Nitrogen Dewer Leakage 2

[mcgyvr]

We just stated using nitrogen in a selective soldering application a few months ago.
We have been getting dewar tanks that are roughly 5 feet high and 2 ft in diameter (3850 cubic feet I believe).
I have a few questions.
#1-Does the nitrogen naturally leak out of the tank when not in use? and if so where..
I know there is a pressure relief valve so I assumed it only leaks out when the pressure of the vent is exceeded..We did hear this once..scared the pants of anyone around..

We haven't gotten fully up to speed/tooled up,etc.. so there are times when it isn't used and is just sitting there for 2 weeks.
#2-Currently 1 big tank will be completely empty in 2 weeks of NO use. Does this seem right?

Our nitrogen supplier says thats normal but it just seems excessive to me.. 2 weeks and a large tank is totally empty when not even used??

 

[btrueblood]

Depends on how hot the tank gets (it's been warm in the eastern US lately, how's it been where you are?), how good the insulation is...but that is a fairly small dewar as industrial dewars go, so yeah, 2 weeks sounds about right.

If you aren't really ready to go with it yet, how about using a few K bottles, or even a cylinder trailer, for ready GN2 supply in the meantime?

 

[mcgyvr]

tank/room is kept at 78 deg C constantly.
I'm just amazed it leaks out that quickly without getting used at all and without ever triggering the relief valve.

 

[MikeHalloran]

If it comes in a dewar, it's not leaking, it's boiling.


Mike Halloran
Pembroke Pines, FL, USA

 

[btrueblood]

78 C?!

That's pretty hot. Might be worth considering a few more insulation blankets, though you may want to do the math (I think you are above the dimensions where critical insulation thickness needs to be considered, but don't recal off hand).

 

[mcgyvr]

haha.. sorry been doing thermal testing in Celsius all week.. Room is 78 deg Fahrenheit.