Posted by Valerie on October 14, 1997 at 12:50:39:

In Reply to: Re: Oxyacetylene Set-up posted by Mike Devour on October 11, 1997 at 13:01:26:

Hi Mike!

Yep, I said:

: : Extinguish the flame by turning off the acetylene torch valve first. Then turn off the oxygen torch valve...If the reverse order is used, carbon deposits are left in the torch every time the torch is turned off.

Yes, there are some sources that say the opposite. The feeling on the other side of the fence is that if actylene is turned off first, soot can be popped back into torch.

When the fuel is turned off first, it effectively extinquishes the flame. Also, the oxygen blows through the torch last. If the acetylene is turned off first, it leaves a trail of soot, which we don't want!

As far as the soot popping back into the torch when you do the oppostite: Experimentation will prove this out. Put on a whole new torch and tip. Turn it on, light and turn off by doing the acetylene first. Do it several times and then take apart the fittings and check for soot. (None) Now do it again but turn off the oxygen first. Take apart and look for soot. (it's there). "Nuff said.

Here is another one of the reasons that you will find the difference in textbooks -

If your torch is malfunctioning and you get a flashback - the flame travels up inside the torch. There is a high pitched whistle and the torch body starts getting hot. In an extreme case, the torch becomes so hot that now the brass torch body becomes the fuel. If we were to turn off the acetylene first, we would still have the components necessary for a fire: air, fuel and kindling (combustion) temperature. We need to take one thing away to stop the fire. So in this case, the oxygen should be turned off first. Then the acetylene is turned off and then the acetylene cylinder valve and the oxygen cylinder valve.

So, in a situation that you are not used to, are you going to think about all that??!! It takes an iota of time to shut both torch valves off and proceed to the cylinders. In most cases, we would hope that your equipment is working fine - so turn off the acetylene first and if there is a problem, shut the thing down and check it over before continuing.

: I'd be happy to kill the acetylene first, as it will cut down on the floating soot that's created after I shut off the oxygen and before I can close the fuel valve.

And that proves that soot is deposited every time it is shut down. Everything else in Victor's book, we all agree on here. But fuel first is taught pretty much everywhere and it seems darned logical to me.

: Which raises another question: another book also tells me to "crack" the oxygen valve, open the fuel valve a little more, and light it like that.

When people shut down the system improperly, there can be a mixture of oxygen and acetylene in the hoses. This happens is both torch valves are open and they are bled down at the same time ... or if one valve is left open while bleeding the other.

It is advised to open the oxygen valve, purge some oxygen through it and then close it before opening and lighting the acetylene. A good idea, but it can be combined in another step - if you always do it this way: screw in the adjusting screw on regulator to desired pressure. Then open up the torch valve and adjust for the actual working pressure with the adjsuting screw on regulator - and looking at the gauge. Then close the torch valve. See, in one step we can both check for the actual pressure you will get when working AND also insure that you bled the system. Nifty, huh? Do the same for the acetylene. Adjust, open torch valve, check pressure at regulator and then close. Now you are ready to light it.

Open acetylene a bit, light and then adjust for a not-smoky flame. Then open oxygen slowly until the outer envelope or blueish flame just disappears into the inner "cone". Any more than that and it becomes oxidizing and will burn the metal.

If this flame is too hot, you can turn down the acetylene at the torch and then still adjust for a neutral flame (described above). There is a range which each tip can work within. Most of us go with the sound of the torch to help indicate the amount of heat (BTU) even though the temperature is the same.

You'll find if the oxygen torch valve is left a bit open when trying to light the acetylene, you get a loud pop when the flame finally ignites. It is best not to have the oxygen on when starting up the flame - it frequently just blows the flame out!

Thanks for the question - ask again if you have more! I have a troubleshooting chart I may post up here soon too.

Happy pyrotechnia!

Follow Ups:

• Re: Oxyacetylene Set-up Gene Olson 10/15/97 (1)
  • Re: Oxyacetylene Set-up Valerie 10/15/97 (0)

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