How do I stop a new rosebud from backfiring?

Guys, I need some advice. I spent about $85 on a new rosebud for my gas torch, and after using it a while, it starts popping really badly and backburning. Of course, at the instant it pops and starts burning/whistling/etc., I shut the gas off and shut the tank valves. I'm running about 7 psi Acetylene and right around that in O2.

What's interesting is that even when I open the acetylene up far enough to burn clean (and its a huge flame), and start opening up the O2, if I do it too fast and bring the torch down to a neutral flame, it blows out. If I do it slowly, and leave a slightly carburizing flame, then it will work ok, but after using the torch for a while to heat up some metal plate, it starts popping like a M-16: "POP POP POP POP.." then it backfires.

Could it be that the reflected heat from what I'm heating up is warming up the end of the rosebud too much? Maybe my gas pressure is too low? Maybe I bought a rosebud that's defective?

I finally got tired of it and put my largest tip in the torch and used it to heat up the metal.... a lot slower, but sure seemed a lot more comfortable and safe..... when this thing starts popping, it scares the crap outa me.

Any help or advice would be most appreciated. r/ Steve Bremerton WA

Reply to
Stephen (Despammed)
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What keeps the flame outside any burner? Gas volosity through burner holes must be faster than flame valocity.

What size Acetelyne bottle are you using? Takes large bottle or bottle bank to supply rosebud. Is Acetelyne bottle pressure low?

Reply to
R. Duncan

Have you cleaned the tip after flashback? Any deposits will make flashback more likely to recur.

Excessive heat can cause it to occur, but more likely is too low a gas pressure. Rosebuds take a LOT of fuel, compared to, say, a cutting tip, and you need to check what the pressure range for YOUR TIP is--it varies with manufacturer, torch, and tip size. If you have long lines or small lines, the pressure drop along the line can cause a lot of trouble.

Do you have flashback arresters on the line?

If you generally cut with the torch rather than weld, the fuel pressure isn't the only issue. Heating tips want balanced fuel/gas mix, and you get the most control when you feed the gas in the proper pressure ratio: a little more than 3:1 Oxy to Acet. So, with 10PSI C2H2, you want about 30-35PSI O2. This is much more like a welding tip than a cuting tip.

Don't worry about the acet flame being clean before ading O2. Get a medium flame, then ad a little O2, open the fuel a little more, etc. For me, this is a two-handed process, takes about a second after I drop the striker, two seconds total. Too long soots up the tip and.... POP!


Reply to

Uulp.... no.... I didn't. I will now, though. Thanks for the advice!

I'll do that. Problem is that my torch was sold by Airgas and is no longer made, and its in like-new condition, so I didn't want to scrap it and get a Victor or a Harris setup... so I got a rosebud that fit the torch handle without really checking the flow requirements.

Yes, on the regulators.

I wondered if that might be the case - need a lot more O2 pressure to drive the gas into the torch to make the right ratio. I'll try it.

Yeah, when I open the acet, I could blacken the whole side of the house.... I don't use this thing inside the garage - I wouldn't be able to find anything! I'll clean it up and try it again, with more O2 pressure!

Guys, thanks a BUNCH for all the help!

Reply to
Stephen (Despammed)

Stephen, that cylinder is pretty small for a large rosebud. Be careful that you don't pull the acetylen out too quickly.

Reply to

That will depend on your burner. If you have a diffusion flame burner then the lack of oxidizer inside the burner keeps the flame outside. (ex welding,cutting & heating tips when only fuel is being supplied)

In a premixed burner (welding,cutting & heating tips with fuel and oxidizer supplied) the flame is kept outside the burner by both the gas velocity and the flame quenching at the tip. If the flame tries to burn back into the tip it is quenched because it looses heat to the tip and the flame goes out. If you get the tip hot enough to overcome the heat loss at the opening then the flame can go into the tip POP and extinguish.

A flashback arrestor is essentially a fine set of screens that will quench the flame in the event of a flashback. If you could get the arrestor really hot I bet it would not work.


Reply to

We used to use an Oxy/Acetylene rose bud to melt lead bars. It always would begin to popping after a period of time. We never could figure out whether we were drawing too much fuel from the tank's, or if the tip was overheating. We finally converted the rosebud to LPG/oxy and the problem was eliminated. (Suspected a large acetylene tank would have helped, but never tried)

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