Dry Nitrogen
Dry Nitrogen
(OP)
I have a submersible tank that our customers fill with 2-3 psi of Nitrogen. One engineer told me that this could be detrimental to the product causing rust and corrosion by forcing nitrogen into a tank that already contains some oxygen. I'm not very good at this..but is this bogus? I know that the tanks are not vaccuumed or anything before the Nitrogen is put in, but what exactly is dry nitrogen?
thanks in advance
thanks in advance





RE: Dry Nitrogen
Best regards
Morten
RE: Dry Nitrogen
By "submersible" do you mean a tank that is going to be used underwater as a Nitrogen source? Something doesn't make sense:
1) You say your customers fill it with 2-3 psig of N2 (I assume you mean gauge pressure, otherwise it's a vacuum);
2) You add that someone told you that this could be detrimental to the product causing rust and corrosion by forcing nitrogen into a tank that already contains some oxygen;
3) You further state that the tanks are not vaccuumed or anything before the Nitrogen is put in.
What is confusing is not knowing what your product in the tank is. Is it supposed to be N2 - or O2? Also confusing is the claim that N2 addition is causing rust (WRONG!) and that the tank already contains O2 (how could it, if your customers filled it with N2?).
The confusion aside, dry N2 can be nothing more than what it is labeled: Nitrogen gas that has no (or nil) water moisture or humidity - just as MortenA states. But what does the moisture (or lack of it) have to do with N2 or O2. Can you clear me up?
Art Montemayor
Spring, TX
RE: Dry Nitrogen
thanks!!!
RE: Dry Nitrogen
It turns out that the guy "who claims to know everything", if he said that N2 causes rust and corrosion, doesn't know beans about what he's talking about.
Oxygen, not Nitrogen, is the main cause of "rust" (ferric/ferrous oxide). In fact, if you want to deter, or arrest" the rusting of steel/iron, you use Nitrogen (as a blanket) to displace the 21% of Oxygen in the air atmosphere. I'm not trying to be insulting by stating that this is high school chemistry; rather, I'd like to point out how basic and straight-forward the process of "rusting" and corrosion is: it's the formation of oxides - which starts with the prescence of Oxygen, not Nitrogen (which is basically an inert, non-reactive gas).
There are other processes that contribute to "corrosion" - acids, salts, bases,etc. But the definition of rust is still: the formation of brittle coating on iron when attacked by moist air and composed essentially of hydrated ferric oxide. Oxygen can also react with copper, silver, and other metals to form the corresponding oxides and give different types of "rusts".
Your scenario is that if the N2 reduces (dilutes) the quantity of Oxygen in your submerged tank, any potential rusting will be inhibited - not increased.
I hope this explanation helps you respond to your critic. Nitrogen might react (in rare, special cases) but I doubt it if we are talking about copper/brass electrical contacts or switches.
Art Montemayor
Spring, TX
RE: Dry Nitrogen
thanks!
Mark
RE: Dry Nitrogen
TTFN
RE: Dry Nitrogen
For pressure purging the recognized formula would be:
number of cycles=ln(RH2/RH1)/ln(14.7/17.7)=ln0.5/ln0.83=3.7, namely 4 cycles.
For sweep purging (if two tank openings are available):
the amount of nitrogen: V ln(RH1/RH2)= V 0.69, namely one "tank volume" would suffice.
Of course, if the original moisture were, say RH1=70%, and the final requested RH2=60%, no purging may be required.
On the other hand if a lower dew point or moisture concentration is required the purging requirements should be recalculated.
I wonder if I am on the right track, and this is the point the "know all" colleague wanted to rise.
RE: Dry Nitrogen
inside the enclosure. Its about the size of a fridge and normally it is pressurized with 2 to 3 lbs. of nitrogen, the contents inside are copper bars, wires, and zinc plated steel components
thanks
Mark
RE: Dry Nitrogen
Humidity can be measured on the gas upon letting it out (after pressurizing) by any psychrometric method.
RE: Dry Nitrogen
Why can't you have your electrical enclosure suitable to IP56 or better?
Regards,
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