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Rob Keller 01-16-2009 05:39 PM

OXY~ACETYLENE !!!!! Safety!!!!!!!!!!
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Rob Here! :thumbup:

Well its been some time since the subject has been brought up & its worth repeating over & over & over again.

Especially since someone ,I will call them Mr. or Ms. anonymous {}omitted a line in the WIKI article I started to write.

Now if you read this you will find information that is not found anywhere else {at least to my Google search}

OK so why Create a fuss?

I think that a person should have the opportunity to make the decision to use or not to use the information that was written.

The fact is the valves are designed to be FULL OPEN or FULL CLOSED.

The Fact is that if there was a back feed fire there is not going to be enuf time to turn off the valve .{period}

NO in between.

It is Cruel to deprive anyone the chance to learn important information ,because A anonymous person feels that its incorrect.

I am open to Constructive criticism .

so sign in & lets work this out.

Now I am off to Reset the Correct information

For what that is worth

Rob Keller :thumbup:

Kevin45 01-16-2009 05:59 PM

I use oxy+acetylene at work on a daily basis. I stress to the others, DO NOT open the valves to the full open position for the same reason. If you start to have a backfeed fire you cannot shut them off in time. Most torches should have a built in spark arrestor but most that have any age on them do not. We use a rosebud quite a bit. A few of the inexperienced ones (before you can catch them) will crank the valves on the tank all the way open, turn the valve on the torch head a little and strike it. When I hear is whistling, I know it is burning back into the torch. It will be so hot that you cannot touch it. So I try to stress, 1/4 turn on the valves and if it whistles, turn the acetylene off first. If a valve is all the way open on a tank it takes quite a few seconds each to close them. Too much time.

whinny 01-16-2009 06:15 PM

hi rob
used oxy/acetylene for years on a daily basis, and was taught from day 1 turn gas on around 1/2 turn but we also has flashback arresters fitted at the bottles where it went onto hoses.Never seen any damage but have heard anecdotally(is that a word) of the odd bottle taking off.
Dangerous lil critters them bottles, we seem to use a lot of propane here now compared to acetylene, higher heat they tell me, also good and quicker cutting!

MARTINSR 01-16-2009 06:25 PM

Metal shop, 1977 open the oxygin all the way and the acy a half turn, set the regulators at 25 and 5 lbs. I never forget, it is ingrained in my head.
I have been doing it this way for 33 years without a problem as far as the acy valve not being all the way open. I don't see a probem with that at all, so I don't understand the point of opening it all the way.

With all the going back and forth on the subject, please clarify for this dumb ars.


ChevyThunder 01-16-2009 06:27 PM

Worked in a few welding shops always heard the same as the other guys are saying.

I don't see your point of the valves are designed to operate all thee way open or all the way closed. This make no sense and I fail to see how partially opening them is unsafe in any way?

In any application where a valve is used that is varaible they KNOW they are not going to be used full open and full closed all the time, thats why they put valves there.

Rob Keller 01-16-2009 06:55 PM

See I started to post this last night when my Puter betrayed me.
I am not here to argue the subject. I have seen a faulty back fire Up from the torch to the regulator.

Trust me when I say;

You will not have any time to turn the valve off.

& the point I am making that no one really is paying attention to is the way the valves are designed.


Quote :OLD RED

Rob, Don't know what I was thinking as you are 100% right and I got way ahead of myself and made that much too brief, I left out the most important parts that is setting up the torch BEFORE lighting and of course SAFETY! Also you have pointed out something else I have preached about for years and that is to OPEN those valves! There seems to be a very common and mistaken (VERY mistaken!) belief that just "cracking" the acetylene tank is the safe thing to do because it is quicker to shut off in an emergency I have had some, sometimes strong, disagreements about this but opening those tank valves all the way is the proper thing to do in spite of what many believe and will argue to the contrary.

Please also read Post #13,14 & 15

You guys can argue this to death all I am saying is :


Rob :thumbup:

oldred 01-16-2009 07:35 PM

Rob is right about those valves, they are designed to positively seal only when fully closed or fully opened and can leak around the stem if only partially opened so open them all the way. It is not uncommon to find advice to open the gas valve only slightly even in "official" publications but you will not find any such recommendation from the manufacturers of the bottles! The advice to just open the gas enough to properly fuel the torch is a "knee jerk" reaction that seems to make sense in that in the event of a fire the tank could be shut off sooner which really makes little sense if you think about it, if the fire is at the tank you will not be able to shut it off anyway and if it is downstream then a couple of turns more at the valve probably would make little if any difference. The problem is that a partially open valve is likely to be the cause of the fire in the first place! If you look at how the valve is made is has a positive metal to metal seal ONLY when fully closed and fully OPEN, anything in between and the only seal you will have is the packing seal around the stem which is not designed to hold much pressure and they most certainly can leak! This happens more often than most people think and fortunately most of the time only a tiny leak will occur but when it is located at the Acetylene valve ANY leak is too much! This argument has gone on for years and because the partially open valve advice has appeared in "official" publications it is likely to continue but the fully open advice also appears in some welding safety manuals and, interestingly enough, from the tank manufacturers. I doubt if we will change anyone's mind because of the mistaken belief that those one or two turns of the valve will somehow make the situation safer but whichever way someone chooses to believe this is a FACT, that partially open valve may be a little faster to close but could very well be the reason for the need to do so!

To those who don't believe this, use soapy water around the valve when you "crack" it open (this advice is also recommended in official manuals) and I think you may be surprised to find out just how often those things leak! When you find one, and it will likely happen sooner than you think, open that valve all the way and a funny thing will happen -the leak will stop! :)

C-10 01-16-2009 08:15 PM

I have thought this through some. And I have also been instructed since high school metal shop, to open the Acetylene a half turn. (take the HS education with a grain of salt, a baseline, but not ideal.)

I will go out on a limb and say, if you are cutting a substantial chunk of steel and it somehow, someway falls and cuts or worse SEVERS both oxidizer and acetylene, first you will, A; crap your drawers, B; run to the tanks and shut them off. This should be the end of it. Even if BOTH tank valves are wide open.

There is enough pressure to keep the flame where it should be, where it meets the atmosphere, at the end of the hose. Isn't this what happens when we crack the valve at the torch to strike the acetylene?

So, back to the valves at the tank, where would you rather have a fire? At the end of a long hose... or at the partially open antiquated valve LESS than an inch from a very large BOOM.

I'll be opening my valves all the way from now on.
"Dollars are like votes, except that they actually count."

pepi 01-16-2009 09:28 PM

I agree full open on the valves, run the gas on the welder the same way.

Just picturing some guy running to shut the gas off is a road runner cartoon staring the Acme welder welding school grad...

question : how many feet to a 1/2 turn ?

can I stand twice as far from the shutoff valve if I open it 1/4 a turn?

bates_k 01-16-2009 11:55 PM

What I was taught 40 years ago, I still use today, 1/4 turn on the acetylene valve,
fully open on the oxygen valve.
It'll cut 1" plate. If you're using 1" plate to build a hotrod, it's gonna be a slow one...


MARTINSR 01-16-2009 11:57 PM

:D Ok, OK! LAY OFF WILL YOU. Just kidding :D

I'll open it up all the way next time.


oldred 01-17-2009 04:22 AM


Originally Posted by bates_k
What I was taught 40 years ago, I still use today, 1/4 turn on the acetylene valve,
fully open on the oxygen valve.
It'll cut 1" plate. If you're using 1" plate to build a hotrod, it's gonna be a slow one...


I too like so many others was taught (at least 40 years ago :) ) that 1/4 turn or so was the way to do it for safety reasons, Not long after I was attending a welding class and during the safety segment the instructor showed us the folly of doing this. They had a cut-away of a bottle valve and when looking at this it becomes quite clear why opening the valve only partially can cause a leak and possibly result in a fire. When only partially open the ONLY thing standing between the gas flowing out of the bottle and the outside atmosphere is that small seal around the valve stem while opening it all the way gives the same positive metal to metal seal as when closed, the way the manufacturer meant for it to be. Usually there is only a tiny leak and any fire that occurs would be small, at first anyway, but it very well could go unnoticed until the heat causes an even bigger leak. I can only remember seeing a couple of bottles that leaked bad enough to actually notice the gas escaping when the valve was opened but I have seen quite a few that were detected by using soapy water to check for leaks, opening the valve all the way always stops these leaks. We kept a squirt bottle of water and dish liquid in our welding carts and anytime a torch was set up inside the shop, bottle change etc, this was used to check for leaks around all the connections. This procedure is recommended by about every safety text I have seen however most people will not bother with doing it but if they did they would most likely be surprised by how often small leaks occur, both at the fittings and that valve if only partially opened. Fellows it can be argued that the extra time to close a fully opened valve MIGHT possibly make a difference but the chances of this are so slight that they are FAR outweighed by the possibility that a leak from a partially open valve could cause the fire in the first place.

techron 01-17-2009 04:59 AM

HOLY CRAP OLD RED, wow i bow down to your knoledge of welding, i was taught to crank the oxy bottle full open, and crank the accet bottlle about 1/2 turn open and make sure the pressures are correct on the gages. i have never blew myself up in 30 years of welding!!! am i missing something???... :D

oldred 01-17-2009 07:58 AM


Originally Posted by techron
I have never blew myself up in 30 years of welding!!! am i missing something???... :D

Yep, you missed a good fire! :D

No joke, most people simply crack the valve because that's the way they were taught but does that make it the right way? Like I said it's a "knee jerk" reaction because it just seems to be the right thing to do but how many of these people are thinking about how that valve is made, or even know for that matter? There is no other reason to not fully open the valve other than to be able to shut it off a second faster but is that really going to make a difference? It is certainly possible that it just might, maybe, if the circumstances are just right but in all practicality it is going to make little or no difference if the valve needs another second to shut off if a fire starts but a leaking valve could make a BIG difference! As I said if anyone is not convinced (most won,t be) just use that soapy water trick, you should be doing that anyway, and it will become apparent just how often those valves leak when only partially open. Try shutting the valve off from full open as fast as you can and ask yourself "is that tiny bit of extra time worth the risk of an unnoticed flame at the valve"? Also why do the manufacturers make the valves to shut off when fully open? There simply is no other way to seal the gas once the valve leaves it's seat except the stem seal and there is no sure way to seal the stem so they use a double taper/seat on the valve, one for the bottom to close the tank and one on top to seal the valve when opened. Why is this double valve arrangement there if it is not meant to be used? Certainly these types of fires are not common but they do happen even if most of the time they are nothing more than just a small flame burning around the valve stem but how safe is that? If you are still using Acetylene tanks now try that soapy water trick, besides that squirt bottle of soapy water makes a dandy little fire extinguisher for those annoying and inevitable little fires that seem to happen while using a torch. :)

ChevyThunder 01-17-2009 11:01 AM

I have seen what happens on a welding truck when buddys brass fittings on his reel cracked. Was leaking just about a neutral mix. Then he started grinding. We almost crapped our drawers when the reel exploded and the hose had a big melted chunk on it.

Good thing nobody else saw.

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