I need someone whose good at math

[c2k5]

So I'm debating on either getting an hpa setup, or getting a nitrogen setup. My local air gas seems to be pretty high on their nitrogen prices, but I'm still wondering if the cost ratio will make it cheaper.

Ok so Airgas will fill a 6k nitrogen tank for $216. Dive store will do a $12 fill at 4500 psi and the tank I'm considering is 44 cubic feet.

Is there any way to figure out which will have more usable air for the price?

[rsterne]

You need to know the volume of the 6K Nitrogen tank.... ie how many cubic feet does it hold at 6,000 psi.... Also the volume of the gun you will be filling and the fill and refill pressure....

Bob

[Roadworthy]

While you're comparing - the tank is rated 6000 psi.  Do they actually fill it to that pressure?  In other words to they fill it to the full rated pressure or some percentage of that pressure?  That could reduce the potential value of their fill as well.

[QVTom]

500 cuft and they are filled to 6K.  That price is 3X the going rate.  Should be 60 to 70$ for a fill.

The 1U cylinder actually holds 590 cf.  Internal volume is ~1.5 cf, Height 51" and Diameter 10".

Tom

[c2k5]

sorry forgot to put the cu ft of the nitro tank, it's 300. Going to be refilling my at44 which has a 230cc resovoir from 2 to 3k psi.

[ronbeaux]

Be aware. I did an incident investigation involving a nitrogen tank that contained hydrocarbons in it when it was supposed to be just n2. It turns out the company didn't follow their own procedures when re-filling the tank. They were supposed to vent it to zero pressure and then pull a vacuum on it to make sure all contaminates were removed. Instead they took the tank back and just topped it off after their client returned it from a job. The client had used it to purge equipment and when the pressure on the system got equal, hydrocarbons were able to back flow into the bottle.

Dive shops only not so good air from the sky and you get air only.

Just saying

[rsterne]

OK, so according to Lloyd's fill calculator.... http://www.calc.sikes.us/2/index.php .... you would get 26 fills from the 44 CF tank if it was filled to 4500 psi.... You would use up 1/3 of the 44 CF of air in the tank by the time it dropped to 3000 psi.... which works out to 14.7 CF....

For a 300 CF tank, starting at 6000 psi and ending at 3000, you would be able to use half, ie 150 CF (assuming it was full to 6000 to begin with).... You should therefore, in theory, get 26 x 150 / 14.7 = 265 fills.... so basically 10 times the number of fills.... At anything over $120 to fill it, you are better off with the 44 CF, 4500 psi tank.... not counting the time and gas to fill it 10 times of course.... However, it does also not factor in the rental cost of the 300 CF Nitrogen tank, or moving it around (VERY heavy)....

Bob

[c2k5]

OK, so according to Lloyd's fill calculator.... http://www.calc.sikes.us/2/index.php .... you would get 26 fills from the 44 CF tank if it was filled to 4500 psi.... You would use up 1/3 of the 44 CF of air in the tank by the time it dropped to 3000 psi.... which works out to 14.7 CF....

For a 300 CF tank, starting at 6000 psi and ending at 3000, you would be able to use half, ie 150 CF (assuming it was full to 6000 to begin with).... You should therefore, in theory, get 26 x 150 / 14.7 = 265 fills.... so basically 10 times the number of fills.... At anything over $120 to fill it, you are better off with the 44 CF, 4500 psi tank.... not counting the time and gas to fill it 10 times of course.... However, it does also not factor in the rental cost of the 300 CF Nitrogen tank, or moving it around (VERY heavy)....

Bob

That's what I came up with a few days ago. A few people on the yellow forum stated they get tons of fills from their nitro tank that don't make sense when calculated. A 294 cu ft tank filling an 88cu ft scba from 3500 to 4500psi over 100 times. I thought my math was way off, but who knows if they're full of it.

[QVTom]

I have a 1u 6k.  It is 590 cf and costs 70$ to have it filled.  They charge 40$ for delivery which is ok because it's 35 miles one way.  I purchased the tank for 839$.  The benefit is no driving or waiting and cost is about even.

[jhm757]

So I'm debating on either getting an hpa setup, or getting a nitrogen setup. My local air gas seems to be pretty high on their nitrogen prices, but I'm still wondering if the cost ratio will make it cheaper.

Ok so Airgas will fill a 6k nitrogen tank for $216. Dive store will do a $12 fill at 4500 psi and the tank I'm considering is 44 cubic feet.

Is there any way to figure out which will have more usable air for the price?

That fill cost is too high. My 6000 psi nitrogen tank cost $60 a year to rent tank and $59 to fill.

However I don't think my tank was a full 6000 psi seemed more like about 5500 psi. They say they fill them to 6000 psi at 70 degrees, it was not 70 outside here in central NY when I got the tank in the beginning of March so that may be why my tank was less than 6000 psi.

One thing I am finding out is that once the tank gets below 4500 psi now I can't get a full fill in my guppy 4500 psi carbon fiber tank. I am actually down to about 3700 psi in the nitrogen tank, so I only get a few fills from the guppy, then back to the big tank, Ok for shooting at home but if I want to take the gun somewhere else and bring the guppy now I only have a couple fills, I'm shooting a .25 Marauder so that is not a lot of shooting. I am actually looking forward to getting it down to 3000 psi so I can go trade it in for a full 6000 psi tank, I'm too cheap to take it back before I get all I can out of it. I have gotten 5 months of shooting out of it so far.

So it is convenient to always have air right here, not running to get smaller tanks filled all the time, and the cost is not bad, but it does have it's draw backs once the tank is getting low.

Someday maybe I will be able to get a 4500 psi compressor and a large carbon fiber tank. If you can afford it that would be the way to go in my opinion.

Jim - jhm757

[c2k5]

Yeah I think I'm gonna sell some odds and ends and get a shoebox. I told the rep that other people are paying a 1/3 to get their tanks filled and he said that's what the rate is here and they won't match any other distributors price unless it's local. Oh well no business for you.

[Sfttailrdr46]

  If you already have an ioless shop compressor with a 3 gallon pancake tank that can do 150psi and regulate the output to 120 psi to feed the Freedom 8,  I get 10 to 12 fills of my. I will probably get a Great White CF tank in the not to distant future Unless I can get a gently used one and make that my range tank . The convenience of the compressor is  well worth the money spent since I shoot almost every day either in my back yard or basement

[c2k5]

I'm most likely going to get the cheaper shoebox. I still have to get a tank to fill. I hear of some people buying recently expired tanks and filling those, I'm kind of iffy on that. I'm not too familiar with how the cf tanks are made and how lenient that 15 year life is. I don't wanna fill up a small bomb.

[Sfttailrdr46]

I'm most likely going to get the cheaper shoebox. I still have to get a tank to fill. I hear of some people buying recently expired tanks and filling those, I'm kind of iffy on that. I'm not too familiar with how the cf tanks are made and how lenient that 15 year life is. I don't wanna fill up a small bomb.

I don't know but I would err on the side of caution and buy a used still good tank like you said a small bomb and lots of small flying projectiles

[PakProtector]

I'm most likely going to get the cheaper shoebox. I still have to get a tank to fill. I hear of some people buying recently expired tanks and filling those, I'm kind of iffy on that. I'm not too familiar with how the cf tanks are made and how lenient that 15 year life is. I don't wanna fill up a small bomb.

I don't know but I would err on the side of caution and buy a used still good tank like you said a small bomb and lots of small flying projectiles

in addition to the straight up idiocy of using expired tanks, I am quite willing to bet heavily that your insurance is not going to cover you if it breaks open. Maybe you'd be lucky and just get killed, instead of being alive to see somebody who got scratched or maimed take everything you have...and the stuff you'll earn in future.
cheers,
Douglas

[c2k5]

I'm most likely going to get the cheaper shoebox. I still have to get a tank to fill. I hear of some people buying recently expired tanks and filling those, I'm kind of iffy on that. I'm not too familiar with how the cf tanks are made and how lenient that 15 year life is. I don't wanna fill up a small bomb.

I don't know but I would err on the side of caution and buy a used still good tank like you said a small bomb and lots of small flying projectiles

in addition to the straight up idiocy of using expired tanks, I am quite willing to bet heavily that your insurance is not going to cover you if it breaks open. Maybe you'd be lucky and just get killed, instead of being alive to see somebody who got scratched or maimed take everything you have...and the stuff you'll earn in future.
cheers,
Douglas

After doing some research it's ok to use an expired tank.

Tank A sold to USA-15 year life span
Tank A sold to UK-30 year life span