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02-26-2007, 04:35 AM #1
A guy I work with turns of the torch one way, I do it the other. Wondering who is right...
I like to follow the manufacturer's (victor) directions and turn off the oxygen and then the fuel gas. He likes to do it the other way. I think harris reccommends doing it gas first and then oxygen. Like my coworker says.
His argument is that his way is what he learned in welding school, and that they said it somehow keeps down soot buildup inside the torch.
My argument is that it causes flashback into the torch when you cut of the fuel gas first. IMHO any flashback is bad and should be avoided. It also seems easy for amatuers to leave the oxygen on because there is no longer a flame with the gas cut off. When the oxygen is cut off first, it is still obvious to the students that I work with that they still need to cut off the fuel gas.
Anyone know if there are AGA or OSHA rules/reccomendations on proper practice, and where I might find a copy of them? I wouldn't care too much, except that we are in the business of teaching a bunch of unruly art students how to weld, and I would like that they be given the most sound information available as to proper and safe work practices.
02-26-2007, 05:14 AM #2
Yeah, I was taught to cut the fuel off first. Plus it makes that cool "pop" sound! I don't think it matters too much, which is why I never say anything when I see someone cut the oxygen off first.
Consulting my Oxy-Acetylene Handbook (Linde/Union Carbide, 2nd edition 1960) states to cut off the acetylene first, then the oxygen. It doesn't go into detail as to why however.
I also like to cut the acetylene first to minimize soot. I usually don't deal with other fuel gasses, so I don't know if it differs with the other fuels.
Edit: I read a lot of conflicting information regarding oxy-acetylene torch use and operation. Some of which is said with authority using terms like never. For example, one site stated that you should never crack open the valve prior to attaching a regulator. I was taught to crack the valve first to blow out any dust or foreign material prior to attaching the regulator. I read the same in my oxy-acetylene handbook(crack to blow out dust). Who do you believe? I don't know if you'll find a "right" answer. Most of the stuff I've read that is conflicting might belong to the category of trivial side information. The info seems to be consistent on the important stuff (like never oiling regulators) but the little details seem to sometimes conflict. So I'm going out on a limb and say that you are both "right".
Just make sure the damn thing isn't lit when you put it away, and turn the cylinder valves off when you are done. Believe me from experience, I did some really stupid things as a child with my father's oxy-acetylene rig. No flashback arrestors, no check valves, and no formal education on the potential dangers, and yet I managed not to blow myself to pieces. I do consider that I was lucky. But I feel that some of these procedural items are unimportant. And yes, I am aware that some of these rules were written in blood, so I do treat oxy-acetylene operations with the respect that they deserve. If you are following the torch manufacturer's directions, you are ahead of the game(assuming the directions aren't some mangled english to chinese and back to english translation, or Engrish ). If the other guy is following what was taught, he is in the clear as well(assuming he was taught by a competent authority). If you want to settle a bet, you might be out of luck.
To answer your other question regarding OSHA, here is some more info. It doesn't address the specific question you asked(that I could tell). It is, however, good reading. Also, I believe that ANSI Z49.1-1967 is appliciable, but I don't know if you can get the standard without paying for it. I believe that the American Welding Society (AWS) also has the same standard as ANSI down to using the same title (AWS Z49.1-1967), but that may have changed, with AWS using a different coding scheme.
I liked what this guy had to say, especially the part about the fourth option on not setting fires or blowing things up by NOT WELDING OR CUTTING, and the last part about "No One Individual Can Reasonably be Expected to Know Everything About Everything...(contrary to what some people would have you believe)"
And don't forget, there's the right way, the wrong way, and the Army way.
And speaking of Engrish, inflammable and flammable are the same, despite the different spelling.
up way too late, and too bored to boot. let's see what others have to say...
[ 02-26-2007, 01:33 PM: Message edited by: Keith Krome ]
02-26-2007, 05:33 AM #3
I was taught fuel gas first, and the reason given being the oxy ''blew out '' what was left of the fuel gas, hence the pop.
I've witnessed it done the other way round and due to a dodgy valve the fuel gas has taken a long time to extinguish, sometimes burning it's way back down the torch looking for more as it were............. I've also picked up torches that others have just finished using and opening the fuel valve found the damn thing already alight!
02-26-2007, 11:09 AM #4
I was taught fuel gas first also. More importantly I think is position - always standing to the side of the regulator. I worked with someone who broke some bones in his hand when the regulator blew apart and into his hand when he opened the bottle.
02-26-2007, 02:10 PM #5
I dont think it really matters. Either way the combustion is external of the tip. It just how many of those little black curlys do you want floating in the air? [img]smile.gif[/img]
Plus they make a gas saver torch hanger that shuts off your torch when you hang you torch on it. It two valves in it and goes inline. The weight from the torch closes the valves. Then when you lift if off you can relight it at the same position as where you left off. They are turning them both off at the same time so I dont think it matters.
02-26-2007, 03:56 PM #6
well sami we agree on this one and that was the same reasion i was given to trun off the gas first. because it can brun back in the tip and i have seen it happen too.
02-26-2007, 05:13 PM #7
bob308 WOW! is there hope for the free world
02-26-2007, 10:51 PM #8
I had that happen once, that I put down a torch, pciked it back up to relight, and it lit itself. That to me says that the torch needs fixing, not so much that it is bad practice... I would never use a torch with dodgy valves, which is why I am the guy who maintains them.
regardless, thanks for the input. If anyone else has more to add, and/or references to official regulatory agencies or technical groups like the AWS, they would be greatly appreciated.
03-04-2007, 10:17 PM #9
Dad taught me to crack the tank valve prior to installing the reg to blow out the cobb webs and dirt. Too turn the gas off then the oxy.
He's late 60's I'm early 40's, we have never had a mishap. What ever you guys figure out to be the right or wrong way, I'm sure as hell not telling Dad he was wrong
03-04-2007, 10:44 PM #10
I too used to be paranoid about how to start and stop a gas axe. then of course I started working on CNC Oxyfule / Plasma machining centers. Every single one of them just shuts off the solenoids at the same time. Either at the manifold or the torch. I have also yet to see an operator turn the regulator screws all the way out when they shut one down as well.
I did notice once in China though that all the welders own theri own regulaotr screws at the plant I was at. When a welde is doen, they take the regulator screw with them to prevent unauthorized use of the equipment. Never thought of that before I saw it routinely done.
03-13-2007, 11:02 AM #11
When you are left-handed it doesn't really matter. The bloody valves are on the wrong side of the torch anyway.
03-13-2007, 07:08 PM #12
I thought everything in OZ was on the wrong side on principle. I mean, look at the way you drive...
03-19-2007, 02:06 PM #13
Gas off first.
03-19-2007, 02:32 PM #14
Shut the fuel gas off first, then the oxygen.
Back in the old days when acetylene was the most used fuel gas, there was a safety slogan about shutting down= "A BEFORE O OR UP YOU GO! [BOOM]"
03-19-2007, 03:40 PM #15
All the stuff people are saying seems to make sense. especially the fact that the flame might not extinguish properly if the fuel gas torch valve leaks a bit. the only thing I can't get my head around is why in their operator's manual the victor people specifically say to turn off the oxygen first.
from the victor manual:
1. First, close the oxygen valve. Then closethe fuel valve. If this proceedure is reversed, a "pop" may occur. The pop throws carbon and soot back into the torch and may, in time, partially clog the gas passages.
the mystery continues...
03-20-2007, 04:55 PM #16
OK now, for all of you experts, which valve do you turn on first to light the damned thing? I have a man who gets his knickers in a big knot when a co-worker turns just the acetylene on to light a cutting torch and spews all the black curlies into the air. According to him, and he's pretty good, you should crack the oxygen just a bit before you open the gas so's not to have all the black thingies.
03-20-2007, 05:12 PM #17
Acetylene first, so that you can get the flame length right, then add oxygen to suit. as someone mentioned in another thread, if you don't have enough acetylene, the tips gets hot and backfires more often. Acetylene should be turned up so that it almost jumps off the tip. If you don't diddle around for so long turning it up, you don't get a whole lot of the black curlies in the air, even with out the oxygen on.
03-21-2007, 01:32 AM #18
I was just in school and it was fuel gas first then oxy. When bleeding the lines turning the oxy off last blew out any residual fuel gas . In terms of lighting the torch the tip about just cracking the oxy valve is what the old guys at my shop taught me to do and it works, no more blow outs. Another lighting tip I was taught was to light the gas then lay the torch at an angle to a piece of scrap before cracking the oxy.
03-21-2007, 03:39 AM #19
I'm wondering if the fuel gas first "rule" was established back when industry used acetylene generators instead of bottled gas. I could see that if you have any problems with the oxygen valves, and cut the oxygen first, then the higher pressure oxygen could be sent back into the lower pressure acetylene, resulting in some trouble. This assumes that there are problems on the oxygen side. If you cut the fuel first, this immediately kills the flame, preventing any troubles.
03-21-2007, 01:29 PM #20
If they had no checkvalves and flashback arrestors then, I could see turning on the oxygen first as a possibly serious problem, and what you say makes a lot of sense. Even today, with no check valves/flashback arrestors, you can easily have a situation where the acetylene cylinder pressure is near or below the oxygen working pressure. especially if you have some bonehead who cranks the oxy regulator in too far.