How much does compressed air weigh?

[Lohman446]

Anyone with quick access to like a 45/45 tank empty, a scale, and then same full of air could tell me this. Or anyone who happens to know, how much does the air in the tank weigh?

[zackzel]

Anyone with quick access to like a 45/45 tank empty, a scale, and then same full of air could tell me this. Or anyone who happens to know, how much does the air in the tank weigh?


I don't know the answer to this but why do you ask?

[Lohman446]

I don't know the answer to this but why do you ask?

Curiousity, arguing with people on PBN

[punkncat]

Curiousity, arguing with people on PBN


That was your first mistake.


I know there is a way to figure this given weight of air at sea level, multiplied by the pressure, etc., etc.,....but it would be negligable and unable to be weighed on a scale I imagine.

[electriceel125]

That was your first mistake.


I know there is a way to figure this given weight of air at sea level, multiplied by the pressure, etc., etc.,....but it would be negligable and unable to be weighed on a scale I imagine.



Im pretty sure its a weighable difference.

[punkncat]

Im pretty sure its a weighable difference.

Is that the same argument going on PBN?

/just curious

[MANN]

let me finish my pizza, and ill go weigh. is it ok that I do 3000 instead of 4500? and it should be the same weight.

[Zneaky]

here is a simple proof.

I always take my Scuba tank to the scuba shop to be filled for PB.

They put the tank in water, because when you are moving that much compressed air, it gets hot.

When they first put the tank in, it floats. As they are filling it, it sinks to the bottom (3 ft).

Now an alluminim sucba tank is only filled to 3000psi, 3500 if you know someone. Your 45/45 is filled with more molecules of air per square inch so it would be heavier per square inch than my scuba tank.

Z

[buzzboy]

We do the experiment in shcool with a balloon. The amount of weight difference between a filled and unfilled balloon is noticible on an electronic gram scale. Saddly I can't remember how much it weighs.

[snoopay700]

here is a simple proof.

I always take my Scuba tank to the scuba shop to be filled for PB.

They put the tank in water, because when you are moving that much compressed air, it gets hot.

When they first put the tank in, it floats. As they are filling it, it sinks to the bottom (3 ft).

Now an alluminim sucba tank is only filled to 3000psi, 3500 if you know someone. Your 45/45 is filled with more molecules of air per square inch so it would be heavier per square inch than my scuba tank.

Z
Beat me to it, air is made of molecules, compressed molecules are still molecules. Molecules have mass, therefore it weighs more filled, much like a football.

[MANN]

my scale for my CO2 says they weigh the same.

[punkncat]

I'm sold. I would like to know how much more my 68/45 weighs full.....

[MANN]

I'm sold. I would like to know how much more my 68/45 weighs full.....

not enough to make a difference

[Tao]

Curiousity, arguing with people on PBN


LOL are they saying COMPRESSED air is wieghtless??? :rofl:

Well so far I have found in my chemestry book:

pressure = mass x acceleration -where acceperation is gravity (9.8)

so double the mass double the pressure or vice versa.

You will need to find what the mass of air is at standard pressure (find out how many mols of each gas there are per cubic inch) and find out how many pounds/square inch standard atmosphre pressure is.

It will be easier to work in kilograms (on earth 1kg= 2.2456lbs) since kilograms measure mass not wieght (and you can baffle all those on BPN :rolleyes: )

[neppo1345]

According to my calculations:

Filling a 68 Cubic Inch tank to 4,500 PSI at sea level will increase it's weight by .4183 kg = .921 Lbs


However that doesn't seem right, meaning I most likely did something wrong.

Joe, where you at?

[Thordic]

I did the math a few years ago.

http://www.automags.org/forums/showthread.php?=21839


Using this formula:

Air has an average molecular weight of 29 (28 for N2*.8 + 32 for O2 * .2)
1 mole of gas at STP occupies a volume of 22.4 L, therefore, 29g {~1 oz)of air at STP occupies 22.4 L

Take you tank volume in Liters (ft3X28.3 or cu in X .0164) and correct to STP (forget the temperature, just multiply the volume by 204 or 306{3000psi/14.7psi; 4500/14.7psi}. This gives you the gas volume at STP.

Divide this volume by 22.4 and you get the weight of air in oz.

Using that, you get the following information:

3000 PSI = 204 atm
4500 PSI = 306 atm

47ci = 0.77 L
68ci = 1.11 L
88ci = 1.44 L
114ci = 1.87 L

So now, just plug it into what I said above, and you get these weights:

47ci 3000PSI tank: 7.0 ounces of air
68ci 3000PSI tank: 10.1 ounces of air
88ci 3000PSI tank: 13.1 ounces of air
114ci 3000PSI tank: 17.0 ounces of air

47ci 4500PSI tank: 10.5 ounces of air
68ci 4500PSI tank: 15.1 ounces of air
88ci 4500PSI tank: 19.7 ounces of air
114ci 4500PSI tank: 25.5 ounces of air

As you can see, the weight of compressed air is not negligible, especially in higher pressure setups.

[68magOwner]

not enough to make a difference
You honestly cant feel the difference between a full and empty tank?

My setup actually balances completley different with a full 45/45 vs the same 45/45 empty

[MANN]

At sea level and at 20 °C dry air has a density of approximately 1.2 kg/m3 ~ 0.075 lbm/ft3

68in^3 = .039 ft^3

so .075lbm/ft^3 * .039ft^3 = .0029 lbm. which is not equal to lbf

1 lbm weighs 1lb

In english an empty tank's air weighs .0029lb

P1V1 = P2V2

P1 = 4500 psi = 64800psf

V1= .039 ft^3

P2 = 14.6956 psi (1 atm) = 2115.36 psf

V2 = 1.194 ft^3

So the volume that the air that is compressed will be ~ 1.194 ft ^3

The weight of that is .09 lb

Edit: it seems that it gains .1 lb

All givens are from my Thermodynamics "An engineering approach" : Cengel & Boles 5th edition.

(I hope its right) :cheers:

EDIT AGAIN: Looks like I did flub up, and was off a decimal place. the diff between a 68 4.5k full and empty is 1lb.

[Thordic]

You're off a decimal place. The math I posted above was done by a chemical engineer and then verified.

[MANN]

You're off a decimal place. The math I posted above was done by a chemical engineer and then verified.

Where? I am a senior engineering student, and work with many chem/mech/civil engineers. They make mistakes too :D

[Paintchucker]

I don't have any scales, but I have a full 68/4500 and an empty 88/4500 and there is a noticable difference in that the full tank feels heavier... Maybe a pound, which would about match the calculations above...

Dang it, now I am curious... I am off to find a scale at a self service post office station. You can't get in trouble with just tanks in the post office can you??? If I am not back in an hour, someone call the Norcross Police Station. :D

[MANN]

You honestly cant feel the difference between a full and empty tank?

My setup actually balances completley different with a full 45/45 vs the same 45/45 empty

nope. I will take tanks to work tomorrow and verify. I know my scale sucks, and is hard to tell the difference. The one at work is accurate to .0001 g.

[onedude36]

I talked to a guy last weekend about it. He claimed 2 oz difference between full/empty on a 68 bottle.

[paintballfiend]

I would solve the question with my massive brain power but my calculator is out of batteries. :p

[MANN]

I talked to a guy last weekend about it. He claimed 2 oz difference between full/empty on a 68 bottle.

which ~.12 lb

[SR_matt]

its down in the ounce range (depending a lot of how much moisture and dirt is in the air)

had to argue with a guy at the field and he eventualy admited i was right
-matt

[Paintchucker]

let me finish my pizza, and ill go weigh. is it ok that I do 3000 instead of 4500? and it should be the same weight.

Huh??? Shouldn't the 4500 weigh 50% more ??? :p


So I got to the post office, and it wouldn't let me get to the screen to weigh the tanks, because the main office is closed and they can't accept a package...

But if you hack around on the menus a bit, you can find it.



Both tanks have a black Rase Cover on them. Arguably, the carbon fiber on the 88 weighs more, but I flunked calculus, and think that weight is negligible...

Empty on an 88/4500 with pure energy reg = 3# 2.8oz

3500 psi on a 68/4500 with bulldog reg = 4# 2.2oz

so about a pound...


I guess to be truly scientific about it, I need to weigh the 68/4500 empty, but I just paid $6.50 this afternoon to fill the dang thing, so that will have to be later! I have some guns to get shooting again from collecting dust too long.

[bentothejam1n]

http://www.pbnation.com/showthread.php?t=1977780
eh?

[MANN]

Huh??? Shouldn't the 4500 weigh 50% more ??? :p

sorry. I should have typed that we will see the diff in an empty and full 3k tank.

I have read ^^, and it seems that his calcs are right. im not sure on some of the conversions.

Either way I feel that weight does not make that much difference. 2-4 lb diff in a marker shouldnt make you better/worse.

[Paintchucker]

Thanks for the PbNation link. That was interesting. Another thread had the actual weights of the tanks and the regs on it.

So I guess the next question in line is how much does a full hopper weigh ???

And does one brand of paintball vary in weight vs. another ???

:rofl:

I do agree on the weight difference to a degree. If I start complaining, I know it is time to work out a bit more. But I will tell you that on a hot JULY Saturday afternoon down here in GA, playing the ION with a 45/45k is a little easier than with the Emag on an 88/45k.

[Beemer]

I did the math a few years ago.

http://www.automags.org/forums/showthread.php?=21839


Ya that was a great thread. Is five years a few? :ninja: For some reason that link doesnt work for me. Here is the one I had marked that works for me.

http://www.automags.org/forums/showthread.php?s=&threadid=21839&highlight=weight

Lohman, read this thread and see the last post By RobAGD he made a nice chart on the Wt. difference between Air and Argon. :cool:

[neppo1345]

You're off a decimal place. The math I posted above was done by a chemical engineer and then verified.

Didn't know you were a chem-e (Edit: Nevermind, I read the other thread).

Anyhow; cool, I was right.

[Lohman446]

Thanks guys. Manike chimed in on the thread in PBN, and since its the Invert forum that basically ended the argument off :)

[Pneumagger]

I got into this argument twice in the past month with different PBNers. Both proclaiming an advantage of using HPA over co2 was the fact a co2 tank is 16oz heavier when filled, and the HPA doesn't get heavier. :tard:

The sad part is that despite all logical evidence, most other PBN members agreed with them.
Somebody needs to explode that server.

[MANN]

You're off a decimal place. The math I posted above was done by a chemical engineer and then verified.

Looks like you were right. I did the math again today because I thought I was crazy, and I must have typed in something wrong. I was off on the decimal. :cheers:

[SR_matt]

I got into this argument twice in the past month with different PBNers. Both proclaiming an advantage of using HPA over co2 was the fact a co2 tank is 16oz heavier when filled, and the HPA doesn't get heavier. :tard:

The sad part is that despite all logical evidence, most other PBN members agreed with them.
Somebody needs to explode that server.
i had an argument with a 43 year old machinest about hpa having weight, it took a dive master to settle it and prove to him there was weight
-matt

[Pneumagger]

i had an argument with a 43 year old machinest about hpa having weight, it took a dive master to settle it and prove to him there was weight
-matt

anybody who's ever had to lug around a an 80+ or 100+ CF tank KNOWS theres a weight difference.

[thecavemankevin]

Or anyone who happens to know, how much does the air in the tank weigh?

duh, 4500lbs :tard: