Cascade System question/ Info

[Kirk king]

ok so i got a question that i know the answer to but just want to see if any one else have ever looked into this.

theres a shop here locally that sells 4500 psi Nitrogen bottles for 1/3 the price of 4500 air tanks and im after chatting with them for hours about this. just say i was to make a cascade system with these Nitrogen tanks, i know from talking to people they say its a NO NO as the pure nitrogen can leach from the steel tank into the fresh compressed air that i would fill them with and could bring the o2 content down and raise the nitrogen percentage.

Some people i have talked to have said leave the valve off them for a few days and it will leach its self out, others have said once its drained and at Atmosphere pressure thats it there good to go.


Personally if theres any doubt i wouldn't go with the Nitrogen tanks as theres too much risk involved in it, but has any one ever looked into this or have tried it?

 

[tbone1004]

I'm not sure I'm getting what you're looking to do. Are you talking about purchasing 4500psi nitrogen cascade storage bottles instead of 4500psi air cascade storage bottles? Then worried what the gas looks like after it sits in the cascade?
If that's the case just buy an O2 analyzer and make sure that it's safe to breathe before you dive it, which you should be doing anyway

 

[Kirk king]

I'm not sure I'm getting what you're looking to do. Are you talking about purchasing 4500psi nitrogen cascade storage bottles instead of 4500psi air cascade storage bottles? Then worried what the gas looks like after it sits in the cascade?
If that's the case just buy an O2 analyzer and make sure that it's safe to breathe before you dive it, which you should be doing anyway

but a nitrogen cascade system can the nitrogen molecule leach into the wall of the tank and then leach back out when say 21% is put in them?? getting into some chemistry and crap with this...

 

[Wookie]

but a nitrogen cascade system can the nitrogen molecule leach into the wall of the tank and then leach back out when say 21% is put in them?? getting into some chemistry and crap with this...

Wut?

 

[Kirk king]

Wut?

ok so if you fill a cylinder with 100% nitrogen under pressure can them nitrogen molecule be pressed into the walls of the cylinder ( leach into) and then say fill the cylinder with hight pressure air can them nitrogen molecule move back from the tank wall to the current 21% mix?

 

[Jack Hammer]

I'd use them without hesitation. Even if Nitrogen could somehow "leach" out of the steel it wouldn't be enough to "taint" your banked gas. Always analyze regardless.

 

[Kirk king]

I'd use them without hesitation. Even if Nitrogen could somehow "leach" out of the steel it wouldn't be enough to "taint" your banked gas. Always analyze regardless.

yeah no doubt to test the air i just this its a big can of worms to open i think if you wants to get real techy with it and all and break down the science behind molecules and all lol

 

[tbone1004]

but a nitrogen cascade system can the nitrogen molecule leach into the wall of the tank and then leach back out when say 21% is put in them?? getting into some chemistry and crap with this...

If it could leach into the metal, it would leach through the metal and if it could do that, it wouldn't be that good of a pressure vessel now would it?
Now, 4500psi, 444cf and you bled it down to 150psi to keep the valve snug is 15cf of gas, 3.3% of full pressure. Topped off with air, and you'd still be at 20% fO2. Not something to bother yourself with. You certainly won't have 15cf of gas "leached into the walls".

Just dump it all the way down and refill. You'll be fine

 

[Wookie]

If you are concerned, when you change the CGA 677’s out for CGA-347’s, rinse the cylinder with blue-gold and dry thoroughly to remove the residual nitrogen. I wouldn’t worry about it myself.

 

[TrimixToo]

ok so i got a question that i know the answer to but just want to see if any one else have ever looked into this.

theres a shop here locally that sells 4500 psi Nitrogen bottles for 1/3 the price of 4500 air tanks and im after chatting with them for hours about this. just say i was to make a cascade system with these Nitrogen tanks, i know from talking to people they say its a NO NO as the pure nitrogen can leach from the steel tank into the fresh compressed air that i would fill them with and could bring the o2 content down and raise the nitrogen percentage.

Some people i have talked to have said leave the valve off them for a few days and it will leach its self out, others have said once its drained and at Atmosphere pressure thats it there good to go.


Personally if theres any doubt i wouldn't go with the Nitrogen tanks as theres too much risk involved in it, but has any one ever looked into this or have tried it?

This is a complete load of...well, "disinformation." Atmospheric air is 79% N2 fer cryin' out loud. I did not look up the CGA valve spec for inert gas vs. air, but the valves are not that expensive if you bother to change them. (I would change them if they weren't the same, but that's me.) If you want them to be "the right color for air," buy a can of spray paint. Blue, IIRC.

Tanks are tanks and N2 is harmless, and does not dissolve in steel to any significant degree. It will not somehow contaminate breathing gas afterward. Buy the N2 tanks. Inspect them. Fill and empty them a couple times so the percentage of N2 inside drops near enough to atmospheric as makes no difference. Fill them again with suitable air, and then fill your tanks from them. If you need O2-clean air, clean them first or have them cleaned *no matter what they were used for previously*. (Actually that's not a bad idea in general.)

If you will pump them and your dive tanks full of air only, you need not analyze, either, except possibly the first time to assure yourself O2 levels are normal after the purging is done. If you will mix, on the other hand, you need to analyze without fail.

Then, go blow some bubbles.