How come flamethrower tanks dont blow up?

[Tab]

I am assuming we can ask non-computer related questions here.

 

[Cogman]

I dont know that this is very highly technical, and yes you can ask non computer related questions here (actually most computer questions belong in the technical forum anyways). The resion is because it is a controled flow forward and they have protection devices that close the valves if the tempature becomes to high (like a gas station's system for preventing someone from lighting a match to a flow of gas)

 

[CTho9305]

And, unless the fuel is full of O2, it can't burn back into the tank past the nozzle.

 

[Tab]

Originally posted by: CTho9305
And, unless the fuel is full of O2, it can't burn back into the tank past the nozzle.

I was thinking the same thing too.

 

[Mingon]

Its also quite high pressure, this should help avoid blow backs.

 

[OrganizedChaos]

they do in c&c generals

 

[UnixFreak]

Its also quite high pressure, this should help avoid blow backs.

Exactly. Although I am sure they have a check valve there as well, a lot of it is pressure. Have you ever taken a bottle of lighter fluid or hairspray and shot flames? The evacuating fuel is coming out faster than it can be burnt.


If you haven't done this with lighter fluid or hairspray, please, please do not try it. Just because it usually doesnt blow up, doesn't mean it won't.

 

[Jeff7]

Originally posted by: UnixFreak

Its also quite high pressure, this should help avoid blow backs.

Exactly. Although I am sure they have a check valve there as well, a lot of it is pressure. Have you ever taken a bottle of lighter fluid or hairspray and shot flames? The evacuating fuel is coming out faster than it can be burnt.


If you haven't done this with lighter fluid or hairspray, please, please do not try it. Just because it usually doesnt blow up, doesn't mean it won't.

I used a can of butane already. That's a good 10-15 foot flame. And when I did it, the flame didn't appear to actually start until about a foot out from the can. As far as I can tell, you'd only be in danger if the flame makes it back to the outlet, and burns the valve. Then you'd be in trouble, as the fuel in the can (under pressure) would suddenly have a very free way out - oxygen mixes, and you have a lovely fiery explosion.
Also, using a non-aerosol sprayer, like a pump, is a bad idea too, as there's just air inside the bottle, right next to the fuel. Bad thing, assuming you don't enjoy serious burns.

 

[TDSLB]

Along these lines....

So if a hydrogen tank, I'm thinking of in a car, were exposed to flames what would be the likelyhood of explosions taking place there? would the tank have to be punctured? would the heat cause the hydrogen to expand, break the tank and then combust?

 

[f95toli]

As long as ypu keep oxygen away from the hydrogen it is stable. If you get some O2 in there: KABOOM!!!
O2+H2 is a really explosive combination.

 

[Harabecw]

Originally posted by: UnixFreakIf you haven't done this with lighter fluid or hairspray, please, please do not try it. Just because it usually doesnt blow up, doesn't mean it won't.

But its soooooo fun!

Someone in my old school (which is surrounded by a forest and trees and what not) burned down half the forest with that...

 

[Shalmanese]

Cars blowing up is a movie fiction. If a car is on fire, the fire will burn until the gasoline runs out. About the only way a car could blow up is if it was involved in a relatively minor collision in which the gas tank ruptures and there are no sparks or fires. After a while, there will be enough gas fumes in the air that a spark would cause it to blow.

 

[Peter]

For the same reason why car fuel tanks don't explode (except in movies), even when you throw a burning match in. No oxygen in it, no burn. Even when the tank is only partially filled, it's all gas fumes in there, no oxygen. The worst thing you'll get is a torch flame on the opening, where the fumes mix with the surrounding air.

 

[moonshinemadness]

Same reason The tanks of Oxyacetalene burners dont, A) the gas comes out at a high enough speed to dissalow burning back and B) Flash back valves are put befor the tank to stop fire entering, dont ask me how they work though

 

[Smilin]

Originally posted by: UnixFreak

Its also quite high pressure, this should help avoid blow backs.

Exactly. Although I am sure they have a check valve there as well, a lot of it is pressure. Have you ever taken a bottle of lighter fluid or hairspray and shot flames? The evacuating fuel is coming out faster than it can be burnt.


If you haven't done this with lighter fluid or hairspray, please, please do not try it. Just because it usually doesnt blow up, doesn't mean it won't.

It won't blow up.

This isn't because the fuel is moving away from the nozzle faster than the flames grow towards it, it's because the proper concentration of oxygen doesn't exist within the container.

An "observational" experiment shown to me in 6th grade:
Teacher comes in the room with an old rusted paint can. The can has a dime sized hole in the middle of the lid and another on the side of it near the base. The teacher has his thumbs over both holes.
He sets down the can and takes his fingers off the holes and touches a lighter to the top one.
A flame about 2 feet high shoots up and stays there.
Over the next minute or so the flame slowly gets shorter and shorter.
When it gets to be about 6 inches tall the paint can suddenly explodes flinging the lid into the air.

With the above observations, explain what happened. One given: The teacher says the can was 100% full of methane when he came in the room.

 

[SharkyTM]

in that case: there was an alternate supply of oxygen into the can.

in all other cases: the reason that the flame doesnt enter the barrel is that (1) no oxygen, and (2) its the vapor that burns, and without air, vapor cant be produced... pretty simple really.

Originally posted by: Smilin

Originally posted by: UnixFreak

Its also quite high pressure, this should help avoid blow backs.

Exactly. Although I am sure they have a check valve there as well, a lot of it is pressure. Have you ever taken a bottle of lighter fluid or hairspray and shot flames? The evacuating fuel is coming out faster than it can be burnt.


If you haven't done this with lighter fluid or hairspray, please, please do not try it. Just because it usually doesnt blow up, doesn't mean it won't.

It won't blow up.

This isn't because the fuel is moving away from the nozzle faster than the flames grow towards it, it's because the proper concentration of oxygen doesn't exist within the container.

An "observational" experiment shown to me in 6th grade:
Teacher comes in the room with an old rusted paint can. The can has a dime sized hole in the middle of the lid and another on the side of it near the base. The teacher has his thumbs over both holes.
He sets down the can and takes his fingers off the holes and touches a lighter to the top one.
A flame about 2 feet high shoots up and stays there.
Over the next minute or so the flame slowly gets shorter and shorter.
When it gets to be about 6 inches tall the paint can suddenly explodes flinging the lid into the air.

With the above observations, explain what happened. One given: The teacher says the can was 100% full of methane when he came in the room.

 

[Smilin]

Yep, that's it.

The gas would rise inside the can as it vented out the top. Air coming in from the bottom hole would replace it. Eventually the mixture of gas and air reached the proper ratio and the flame immediately jumped in and ignited everything at once.

It was a pretty nifty demo for junior-high. Scared the class awake that's for sure.

 

[toastyghost]

Originally posted by: UnixFreakHave you ever taken a bottle of lighter fluid or hairspray and shot flames?

i plead the fifth

What is "faster than it can be burnt"? This really just relates back to the oxygen argument, since the technical definition of burning is rapid oxidation. The pressure only affects the separation between the wielder and the point where the fuel and atmospheric oxygen mix. So if you said oxygen, you're right. If you said pressure, well... you're kind of right but only because the oxygen people were right first.

 

[kaizersose]

my college chemistry teacher did a cool demostration. he filled one giant balloon (three foot diameter) with pure hydrogen and one with a mixture of hydrogen and oxygen. then he put a candle on a giant stick and put the flame underneath the one with pure hydrogen. it made a pretty cool little explosion, nothing crazy. then he put it under the one with the mixture. i have never felt a shock wave like that in my life. it shook the classroom so hard, chalk dust flew 5 feet off of the board and just kind of hung there for a few minutes. it was pretty sweet and a great lesson about why you need oxygen for continuous burns (explosions).

btw - the oxygen hydrogen mix is what some of the space shuttle boosters use(d). the solid boosters use a nasty ammonia derivitive thats wicked dangerous.

 

[toastyghost]

Good example.. I've seen the balloon trick before and it definitely shook the walls of the auditorium where they were having the demonstration.