popping oxy/acetylene

hello im new on here is this the right way to start a new post?? i have used my oxy/ace on and off for years, with no real problems, welding steel and heating work with the torch sometimes to bend sections. some of my stuff got stolen a while ago and now i have a new set, the same, but now i have problems... whenever it gets to welding heat the handset pops, spraying me with molten metal.

i have tried tightening it all, cleaning it all, having handset checked at supplier, altering pressures, distance from work, everything i can think of and im getting so frustrated. the problem is that i was never taught correct pressures to use, i must have been spot on by chance for years, and now i dont know what to set the guages at. i have looked online, and i cant find any numbers that correspond to the numbers on my guages, OR any settings chart that are the same as the next one..... : ( its all psi numbers and i cant find any conversions that make sense. i am wondering why it seems so difficult to get right, when it went without hitch before. the guy at the welding supplies just told me its the pressure, to keep fiddling with that, and that ox/ace is difficult to get right, but even he did not have correct pressures to tell me, its mad!! i will probably have to take a short course to get it straight in my head. but i need to use it this week again and it makes me very tense waiting to be splattered with hot blobs... :) !

Rich Waugh's picture

That popping is your torch

That popping is your torch backfiring inside the tip due to getting too from reflected heat off the work piece. It can also happen if you pull the torch tip too far away form the weld puddle so that the flame entrains additional oxygen form the surrounding air.

To properly set the pressure for your torch do this: Set the oxygen regulator to about 15-20 psig. Keep the oxygen valve on the torch closed for now.

With the acetylene regulator set to about 3 or 4 psig, open the acetylene valve and light the torch. You should get a bright yellow flame with perhaps some black soot at the tip. Open the torch valve until the flame is free of any soot but is not jumping away from the tip. If you need to turn up the regulator a bit, that's fine.

Once you have a steady roaring yellow flame, slowly open the oxygen valve until the flame forms a perfect little light blue cone and the sound is a hiss, not a roar. The outer, darker blue cone should be well-defined with just a slight tinge of yellow at the tip. You now have a neutral welding flame that is set properly for that tip.

If you use the same tip regularly, it is best to learn to set the flame with the regulators while the torch valves are wide open. Once you determine the proper pressures to set the two regulators at, you can set them there, open the torch valves and light the torch, then fine tune the flame.

In no case do you want to set the acetylene pressure higher than 14 psig.

When welding, the tip of the inner light blue cone should be just touching the molten weld puddle.

johndach's picture

acyt torch popping

Rich is right on. Also, be sure the "o rings" on the end of the torchhead that you screw into the valve handle are in good shape. A leaky "o" ring here can cause all sorts of backfiring problems. I ALWAYS have a number of these tiny "O" rings in the shop and change them whenever I see any fraying, cracks or "they just look oldish". Cheap insurance too!! Get them from your welding supplier as they are odd sizes not regularly available in hardware stores, at least in the stores around here....

John Dach
web site: http://www.MLCE.net

warren's picture


The two things that I find causes the molten splash are tip size and a clean tip. If you are using too large of a tip it is a tendency to turn it down too much to control your puddle and then what happens is you put the tip to close to the work, or which I call sticking the tip in the puddle. Also the same thing will also happen if your tip is not clean and you turn the torch up higher to gain a good puddle.

www Metalrecipes -- heat and beat to the desired shape, repeat as necessary.

tempest's picture

thankyou guys! yes i think i

thankyou guys! yes i think i am too near and the nozzle is getting too hot - i will attempt to get a bit further away on monday and see if it helps. thanks for your replies - i have been using the torch to heat up some 25 mm round section which i cannot get into the forge with, and it has been lovely and quiet but as soon as i start to use it to weld, i have ben getting the popping, but i guess i am getting it much hotter and am going closer. also thinking about it i reckon like someone said, the nozzle was slightly too large, adding to the problem. the other thing is the pressure settings i can find online and like you said (top comment - rich?) do not seem to correspond to my guages :( - and they are new ones, my ox goes 0 then 5 then 10... and my ace goes 0.5, 1.0, 1.5, 2.0 and 2.5... but all the charts i look at say between 40 and 60 psi for ox and about 10 ( and no more than 14 ) for acetylene.. i struggle with numbers anyway and for this reason have been very confused.! i think mine is bar numbers but i cannot find a conversion that makes sense.. im sure im being silly but it has frustrated me for a while now which is why im asking you lot!..... :)

Rich Waugh's picture

Those regulator gauge

Those regulator gauge numbers cannot be bars - if they were, your acetylene would start at a dangerous pressure and go up beyond the spontaneous explosion point. So something isn't kosher there.

Your gauges may be reading in metric designation. Those numbers match the metric readings on my dual-scale gauges; 0.0 to 2.5 (0-35 psi)on the acetylene and 0.0-7.0 (0-100psi) on the oxygen, so you want to start with the acetylene at about 0.3 - 0.7 (4-10psi) and the oxygen at between 0.7 and 2.0 (10-30psi).

Smaller tips will require lower pressures and the larger tips will require pressures nearer to the top of the range I gave you. You shouldn't need to exceed 2.0 on your oxygen unless you are using a cutting head or a huge rosebud. Correspondingly, the smallest 00 or 000 welding tip may only want 0.25 acetylene and 0.5 oxygen to achieve a nice neutral flame with the torch valves wide open.

Never exceed 1.1 (14psi) on your acetylene pressure or you risk a spontaneous explosion in the torch or hose.

tempest's picture

rich thankyou SO much - THAT

rich thankyou SO much - THAT is the information i have been looking for and seem to be unable to find - that conversion, has put my mind at rest!  i know all about lighting up procedure cleaning general use, but NOT the correct pressure, like i said i think i had something set up for years without really noticing, not changing the nozzles much, just working with 2 or 3 mm sheet, but since changing the equipment and the use, i have noticed my lack of knowledge about the pressures.! thankyou very much:) i dont often use the gas torch for welding, usually the mig is more convenient, but occasionally it is perfect for a tiny neat weld, and for awkward access. and of course for the odd heating application that is impossible in the forge. Thanks once again!

Rich Waugh's picture

You're quite welcome Beth,

You're quite welcome Beth, I'm glad I could help.

And, Welcome to ArtMetal!

tempest's picture

thanks rich for the welcome

thanks rich for the welcome - these kind of forums are a great support when you are working on your own! 

pakmenu's picture

convert psi to bar

Looks like they are bar's readings after all, the gauge goes to about twice what you would safely allow it to reach. Anyway here's a good free converter:
PS: at first i thought MPa (MegaPascal) it's commonly used for pressure gauges, 1bar=0.1MPa / 1MPa = 10bar, but using the converter i found 35psi converts to indeed about 2.5 bar, and 100psi to about 7 bar.

Rich Waugh's picture

You are in deed correct -

You are indeed correct - those numbers are bars. One bar being atmospheric pressure at sea level at normal temperature, which is roughly 14.7 psig. I mis-read the poster's numbers and said they couldn't be bars, which was wrong. To compound my error, I stated they were possibly metric, when I know full well that the modern metric nomenclature is in megaPascals (MPa's), though I'm more used to dealing with the older metric designation of gram force per square centimeter (gm-f/cm²) on the oil pressure gauge of my Chinese tractor.

Thanks for pointing that out.

tempest's picture

thanks you two - it is

thanks you two - it is frustrating that my guages seem different from everyone else i talk to and every reference i read! like i said, numbers and conversions not my strongest point, but im aware that it should be correct for safety. thanks for the conversion link, i will try to work it out again! :) 

tempest's picture

does everyone agree that

does everyone agree that this means 0.9 bar is my safe limit for acetylene?! i now have two readings one for actual guage pressure and one for differential pressures something or other. i am at a loss as to why i cant find a chart with the correct welding temps written down : ( thanks for your patience - just want to be sure i have this right.....

Rich Waugh's picture

You are correct - 0.9 bar

You are correct - 0.9 bar (13.2 psig) would be the maximum safe pressure for your acetylene. Though you probably won't often use it anywhere near that high unless you're running a sizable rosebud heating tip.

Keep in mind too, that if you are using a big rosebud, you may need an acetylene cylinder larger than the medium-sized 140 cu/ft cylinder that is commonly used with oxy/acetylene torch sets. When you draw acetylene off a cylinder too fast for the size of the cylinder, you risk inadvertently drawing off some of the acetone that the acetyyene is dissolved in inside the cylinder. This can damage regulator seals and diaphragms and hose linings.

tempest's picture

thankyou rich - i dont have

thankyou rich - i dont have a rosebud, and have always used a larger welding nozzle to heat sections i want to bend ( which is not That often) do you think this is bad practise for any other reason? im not drawing any more off than i would be if i was welding though ( presuming i have had the correct pressure!) 

warren's picture

You are fine

The speculation of drawing off the acetylene too fast you would have to really have a very large rosebud and doing it for a very long time.

Just for what it is worth too on the molten splatters, these probably will always occur once in a while it is just part of gas welding.  I have been gas welding for over 40 years and I still get the blasts every now and then. Wear the proper clothes (all cotton everything) a leather apron. and I like a darkened face shield.



www Metalrecipes -- heat and beat to the desired shape, repeat as necessary. warren

Rich Waugh's picture

You'll be fine with that,

You'll be fine with that, Beth. It does take a large rosebud to draw more than a 140 cu/ft cylinder can supply, though I've done it and it doesn't take too long with a big one - I've had it start pulling acetylene in two or three minutes with a big rosebud. No problem, I just manifolded another acetylene cylinder to the first and all was well.

Since then though, I've switched to using oxy/propane for heating and cutting and only use acetylene for welding. No problem on pulling too much propane, as if I do it merely freezes the valve and slows the flow. Propane uses a bit more oxygen but the savings is big anyway compared tot he cost of acetylene these days. You just can't weld worth a darn with propane so I still have acetylene for that.

Warren is quite right about popping occurring from time to time when gas welding. Happens to me, too. It is only when itis happening too much that it becomes a problem as it cruds up the tip and spatters hot metal around. Which is why Warren mentioned the proper safety gear.

tempest's picture

yes - i am used to a small

yes - i am used to a small "normal" amount of popping for years, but this was every time i got to welding heat, and then every couple of minutes, REALLy unrelaxing, plus damaging and sooty for all the kit? i always wear goggles, but had taken to full face because of the constant spatters! thanks for all your replies. i ought to consider propane mix for heating, acetylene is very expensive.....