[Barrybomb]

Originally Posted by 61 chevy

I would venture to say the 260 + 260 cubic feet. ...So 260/12 ( my uneducated guess on cfm of hvlp gun )=21.666. So I would guess that you would have no more than 21 minutes of supply available at this rate. Although the actual time would be less if you figure in the effect of flow verses presure. It is a holiday weekend and I refuse to embark on such mathmatical formulations.

I don't think that the formula is quite that simple,but then again I haven't started driking yet,LOL!

I'm guessing:
You start with the volume of the tank (approx 5 cubic feet?)
and multiply by 3000 psi (with some factor)to get the total volume of air in the tank. Once knowing that you could figure out how long you could disperse that air at a rate of 50psi at 12CFM.

Can somebody get their school teacher wife on this? (LOL!)

[BarryK]

I apologize to everyone on here and most of all to the poster or starter of the thread.

I found out I wrote this this afternoon when a friend sent me an email offering his third grade daughter's science book.
You can't imagine the horror when I saw this post but thats life.

I don't remember writing it or can I offer a reason why other than I was being hateful and why I drove home and got on the computer, I don't know as I don't remember doing the drive home or the computer. If I posted anywhere else, forgive me but I don't want to know about it as this is bad enough.

There is no excuse and I offer none but I did it and all I can say again is I'm sorry and embarrassed.

Barry

[oldred]

I have used Nitrogen for years to purge tanks prior to welding on them As stated Nitrogen makes up the majority of the gases in the air we breath and the only hazard would be if you confined it in an air tight compartment and displaced the Oxygen which could lead to suffocation but if your paint area is airtight you are going to have bigger problems than Oxygen displacement! Actually using Nitrogen would seem to be safer than compressed air because it would significantly reduce the danger of fire but my concern would be having enough volume on hand to do the job and finding a regulator/flow meter that would flow that kind of volume, might be a problem. You can get liquid Nitrogen in large cryo tanks at most welding/gas suppliers and these will contain as much gas as several pressure tanks and may not be a expensive as you might think. I have for years used these cryogenic tanks and the liquid Nitrogen to freeze steel pins and bushings to shrink them when the fit has to be really tight, this is a common procedure around the mines.

[Barrybomb]

Between the last two posts and the mathematics,I believe I am now going to begin drinking...heavily.(LOL!) This thread has now covered painting,chemistry,geometry,mathematics,mining and psychosis! I'm calling in sick Monday.(LMAO).

[oldred]

The reason I mentioned the mining is that is where I used the liquid form of this gas and I did so to make the point that it is more commonly used and a lot easier to obtain than most people might think. The question was about using Nitrogen to spray paint with and I just thought I would mention one option that no one had talked about yet. This is the second time I know of that this has been asked so apparently some are thinking about doing it for one reason or the other and even though I have never done this it would seem to me that given enough volume it should work just fine. For sure you would have a VERY clean, dry, oil free source of pressure and I am curious as to how well this might work.

[dh79]

One thing to remember is that if you take a pressurized gas and release it, the gas will be very cold. I'm not sure exactly what would happen, but I don't think the reducers would react well to sub-zero temperatures. It is entirely possible that the cold spray will take moisture out of the air and freeze it into your paint. Ice crystals in the paint would not be good. Paints are designed to be used with compressed (and therefore warm/hot air). I don't think cold nitrogen will work well.

[oldred]

dh, Darn good point you have there and that may very well be a major drawback to doing this. For sure the gas from the the liquid would be incredibly cold, even the gas would be more than -150 deg close to the tank so it would definitely have to be allowed to warm up before entering the spray gun since at that low temperature it would not only freeze the paint it would also freeze the rubber air hose! While I am sure warming the gas would be simple enough it is just one more thing to consider that when combined with other likely problems could make this impractical even if it is possible.

[Buds34ford]

Hey guys,
Just trying to keep the facts right. Nitrogen is lighter than air and Oxygen. The molecular weight of N2 is 28 air is 29.2 and O2 is around 30. My numbers most like are a little off since I'm using my memory! But the bottom line is they are all very similar. The earths atmosphere is made up of about 80% N2. So adding a tank of N2 to it will have be a very low health risk unless you are working in an air tight compartment. The main advantage of using 100% N2 is O2 can be very reactive with many substances. Get rid of the O2 and you have little chance of corrosion etc.

[Chevrolet4x4s]

Originally Posted by BarryK

Did not know that! now I do.

Nascar Has been using the nitrogen to air up their tires for years ......doesnt build up as much as air.

Shane

[MARTINSR]

It has been around for a number of years in cars all over the roads. When you see green valve caps, that means those tires have nitrogen (or at least they supposed to. ) It doesn't heat up and expand as air does.

Brian

[oldred]

Spraying with Nitrogen would add ZERO health risk since most of the air around us is already Nitrogen it would simply mix with the air and would not pool up in high or low places. The only danger would be displacing the Oxygen but this would not be a problem either because the paint area would have to be ventilated, if it is not then the paint over-spray would reach toxic (and blinding) levels long before the Oxygen depletion became a problem. The more I think about this the more practical it seems if someone just needs to do just one job and has only a tiny compressor, it would be kind of like a giant rattle can . Maybe the Cryo tanks would be a bit of over-kill however two or more pressure tanks connected by a manifold (these are available) and using a regulator capable of enough flow this should work and would eliminate the need for a high volume compressor plus it would provide very clean and dry propellant.

[joe_padavano]

Originally Posted by confused

they are starting to use nitrogen in automtive tires now. shop air in tires will be obsolete soon.

Considering that shop air is already 80% nitrogen, I'm struggling to understand the advantages (other than marketing and the silly green valve stem caps). As for the nitrogen being drier, well, what's the first thing you do when mounting a tire? Yeah, swab the beads...

[oldred]

Joe, I am with you on this one I have seen these big Nitrogen units for airing tires and I fail to see the advantages in spite of the claims of better fuel mileage (EVERY gimmick claims that!) and longer tire life. While MAYBE the rubber in the tire MIGHT last longer with no Oxygen inside I can not believe that tread life could be extended and since that is the end of most tires, not rubber deterioration, how the heck can tire life benefit? Maybe all this is true and someone can explain how but I remain highly skeptical at this point and I doubt that Nitrogen will ever completely replace air in tires. JMO and I am open to education on this one

Barrybomb, Now we are on to tires so I may have to start drinking with you

[Bob C]

It doesn't expand near as much with heat so you can maintain a more even tire preasure. We use it in race tires because we might only run 5 lbs of air and when the outside temp gets hot your tires can build a couple of lbs.
Bob

[Barrybomb]

Originally Posted by 61 chevy

I would venture to say the 260 + 260 cubic feet. ...So 260/12 ( my uneducated guess on cfm of hvlp gun )=21.666. So I would guess that you would have no more than 21 minutes of supply available at this rate. Although the actual time would be less if you figure in the effect of flow verses presure. It is a holiday weekend and I refuse to embark on such mathmatical formulations.

You know,I found a couple of tables for calculating the volume of gas in a compressed cylinder and found the volume of the Oxygen cylinder used in my Oxy-Acetylene torch setup (and probably the same size cylinder for Nitrogen,about 5' tall,called a K cylinder) 1.76 cubic feet-I would have figured more,but filled to about 3000psi, the one tank should last around 20 minutes at 12CFM @50psi. I had to do little estimation of a few factors but it should be close,it backs up the estimation by 61 Chevy above (nice job!).

That's 20 minutes(or slightly less) of trigger fully depressed,as if you just sat there with the trigger all the way down.Maybe someone with more painting experience than I could give an idea on about what percentage of the time during a paint job the trigger is down and the paint is flowing (not time spent moving around the car,getting position,starting and stopping etc.) Maybe someone could give you an example on how long it takes to lay down a complete coat on a particular car and for what percentage of that time the trigger is down and you can then figure on how far you can get on a tank.

The pressure to which the tank is filled by your supplier will also effect the entire equation of course.