What Risk Of An Explosion In A Car Fire? Lpg & Petrol.

[pattayadingo]

For the purpose of this topic let's say you have a car on fire and there are no fire appliances in attendance here in Thailand.

Immediately after an accident the fire starts under the crumpled / open bonnet and is allowed to burn uncontrolled. Within a few minutes the fire has spread to the mid section of the car and is now blazing away merrily.

The LPG gas tank is in the boot of the car and 70% full of gas. The petrol tank is also about 70% full.

Often the movies are not like real life and there in the movies we often see the fuel tank explodes.

What are the realistic chances in real life of either or both tanks exploding?

Or will the petrol and LPG gas simply burn off through the fuel pipes?

Thanks.

[transam]

If l had a ''gas'' tank in the boot l would get away as far as possible .

In my fun ride l had a fuel tank and nitrous bottle in the boot/trunk, but l had welded sheet over the frame that supported the back seat, essentially closing of the cabin.

[necronx99]

First off, this is the sort of thing you really want to take care of quickly,not ask for help on the interwebs.

Speed is of the essence.

Explosions generally do not happen, not in the big bang and bits of car going everywhere way. There might be a bit of a chance of a pop if the tank was practically empty (full of vapour only) but not a full tank.

The fire though will quickly intensify when it his the tanks. LPG tanks have pressure valves and when it gets to that it will just jet burning gas.

If the tanks wasn't secured properly or has come loose in a crash it might go for a ride.

[VocalNeal]

Only if the the car in question was a Pinto driven by Ralf Nader.

[overherebc]

I'm not sure so asking are the LPG tanks just tanks that are pumped full of gas or do the they have some kind of filling that holds the gas similar to acetylene bottles that are full of Kapok and something. ( I'll remember just after I post )

[pattayadingo]

First off, this is the sort of thing you really want to take care of quickly,not ask for help on the interwebs.

Speed is of the essence.

Explosions generally do not happen, not in the big bang and bits of car going everywhere way. There might be a bit of a chance of a pop if the tank was practically empty (full of vapour only) but not a full tank.

The fire though will quickly intensify when it his the tanks. LPG tanks have pressure valves and when it gets to that it will just jet burning gas.

If the tanks wasn't secured properly or has come loose in a crash it might go for a ride.

In essence then it would act more like a blowtorch or s simple jet of gas until the gas died away?

What about the petrol tank would that also just leak the burning fuel and not likely to explode?

[transam]

First off, this is the sort of thing you really want to take care of quickly,not ask for help on the interwebs.

Speed is of the essence.

Explosions generally do not happen, not in the big bang and bits of car going everywhere way. There might be a bit of a chance of a pop if the tank was practically empty (full of vapour only) but not a full tank.

The fire though will quickly intensify when it his the tanks. LPG tanks have pressure valves and when it gets to that it will just jet burning gas.

If the tanks wasn't secured properly or has come loose in a crash it might go for a ride.

In essence then it would act more like a blowtorch or s simple jet of gas until the gas died away?

What about the petrol tank would that also just leak the burning fuel and not likely to explode?

It's the gas that explodes, any fuel mixed with the correct amount of oxygen is a bomb.

[WarpSpeed]

Only if the the car in question was a Pinto driven by Ralf Nader.

Or an older Chevy pickup with saddle bag tanks..

[WarpSpeed]

First off, this is the sort of thing you really want to take care of quickly,not ask for help on the interwebs.

Speed is of the essence.

Explosions generally do not happen, not in the big bang and bits of car going everywhere way. There might be a bit of a chance of a pop if the tank was practically empty (full of vapour only) but not a full tank.

The fire though will quickly intensify when it his the tanks. LPG tanks have pressure valves and when it gets to that it will just jet burning gas.

If the tanks wasn't secured properly or has come loose in a crash it might go for a ride.

In essence then it would act more like a blowtorch or s simple jet of gas until the gas died away?

What about the petrol tank would that also just leak the burning fuel and not likely to explode?

In essence then it would act more like a blowtorch or s simple jet of gas until the gas died away?

What about the petrol tank would that also just leak the burning fuel and not likely to explode?

Petrol in liquid form is actually not explosive by itself, notice I said "not explosive" not 'not flammable' it's when it spreads out and can mix volatile amounts of air with it that it becomes explosive so as long as it stays contained it will not explode in that sense but merely burn off as it contacts fire and air. LP or NGV is more volatile but the tanks are much stronger and less likely to be damaged on impact though NGV tanks are fiberglas pretty volatile in itself curiously.

The weak points are the valves, fill inlets and piping which are brass and copper respectfully for the purpose of bending instead of fracturing on impact and there is a high pressure blow off valve to allow pressure to vent in the case of a fire as it heats the gas inside, of course you wouldn't want to be anywhere near the car if this was happening and is most definitely toast (literally) but an "explosion" is less likely..

Unfortunately many cars like Jazz's these days have plastic fuel tanks ..

[monty]

They'll all burn happily and rather heftily, but explosions wil be very rare.

Petrol needs to evaporate and mix with oxygen to explode, and gas tanks have pressure blow of valves, releasing the gas in a controlled non explosive (but fiery) way.

Also, when an lpg (or cng) line breaks or ruptures, the safety valve at the tank should close immediately. It detects a much higher flow then during normal operation and reacts on that.

Most vehicle fires start under the bonnet and get sustained through a steady supply of petrol...

The only accepted increased fire/explosion risk on lpg vehicles is with very slow leaks, as lpg is heavier then air and can pool on the ground creating a big bubble of explosive mixture...

Hence why most countries do not allow lpg vehicle to park in enclosed parking areas.

Cng is less dangerous (in open air) as lighter then air, so slow leaks will just see the gas disapear into the air.. Still just as dangerous in car parks as it will just collect against the ceiling!

Having a cooking gas bottle in a fire is much more dangerous.

They keep getting hotter until they blow, ripping up in red hot pieces and being hurled away in all directiond at bullet speed!

Sent from my GT-I9001 using Thaivisa Connect App

[pattayadingo]

I'd like to thank you all for your replies on this.

Apologies for not getting back to the topic sooner.

Very interesting observations and answers that give a lot clearer idea of what might happen along the way. It is not a topic I've seen talked about much and it does make you consider the safety issues when considering if you should buy an LPG motor or not.

Obviously it is best to have a fire extinguisher on board and if not, to get out of there and clear as fast as you can.

[sezze]

Well , it's been tested many times before . LPG vs petrol and the petrol is much more likely to have a blast , although not nearly the size you see in movies .

The reason is pretty simple , the gastank itself is a bunker which contains the gas ( liquified for LPG ) under pressure with safety valves for overpressure . The petrol tank is just a barrel holding the liquid , no pressure and no safety valves .

Imagine a fire , the fire hits the gastank and it will heat up . By adding the heat , the pressure will rise and short bursts of gas will be released . These flamed are rather small and very pointed . When the gas itself is finished evaporating the pressure will not rise nomore so nothing will happen more .

In case of the petrol tank , the liquid petrol will start to heat up and evaporate . These gasses are not released by safety valves but by natural aspiration . The tank is not nearly as strong as the gastank itself so at a certain point the wall of the tank melts away and all petrol is released uncontrolled .

In case of a crash , both tanks are well secured but incase of a rupture , the gastank releases the gas under pressure in the direction of the rupture . For the petrol tank , the fuel just runs out , out of the rupture and by nature of the liquid it will spill everywhere .

On youtube you will probably find the movies of gastank vs petrol vs diesel hit by gunshots and in general carfires . Normally the petrol is by far the most dangerous type .

In case of a natural gas tank , i've never seen the images before but i guess it is roughly the same as the lpg tank . The only problem there would be a rupture , because of the very high pressure inside ( it might actually explode ... but i do not not know ) .