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how much oil for a tank of propane?

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Old November 14th, 2010, 14:17   #31
MadMax
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Quote:
Originally Posted by ThunderCactus View Post
I think you should power your GBB pistols with oxygen instead of propane.
I actually had someone bitch me out for making a sh*tty adaptor because it wasn't threading onto a disposable oxygen bottle. Oxygen bottles have left handed threads that are otherwise similarly dimensioned to disposable propane bottles. A customer a few years ago wanted to use oxygen because the bottles are pressurized to 400psi (I think) instead of the 130psi on propane.

I was doodling around with the injector design around then and was considering how one might shoehorn enough oxygen into a propane bottle to make things dangerous and I couldn't come up with an easy way to get to a dangerous mix because the injector had such a small shot volume and air is about 80% inert gas.

The situation completely changes when it comes to a pure oxygen bottle pressurized to 400psi. Shooting 100% 400psi oxygen into a partially propane filled GBB mag can reach ideal gas mix conditions. All you need is a little liquid residue in a mag and you can reach high pressure (26atm!) ideal mix conditions.

As a bit of beer coaster estimation:

-room temp: 300k
-adiabatic flame temp of a propane oxy flame: 2800k
-plugging ideal gas law which works really well at high temps: 9.3x pressure factor

Some Gr 12 chemistry! Atoms indicated in lower case because I can't figure out subscript

-c3h8 + 5o2 ---> 3co2 + 4h2o (balanced formula for ideal combustion)
-6 moles on reactants : 7 moles for products
-assuming everything goes to vapor after combustion (pretty good assumption I think): 1.14x pressure factor

If you were working with reactants initially at atmospheric pressure you'd get a pressure of:

9.3 x 1.14 = 10.6 expansion factor = a mere 160psi

However you start off with things at 400psi (26.6atm!)

26.6atm x 10.6 = 282atm! = 4230psi!

Our crappy cast aluminum magazines are not engineered to contain a 4.2kpsi explosion...

Stay in school. All the stuff I used is high school level and it works in ideal gas situations far from condensation conditions.
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Old November 14th, 2010, 14:57   #32
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http://www.rodenator.com/pests-contr...eos-rodenators

Maybe the folks who want to mix in Oxygen should just get into pest control.
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Old November 14th, 2010, 15:25   #33
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Stop me if I'm wrong, but this is how it went, right?
TNL: Hey guys, how do I do this fairly undocumented and generally bad idea thing?
Others: Don't do it, this is a generally bad idea.
TNL: Okay, well I (over)did it, we'll see how it goes. Thanks for the advice guys!
Others: *facepalm*

In all seriousness, I hope it goes well, and I hope most people never really try this. As Madmax and others explained, this requires some precision and a lot of care, 2 things most people don't really have. I also don't really believe the benefits will outweigh the risks in any way possible...well, except possible lulz.
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Old November 14th, 2010, 21:22   #34
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well the way I add the oil isnt by injection like the contraption madmax made, I have an adapter that lets me refill the 1 lb bottles from the 20 lb tanks, so I figured if I put some oil in that adapter before refilling the bottle, I'd get oil in it.
I seem to have gotten the right amount of oil as well, when the mags overfill there is just a very light oil residue on the mag base, definatley not over saturated.

either way its better than before where i would just forget to oil my mags altogether, or do it once at the start of a game and forget to do it ever again afterwards
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Old November 15th, 2010, 00:23   #35
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That's an interesting idea TNL. Be sure to purge your lines with propane before refilling a bottle so you don't push air. It may be difficult to get a consistent fill into a propane can though. They have single port valves with no overflow features so you can only transfer liquid until the pressure equalizes between the tank and bottle.

IMPORTANT: be sure that a gas space remains in your bottle. If you manage so fill it completely with liquid, with no gas space, you will subject the bottle to pressures exerted by the expansion coefficient of the liquid. A single phase fill (only liquid) can exert very high pressure when temperatures get warm. Luckily disposable propane bottles have a pressure relief valve so you probably won't blow them up, but you'll have a propane leak.
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Old November 15th, 2010, 00:27   #36
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ive had an over pressure valve go off once after filling
the refilling rig is simply a thread adapter that goes from the tank to the bottle in about an inch of length, all you do is freeze the bottle, then hook it up to the tank and flip it upside down, turn the valve, then shut it again when the propane stops flowing, seems to consistently fill it up with just a little bit of gas in the top, so I just added some oil to the void in the adapter so it goes into the bottle along with the propane
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The apartment I am in right now costs $100 a month.
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They're called priorities. Get yourself some.
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Old November 15th, 2010, 00:40   #37
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Cool.

The oxygen/propane trails are interesting.
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Old November 15th, 2010, 00:54   #38
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Derp.

I don't get it.
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The apartment I am in right now costs $100 a month.
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They're called priorities. Get yourself some.
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Old November 15th, 2010, 01:06   #39
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I cant stress enough how much I hope your doing this outside.

Especially if your refilling propane tanks from the larger BBQ sized ones.
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Old November 15th, 2010, 01:09   #40
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yes outside, especially cause after i disconnect the tank all the propane from the adapter gets released...
that and Im about 5 feet from the furnace, propane not so good
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Originally Posted by Kid View Post
The apartment I am in right now costs $100 a month.
My average spending on food per day is less than $4.
My airsoft spending in the last month and a half has totaled over $1400.
They're called priorities. Get yourself some.
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Old November 15th, 2010, 01:23   #41
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Cool.

The oxygen/propane trails are interesting.

I think you might just stay with the propane trail... (if you still want to follow this idea)

In general, OIL + OXYGEN + PRESSURE = DANGER! HIGHLY FLAMMABLE

But is the pressure high enought in a propane tank to make the oil catch in fire? What percentage of oxygen should be used to have a "safe" oxygen/propane mix? Does this kind of silicone oil catch in fire like any others?

Questions that seems to be unanswered for now so I'll stick to what I learned in my welding courses: Oil + Oxygen makes nice experiences in chemistry labs but they should always be keep away from each others in real life ...
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Old November 15th, 2010, 01:28   #42
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well wouldn't oil in a mag be the same as oil in a tank? just larger volume? so if your mags aren't catching fire, I don't think my tank will either
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Originally Posted by Kid View Post
The apartment I am in right now costs $100 a month.
My average spending on food per day is less than $4.
My airsoft spending in the last month and a half has totaled over $1400.
They're called priorities. Get yourself some.
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Old November 15th, 2010, 01:40   #43
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I belive the O2 chat is re that verminator post. It runs two separate tanks and the gases mix as they inject into the ground. The gases are not mixed in a single tank prior to use.

It's for pest control and not a safe and cheap way to charge airsoft mags. The gas mixture explodes in a porous space like a rodent den. In a pressure vessel like a magazine it would be dangerous, in a 16.4 oz cylinder someone tried to re-charge it would be lethal.
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Old November 15th, 2010, 01:46   #44
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well ill be sure to not inject my bottle with any oxygen
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Quote:
Originally Posted by Kid View Post
The apartment I am in right now costs $100 a month.
My average spending on food per day is less than $4.
My airsoft spending in the last month and a half has totaled over $1400.
They're called priorities. Get yourself some.
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Old November 15th, 2010, 01:58   #45
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Silicone oil is soluble in liquid propane. Both are non polar compounds. The solubility of silicone oil in liquid propane is the reason my grenades need such frequent lubrication. The flash evaporation of propane is a very effective degreaser which strips out the oil. My grenades can go longer between oiling when running HFC134a, which is polar. The rapid evaporation still strips out oil, but not as effectively as propane which solvates it before aerosolizing it.
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