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Thread: Who says LPG cylinders explode??

  1. #41
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    Its strange because people expect gas bottles to explode in a fire, while it does happen it is not the norm venting looks spectacular but is normally not a problem unless the tank is pointing the wrong way. Both RFS and CFA recommend pointing valves away from buildings (common sense)
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  2. #42
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    For a cylinder to BLEVE (explode - non technical term ) a few things have to happen.


    • It needs to contain a gas, liquefied under pressure.
    • The cylinder has to have flame (or excessive heat) impinging on the vapour space (ie above the liquid)
    • The metal the cylinder is made of needs to get hot enough to fail from the internal pressure.


    When it fails the liquid rapidly expands into a gas cloud and if it's a flammable gas catches fire.

    Hence the term BLEVE - BOILING LIQUID EXPANDING VAPOUR EXPLOSION

    The smaller the cylinder the less likely this happens as the fusible plugs will let go and the cylinder vents all the gas before it gets to the point of metal failure (not that you would want to rely on this).


    Martyn

  3. #43
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    dmdigital is offline OldBushie Vendor

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    The Cairns incident was 1987.
    http://www.emergency.qld.gov.au/publ..._05_p16-19.pdf

    Probably the most easily seen video of what a BLEVE produces is the Mythbuster's footage of when they rig a hot water PV to explode: YouTube - Mythbusters water heater . This clearly shows what can happen without the fireball ('cause its water vapour). The fire portion is the damage after the event in the case of LPG.
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  4. #44
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    Mythbusters also did a propane cylinder and failed to get it to explode.

    It was full so what bushie said would probably apply.

  5. #45
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    Quote Originally Posted by hook View Post
    Photos on the TV news for the VIC 09 bush fires show gas bottles still standing next to burnt down houses.
    Found it real strange to see.
    It is actually more common than most people think for an lpg cylinder to remain intact. Still on approach you need to treat them as a high priority exposure. If the fire is not near by (eg house fire) disconnect them and move them to a safe area. If they have been heated or in the fire they need to be cooled with water to a safe temp and moved with protective sprays.
    As said with a BLEVE they can go off if the valves, plugs fail or they are exposed to extreme temperatures in fires.
    With cars it is not nrmally the gas cylinder that causes the drama but the fact that the vent valve vent tube usually becomes blocked or the vent valve vents to the interior of the vehicle not the exterior as required. Usually a gas build up in the car and then an ignition source causes the gas build up to iflame and explode. This then can cause the lpg cylinder to go as well, so its not actually the cylinder at fault most of the time. I have also seen lpg cylinders still perfectly intact after an lpg leak and explosion in cars. Another way some of these issues occur is through the incorrect transport of lpg cylinders on their side. They are not designed to be carried like this and anything over a 9kg domestic cylinder or a registered automotive lpg tank is not allowed to be carried inside a motor vehicle or lying down. Most of the issue hers is valves can get damaged and leak.
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  6. #46
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    Quote Originally Posted by dm_td5 View Post
    The Cairns incident was 1987.
    http://www.emergency.qld.gov.au/publ..._05_p16-19.pdf

    Probably the most easily seen video of what a BLEVE produces is the Mythbuster's footage of when they rig a hot water PV to explode: YouTube - Mythbusters water heater . This clearly shows what can happen without the fireball ('cause its water vapour). The fire portion is the damage after the event in the case of LPG.
    Or this one of a real LPG BLEVE

    YouTube - Train car explosion bleve


    Martyn

  7. #47
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    Well I just spent the week auditing bulk gas tanks on 33 fire affected properties around Wandong through to Narbethong- could'nt get into Marysville- there are 40 properties to see there. We did'nt visit if the fire was more than 150m away so went past around another 40.
    I guess you could say we saw the total variations in fire affected gas tanks & cylinders, but no Bleve's
    The 190/210kg vessels (440 Litres) took the heat pretty well overall. Most vented off successfully, some lost all the gas through melted supply lines - usually if the tank was away from the burnt out house- and these did not vent.
    A few were totally destroyed- all the paint burnt off, and valves melted, however there was total destruction all around when this happened. The common thing that happened was the contents guage melted and all that was left was a hole where it was, & 4 screws that held it in place.
    The boss has decided to take over my run, he can have it, he's in for a shock & I've seen enough, although this is the first I've said it.

    I will always remember one one particular house out of Wandong, there was total destruction all around- all neighbouring houses, sheds etc & the forest may never recover, it was right in the middle of the firestorm, a weatherboard house & the fire must have jumped over it. I put it down to it having a European type front garden. The 1300 litre gas tank there had only the slightest suntan on the stickers

    Attached is a pic of a melted padlock & another of the contents guage gone.They are different tanks.




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