# Thread: How Convert volume to air gallons

1. WeldingWeb Foreman
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## How Convert volume to air gallons

Could use a little help/confirmation. My deceased father left many garage items and one is an upright (on wheels) air cylinder. Pics tomorrow to follow. It measures approx 20 inches in diameter and 40 inches high. If my rough math is near correct that equates to about 12,500 cubic inches volume.

What I am trying to do is estimate the air capacity in gallons. Just looking at my sears 25 gallon compressor, I am leaning towards 55 gallons or so of air capacity. Does that sound reasonable?

Then, I wonder what air pressure to be safe. It seems similar to an old propane tank but somewhat stouter. I expect it should be pressure tested. However, it seems far better than my sears 25 gallon. I am currently filling it to approx 75 psi, and the volume helps.

The tank comes in handy, it has a handle welded to it and attached to the handle is a cup (piece of pipe) that fits nicely over a 2 inch ball when tilted forward and attached to lawn tractor or whatever. Makes for a handy portable air tank.

So, am I close at 50 to 55 gallons? I can sense the responses bout tank rupture, so we are prepared. Thanks folks..

2. Master Welder
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## Re: How Convert volume to air gallons

Originally Posted by geezer
Could use a little help/confirmation. My deceased father left many garage items and one is an upright (on wheels) air cylinder. Pics tomorrow to follow. It measures approx 20 inches in diameter and 40 inches high. If my rough math is near correct that equates to about 12,500 cubic inches volume.

What I am trying to do is estimate the air capacity in gallons. Just looking at my sears 25 gallon compressor, I am leaning towards 55 gallons or so of air capacity. Does that sound reasonable?

Then, I wonder what air pressure to be safe. It seems similar to an old propane tank but somewhat stouter. I expect it should be pressure tested. However, it seems far better than my sears 25 gallon. I am currently filling it to approx 75 psi, and the volume helps.

The tank comes in handy, it has a handle welded to it and attached to the handle is a cup (piece of pipe) that fits nicely over a 2 inch ball when tilted forward and attached to lawn tractor or whatever. Makes for a handy portable air tank.

So, am I close at 50 to 55 gallons? I can sense the responses bout tank rupture, so we are prepared. Thanks folks..
Well... since there are aprx. 7.48 gallons in a cubic foot..... and you have a cylinder with 12,566+ cubic inches in it... seems easy enough

12,566 / 1728 = 7.2719 (FT3)

7.2719 X 7.48 = 54.39 (GAL)

3. Master Welder
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## Re: How Convert volume to air gallons

I believe tackit... or maybe it was someone else??? had a thread on hydrotesting your own tanks here somewhere that way you could at least 'proof' test your tank and make sure it has a relief valve on it for somewhere below where you test to

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## Re: How Convert volume to air gallons

[QUOTE=ronsii;8781571]Well... since there are aprx. 7.48 gallons in a cubic foot..... and you have a cylinder with 12,566+ cubic inches in it... seems easy enough

12,566 / 1728 = 7.2719 (FT3)

7.2719 X 7.48 = 54.39 (GAL)[/QUOT

7.48 for dry calculations. You are correct sir, should have figured that myself. Anyhow, my Kentucky windage was on target.

5. Master Welder
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## Re: How Convert volume to air gallons

Oh, here's tackit's thread on the DIY hydrotest... https://weldingweb.com/vbb/showthrea...te-of-at-tank/

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## Re: How Convert volume to air gallons

Much obliged sir

7. Master Welder
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## Re: How Convert volume to air gallons

Originally Posted by geezer
Much obliged sir
Yer welcome

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## Re: How Convert volume to air gallons

geezer

Originally Posted by geezer
. . . I can sense the responses bout tank rupture, so we are prepared . . .
Your post - sound like you are trying to kill the entire neighborhood - what,
is the end use, of your Manhattan Project - reverse engineering . . .

hth

Opus

.

9. ## Re: How Convert volume to air gallons

It is 231 cubic inches to 1 gallon
It is what for a long time and hand calculator

But today I use a app
Faster too and most convention
See at

Dave

Originally Posted by geezer
Could use a little help/confirmation. My deceased father left many garage items and one is an upright (on wheels) air cylinder. Pics tomorrow to follow. It measures approx 20 inches in diameter and 40 inches high. If my rough math is near correct that equates to about 12,500 cubic inches volume.

What I am trying to do is estimate the air capacity in gallons. Just looking at my sears 25 gallon compressor, I am leaning towards 55 gallons or so of air capacity. Does that sound reasonable?

Then, I wonder what air pressure to be safe. It seems similar to an old propane tank but somewhat stouter. I expect it should be pressure tested. However, it seems far better than my sears 25 gallon. I am currently filling it to approx 75 psi, and the volume helps.

The tank comes in handy, it has a handle welded to it and attached to the handle is a cup (piece of pipe) that fits nicely over a 2 inch ball when tilted forward and attached to lawn tractor or whatever. Makes for a handy portable air tank.

So, am I close at 50 to 55 gallons? I can sense the responses bout tank rupture, so we are prepared. Thanks folks..

10. WeldingWeb Foreman
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## Re: How Convert volume to air gallons

Originally Posted by OPUS FERRO

geezer

Your post - sound like you are trying to kill the entire neighborhood - what,
is the end use, of your Manhattan Project - reverse engineering . . .

hth

Opus

.

Well I sincerely hope not, my closest neighbor is 1/4 mile away. Happy Thanksgiving

11. ## Re: How Convert volume to air gallons

For high-pressure cylinders, they put the tank into another tank filled with water, and then even if it blows, it blows up vertically and not horizontally.

The reason there is real concern about quickly filing a tank is that heat is generated when you condense any gas. The heat from condensation can cause, metal to glow red almost instantly. Over the years when starting up large rack systems with large compressors, I have seen a large metal vessel the condenser that was supposed to be water-cooled but was not getting water, heat to emit radiant heat in three seconds. The tank weighs several hundred pounds and it just starting radiating heat in a couple of seconds. If you have ever seen melted reeds in a compressor head you know the power of condensation.

That is the danger of draining propane tanks too quickly. You can have nearly zero pressure over the liquid propane. I have heard where an icy tank was dropped or warmed and it detonated. Never did much testing but the information seemed sound and came from some pretty rugged boys.

Sincerely,

William McCormick

12. WeldingWeb Foreman
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## Re: How Convert volume to air gallons

Originally Posted by William McCormick
For high-pressure cylinders, they put the tank into another tank filled with water, and then even if it blows, it blows up vertically and not horizontally.

The reason there is real concern about quickly filing a tank is that heat is generated when you condense any gas. The heat from condensation can cause, metal to glow red almost instantly. Over the years when starting up large rack systems with large compressors, I have seen a large metal vessel the condenser that was supposed to be water-cooled but was not getting water, heat to emit radiant heat in three seconds. The tank weighs several hundred pounds and it just starting radiating heat in a couple of seconds. If you have ever seen melted reeds in a compressor head you know the power of condensation.

That is the danger of draining propane tanks too quickly. You can have nearly zero pressure over the liquid propane. I have heard where an icy tank was dropped or warmed and it detonated. Never did much testing but the information seemed sound and came from some pretty rugged boys.

Sincerely,

William McCormick

Well I am certainly better informed. Appreciate and experienced heat generated from compressed gases, but penny really dropped with propane example. I dunno if the cylinder is an old propane bottle or not, it seems stouter and the gentleman who actually thought this up was a retired pipeline welder from years past. I have used it twice and try to keep pressure to max 75 or 85 psi. That helps to inflate tires around the place, like an old farmall H that was setting in the garage for approx 5 years and had a low tire.....got'er running to. Thanks again for posting.

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## Re: How Convert volume to air gallons

I think William needs to brush up on the definitions of "condense" and "compress".

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## Re: How Convert volume to air gallons

Here is a couple shots of the beast, crude but works.

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## Re: How Convert volume to air gallons

I blew it, did not turn my phone sideways.
Last edited by geezer; 11-28-2020 at 06:08 PM.

16. Master Welder
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## Re: How Convert volume to air gallons

By the looks of the welds on that I'd haul it to the scrap yard. That weld along the side scares me to look at it.

17. ## Re: How Convert volume to air gallons

I'm going with nope.

That one needs to be retired and made into a cooker of some sort

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## Re: How Convert volume to air gallons

Originally Posted by mla2ofus
By the looks of the welds on that I'd haul it to the scrap yard. That weld along the side scares me to look at it.
yup, no eye appeal at all. Like I say retired pipeline gent from years past with AC only machine and lots of candles on the cake. Maybe I should have waited for a rainy day with lots of haze prior to taking a pic, however, your comment valid.

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## Re: How Convert volume to air gallons

I'm going with nope.

That one needs to be retired and made into a cooker of some sort
Noted: And good recommendation

20. ## Re: How Convert volume to air gallons

Originally Posted by mla2ofus
I think William needs to brush up on the definitions of "condense" and "compress".
They are pretty much the same, the reason we call a condenser a condenser is that in refrigeration, that is where the hot gas is condensed and turned into a liquid. You can say it is compressed into a liquid and that would also be a true statement. The condenser is where the hot gas compressed by the compressor loses its heat and so the action of condensation can occur. However, before you reach a temperature and pressure that will liquefy the gas it is being condensed and that causes heat.

With very cold liquid propane, believe it or not, it cannot absorb sudden heat, you would think it would be hungry for heat and it is, but just not sudden heat. So the surface of the liquid superheats much like the surface of a cathode in a cathode ray tube and boils off a layer of liquid propane in an instant, which increases pressure and causes more heat and more pressure.

Sincerely,

William McCormick

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