Physics and a Nitro Tank

[Mr.Danger]

When my air guy fills HPA tanks, he fills them quick enough to heat the tank consideribly. When he handed me the tank one time, it was full and almost too hot to handle. True to the laws of physics of course, once the tank cooled down, the pressure within the tank also dropped. Then I remembered my chemistry class. According to (insert name of law) as the pressure within a closed container increases, so does the temperature. Likewise, when the temperature of the container increases, so does the pressure. This lead me to pose this question: Would raising the temperature, and thus the pressure inside, of a partially filled HPA tank offer you more shots than one kept at a cooler temperature ?

[SlartyBartFast]

When my air guy fills HPA tanks, he fills them quick enough to heat the tank consideribly. When he handed me the tank one time, it was full and almost too hot to handle. True to the laws of physics of course, once the tank cooled down, the pressure within the tank also dropped. Then I remembered my chemistry class. According to (insert name of law) as the pressure within a closed container increases, so does the pressure. Likewise, when the temperature of the container increases, so does the pressure. This lead me to pose this question: Would raising the temperature, and thus the pressure inside, of a partially filled HPA tank offer you more shots than one kept at a cooler temperature ?

If it was too hot to handle, the tank may now be dangerous.
Yes, heating the tank might get you more pressure. But see previous.

[ScatterPlot]

as the pressure within a closed container increases, so does the pressure.

E-gad, man, that's genious!


:p

[Mr.Danger]

Sorry, you know what I meant.
Anyway, "too hot to handle" may be a bit of an exaggeration, but it was warm enough to make my hands sweat. So, before a tournament would it be worth while to leave a tank in the car to "warm up", or would it be doing more harm than good to the tank and/or marker for the sake of a few extra shots?

[ProX9]

when air is hotter it is also less dense, not in the case of a closed container because it cant expand but when it goes into the gun im pretty sure it would take a larger volume of hot air to do the same thing as room temp air.

[SlartyBartFast]

Sorry, you know what I meant.
Anyway, "too hot to handle" may be a bit of an exaggeration, but it was warm enough to make my hands sweat. So, before a tournament would it be worth while to leave a tank in the car to "warm up", or would it be doing more harm than good to the tank and/or marker for the sake of a few extra shots?

Before a tournament?

How about just getting a decent fill while you have the time.

And you can't tell me you're emptying a tank every game.

Read the article I linked in the thread about wet SCUBA fills. I'm too lazy to search right now.

[ScatterPlot]

Well I can empty a tank a game, especially when it's a 45/45 on an automag not getting full fills :)

[SlartyBartFast]

Well I can empty a tank a game, especially when it's a 45/45 on an automag not getting full fills :)

Well, get a bigger tank, or get better fills. ;)

[nicad]

Boyle's law is what your looking for.
Volume, pressure, and temperature are all directly related.
Change one, and one or both of the others will change.

If you Google it there are countless equations and even calculators for it..

out!

[ScatterPlot]

PV/T=PV/T

There's no subscripts in this, so I'll jst tell you- the ones on each side are for the 2 different "times"- say the left was original, then you change something and find out on the right.

[Papabyrd]

PV=mRT

or PV=nRT

or P=pRT (where p is density-rho)

[latches109]

Rapidly filling a paintball cylinder results in heating of the gas (air/nitrogen) and the cylinder. If filled too fast, this heat can become excessive resulting in damage to the cylinder. Such damage can lead to failure of the cylinder, potential property damage and personal injury or death. Care must be taken to fill the cylinder at a rate so the cylinder temperature does not become too hot to hold in your bare hand (140°F or above).

http://www.carltech.com/new-composite/pbfastfill.html

[SlartyBartFast]

Care must be taken to fill the cylinder at a rate so the cylinder temperature does not become too hot to hold in your bare hand (140°F or above).

http://www.carltech.com/new-composite/pbfastfill.html

It's about time that cylinders had an indicator that changed colour at the 'danger' temperature embedded in the epoxy.

Until someone gets killed at a self-service fill station, I doubt anything will be done to regulate the filling of paintball cylinders.....

[latches109]

true.

[St Elmo's Fire]

I'm not an advocate of messing with the pressure in a tank like this, and I would not recommend this. But, if as your tank began to empty, you started to heat your tank up a bit, I expect that it would increase the number of shots you had available. You could do this before-hand as well, but I don't suggest you fill a tank to it's limit, and then pressurize it further.

But, yes. Further heating of the tank would build up pressure, but the only time I can see this being feasibly used is in the middle of a match when you're starting to run low. I can't imagine a whole lot of paintballers are emptying 45/45s in a single match though, so it's not an important factor. There is no real advantage to heating the tank beforehand, you might as well have overfilled the tank.

And for those who do empty 45/45s in a single game, you might consider a larger tank. Heating your tank wouldn't buy you that many extra shots, considering that the equations need to be done in Kelvin. For a person in an 80-degree field, to heat their tank to dangerous amounts of 140-degrees...

300 Kelvin -> 333 Kelvin.

You'd get a little more than 10% more shots than you have left. Doing this to a tank though could cause damage to the tank, which endangers your life. Furthermore, if the tank were full and not at least partways empty, you run the risk of over-pressurizing the tank.

[St Elmo's Fire]

And just to ask, do you really want to haul around an N2 tank that is 140-degrees? That's a little hot.

[TheTramp]

I've chilled a tank in my freezer then filled it off a 3300psi SCUBA tank. It was pretty cool because the fill heated the frozen tank up to about room temp so there was no cool-off pressure drop when I was done.

[Muzikman]

If people just took the time and filled a tank at a reasonable rate, you would get a full fill.

[Lohman446]

The new fill stations at the field are designed to be slow, it takes about 2 minutes to fill a 68/45 tank. People complain, but I expect it is better than the old systems (even if it is still not the "correct" way to do it). It did result in having to add another fill station though to avoidl ines.

[Gunga]

I've chilled a tank in my freezer then filled it off a 3300psi SCUBA tank. It was pretty cool because the fill heated the frozen tank up to about room temp so there was no cool-off pressure drop when I was done.

I don't know that that's any better than getting the tank too hot. You're still subjecting the tank to thermal stress. Who knows...it might actually be worse as the aluminum sleeve & fiber wrap are cold which might reduce their tensile ('strechy') strength as compared to when they start out at ambient temperature.

But then I'm not a materials engineer, so I may be talking out of my booty. ;)

[MarkM]

A lot of things have come about because of the time honoured answer of "because we have always done it that way" this very often means a lot of things are being done dangerously. Those fill rigs that slam 5000psi or 4500 straight from empty with no slow fill option are a perfect example. The chilling of tanks is another no no the tanks we used to use for Shockers (shoebox) were filled with C02 and to get a proper fill you chilled the bottle, the only trouble with this is that the constant chilling and then heating up of the tank will ultimately result in the ally coming away from the fibre wrap, you won't notice this externally but it is happening and the odds on a bottle used in this way are high in favour of it failing an Hydrostatic test. There might even be a warning somewhere or other about not using those bottles for C02 but I may be mistaken on that, the chilling and bottle failing Hydro test problem is correct though.

[TheTramp]

Hmmmm...I'm glad I've only done it a couple of times. :eek:

[Hairball]

Answer to the original question: No.

The pressure may increase with the temperature, but the volume stays the same.

Maybe that's already been said, but I'm too lazy to read the entire thread.

[Hairball]

PV=mRT

or PV=nRT

or P=pRT (where p is density-rho)

First equation should be PVM=mRT

Sorry for the double post, just wanted to nitpick

[trains are bad]

only trouble with this is that the constant chilling and then heating up of the tank will ultimately result in the ally coming away from the fibre wrap, you won't notice this externally but it is happening and the odds on a bottle used in this way are high in favour of it failing an Hydrostatic test. There might even be a warning somewhere or other about not using those bottles for C02 but I may be mistaken on that, the chilling and bottle failing Hydro test problem is correct though.

This is WRONG!

This is a paintball myth that needs to die. Running CO2 and chilling tanks with CO2 will not hurt them. I looked around for evidence substantiating this and even called luxfer and asked them directly. Just because you read it on the internet does not mean it's true.

[MarkM]

This is WRONG!

This is a paintball myth that needs to die. Running CO2 and chilling tanks with CO2 will not hurt them. I looked around for evidence substantiating this and even called luxfer and asked them directly. Just because you read it on the internet does not mean it's true.

I didn't read it I was told this by three seperate people one very well known on here and another very well respected airsmith from the UK and the third by the Official supplier of Air to the Millenium.
The conversations was about a slightly different subject but came around to this subject.
I was talking about ally and fibre wrapped bottles NOT the all ally bottles for which I agree there isn't an issue with the use they are put to.

[bojangles1983]

PV=mRT

or PV=nRT

or P=pRT (where p is density-rho)


ARGH! those $&%* formulas again! those things haunted me all through physics 1! anyways, a few years ago I always heard about people wrapping up the little hand warmers inside their tank covers right before they went out and played, the heat from the hand warmers would theoretically give you a bit of expansion/pressure but i really wonder if it would have been enough to get you more than a couple extra shots. IDEA: just wrap an electric blanket around your tank and head out to the field., just make sure you've got enough cord!

[CoolHand]

I didn't read it I was told this by three seperate people one very well known on here and another very well respected airsmith from the UK and the third by the Official supplier of Air to the Millenium.
The conversations was about a slightly different subject but came around to this subject.
I was talking about ally and fibre wrapped bottles NOT the all ally bottles for which I agree there isn't an issue with the use they are put to.

Nah, he's right Mark.

Called Carleton myself to confirm (years ago now), because I had been using a Shoebox on CO2, and was concerned (because of the rumors). I was told that unless I was somehow filling with liquid oxygen, the bottle should be fine (and since liq N2 or O2 needs a much higher pressure than 3kpsi to remain liquid anyway, its not a problem). Fiberglass wrapped bottles may have been susceptible, but since no one uses fiberglass anymore, that's also not a problem.

Heat is the big killer here, not so much from thermal cycles as just degradation of the resin via decomposition at high temps.

That's what I got.

Ask Manike next time you run accross him, IIRC he got the same line from them or Luxifer (I can't remember which it was ATM).

[MarkM]

Nah, he's right Mark.

Called Carleton myself to confirm (years ago now), because I had been using a Shoebox on CO2, and was concerned (because of the rumors). I was told that unless I was somehow filling with liquid oxygen, the bottle should be fine (and since liq N2 or O2 needs a much higher pressure than 3kpsi to remain liquid anyway, its not a problem). Fiberglass wrapped bottles may have been susceptible, but since no one uses fiberglass anymore, that's also not a problem.

Heat is the big killer here, not so much from thermal cycles as just degradation of the resin via decomposition at high temps.

That's what I got.

Ask Manike next time you run accross him, IIRC he got the same line from them or Luxifer (I can't remember which it was ATM).

Who did you think the very well known person on here was ;) But then sometimes things are changed in perception after greater understanding is found. So since my conversation with Simon more info might well have come to light. Also think of the period of when the Shoebox Shockers were made and the bottle technology at the time...I did say "we used to use" (past tense) for the Shoebox Shockers. The biggest crock is the bottle standard test rules and certification but that is a whole different thread. I had actually on my first reply gone into that stuff in some depth but my pc decided to lock up...I really must buy a new graphics card..so I lost the post. :(

[CoolHand]

Yes, I too also hate it when a good post bites the dust due to a computer puke.

Oh well.

The point here is that fast fills suck, too much heat in the bottle sucks, and that the ten or twelve people in the world who actually still use a 68 cu CO2 tank aren't going to blow up randomly. I don't think that was ever in question, but rather that the tanks may not pass another hydro test.

Its not a big enough point to bicker over really.

I just want folks to start treating their tanks like the high pressure vessels they are, instead of footballs or tumbling mats. :wow: :nono:

That is all. :cheers:

[Hairball]

Also remember.. "Don't mill your tank."

[MikeRosenthal]

The point here is that fast fills suck, too much heat in the bottle sucks, and that the ten or twelve people in the world who actually still use a 68 cu CO2 tank aren't going to blow up randomly. I don't think that was ever in question, but rather that the tanks may not pass another hydro test.

I'm trying to find a link but can't right now, But this is exactly what I had found on one of the Bottle manufacturer's website.

They didn't recommend using C02 in their fiber wrapped bottles because it would negatively affect the bottles chances of passing a Re-Hydro Test. However the bottle would be fine for use during it's normal life time. I'll keep looking for the link...

-MR

edit; Whoops didn't realize this was so Old.... Sorry...