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Noob question: Propane Oxy problem keeping flame

G

Gennady

Active Member
Hello team.
By chance aquired gas welding/brazing kit and tried to use it for the first time. Instead of acetilene i am using LPG from regular BBQ. There are regulators on both cylinders - propane and oxygen, Tip that I only have is marked 701 0.1 So the actual problem is flame is "thrown" away from tip and goes out. I can have propane flow on a very, very low level to have flame stable. then I am adding oxy and managing to receive proper flame form, but it is very small. Not enough to braze any significant part. What is wrong with my setup ? tip is too small ? Propane and not acetilene ? else?
Thnaks in advance.
 

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Using propane for cutting is a piece of cake and starting a fire is easily done if you have something incombustible for the flame to blow against while adjusting. Use 5psi pane and 35 oxy settings.
Now, for a welding tip, as constructed for acetylene, it will be very unstable on propane. I don't know why but Propane fires need a recess in the tip, similar to a propane cutting tip. I have drilled my recess by this rule of thumb: If the jet hole is 1/6", then drill a recess 1/8" diameter by 1/8" deep. This willl give you a rock steady easy lighting flame.
I just used a hand held drill and a not too sharp drill bit, because a sharp bit will tend to suck itself into a pilot drilled hole. You can experiment as to slowly increasing the depth and diameter til you achieve a stable flame. Remember to use a tip cleaner on it after drilling.

If you need, I can post pictures of mine
 
To me it sounds like a mixing problem. There isn't enough oxygen mixed into the gas to keep it burning well at the tip.

I bet @Ironman 's tip recess fixes that.
 
I've never tried what @Ironman suggested, but sounds like it would work, the tip is recessed in a propane cutting tip

You are not doing anything wrong, getting a flame off a standard welding tip with propane is a tough go, I normally just braze with the cutting attachment, but I think I'm going to try @Ironman 's trick the next time

Holding the flame against something when your adjusting will make it easier to get it lit and adjusted, this is also what I normally do
 
phaxtris said:
Holding the flame against something when your adjusting will make it easier to get it lit and adjusted, this is also what I normally do
Click to expand...

Yup, mixing. Your trick is a pretty good one! A barrier of some kind is a great way to get gasses moving around!

I like @Ironman's recess cuz it's always there doing its job. But your barrier prolly does superior mixing.
 
My understanding is as the velocity of the oxy mixture increases it blows away from the tip. Acetylene burns faster than propane so a higher pressure/velocity can be used and still keep the fame on the tip. @Ironman ‘s recessed tip allows the propane mixture to slow down allowing the propane flame to stay at the tip at useful pressures.
 
Johnwa said:
My understanding is as the velocity of the oxy mixture increases it blows away from the tip.
Click to expand...

Interesting John. I like that explanation.

The flame speed of Acetylene is only about double that of Propane but you are playing with a balance that's easy to push one way or the other.

The flammability range difference is also interesting. Propane is only flammable between roughly 2.5 and 10% (in air) while Acetylene is flammable between 2.5 and 80. I wonder how that ratio works in pure Oxygen?
 
I have seen this effect a number of times, flairing off storage tanks for piping repairs and changes. The propane flame will sometimes be a foot or more beyond the end of the pipe. As the pressure drops the flame moves closer to the end of the pipe. Velocity verses pressure and pipe diameter. Temputures also play a part in this. The propane will not burn unless the air mixture is right, the border area/ outer envelope has a better air mixture able to support burning.
What you don't/never want is a vaper cloud with any of it at the mixture for ignition.
Note, vaper clouds can be any size!
 
Indeeed, I am regulating presure down to the bare minimum. What I notised , though - even pure propane tends to be pushed away from the tip as I am increasing the flow Anyway, I will try again tomorrow. Regarding resses - I am bit chicken to ruin my only tip of the torch . I am in search for another one or two to have spare... just in case.
 
i made a video, modified a welding tip with a drilled recess like @Ironman had suggested, it is still more tricky than with acetylene, but it works, vs hardly at all with a stock tip

used a random drill bit (happened to be a #38), drilled a slight recess, works like a charm. Light the propane, put it against something, open the oxy, if it wont "connect" into a cone, back off the propane until it does, then you can slowly increase both, it is tricky (as you see i blew it out once), but it works, this is with a #2 tip, pressures ? around 5 on both? my gauges are so beat up its mostly guess work

IMG_20240717_185228726.jpg


and how it is to light a normal propane cutting tip, you can see the dramatically recessed orifices

 
phaxtris said:
i made a video, modified a welding tip with a drilled recess like @Ironman had suggested, it is still more tricky than with acetylene, but it works, vs hardly at all with a stock tip

used a random drill bit (happened to be a #38), drilled a slight recess, works like a charm. Light the propane, put it against something, open the oxy, if it wont "connect" into a cone, back off the propane until it does, then you can slowly increase both, it is tricky (as you see i blew it out once), but it works, this is with a #2 tip, pressures ? around 5 on both? my gauges are so beat up its mostly guess work

View attachment 49901


and how it is to light a normal propane cutting tip, you can see the dramatically recessed orifices

Click to expand...
Brilliant. Thanks a lot Ryan !!!
 
Gennady said:
I am bit chicken to ruin my only tip of the torch .
Click to expand...

There is another way to do the same thing.

Instead of drilling a recess, add a cap. If you have a drill press, a mill, or best of all a lathe, you could make a tight fitting cap that attaches with a set screw that makes the same recess by adding material instead of drilling it away. Just add a collar instead of drilling a hole. That way you don't risk ruining your only tip.

This would also facilitate experimentation.
 
The downside is the bulk, though. The only time I want to use a welding tip to weld or braze is in a tight area, otherwise I use the cutting tip.
The other issue is the diameter of the hole, which cannot be smaller than the tip OD.
Tips are cheap, and if you are wringing your hands in anguish because you think you wrecked it, grab a file and file that little recess right out of there and stroke the edges round again.
 
Gennady said:
Have you seen that replacement tips anywhere ? Any particular store or link ? There are Victor style tips with screw-on collars but not tips with thread on its own.
Click to expand...
Yes, many years ago when I was 16, my first propane cutting torch was a LA, and I forgot the model. I used it for almost 20 years, until I went to Victor, never looked back. Back then welding suppliers were disgusted with the thought of propane and the money they were loosing. I went to buy my first tip at the local Liqkweed dealer and he was explaining to me why propane was no good. And it would take 3 years to order from the US.
My eyes were glazing over, and then I noticed the torch hanging on the display board behind him, sporting a nice new LA #1 propane cutting tip. "Oh, look, a Propane tip! can I buy that one"?
He never said another word, except OK.
I honestly have not seen a LA torch for sale anywhere lately. I'm sure they are out there but I don't know where.
Have you tried Amazon?
 
That LA stuff has been out of production for at least what, 20 years ?

The seat does look similar to a victor seat, maybe find a cheap victor tip and see if it works, or just buy a whole knock off victor torch, they are pretty cheap
 
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