tank liquid volume changes if you think appropriate.
3) Subtract from this any credit for make-up N2 volume as Irashal points out.
4) This result is then corrected to an actual storage volume at reciever pressure, to get a vessel size.
5) Apply an engineering reasonability check on the vessel size vs the consequences of getting some air into your tanks- i.e. you might accept a vessel smaller than worst case calculation so you are covered 90% of the time; or reduce some fat from the calcs by assuming tanks have a 50% level, etc.

best wishes,
sshep