Oxy/acet torch questions

I have just picked up a med duty Victor torch/cutting set and I had some
questions...
My kit doesn't come with backflow/arresters and I'm wondering if I should
worry about using the torch without them? I'm using the smallest sized O2
and acet bottles my supplier carries so I don't know if that makes a
difference from a pressure standpoint?
The manual that comes with the kit suggests using the arresters but I wanted
to ask from a 'first hand experience' perspective as to whether or not I
truly need them? I don't want to have a fire or blow myself up but I've
been using portable 1lb MAP torches for years and never had a backfire,
problem, etc...
Is there any other advice you could offer a noobie like myself? My first
two projects are going to be fixing the exhaust on an old project car and
building a welding cart. Should I use coat hanger to weld the exhaust with?
I've heard this works very well.
Can I weld the exhaust with the MAP torch or is it not hot enough? I'm
itching to get this torch fired up but I have visions of causing a problem
without the arresters in place...
Thanks for any and all advice.
Andrew.
Reply to
AWN
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Backflow preventors would be on my list but it wouldn't stop me from working.
Reply to
Tom Gardner
It is not really necessary. But from a security standpoint, it is a really good idea and an investment worth having. Doesn't cost that much. Less than a house or two. :-)
No difference that has an influence on the work.
Nick
Reply to
Nick Mueller
I'm no O/A expert, but a couple thoughts on the arresters:
- O/A built the entire modern world, and all before the arresters were invented.
- The US is lawsuit crazy and if arresters were truly essential, the product liability insurance carriers for Victor, etc. would insist that such arresters were included as standard equipment rather like the crappy anti kickback chains included with even professional grade chain saws (they get thrown out by the pros).
- If you want the extra security of arresters, get the combo quick connect / arresters so you get some actual utility for your investment.
Reply to
Pete C.
Acetylene isn't the most stable stuff in the world, it has been known to go "BOOM!!" with little provocation and that will ruin your day... Google "acetylene deflagration" - but only while wearing your Peril Resistant Sunglasses.
Flame propagation in Oxy/Acetylene is 5000 FPS - a lot more vigorous than MAPP, damn near explosive.
Even with a serious case of "New Toy Jitters" I would wait to fire it up until you have a set of arrestors. They aren't that expensive and are widely available at any decent welding supply store.
(The only reason they don't come with the torch is price - the competition that doesn't include the check valves can sell for less. Some people don't stop to realize that initial price alone isn't the sole criteria for buying durable tools.)
I put a set of Western Enterprises hose QDs on both the torch and regulator
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have arrestors built in - that gives you two check valves between the torch and bottle, and more if you couple multiple lengths of hose.
You *can* use coat hanger wire or other "Mystery Metal" as filler - but you really shouldn't. When you are starting out you don't know if it's a materials problem or a technique problem, so using known materials eliminates one of the variables.
Another thing you should have before you start welding on anything is a large dry-chem fire extinguisher, at the very least a 5-pounder. A 5-pound CO2 as the alternate choice is nice, much less clean-up. And a charged garden hose with a trigger nozzle (or the knockoff Fireman's Fog Nozzle) as the last resort, in case something wood or fabric gets going.
Things WILL catch on fire whenever you start waving a torch around, you need to be ready to put them out. Without running around looking for the stupid thing.
And cars have large quantities of gasoline, which makes having the Dry Chem or CO2 extinguisher readily at hand mandatory, something that works on flammable liquids when water will not.
MAPP, Propane or Air-Acetylene can be plenty hot for brazing, but usually are not hot enough for real welding.
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Reply to
Bruce L. Bergman
I took the liberty of copying and posting your message in sci.engr.joining.welding
Cruise over there and see the posts.
Steve
Reply to
SteveB
It's just a peace of mind thing. We all do lots of jobs with no/minimal/incorrect PPE. (Personal Protective Equipment) This is not in the same category, but the point is similar. You're trying to prevent for the worst situation. I have had slag fly from where I was welding and set things afire. If the hoses were near them, they would have ignited, too. But, with the positive pressure, they would have just spewed. It's when you have a blowback, and the gas INSIDE the lines gets on fire that you're in trouble.
I don't know any statistics on injuries or fatalities without the arrestors. I have never heard of any, and I've been welding since 1974.
I bought a torch set recently, too, and I'll go spend the $$$ to get a set, but that's just the way I am. I have a tendency to have regular worst case scenarios.
I suggest that you Ping Ernie in the sci.engr.joining.welding group and ask him. He knows more about welding than the sum of the entire population who knows anything about welding.
You can take what he says as gospel.
And the sci.engr.joining.welding is one great newsgroup.
Steve
Reply to
SteveB
Thanks Steve! As to your post on worst case scenarios... I ran into my basement shop today to grab something quickly before dinner guests arrived.... And... I knocked over a cast iron table saw wing right onto my bare foot against concrete. Needless to say, after the smashed metatarsal and 5 hour hospital visit, I have my crutches to remind me of my stupidity for the next 6 weeks or so...
The lesson... Boots in the workshop (ever slippers would have been better than bare feet). Second lesson... Leaning CIRCA 1960 table saw wings against a shop wall rather than installed on the saw or stored properly IS a recipe for eventual disaster.
Thanks again, Andrew.
Reply to
AWN
The purpose of the backflow preventer is to prevent oxygen being forced into the fuel cylinder (at times when the fuel cylinder pressure is below cutting oxygen pressure) and vice versa. It's likely to be a bad thing if this happens, especially if you're using acetylene. In my opinion, safe working practices, adhered to scrupulously, are nearly good enough to get by without bothering with backflow preventers on your torch.
I see flash arrestors as more of a personal choice, I don't feel that I need them nearly so bad as the backflow preventors but I sure ain't gonna ridicule anyone over them.
You can weld with coathanger wire, no problem there as long as you're not expecting too much. Pretty unpredictable alloy but adequate for an exhaust job that nobody is going to look at.
I don't know about welding with mapp, it's not advised to weld with propane (because it's not possible to control the amount of oxygen and carbon available to the puddle). I suspect mapp to be the same but nobody says you can't try and see what happens, especially with an exhaust system.
As others have advised, careful with the torch, Eugene, 'specially under the car. Setting your stuff on fire in the driveway is sure to make the authorities soggy and hard to light..
John
Reply to
JohnM
The use of arresters was considered good practice over 25 years ago in the UK. It's nothing to do with product liability, it's just plain common sense.
Reply to
Mike
I appreciate the response - thank you. I have a concern though... I went to see my local welding supply house (PraxAir) today. They suggested to me that I should only use ONE set of flashback arresters or backflow preventers. He said that if I were to put a set at both the reg and the torch, I would lessen the pressure to the extent that I could cause a problem. I didn't understand why slightly tweaking the positive pressure at the reg wouldn't solve this but that's why I went to see the pros for an opinion. He did, however, say that O/A welding without preventative measures such as arresters or backflow prevention was risky and may or may not be a problem. He mentioned that some guys like them at the torch and some at the reg. He then went on to say that all Victor torches are now built with them at the torch (he figures they must know what they're doing or they'd be leaving them off the torch and advising them at the reg).
I just plain don't want to fall down and go boom!
Thanks again, Andrew.
Reply to
AWN
...very valid points... Thanks!
Reply to
AWN
According to my local shop, all Victor torches or reputable quality have the arresters built into the torch now. I haven't necessarily found this to be my experience but I digress... The advice on the QC function is good sound advice... Thanks again! Andrew.
Reply to
AWN
If anyone is interested, I gleened a little education from this link:
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Thanks. Andrew.
Reply to
AWN
It has everything to do with product liability in the US.
Reply to
Pete C.
"AWN" wrote
If it went BOOM, I doubt you'd hear or feel much. That video of the exploding bottles at that gas supply yard in Dallas a few weeks back was just unbelievable. I think it did make believers out of some who said, "What's the worst that could happen?"
Some of those tanks went a quarter mile.
Steve
Reply to
SteveB
Nice site, Andrew.
To me, it's just a personal thing that can be debated all day long with no conclusions.
I see guys all the time welding professionally for rather large companies. In T shirts, cotton gloves, no ear protection, frazzled jeans, all sorts of things that are a recipe for a bad day.
To each his own.
If you're going to do this stuff, it's nice to have all your fingers and toes and be able to hear and see. If you lose one of those, they usually send you home.
Steve
Reply to
SteveB
They really don't take much "cracking pressure" to open, so multiple checks is not a big problem. I have them at both ends of my 25' hose, sand if I get a 50' I'll get another set for that. Makes it nice when the torch can live in the nice protective "Welding" toolbox, and not have to stay connected to the hose and regs to get beat up, or require a wrench every time.
To avoid BOOM-ness, follow the rules in the book.
First: No copper tubing or components AT ALL in the Acetylene circuit, or any brass that isn't designed for the use and is below the copper percentage that is trouble. Copper Acetylide salts will form, and they are explosive and shock sensitive. (Not a good combination.
And when they say "USE NO OIL" on the Oxygen gauge, they are not kidding. You don't get any oil, grease, thread sealants or any other possible contaminants anywhere near pressurized Oxygen unless they are designed for the purpose. Spontaneous rapid oxidization - fire.
Store the bottles in the shade and keep them secured upright. If they have safety caps (large rental bottles) keep the caps on whenever transporting and when not in use for long periods.
Never transport gas bottles casually in a car or van - you really should use an open truck bed, but not everyone owns a truck... The bottles have to be secured upright, and kept in a well ventilated area - cool and out of the direct sun. If your truck has a shell on the back, leave the door and all the windows open. Go straight home from the welding supply and get the bottles out of the trunk and properly stowed in the shop.
If you must transport them in the trunk of a car, the trunk lid should be wedged open with a cardboard box and a strap to provide lots of ventilation, and the bottle(s) secured upright to a milk crate or the trunk hinge bracket.
You might have to build a 'bottle holder box' with a big 2'x2' slab of plywood on the base, so the bottles drop in the box and are held upright. Then you lasso the top of the bottle and secure to three or four points with motorcycle straps - the trunk hinge points on both sides and the lid latch striker works.
And don't try playing the Anvil Chorus using a big hammer or wrench on the top of the Acetylene bottle as the anvil. And always have the bottles secured to the wall, or secured in the cart, or in a crate so they can't just fall over. It takes a lot of banging and dropping to set off a deflagration, but you don't take unnecessary chances either. Be deliberately gentle when handling them.
That's the biggies - I have to get up early.
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Reply to
Bruce L. Bergman
That was a few months ago actually. I drove past there a week or so after and the remains were quite impressive.
Reply to
Pete C.
Thank you for correcting me and making me feel right at home. My wife does that a lot, too.
Steve ;-)
Reply to
SteveB

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