Propane fireball! YIKES!

So basically I've been trying to track down this leak somewhere in my DD system. It's a mysterious leak, I seem to have check everywhere but with absolutely no luck. I swear I'm filled and uncharged the system 10 times looking for where this thing is at.

Finally, after refilling, de-gassing, etc. the system 10 times with some cheap propane, I find it. By now I'm so friggin' tired of dealing with it I leave it alone. I come back an hour later determined to fix the leak and get the parts all warmed up, glowing red, start brazing them together with some silver solder and then BOOOOOOOOOOM! The part I was working on blows off (literally) and a GIANT FIREBALL 4 ft. wide and 6 ft. tall appears in the air. At this point I've jumped up, tripped on the chair I was sitting at, and fallen onto my back next to a wall 4 ft. away from the fireball, thinking "Oh pickle sticks (for the lack of a better word), I forgot to decharg the system all the way!"

The fireball died out in about 30 - 40 seconds (though it seemed longer) and a small flame arose from the pipes I was brazing together. Nothing was broken, nothing was harmed, and I am an extremely lucky guy. I guess that in all the times I've recharged the system I forgot just this once (and that was all I needed), and nearly killed myself. Well I just got done brazing up the parts that blew apart, this time with no propane in the system!

Lessons learned:

Make sure there's no propane in the system before brazing.
Make sure you're not in a chair that will trip you if you jump up.
Make sure you buy products that say "idiot proof" on the outside from now on.
Singed hair smells funny.
Parents greatly dislike fireballs.

Just thought I'd mention before it was asked. No. I did not get any pictures. =)

wow... your very lucky.

Personally I would have charged the system with an inert gas when checking for leaks. N2, CO2, or even helium. Even the helium intended for use in baloons with oxygen for the kids that mess around with it too much would work well.

When pressurizing the system, soapy water will bubble up at a leak making it easier to find. The old candle trick works ok too as long as your not changed with propane.

nvidiaOCmaster said:

wow... your very lucky.

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There really isn't any luck involved, propane is propane and not very explosive. When I was a kid I would see how violently I could get the top of the grill top pop off after filling it with propane and lighting it. It would lift it pretty well but thats not much bang for all the propane used.

I'd say it was pretty explosive. The blast blew apart a pipe to pipe joint done with 56% silver solder. Strong stuff. Granted it was weakened a little bit by my brazing a few inches away from it, but even still, the pipe shot off, lol.

i wont use propane

somone will kill them selves before long messing with this sh*t

To be honest with you, it wouldn't have been a problem if I hadn't been an idiot by not uncharging the system first.

Also, without a torch heating the system up (with propane inside), there's no way it would or could have exploded. I had the torch on it for a full 2 or 3 minutes before it went pop.

lol... i would be careful in the future with that s**t

And this is one of the reasons I'm not using extreme cooling cause soon as I heard that propane was one of the parts required I slowly walked away.

I would never leak check, or purge with propane, nitrogen is readly available and cheap. I'm going fill my system with propane though, if I could I would probably use R507.
Propane can be safe as long as you treat it like a flamable pressurized gas

In my 'expert' opinion, the problem is not that you did not fully decharge your system, it was that there was air in it. If there was only propane in they system, it wouldn't blow. When you decharge your system, do you vacuum it, just let it decompres, or try a quick purge with an air hose?

Another posibility is that if you had just let it decompress then started brazing, the heat would build the pressure back up again until the joint near where you were brazing gives way and the refrigerant spews out creating the fireball.

Strida said:

Just thought I'd mention before it was asked. No. I did not get any pictures. =)

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That picture would be worth a million words for those who are learning extreme cooling

Glad to hear your ok though, I will stick with my mach 1 for now!

When I decharged my system I just opened up the manifold, letting the gas out. I've actually had trouble with the pressure building back up as I've brazed up a leak, and then just bubbling the silver solder.

The vacuum pump I'm using was borrowed and it's an old compressor, looking like it's from the 50s/60s and made of solid cast iron. It's a PITA to lug around @ > 100 lbs, and even when the suction line is closed off it still pumps out a bunch of air from the exit. Obviously there's a leak in it and it's worthless. I did try and vacuum the system though, just wasn't very hopeful of it being a quality job.

I would purge with air, but have no air compressor. Is there any way around this?

I would say you have quite the dangerous system there. Propane is safe if there is no air in the system. If you can't pull a full vacuum, then you are going to have a combustable mixture when you charge the system. Next time you charge the system, pull a vacuum then break the vacuum with the propane about five or six times. Assuming you get 90% of the gas/air out each time, you would have an oxygen concentration well below what is necessary for combustion after the fourth or fifth vacuuming.

I would rather not have a bomb sitting by my head at my desk thanks lol. And yeah propane is very explosive when its contained pressurized in a small space aka a phase change system. I wonder is there is a way to get ahold of those old containers of freon that used to be "illegaly" available for charging car AC systems?

Strida said:

When I decharged my system I just opened up the manifold, letting the gas out. I've actually had trouble with the pressure building back up as I've brazed up a leak, and then just bubbling the silver solder.

The vacuum pump I'm using was borrowed and it's an old compressor, looking like it's from the 50s/60s and made of solid cast iron. It's a PITA to lug around @ > 100 lbs, and even when the suction line is closed off it still pumps out a bunch of air from the exit. Obviously there's a leak in it and it's worthless. I did try and vacuum the system though, just wasn't very hopeful of it being a quality job.

I would purge with air, but have no air compressor. Is there any way around this?

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Wow....
#1. When you have propane sitting in the system and letting it out... what do you think is INSIDE system... air? vacuum?... obviously propane...
#2. Vacuum pump can't be skipped. It is a must. In fact, If you can't pull the lowest gauge will go on manifold, that vacuum pump isn't worth a dime for this use.
#3. Purging with air? That is the last thing you want to do. You will have to replace oil in compressor, replace filter drier. Air is your enemy. Moisture in AIR is your enemy. I would be surprised if you even get near to decent temp without system fluctuating wildly without proper triple evacing (with nitrogen mind you). What happens is the moisture that wasn't vacuumed out will freeze up inside capillary tube and block the liquid... which will swing wildly in temp without proper evacing.
For this reason, I braze all system usually under 10 minutes after prepping to reduce any contamination of air. Compressor oil is either drained or freshly not opened (to be charged with my oil pump later if I drain it with new oil), filter drier gets opened up last and maybe stay on air for a minute or so. (I am being anal though, about 10 minute is considered fine by most for filter drier and compressor about 30 minutes or so... )

Just got to the end of this, and forgot who said propane wasn't that explosive, but don't kid yourself!

Propane caused one of the top 10 in the worlds biggest explosions of all time and it's VERY explosive...under pressure even moreso. What happened to the OP was called a BLEVY, and yes he was very lucky.

The explosion I told you about? It literally scoured everything for 3 block wide radius, blew a fire truck over 400' through the air, and the mushroom cloud of fire towered above a helicopter that filming the event and the chopper was 800 AGL (above ground level).

Pumping propane up to pressure is NOT a good idea, and bazx is right...somebody is gonna get killed. This practice is beyond dangerous...it's suicidal. Use inert gasses in these things...you'll live longer.

jinu117 said:

Wow....
#1. When you have propane sitting in the system and letting it out... what do you think is INSIDE system... air? vacuum?... obviously propane...
#2. Vacuum pump can't be skipped. It is a must. In fact, If you can't pull the lowest gauge will go on manifold, that vacuum pump isn't worth a dime for this use.
#3. Purging with air? That is the last thing you want to do. You will have to replace oil in compressor, replace filter drier. Air is your enemy. Moisture in AIR is your enemy. I would be surprised if you even get near to decent temp without system fluctuating wildly without proper triple evacing (with nitrogen mind you). What happens is the moisture that wasn't vacuumed out will freeze up inside capillary tube and block the liquid... which will swing wildly in temp without proper evacing.
For this reason, I braze all system usually under 10 minutes after prepping to reduce any contamination of air. Compressor oil is either drained or freshly not opened (to be charged with my oil pump later if I drain it with new oil), filter drier gets opened up last and maybe stay on air for a minute or so. (I am being anal though, about 10 minute is considered fine by most for filter drier and compressor about 30 minutes or so... )

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Yes I realized there was propane in there, just figured it would be okay since I had brazed it like that several times before. On the other hand, when I had my accident I had forgotten that I hadn't uncharged the system earlier. That was just stupidity on my part.

Vacuum pump, well, at least I tried. Right now I'm not going for hardcore 24/7 use. I'm still having fun fiddling around. Also, I had to buy a gallon of oil so if I do need to replace it, no big deal.

Purging with air was another person's idea so that I could seal up a leak without worrying about propane being in the system. I don't even have any way of doing it so don't freak out, it's not going to be done. Just so you know, even though I have a small leak I did get the system up and running for about a day, and lowest temp reached was -45C, and it stayed there fairly consistently. I guess my POS compressor/vacuum pump worked well enough.

@ jinu117 - To be honest with you I can't say that I appreciated the tone of your post. All I'm getting from it is "You're stupid!" when most of the things you've pointed out are things I was asking advice with. I thought that kind of behavior was generally found on boards like XS, but not here. However, I do appreciate the advice that you gave me indirectly by telling me how "you" do it, which I assume is the proper way.

LabRat23 said:

I would say you have quite the dangerous system there. Propane is safe if there is no air in the system. If you can't pull a full vacuum, then you are going to have a combustable mixture when you charge the system. Next time you charge the system, pull a vacuum then break the vacuum with the propane about five or six times. Assuming you get 90% of the gas/air out each time, you would have an oxygen concentration well below what is necessary for combustion after the fourth or fifth vacuuming.

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Just so I fully understand this...

Pull a vacuum for XX number of hours,
replace vacuum pump with propane,
squirt a bit of propane into the system to break vacuum,
repeat.

If I'm doing a method such as this, how long (with a new compressor used as a vacuum pump) should it take to get to 90%? I was thinking 2-3 hours, this too long/not long enough?

I talked to a local HVAC guy and he said that I shouldn't even need to vacuum the system, that it would be just fine. I'll take your guys' advice over his, but I guess that's what got me thinking it wasn't a huge deal if my compressor wasn't pulling a lot when I vacuumed.