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Re: Does a empty oxygen cylinder weigh the same full? [Re: Corporal Kielbasa]
    #6483355 -

Quote:
Nast:
Compressed O2 has a molar mass of 32g/mol
At 17atm(249psi) there is 0,695moles of O2/litre
if your tube is 5l then the compressed air weighs 111g


i know there is a descrepency over how people write numbers.
you mean 0.695 ?

Are you telling me that my tank weighs 22.24 grams more when it is full.

That isn't really that noticable when you concider the tank weighs around 80lbs. or so.


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"With an abundance of Cyanescens... i would never touch another Cubensis again."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: badchad]
    #6483692 -

badchad said:
What about a tank of helium?

Does that weigh more or less when full..... ponder ponder.


the tank should weigh the same as empty i suspect.helium is a bit lighter than o2.


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when you become one with nature,nature becomes one with you.if you never try it you will never know the truth!

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Re: Does a empty oxygen cylinder weigh the same full? [Re: entheodome]
    #6483810 -

Not if the helium is compressed. If the helium is compressed to the point it is heavier than the o2, then naturally the tank would weigh more.

If the tank contained uncompressed helium, then it would weigh less.

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Re: Does a empty oxygen cylinder weigh the same full? [Re: entheodome]
    #6483936 -

entheodome said:
badchad said:
What about a tank of helium?

Does that weigh more or less when full..... ponder ponder.


the tank should weigh the same as empty i suspect.helium is a bit lighter than o2.


Nope!

Compressed helium is a hell of a lot denser than air. You don't generate lift with something denser than air unless you're on bizarro world. Even if the helium wasn't compressed, the difference woud be marginal... those tanks are heavy as hell and helium is drastically less bouyant than most people realize.


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I find your lack of faith disturbing

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Konnrade]
    #6483959 -

LOX is totally rocket fuel. Not to a lesser extent at all... It's extremley difficult to manage, but the ISP is amazing. There are certainly better fuels out there, but none that we've been consistently able to tame.

Edit: also, O2 boils at -183* C, if your tank wasn't refridgerated (and I'm not talking about the kind in your kitchen), then it's not liquid oxygen.

Edited by ApJunkie (01/21/07 07:46 PM)

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Corporal Kielbasa]
    #6484032 -

Helium 3 is where it's at :thumbup:

Quote:
LOX is totally rocket fuel. Not to a lesser extent at all... It's extremley difficult to manage, but the ISP is amazing. There are certainly better fuels out there, but none that we've been consistently able to tame.


LOX is an oxidizer, it needs a reducer to become a rocket fuel. Its specific impulse derives from the combustion reaction.

LOX + powdered lead has a lousy specific impulse
LOX + methylhydrazine has a staggering specific impulse

It's not the LOX its the interaction of both.


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Omnicyclion.org
personal empowerment for the world

:nyan: LGBT - Love God Before Tradition :nyan:

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Re: Does a empty oxygen cylinder weigh the same full? [Re: ApJunkie]
    #6484064 -

It seems also that your dealing with small volumes of air too. I have been around Scuba all my life, my parents are both certified instuctors, and my dad used to teach all the time.

When i was into diving, we would deal with high pressure, and fairly high volume tanks. Generally I used a aluminum 80 tank. Which is 80 cubic feet of air at 3000psi. I always used a aluminum tank vs. steel because as you run low on air in the tank, it actually starts to become buoyant. And after filling it, it would become VERY warm, so they are usualy filled while in a large tub filled with water. And more than once have we had to just open a tank up to empty it, and every time the valve forms a thick layer of frost and ice. Simple physics, but still cool to watch.

But yes, the tank WILL be hevier if it has any compressed gas in it, save for some volumes of He and H, due to there natural weight. it may only be a few ounces or so depending on the pressure and volume of the cylinder.

And at the facilitiy my dad worked at, the owner has about 150 or so of the 8 foot tall tanks. They are all linked together in a high pressure bank (5000psi) and a low pressure bank (3000psi). And let me tell you, moving one of those fuckers around when its full of a heavy gas like Argon (used for a insulation gas when dry-suit diving) vs. helum (for heliox, or trimix), or even an empty tank, give me an empty one any day.

Oh and i doubt i have seen anyone jump higher or have the shit scared out of them more than when one of my buddies was over and a high pressure bank tank blew a burst disk. It sounds like a gernade, and then the most high pitch squeil you will ever hear. Untill the tank is empty and isolated, but it still bleeds out for ~10-15 min.


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Only two things are infinite, the universe and human stupidity. Im not too sure about the former.      -Einstein

Of course the rules need to be enforced, but the goal of law and order should be to create a just society, not to enforce laws. -Unknown

“I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.”  -Stephen Roberts

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Re: Does a empty oxygen cylinder weigh the same full? [Re: ThirdEyeOpening]
    #6484187 -

ThirdEyeOpening : A few ounces? What about 24.24 grams. or 111 grams? What about the scientific evidence posted in the thread earlier?

We are taling about pure oxygen. The kind that is not OK to breath.

The air we breath is Oxygen by only a small percent. I forget what it is but its less then 20% and the majority is Nitrogen.


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"With an abundance of Cyanescens... i would never touch another Cubensis again."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: pscyanescens]
    #6484284 -

You must make a distinction between mass and weight here.

By adding a gas to a cylinder you are necessarily increasing its mass.

However, at low pressures, H2 and He have a lower density than air (~79% N2, 21% O2) and as such, an effectively lower weight. COMPRESSED gases, of course, are at a higher pressure than atmospheric, and will be more dense than usual, resulting in MORE weight.

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Re: Does a empty oxygen cylinder weigh the same full? [Re: pscyanescens]
    #6484318 -

I can't believe this thread is still going.


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He was a cowboy in one of the seven days a week fights. No business, no hangout; no friends, nothing; just what you pick up and what you need.

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Chesh]
    #6484321 -

Chesh said:
You must make a distinction between mass and weight here.

By adding a gas to a cylinder you are necessarily increasing its mass.

However, at low pressures, H2 and He have a lower density than air (~79% N2, 21% O2) and as such, an effectively lower weight. COMPRESSED gases, of course, are at a higher pressure than atmospheric, and will be more dense than usual, resulting in MORE weight.


My question once again. How much weight. I know it will increase somehow. You are adding sometihing to it. Is it noticable? 24g or 111g is not that noticable, given the tanks weight.


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"With an abundance of Cyanescens... i would never touch another Cubensis again."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: pscyanescens]
    #6484327 -

Kid_orgo: Why nobody has answered the questions i just asked above. I hope this thread doesn't die unanswered.


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"With an abundance of Cyanescens... i would never touch another Cubensis again."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: pscyanescens]
    #6484399 -

How many liters does your tank hold? how high pressure?

If the pressure is 249ponds per square inch and the volume is 1 liter then your tube weighs about 22.2g more when its full.

Larger tubes can have much higher pressure and have much larger volume and are therefore much heavier.

the formula you use is this:

mass=n*M=((P*V)/(R*T))*M

P=pressure
V=volume
R=0.08206
T=temperature in degrees Kelvin
M=molar mass
n=number of molecules(in moles)


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Rodney Brooks on Robots
Nalim said: "Quoting yourself is retarded."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Nalim]
    #6484431 -

Yeah, pscyanescens, i'm sorry for not answering your question directly. As Nast said, the amount of gas, and thus the change in weight depends on the volume, as well as the pressure and identity of the gas, and i didn't see a specific volume listed.

Nast: the molar gas constant you listed is for Liters and Atmospheres. To change it into Liters and PSI, multiply by 14.696 PSI(in 1 Atm) =
1.206 = R ...i think....

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Chesh]
    #6484564 -

1 psi = 6,8046 · 10^-2 atm = 0,06805
R is indeed a konstant that depends on which units you use..
the units I used to calculate the stuff above is Liters, Atmospheres and degrees Kelvin...

If you are going to use other units then you need to look up the universal gas constant for those units(or calculate it, I just dont feel like it right now, it just might be what you said Chesh)...


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Rodney Brooks on Robots
Nalim said: "Quoting yourself is retarded."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Nalim]
    #6484592 -

OK i am very very sorry

My stupid friend who i asked to check the tank size, came back and said it was 249 PSI.

I just looked at it and it says 249 CUFT
I am going to take a stab in the dark and call this Cubic Feet.

Can anyone give me a conversion to do the math with this?
Here is a picture.


I was thinking 5 liters???? This is the second to largest tank they will give us before we get bumped up to a liquid oxygen tank.

And as far as liquid oxygen goes for being rocket fuel, Oxygen is an accelerant, i could be wrong but i know it is not actually flammable. It just gives more power to the flame. Try holding a lighter up to torch with the oxy running. It wont light, it will just make the flame from the lighter hotter. This is the reason i need to mix it with propane before i have a workable flame.


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"With an abundance of Cyanescens... i would never touch another Cubensis again."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: pscyanescens]
    #6484648 -

1 cubic foot is equivalent to: 28.316846592 liters (from wikipedia)
I still need to know the pressure in the tube to be able to calculate the weight of the O2.

Quote:
And as far as liquid oxygen goes for being rocket fuel, Oxygen is an accelerant, i could be wrong but i know it is not actually flammable. It just gives more power to the flame. Try holding a lighter up to torch with the oxy running. It wont light, it will just make the flame from the lighter hotter. This is the reason i need to mix it with propane before i have a workable flame.



this is what rocket-fuel is and what happens when it burns:
O2 and H2 is rocket-fuel, the reaction that takes place is;
½O2 + H2=>H2O+energy


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Rodney Brooks on Robots
Nalim said: "Quoting yourself is retarded."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Nalim]
    #6484655 -

and the temperature.

if you know your volume, temp, molecular weight, and pressure, the mass is just:

m = p*v*M/(R*T)

remember to always use absolute pressure (not gage), and to keep your units right. 1 atm = 14.7psi = 1.013x10^5 pascals. Use Pascals. R = 8314 J/kgmol.K. M = molecular weight (in kg/kgmol.K) And use kelvin for temp (deg celsius + 273).


edit: sry, i didnt really read the posts. this was already answered.


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Edited by Colbadol (01/22/07 04:57 AM)

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Re: Does a empty oxygen cylinder weigh the same full? [Re: Colbadol]
    #6484680 -

Well i don't know how to determine the PSI. However on my regulator, i can turn it ll the way up to 300 PSI. It will more then likely go further, however i am reluctant to turn it up that high. The regulator should be able to take it, but i am overly cautious with allot of things.


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"With an abundance of Cyanescens... i would never touch another Cubensis again."

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Re: Does a empty oxygen cylinder weigh the same full? [Re: pscyanescens]
    #6484722 -

i looked around online at oxygen tanks of similar size, and those were all around 2200psig max.
2200 + 14.7 = 2214.7psia = 15.26MPa
250ft^3 = 7079.2L = 7.08m^3
M = 32
T = 21 + 273 = 294K


m = 15.2e6 *7.08*32/(8314*294)
m = 1408.86kg

idk, that seems very high. i prob made a mistake, lol sooo early in the morning

edit: oh yeah. when the tank is empty:

m = 1.013e5*7.08*32/(8314*294)
m = 9.38kg

difference of about 1400kg?
yeah. i think i made a mistake.


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Edited by Colbadol (01/22/07 05:52 AM)

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