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LP Cylinders question
Here is a question that was posted, but no place to reply, so I copied ans pasted here,
L.P.G cylinderPosted by OKELEYE, ISRAEL on November 28, 2008 at 5:32am in General Firefighting & Rescue Discussion
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the instruction is that if one needs to cool a leaking l.p.g cylinder one would have to spray water BUT AVOID THE VALVE SO THAT IT DOES NOT FREEZ. my question is what makes the difference from rain falling on the valves from time to time and spraying water on it?
L.P.G cylinderPosted by OKELEYE, ISRAEL on November 28, 2008 at 5:32am in General Firefighting & Rescue Discussion
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the instruction is that if one needs to cool a leaking l.p.g cylinder one would have to spray water BUT AVOID THE VALVE SO THAT IT DOES NOT FREEZ. my question is what makes the difference from rain falling on the valves from time to time and spraying water on it?
Replies to This Discussion
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Permalink Reply by Bull on
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Im assuming your cooling because of a fire. If you freeze the pressure valve when its on fire, it will burn inside and build up pressure and explode. If its not on fire, no pressure, no explosion. I think thats what your asking ???
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Permalink Reply by Jay Nicholson on
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There are different types of heat. radiant heat... and heat of compression. When you take a gas and compress it, it heats up. If you decompress it, it cools down. Now if you have a rapidly decompressing LPG tank and you spray water where you don't want it, it could easily cause an ice plug. Bad thing to happen.
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Permalink Reply by FETC on
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This is one of a bunch of different types of gas related emergencies... I have never heard of a fire burning inside the tank, freezing the leak and then exploding? The product inside a cylinder boils (due to being heated from the outside of the tank) then expands causing increased pressure within the cylinder, then the tank ruptures from the increased PSI. Has nothing to do with fire inside, not enough O2 to sustain fire so let's get back to the question...
The only time cylinder valves will freeze is if the propane product is leaking from the valve assembly. The old trick you mention, (to be used as a last resort) is when the leak can't be contained but needs to be reduced for greater safety during an evacuation process because of high LEL readings in the immeidate area. We would, under protection of 250 gpm. wrap a wet towel around the valve assembly and let it freeze. (Gas guys have done this without protection but they are nuts anyways) I have only seen one valve actually freeze enough to ALMOST stop the product leak. Bought us some time at reduced LEL's.
When it is raining and no product leak, then there is nothing to freeze...
If the pressure relief valve is flowing on a cylinder, then you should be concerned with a BLEVE, establish a blast zone perimter, establish a solid water supply and flow a minimum of 250 gpm onto the tank. Remote monitors? The relief valve is popped most likely due to radiant heat exposure from a nearby fire and the cylinder needs to reduce internal pressure. In this scenario, it is completely different from a leaking valve assembly and you WOULDN'T WANT TO freeze the leak, (if you could) but also unlikley...
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Permalink Reply by Paul Montpetit on
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If the Propane is leaking it comes out at minus 44 degrees...water will naturally freeze at that temperature...rain is falling on the OUTSIDE of a sealed tank...not on the propane...if you spray on the leaking valve it may very well seal the valve and the impinged tank might over heat and without the valve a BLEVE may occur...I just went to a "Propane Emergency" course offerred by FASY....Paul
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Very true Paul. (if in fact the valve is leaking from what you call impingement or what I call exposure).
Without any exposure, example an isolated valve assembly leak with no fire, then no internal pressures / NO BLEVE concerns.
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I agree ...but, why would someone spray water on a tank just because it is leaking...?? If it is just a leak and there is no flame inpingement either shut the line off or if it is the valve then water will not do any harm and it will actually seal the leaking valve.....caution....DO NOT touch it with firefighting gloves...they WILL NOT protect your hands...have to use the heavy rubber/vinyl insulated gloves...we used towels saturated with water and wrapped them around the leak...it works...seals nicely....Paul
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Exposure control from within a tank farm where they bulk load product to delivery trucks. How about a large above ground tank near or within a housing complex? There are times that the evacuation process is taking too long, ignition sources are too many, or not enough manpower to complete both and letting the gas flow is not an answer, so using the control method for vapor dispersion or sealing a leaking valve wins.
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