Using Nitrogen vs. compressed air fills for Carbon Fiber fill Tank

Same happened with my local FD. Only thing the weld shop might say. "it's not labeled". Nitrogen. 

The worse part of the N2 deal is that I stare at a liquid N2 tank all day long at work.

As of now I'm like others I"m leaning to a compressor, but dry stable N2 would be great. Taking it from a warm climate to cold would be great. Having someone else drop it off bonus. But if I can't get the price down to something I can afford over the long haul.

Dave

mobilemail said:

I see welding supplies at auctions now and then. What are the chances of buying your own nitrogen bottle at an auction, and just having a supplier fill it?

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New to this forum, but I am a long time user of cylinder gas and dealing with weld supply shops. Most of them want proof of ownership to verify that the tanks are not stolen. There is also the matter of pressure testing. If you lease the tanks, the supplier is responsible for the periodic testing that is required. If you own them that cost is on you.

The lifetime or 90 year lease if it's an option in your area is a good choice, you don't pay monthly rental (demurrage -old school for rent)

I haven't been over here for a while, https://groups.yahoo.com/neo/groups/Compressor_Team/info is a HPA compressor forum mostly for dive compressors, but the info is good :>)

Jim Sheldon is the resident guru over there.

Paul

Great thread!!! I've been considering a Air Venturi 4500 psi compressor but I know that I'll be repairing it within a few years of purchasing it. I'm currently using a Shoebox but it takes forever to top off my scuba tanks and it's fairly high maintenance. 

I'm wondering if someone could give me an idea of how many top offs I could expect on a scuba tank if going from 2800 psi up to about 3400 psi? This would be from a 6000 psi 444 Cu Ft. Cylinder which I'd obtain at my local welding supply company.

This sounds like it may be the best option if I can get a reasonable number of top offs.

This is my favorite PCP tank calculator as it uses a more realistic compressibility for air than "ideal gas": 

https://sye.dk/airgun/

The only way you're going to get a tank filled at the fire department is if you have a relative who will bring it in to work with them. They'd be crazy to fill tanks for the public.

Razor - not sure if you checked out that calculator I linked, but for a 6K cylinder that starts full (ie, at 6000 psi), you could refill a Marauder rifle (215cc reservoir) from 2000 psi to 3000 psi about 440 times. A full 6K tank actually contains over 15000 L of nitrogen. I have a 6.8L CF tank that I fill from the 6K cylinder to 4300 psi. Once my 6K cylinder drops below about 4000psi, I'll just fill my my CF tank as high as the cylinder will take it, then top it up to 4300 psi with my YH.