Gas Cutting Problems

Rgillard · May 30, 2007

Hi Guys,

My Brother was out in the shop this evening cutting some checkerplate steel with the oxy acetelene setup. One problem he kept encountering was that when he initially lit the flame and went to adjust it there would be a bang and the flame would go out. It was only a brand new nossle tip so Im assuming that it wasnt dirt. Im sure some of you guys have encountered this problem. I came into the shed with him about to cut the torch up with the angle grinder it was frustrating him so much. Any help/tips would be most appreciated..

Rgds,
Ronan

deerhunterf350 · May 30, 2007

On the torch you have 2 adjustment knobs one for A (acetylene) one for O(Oxygen) , you want quite a bit of A , to the point that it is burning a deep orange flame with black soot floating in the air with very little O , when you first light the torch. Then you gradually adjust the O to a clean Blue Tip, hit the O handle for blowing and the adjust the O again to a clean / Sharp blue tipped flame.

If the O is turned on with not enough A , then you will get a LOUD SNAP/POP , it "BLOWS" itself out , Oxygen will not BURN by itself it needs Acetylene to BURN and the Oxygen adds "Oxygen" to the fire, making it burn hotter.

Hope this helps

Dan

john_bud · Jun 4, 2007

I have the same issue. Partly it's due to my never really mastering the O/A torch.

There are 3 knobs for the cutting torch.

Start off by closing all three.

Set the Acet regulator for 6-7 psi flowing.
Set the O2 regulator for 25-30 psi flowing.

Light the torch and increase the A flow until you have a big yellow flame. Turn the bottom O2 knob full on. Nothing should happen as you still have the top knob closed. Slowly open the top knob to adjust the flame to a sharp blue. When you hit the cutting lever, the full pressure 02 will go out the center hole. Should work perfect.

The trick is the bottom 02 knob is full open and the 02 flow for pre-heat is adjusted with the top knob.

Well, that's what I do any way. Am actually eagerly awaiting a real pro's input to learn if that's right or not!

jb

DieselPower · Jun 4, 2007

deerhunterf350 said:
On the torch you have 2 adjustment knobs one for A (acetylene) one for O(Oxygen) , you want quite a bit of A , to the point that it is burning a deep orange flame with black soot floating in the air with very little O , when you first light the torch. Then you gradually adjust the O to a clean Blue Tip, hit the O handle for blowing and the adjust the O again to a clean / Sharp blue tipped flame.

If the O is turned on with not enough A , then you will get a LOUD SNAP/POP , it "BLOWS" itself out , Oxygen will not BURN by itself it needs Acetylene to BURN and the Oxygen adds "Oxygen" to the fire, making it burn hotter.

Hope this helps

Dan

Actually you only need the acetylene to get started. Once you have a good cut started you can actually turn off the acetylene and continue to cut with oxygen only. It's a little trick I learned from a old ship builder from the Baltimore ship yards. It only works on rather thick steel as you don't generate enough heat in thin steel to keep the oxygen cutting. It's a interesting trick none the less.

Usually if you are getting a BANG you are turning the oxygen on to fast and overwhelming the acetylene. Turn the oxygen on slowly until you get a nice blue flame at the tip. If you have to much oxygen it blows out the flame.

Defective · Jun 5, 2007

Warning: The following is somewhat pedantic. (On the other hand...it works

)

Here goes...steps to light a cutting torch (based on my Harris combination kit):

1) check that everything at the torch end is closed
2) check that the regulators are unset (handles loose)
3) open the oxygen valve (tank valve) all the way
4) open the acetylene valve 1/4 turn
5) set the oxygen regulator to 40 (according to the chart for my cutting tip)
6) open the acetylene valve on the torch
7) set the acetylene regulator to 7 (again...according to chart)
8) close the acetylene valve on the torch
9) open the primary oxygen valve on the torch (the one near the hoses) one full turn
10) squeeze the cut lever for a few seconds to purge the line
11) open the acetylene valve just enough to get some flow
12) use the sparker to ignite this flow
13) slowly turn up the flow until it stops making soot
14) back it down just enough to close the gap between flame & the tip
15) slowly open the secondary oxygen valve until the flame looks good (about 1/4" of cone & no feather for my usual needs)
16) give the cut lever a squeeze & observe...the flame shouldn't change much

Seems like a complicated process...but it takes less than 10 seconds once you've done it a few thousand times.

john_bud · Jun 5, 2007

Hey, isn't that what I said? Only you did it in a much more clear and understandable way!!

AlanB · Jun 5, 2007

Sounds like you had oxygen flowing when trying to light, as DP said, that is what gives you the bang.

Another problem folks encounter is turning the acy up to too much flow when trying to light, it will be burning away from the end of the torch, and will extinguish itself, counterintuitive, but you actually need less acy to keep it going.

Assuming regulators are set right etc, things I do esp when grabbing someone else's torch.

crack open all valves, and gently reseat them, often, folks that do not use torches seem to think they need to get the valves "tight" to work, then when you try and open them gently, they will not open.

Insure that the bottom oxy valve is full open (assuming a combi torch set)

Just crack the acy valve slightly and light holding the spark lighter in your LEFT hand..... Yes, they are designed to work in your left hand to hold the flint against the steel (I realize that was not your problem, but it always amazes me when folks try and light them using their right hand and do not understand why it does not work well)

If it does not immediately light, try again, allowing some acy to cup in your striker if you have a cup type (never mind if you have an open striker

Slowly increase Acy until it lights.

Set your acy once lit to a steady burning flame, not standing off from the tip.

Slowly crack the oxy adding oxy, watching the flame pull in towards the tip.

Normally you want a neuteral flame, so slowly add oxy until your tips come in and you have a nueteral flame, ie, the feather goes away from the inner cones.

Insure that you have as many cones as you have holes in your tip and they are fairly even

Apply the oxy lever, and it should make the sound of a bedsheet ripping as you pull it in adding oxy.

Diesel, my dad always used to Pi$$ me off how he could reach down and cut his acy off and continue burning with just the oxy. He would pretty consistently do it on 3/16 and 1/4 and it always drove me nuts, I have never been steady enough to do it on anything that thin, then again he could scarf off 1/2" nuts and leave the bolt threads intact. He would always smile and talk about years in the junk yard.

Defective, I love the last line.

Defective · Jun 5, 2007

pretty much...

Maybe a change or two in sequence & an emphasis on checking the charts for specific numbers. Bit more detail of course...

What I didn't put in is the shut-down & repeat steps for when I realize I didn't unwind enough hose...annoying...