The dangers of gas cyliders

[ProfJohnL]

Some of you may remember me writing about how a 47Kg gas cylinder became a missile and demolished a warehouse wall, thankfully without injury. Just as reminder of how important it is to carry store and use LPG cylinders safely just watch this Youtube video of a Russian lorry incident and the dangers. Pay attention to distance some of the damaged cylinders are projected both by the explosions but also how some are literally turned into ballistic missiles as the burning LPG thrusts the cylinders along.

http://www.youtube.com/watch?v=FQFphkoiq3g#t=137
What I don't know is if the Russian bottles have the same safety features we have in the UK, but even with UK safety devices I would still expect cylinders to behave the same in a similar conflagration.

This is one of the reasons I frequently reinforce the gas safety messages.

 

[Surfer]

Some of you may remember me writing about how a 47Kg gas cylinder became a missile and demolished a warehouse wall, thankfully without injury. Just as reminder of how important it is to carry store and use LPG cylinders safely just watch this Youtube video of a Russian lorry incident and the dangers. Pay attention to distance some of the damaged cylinders are projected both by the explosions but also how some are literally turned into ballistic missiles as the burning LPG thrusts the cylinders along.

http://www.youtube.com/watch?v=FQFphkoiq3g#t=137
What I don't know is if the Russian bottles have the same safety features we have in the UK, but even with UK safety devices I would still expect cylinders to behave the same in a similar conflagration.

This is one of the reasons I frequently reinforce the gas safety messages.

Makes you wonder what would happen with the Gaslite type bottle?

 

[RayS]

Quite some video Prof. and makes you think. I don't know the details of gaslite type bottles but assume they will have similar proof stress to the previous types. If they have been down rated, then it whoud actually improve the situation as the bottle shold fail at a lower pressure and thus contain the explosion less well, so you would get more fire sooner but less bang to be technical about it.

Reminds me of my young days commissioning control on motor ships at sea. The correct answer to the question 'What steps to you take if discovering an engine fire at sea ?' was 'Bl**d* great ones at high speed in the opposite direction'

 

[ProfJohnL]

Hello Ray,

You wrote " as the bottle shold fail at a lower pressure and thus contain the explosion less well" Its actually a slight miss conception to suggest that LPG cylinders explode. They don't explode because of the gasses fuel capacity, as the gas needs free air to mix with mix with free oxygen to produce a flammable mixture. That simply can't happen inside a cylinder unless it has been tampered with or damaged possibly by shrapnel from other items in the fire.

LPG cylinders only contain LPG, which is indeed a high energy fuel, but LPG only becomes flammable and explosive when it has access to free oxygen. Unlike true high explosives LPG does not contain oxidants and so will not explode inside the cylinder.

I have seen a slow motion film an over heated LPG cylinder. The cylinder split, I assume by the rising hydraulic pressure of the LPG inside. Initially the combined gas and liquefied content bursts out under pressure and seems to quench the flames in the vicinity of the split, The liquefied gas starts to boil into vapour and the cloud of vapour expands. The cloud starts to burn at the edges where the vapour has access to some oxygen. I assume the thermals created by the burning gas break the vapour cloud up and allow more rapid mixing with air and as that increases the speed at which the flame front encroach back to the cylinder. At this point the flame speed was fast enough to be classed as an explosion, and the cylinder became a projectile.

Near the end of Russian video you can see a cylinder scooting down the road towards the cameraman. In this case its the valve assembly thats lost, The the cylinder was lying down and the escaping gas acts just like a plastic water rocket and the cylinder can become ballistic. It has a plume of fire, but that will just be the vapour burning. as the the cylinder does not have the 'A typical' rocket motor nozzle, the flame is not directed and adds nothing to the motion of the cylinder, its just the vapour burning off as it gains access to the air.

 

[PhilGrace]

Prof John,
Its just as you describe..... whilst the escaping vapour burns that's OK but there can be worse. What is known as a BLEVE. Or in plain English a Boiling Liquid Expanding Vapour Explosion.
This was the scenario at Mexico City in 1984: perhaps worst example.
Phil

 

[ProfJohnL]

Hello Phil,

Welcome to the topic. Yes there is a school of thought expressed to me by a Fire Training provider, that where an LPG cylinder is venting and the vapour is burning, it represent less of a danger than if the liquified gas was escaping. Both the Liquefied gas and the gas vapour is heavier than air and will naturally migrate to the lowest available point. This can be drainage systems and can have the potential to carry fire or explode as in the Mexico City Incident. If the vapour is burning off then the the product of combustion naturally rise and of course their fuel energy has been used used up or rendered into non flammable components.

The other danger from the Liquefied gas is if it come into contact with skin, the rapid boiling of the gas draws heat energy from what ever it touches and rapidly cools it, and if its skin it can cause very serious deep frost bite. - just as serious as hot burns from burning gas.