I plan to take a class in gas welding, in the meantime I've been reading a couple of books on it and that's what created my question.
Some books say to turn off the oxygen first when shutting down your torch, others say to shut off the acetylene. Which one is correct or are there different answers for different types of torches. Thanks in advance for your help.
Tony Martinez
Acetylene first.
This promptly extinguishes the flame.
If you close the oxy first, you're left with a soot producing flame still burning.
Once you try it, you'll see why.
Tim
I think the sequence currently taught is to turn off the oxygen first. The theory behind this is if there is no oxygen you cannot have fire. If there were to be a flashback inside your torch and you turned off the acetylene first, it would continue to burn back because oxygen is still present. I know 50% of the people turn off the oxygen first and 50% turn off the acetylene first but this was how I was taught. Hopefully the flashback arrestors would take care of any problem like this though.
I have to agree with TimGary on this one. I was taught to shut off the acetylene first in an apprenticeship program over 30 years ago. In fact, I dug out my old Modern Welding manual (vintage 1970) to check on it. However, I also have a Victor cutting guide that came with a torch I purchased about 6 years ago. That guide says to shut off the oxygen first! So, I guess either way is right, or wrong, depending on who you talk to, or maybe how old you are. Welcome to the wonderful world of welding.
Turn off oxgen first then fuel untill its a small flame then turn oxgen on it will make a pop nosie then turn off. this asures its off and no burn back to bottles.
Tony,
Years and years ago I was taught to turn off the acetylene first, then the O2... I do like wfriii's suggestion of closing both by shutting down the acetylene, letting the fuel burn while purging itself from the hose, and extinguishing it with a little blast of O2 just before it burns itself out... it's unsafe to leave the acetylene in the hose anyway.
I think, as long as you're learning, it would be good to look into how these torches are built and become familiar with the nature of the hazards you are trying to avoid.
The stock, legal answer to your excellent question is "refer to manufacturer's instructions" There are, by the way, various specific arrangements used to mix the fuel with the oxygen within otherwise similar torches... so "yes" to your other question about "are there various kinds of torches" but I don't pretend to be expert in torch design and engineering or to be able to discuss how they relate to shut-down procedures.
Good luck & regards,
D
FWIW-proper shut down of oxy fuel equipment is important. The proper sequence can add years of life to your equipment, as well as safety.
Shut down the oxy first, and the gas second. The reasons for this are as follows-
1-this eliminates the "pop" that can send carbon back ( if acetylene is used ) into the torch. This carbon ( inside torch ) can be heated to a critical temp, causing flashback, preignition, or burning inside torch.
2-Using this procedure gives a check on the integrity of the torch valves, everytime used.
If the oxy is shut down first, and a "pop" is noticed upon shutting off the gas, then the oxy valve is leaking.
3-if the gas is shut off last, and there is still a small flame at the torch tip-you can be sure that the gas valve is leaking.
4-this is also the recommendation of Victor Equipment.
Hope this helps
Good Luck
brande
Turn off the oxygen first then the fual gas
Although I can understand why some like to shut off the gas first, I was taught the oxygen is supposed to be shut off first. In fact I think one can read that in the literature that comes with torches.
We were instructed that the small "pop" that can be heard by shutting off gas first is really a small flash-back that could severely damage the equipment over time. Flashback arrestors are supposed to prevent big problems but are not supposed to be used as the primary safety mechanism. Proper operation is the primary safety mechanism.
CHGuilford
my current welding instructor taught the class to turn the oxy off first, so that is how i do it. Its interesting to hear that some people turn the o2 off first, oh well im a newbie anyways, ill try it both ways tomorrow at school.
Robism,
For the sake of my reputation here I reference Oxy-Acetylene Handbook second edition published by Linde (Union Carbide) who I believe is now ESAB... I promise the procedure I described would be specified in this text... I cannot promise it's the "right" way.
Over the past 30 or more years my equipment seems to have survived the procedure. If I were production welding all day every day it might be a different story, I dunno, but it's clear the "pop" during shut-off should be avoided. If you dislike black sooty strings in your hair, clothing and all over the shop you'll quickly learn the technique to turn the acetylene lower in order to avoid the mess.
I believe the advice we will all agree with is not to shut off a full flame but to lower it first and purge the fuel line before stowing away the equipment.
Regards,
d
okay here goes this is straight from the oxy acetylene handbook 3rd edition, setup and operation of equipment chapter; Stopping Work"to extinguish the flame, first close the torch fuel gas valve, then the oxygen valve. Closing the fuel gas(acetylene) valve first reduces the chance of allowing unburned fuel gas to escape and be ignited accidently." So there it is, i guess now i know for sure, but what about" dont beleive everything u read"??? oh well.
Another 2 cents
My oxy-fuel equipment is Victor brand, so I will share data from the Victor (Welding, Cutting & Heating Guide)
"When you finish your welding operation
1. First, shutt off the torch oxygen valve. Then, shutt off the torch fuel valve. If this procedure is reversed, a "pop" may occur. The "pop" throws carbon soot back into the torch and may in time partially clog gas passages."
This step is backed by Victor's excellent supplimentary oxy-fuel training video. In fact this video will also tell you that to obtain the proper fuel gass flow in cutting and welding operations that the fuel flow rate should be increased until the black stuff dissipates (before introducing oxy). This is important. Most internal torch fires in Oxy- fuel operations are caused not by over heating the torch but by fuel gas starvation! Having the right tip for the torch and the correct fuel gass flow considerably reduces those squealing internal flashbacks.
So I guess the moral of this story is to... consult the manufactures operation/safety instructions for a particular piece of equipment. Textbooks are nice but cannot possibly cover operational procedures for every style of torch. Secondly make sure your directions are backed with sound reasoning and ask questions if it doesn't make sence.
Lawrence
Another two "sense",
Everyone seems to be whipping out literature from all sorts of places to back up their ideas, so let me quote from the "Welding Handbook Volume Two Seventh Edition"(newest one I have here). On page 484, under a paragraph titled, "Operating the torch", it states and I'm quoting....." A torch is extinguished by rapidly closing the torch valves in the sequence recommended by the manufacturer."
Good Advise?
Consult your torch mfg. for proper shut down.
John Wright
Tony,
Good Post, lots of info from various sources. Keep the good questions coming,
John Wright
Interesting.....by scrolling through the posting the unoffical score is 7 to 4 in favor of oxygen first.
kam
kam,
So are you saying that there are 7 Victor torches (oxy 1st shut downs) and 4 other possible brands (fuel 1st shut downs) being represented here :-)
John Wright
hehe.....are there brands other than Victor? A torch by any other name.... I did purchase a new Smith recently and really like it. Not going to retire my old victor quite yet. Heard they were making the new victors down Mexico way that is why I thought I would give Smith a look.
As far as shut down procedure for me I always back the fuel down alittle first then shut off the oxy then the fuel. Not really sure if that is the best way....but now you got me thinking. Maybe I will just break down and by a plasma cutter.....but.....should you shut down the electrical power to the unit or the air supply first???????
kam
I'll stick to my first recommendation...consult your mfg's operational recommendations.
(how was that for dancing around the question?:)
John Wright
funny on friday when in class i decided to turn the gas down a bit to about a 1/4" flame then turn the oxy up and it shut off pretty nice, no pop, i think thats how i will do it from now on.
Just to reinforce what Lawrence and others above have been saying above, I was recently talking to a torch repairman who told me that the newer Victor torches (with built-in flashback arrester) are frequently coming in for clean-out of carbon deposits in the arrester. He thought it was probably due to not following MFG's instructions for shut-down
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