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B.L.E.V.Es
I need some help guys! We're talking about BLEVEs at my next dept. meeting and honestly, I don't know what one is. Of course, I know the text book definition, but as a member of a rural dept., I've never dealt with one. If you feel like sharing, Please leave your experiences with these nasty little buggers..
Stay Safe,
Michelle
Stay Safe,
Michelle
Replies to This Discussion
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Permalink Reply by SgaFemaleFirefighter on
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that would be my actual name there Tony.......
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Permalink Reply by Ben Waller on
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Technically, the rupture of an enclosed cylinder like a drive shaft is an "overpressure rupture", not an explosion. It will make a loud noise and throw shrapnel, but won't have a fireball.
A BLEVE is an overpressure rupture caused by boiling of a flammable compressed liquid in the cylinder. It has the loud noise and shrapnel, but will also have the fireball.
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Dennis,
Gasoline tankers don't generally BLEVE, because the aluminum tank tends to melt down rather than overpressuring and exploding. Could you give us more information on what happened in the incident to which you refer?
Ben
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A lot of LPG companies use LPG for vehicle fuel in their staff cars and service trucks. If the trunk is open, you can just attack it with a hoseline from the rear. Use lots of water to get quick knockdown and minimize personnel exposure.
If the trunk isn't open, you may be able to jam a piercing nozzle through the trunk lid and attack the fire indirectly.
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You can usually tell that a vehicle uses LPG fuel by the differences in the fuel filler. They're not always exposed to the outside, but they usually look something like the ones here: http://www.energyshift.co.uk/pics.htm
Note that some "autogas" vehicles are a sole fuel, some have driver-selected dual gasoline and LPG fuel systems, and that some LPG fillers are hidden behind the license plate as in some 1960's and 1970's U.S. sedans.
There is also some pretty good information on LPG conversion kits for vehicles, how they're made, and how they perform here: http://www.lpg-kits.com/why.htm
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Cap,
An "empty" LPG tank (actually a tank with vapor residue, as Scott pointed out) will BLEVE more quickly than a "full" LPG tank. Most BLEVEs occur one of two ways;
1) Fire impinges on unprotected steel over the vapor space and the steel fails
2) A liquid hydrocarbon fire beneath the cylinder eventually boils all of the liquid out, then the steel fails.
A full LPG tank has compressed liquid filling around 70% to 80% of the cylinder. The upper part of the cylinder is a vapor space. When fire impinges on the liquid space, the liquid acts as a protective mechanism, because it boils off and then vents out of the pressure relieve valve. The more liquid in the cylinder, the longer the steel shell of the tank will last before it fails. Fire impinging on the vapor space is more immediately dangerous, because there is no liquid inside to help cool the inside of the steel.
If there is very little liquid - or no liquid - in the "empty" cylinder, the entire cylinder essentially is vapor space and subject to very rapid failure no matter the angle from which the fire impinges the cylinder.
The photo shows an example of how situation #2 can be prevented by a Class B foam attack on the hydrocarbon spill as well as on the involved vehicle.
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Permalink Reply by Tony P on
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Thanks Michelle, I was confused, I thought there may have been a mistype of Michael (Vito).
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Permalink Reply by Scott on
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We see some of these in fleets as well but they are CNG. The WI state University system uses a lot of CNG and there are some PD's in smaller communities that have duel fuel cars. CNG and gasoline.
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Permalink Reply by Jay Griffin on
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Hey Michelle I lived through an LPG bleve in 1998 I was first Due Engine to a reported house fire approx. 4 miles out of town. what had happened was due to rising price of gas the home owner had local gas co. install extra tanks to go over the winter. One of the tanks Mfg. in 1948 had rusted out on the bottomleaking gas traveled to the house found a spark and bang instant torch .When we came in we did not know we had a tank fire as we started pumping a 100 pound tank bleved due to flame impingement from leaking tank. The reason we're here today is that we were down by the house and the tanks were on a small knoll ,my nozzle man was blown ass over tea kettle and i was blown into the pump panel of the truck. no burns but we both suffered some hearing loss and had lots of aches and pains. After the investigation we were asked if we wanted the remains of the bleved tank .we still bring it out when we have a training class on LPG. so remember it can happen to any Dept.
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My jurisdiction mandates underground installations for LP gas tanks in residential locations in order to prevent exactly what you described. It makes protecting them easy during a wildland interface fire - you just shovel dirt over the dome.
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With the underground installation Ben, do you have a requirement for these tanks to be pressure tested on a regular basis?
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