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Oxygen / Propane Torch Problem - What Am I Missing?

Hi everyone,

I’ve been using a Smith Little torch with disposable propane tanks and an Extreme Oxygen EX-05 oxygen generator in my home studio for about six months now. I’ve never had any major problems with it, but today my flame keeps blowing out on my when I introduce the oxygen. I haven’t used the torch for three days; it was working just fine before this. The problem is currently extremely consistent – happens each time I try to make a flame.

Here’s a video of what happens when I introduce the oxygen.

I’m a beginner when it comes to troubleshooting torches, so I’m not sure what variables I should be looking at. I replaced my propane tank with a new one in case it was low. I switched out torch tips from a #6 to both #5 and #7 with no difference. I bled all my lines a few times. I rarely have my oxygen generation pumping more than 2 LPM of o2. I don’t know what the propane is at because I don’t have a gauge on that regulator.

Anyone know what’s happening to me here? I suspect the answer is obvious, but I don’t know what it is! Any help appreciated – I have a few projects due to clients this week and am up a tree.

Thank you!


Have you tried starting the generator in advance, maybe 20 minutes before using it?

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No, quite the contrary. I usually only fire it up about 30 seconds before I use it. And I always keep the o2 valve on my torch closed while it’s “charging” – I checked with the generator company early on and they said that was fine. It hasn’t been a problem to date, but maybe some variable somewhere changed and it suddenly is?

The video is a big help. Looks like you have your oxygen pressure too high. Either that or you are opening the oxy valve too far and too quickly. Just crack it and then gently continue to open it.

Jerry in Kodiak


Thank you! I wondered if that was it, but wasn’t sure. I’ve spent the past 20 minutes messing with the volume of o2 my generator’s putting out (I don’t actually have a way to control pressure since it’s not a tank), and that’s helping.

I also think I was making a mistake by leaving my o2 torch valve closed while I was running the generator but not using the torch. Maybe I was creating a buildup of o2 pressure that was blowing out all at once when I introduced it to the propane. Why this is only a problem now instead of past months, who knows, but there it is.

Now I’m leaving the o2 valve on my torch open while the generator’s running (though not when I’m lighting it, clearly). That plus lowering the volume of o2 from the generator = two successful bezels soldered so far.

Thanks again. Very helpful! :slight_smile:

Where is the pressure set on the oxygen side.

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Because it’s a generator, there is no way to control or read pressure from the generator. I have a knob that controls volume (liters per minute). For the past six months I’ve had it set at the max and was generally pumping between 1 and 2 LPM through the torch. I’ve experimented this afternoon with lowering the volume coming through and it’s working a bit better.

When you controlled the liters per second you were controlling the pressure. Given a fixed orifice, the only way you can control the volume of gas that passes through it is by varying the pressure that is driving it. You have a fixed orifice in the torch tip. You have a variable orifice in the valve you are using to control the flow. Think of a garden hose with a weak spot in it. Open the faucet valve and if the nozzle is wide open you;ll probably have no problem because there is not much pressure in the hose. Close the nozzle and the pressure in the hose rises and you’ll probably blow a hole in the weak spot because of the increased pressure against it.

Jerry in Kodiak

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Really really helpful. Makes perfect sense. Thank you!

on occasion, my torch will act exactly like that until I run a cleaner
through the tip. … . even though it looks clean … and then it lights

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The difference might be a warmer overall room temperature (spring) affecting the behavior of gases.

What do you think? What’s your environment? Eg, my studio is pretty darn chilly all winter and it takes a while for all equipment to warm up after I turn on the heat.

Unless of course you’re writing to us from Oz. (-:

  • Lorraine
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Same! Usually cleaning the tips does the trick for me when it pulls this stunt, but not this time.

Could be! I’m in Boston. I have central heat/AC though, so my apartment is usually fairly constant in temp (I turned a guest bedroom into my studio). I wondered about that, though.

Thanks for the input, everyone! This was my first post here and you certainly all came to the rescue.

I solved the problem by a) leaving my o2 valve on my torch open while the generator was warming up and b) reducing the volume/pressure of o2 coming from the generator to my torch.

I think that because I had the o2 valve on the torch shut off while my generator was warming up, when I did intro the o2 to the propane, I got a big whoosh of it that blew out the flame. Why this is happening now and didn’t happen for the last six months, I continue to have no idea, but I’m happily soldering again. :slight_smile:

I usually have to run my oxygen generator for a few minutes with the torch valve open to clear the air from the O2 tube after I’ve not used it for a few days. Then I close the O2 valve on the torch and light it in the normal way. it’s amazing just how much air the hose can hold - if you switch off your O2 generator with the torch lit you can see just how long it lasts before the O2 runs out.


Really validating you’ve had that experienced. I wondered if the days of letting it sit idle had something to do with it. Never tried leaving it run after I turned off the generator, but totally going to now.

It should only take a minute or two to get adequate O2 to light the torch. 3 LPM is the target that I look for on my EX10. I would assume the same for the EX5. You can very easily blow out the flame on the Little Torch. Make sure that all the hoses are tight as well as the tip to handle. Have you tried a new or refilled cylinder? Tips can get dirty. I clean my Meco and EZ Torch tips often, but don’t use the Little Torch enough to have been compelled to clean the tips. I usually put my tips into the ultrasonic sink. Look at a new set of tips from Paige Tools. They make very nice tips for propane and O2 torched like Meco, Little Torch and Hoke. They make all the difference in the world. Richard at Paige is also a lot of help on these types of problems and may chime in with suggestions if he has any. Good luck…Rob

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open the gas valve on the torch and just barely introduce the gas (works for acetylene and propane), light the torch and then increase the flow from the tank until the flame separates from direct contact with the tip. That is when the volume is high enough that a gap shows up between the tip and the flame. That pressure is the correct maximum setting for the gas. Then open the oxy valve on the torch and slowly add oxygen until the flame is correct. With acetylene it is a dead on specific point. As you add oxygen the flame will gradually go through a stage at which the flame has three distinct “layers”. As the oxygen is increased the central part will gradually merge with the outer part at which time you have achieved a neutral flame. Note the oxygen pressure. That is the one you want. Each size of tip will have it’s own distinct pressure setting. Propane is a bit less exacting as you don’t have the distinct layers to guide adjustment but need to rely more on experience. With a bit of practice too much oxygen does become apparent and as does too little.

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Hi There.
Technical Ted here, your O2 generator is making this gas by electrolysis of water.
a good system.
As you said it suddenly wouldnt respond as it used to do, then something has changed. Therefore the knob ? to which you refer is either a electric variable device or a gas needle valve.
guessing an answer like most who posted so far is not the way to go. Also your not the sort who fixes things yourself, so the first thing to do is to call the makers and ASK what the knob does, and can they supply a spare if needed?
Do you have any one competent to take the cover off and have a look?
Things do fail, and with gasses you DO need to play safe.
Ted who fixes things all the time
Let us know what the makers answer is.

Ted…I think that they remove the nitrogen by compressing air and passing it thru filters and a sieve bed. What is left is fairly pure O2. Concentrators need very little maintenance other than changing filters. I suspect that the sieves will eventually fail at which point I buy a new concentrator. Meanwhile, I have had a ready supply of O2 , no expensive high pressure tanks to fill, no regulators to buy and adjust and, most importantly, the safety issues associated with high pressure tanks is gone. I do keep a small O2 tank in my garden shed just in case. I keep the flow around 3 LPM for the Meco, maybe less for my Little Torch. The lighting process is the same for all torches. Turn everything off. Open the propane tank valve (I use a nonadjustable regulator on a 1 lb. refillable propane tank). Crack the gas valve on the handle, light the gas, slowly open the O2 valve, adjust the flame and I am good to go. Obviously there are connections that could be loose, valve that need to have the gland nut tightened, needle valves that need to be cleaned or replaced, tips that need t be cleaned. These suggestions have all been made in previous posts. I look forward to hearing what works to solve the problem…Rob

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