Why dont fuel tanks explode

[thexav]

If you put a lit match into a fuel tank you would expect the tank to explode like they do in films but this doesnt happen in real life.

Why not? I thought petrol vapour was flammable.

If you are wondering how I know this a friend tried it when he was about 8 and playing with his dads car keys. I just wonder what he would have done if it had exploded! The things kids do:blink:

 

[HDi fun]

I haven't tried this recently. I suppose that neat petrol vapour is not combustible in the absence of oxygen. Once the match hits liquid fuel it's extinguished. So you might get a better result by leaving the filler cap of for a few moments to get some air in there.

 

[Wcnwzrd]

i know that they did the fuel leak trick the movies always use on mythbusters (the one where you poke a hole in the fule tank and light the gas trail to blow up the car), no matter how hard they tried no boom from the tank.

 

[HDi fun]

That's because the flame front is extinguished by the neat fuel when you reach the hole. Petrol cannot burn without oxygen

 

[Wcnwzrd]

i know that part. we used to spend our spare time back home blowing stuff up. quite fun as long as you leave the shine to those not setting it up. we weren't just a bunch of hicks in the sticks, well we were, but we actually spend time to plan and set up everything. quite fun on a lazy saturday night.

 

[prevtec]

i know that they did the fuel leak trick the movies always use on mythbusters (the one where you poke a hole in the fule tank and light the gas trail to blow up the car), no matter how hard they tried no boom from the tank.

mythbusters is actually a good show

 

[prevtec]

the reason why a match wont light petrol when its dropped into is because petrol - liquid
soaks and drowned the match before the flame can actually heat the petrol

example
when petrol is poured on a bonfire, you use a paper thats lighten to flame it
but it takes a few seconds for the petrol to reach its flamable point

 

[HDi fun]

petrol vapour mixed with oxygen is very flammable at room temperature. Diesel takes some heat to get going

 

[obi_waynne]

Yet you see petrol alight when it floats on water or on a road and you can light brandy on a Christmas pudding.

As has been said the match will likely be extinguished long before it gets near to the petrol, however there is actually a safety feature in fuel tanks.

Petrol tanks are actually filled with a metallic mesh that looks a bit like a scrub pad. The idea is that heat is conducted away quickly and that the temperature to create ignition is never reached.

 

[HDi fun]

Do these mesh things occupy a space in the filler neck of is it the whole base of the tank?

 

[obi_waynne]

I understood it was in the whole tank. There was a fault on Astras where a fuel pump could cause a static spark if the car was not earthed. They did a big recall and fitted a new filler cap so they seemed pretty worried about it.

 

[HDi fun]

No great loss then, gets a few of 'em off the road

 

[obi_waynne]

Thats Vauxhallist! Or are you just winding someone up?

 

[prevtec]

No great loss then, gets a few of 'em off the road

ha ha, too right
over in ireland vauxhall are called opel
O-OH
P-PLEASE
E-EXPECT
L-LEAKS
so they were right to be worried

 

[prevtec]

Thats Vauxhallist! Or are you just winding someone up?

im not against vauxhall or opel, they are just prone to break downs and gaskets
ive had an ashtray and costed me 700 euros to fix the head
i lost a lot of money to an opel

 

[HDi fun]

Bit of both really.

 

[obi_waynne]

Thought so