Cutting torch popping a lot

joel_bcOctober 26, 2009

What makes my cutting torch (Victor brand) start popping rhythmically? This is during the pre-heat. The 'snaps' or pops aren't too loud, and it stops when I give the extra oxy with the cutting lever.

I keep the orifices in the cutting tip clean (and it's a pretty new tip), and I've got new O-rings where the cutting head fits into the torch handle. I've been running the reg pressure levels - with a medium-size tip - at about 8lbs acetylene, 25lbs oxy.

The torch still cuts... because once I've pre-heated a corner I just pull lever and cut away. But it's annoying during the pre-heat, and I'd like to figure out what's wrong.

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A few more bits of info: It's an almost-new #2 Victor cutting tip I've been having trouble with. My #1 (smaller orifices) tip works fine. My acetylene tank is about 40% full, and O2 is about 95% full. I make sure that, before pre-heat light-up, my tank valves are open amply.

I've experiemented with setting the acetylene level at the reg at 5-8 lbs, and experimented with the O2 at 25-35 lbs.

I make sure I've got a nice acet-only flame at light-up, and I make sure the flame isn't "jumped" off the end of the tip - then I add the oxy to adjust to little hard-blue pre-heat flames. But the #2 tip just pops rhythmically and sometimes blows its flame out during pre-heat (but once I pull the extra-oxy lever, the flame steadies and continues, with no pops - until I let go of the lever again.

    Bookmark   October 31, 2009 at 6:17PM
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Let me start this by stating that I am not a real welder, but I do use torches. A possibility is that you have an air leak where the tip seats. The leak could be someplace else, but since the other tip works the seating of the problem tip is suspicious. I was told to rotate the tip in its seat as you are tightening it before you give it the final pull. You might give that a try.

    Bookmark   November 1, 2009 at 5:29PM
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I joined Garden Web just to comment on your problem. Actually it was at my wife's suggestion, she has been an active member for some time.
I loved my old Victor torch set, and it gave me incredible service until I made the mistake of lending it to a guy tearing parts off a car. He was too lazy to walk for a hammer, so he would make a bad cut, and then turn the torch over and use it for a hammer.
The thrill of Victor became the agony of defeat.
Popping in either welding or cutting, or even general heating for that matter occurs when the tip temperature exceeds the threshold for popping to occur. Contrary to intuitive problem solving, this condition is remedied by turning up the heat. The gas flow through the tip cools the tip body.
You are aparently aware that the acetylene flame shouldn't be dancing off the end of the tip prior to introducing oxygen, however you may be being overly cautious and consequently finalizing your gas adjustments at a setting too low to prevent popping.
I found that on occasion I would have a tip which would pop for no apparent reason, and I could always convince it to behave by taking the acetylene only flame out till it quit smoking (another starting reference point) going past that till the flame left the tip, backing off till it re-attached itself to the tip while noting how far you had to close the valve to go from leaving the tip and returning.
This amount of valve movement will be recalled in the next step. When the acetylene flame is back in contact with the end of the tip, start to bring up the oxygen, but don't go all the way to a neutral flame just yet. When you are about half way to a neutral flame with oxygen, go back to the acetylene valve and open it about half of the amount you needed to back it off to get the flame to come back to the tip. Finish by increasing the oxygen to a neutral flame and you should have no popping.
If this gives you a heat level in excess of what you need for your typical cutting jobs, consider dropping one number on the tip size. The gas savings will pay for the tip over a fairly short amount of time, and you will realize another benefit of having a more docile cutting flame which will allow more precision cuts and a narrower kerf. (I don't know if kerf is a welding term or not. I hear my wife say it when she talks about sawing wood.)

    Bookmark   November 15, 2009 at 12:18PM
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Well Stan I don't know if you helped Joel out or not, but I recently aquired a cutting torch setup myself, used, and have had a little problem with the popping myself. I printed out your post last night and took it out to my shop where I was preparing to cut some 4" circles out of some 3/16" sheet steel. I set it up just like you said, and no more popping!

Thanks for the explanation.

The guy I got them from gave me a package with a flashback arrestor set. What do you think, should I put the arrestors on? Looks like a real pain, there are a bunch of calibrations you have to do after installing them.

    Bookmark   November 19, 2009 at 10:53PM
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Also, the instuctions for the torches say when finished to shut off the oxygen first, but a book I am reading says to shut off the acetylene first. What's up with that??

    Bookmark   November 19, 2009 at 10:56PM
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JoeFix2. Glad my longwinded post helped somebody out. I never used flashback arresters, and I don't want to comment on their benefits because I would only be guessing.

Having properly disclaimed, I believe that flashback arresters prevent explosions within the hoses. I never understood how mixed fuel gas and O2 both got into the same hose. I recall hearing accounts of explosions destroying regulators, but again no personal experience.

Re: which gas to shut off first.

I've seen conflicting shut down instructions on torches from different manufacturers. What I've always adopted as my standard sequence is to turn off the fuel gas first, and then the O2. This method usually causes a small pop, but to reverse and turn off the O2 first, there is frequently a large pop after the flame disappears back into the inside of the tip. I believe this contributes to tip clogging, since there is usually a puff of black smoke with the pop.

I've been away from gas welding for about 10 years, and it felt good to at least write about it in the previous post, even if I'm not doing it now.

I'll always be a gas welder at heart, because now 75% of my welding is TIG, which was basically all learned on top of the skills I had previously developed gas welding (not brazing, real welding). I still wield a torch, its just an electric one now.

I'll keep checking back here to see hoping to learn more about flashback arrestors if somebody with a knowledge of them posts a reply.

    Bookmark   November 22, 2009 at 11:09PM
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My torch pops and blows out as soon as i press the cutting lever. And the handle gets real hot real fast as soon as it happens. I haven't used a torch in over ten years and can't remember all the adjustments.

    Bookmark   March 5, 2011 at 9:08AM
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"I never understood how mixed fuel gas and O2 both got into the same hose. I recall hearing accounts of explosions destroying regulators, but again no personal experience."

You do not need O2 in the acetylene hose ot hae a problem if the regulator output is set to high.
Acetylene can break down all by itself at high enough pressure.
That is why it is dissolved in the cylinder.

Ever noticed the red zone on the acetylene regulator output gauge?

That is the danger zone where free acetylene can break down with no oxidizer.

There will be oxygen in the lines when you first start up, and it is also possible to force oxygen into the line by accident.

    Bookmark   March 30, 2011 at 2:48PM
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