Cascade System question/ Info

[Kirk king]

changing valves in these bottles is a complete and utter PITA so if you can get the supplier to swap to CGA347 for air if they will, and if not see if they'll go to CGA580 which is helium and nitrogen

isnt CGA 580 only goot for 3,000

 

[tbone1004]

isnt CGA 580 only goot for 3,000

officially yes. If in a commercial fill station I wouldn't use them, and you should ask them for CGA347's, but that is an air only connection and they may not want to do that.
Either way, if it's personal fill station I'd just leave the valves as is

 

[nadwidny]

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.

Sounds like you were talking to people at the LDS.

 

[Kirk king]

Sounds like you were talking to people at the LDS.

lol nope im the LDS for over 500 miles each way......

 

[rjack321]

lol nope im the LDS for over 500 miles each way......

As you have discovered, gas suppliers make up almost as much BS as dive shops.
N2 does not "leach" into steel. Acetylene does however, which is why the insides of acetylene tanks are actually designed to be semi porous.

But N2, He and Ar are all functionally inert. I'd just drain them and use them if the burst disk are adequate for your needs. If not I would swap the valves. You dont want to do that yourself, its a royal pita to torque them correctly. Have your hydro shop do it. If the hydro shop is the ones telling you about the chemistry of N2 and steel well, maybe just tell them to stick to hydros...