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.
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<snip> Backflow preventors would be on my list but it wouldn't stop me from working.
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They may stop you from DYING!!!! BGPlank

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On Tue, 30 Oct 2007 00:58:10 GMT, "Bert Plank"

On the other hand I started welding with oxy-acet in 1950 without back flow arrestors and haven't blown up yet. In fact I have never seen a "flow arrestor" they don't seem to use them over here.
Bruce-in-Bangkok (Note:displayed e-mail address is a spam trap)
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On Tue, 30 Oct 2007 19:05:52 +0700, Bruce in Bangkok
SNIP

Hey Bruce,
I don't doubt that you have never met anyone that has found the purpose for them from personal experience in the non-use of back-flow preventers.
Maybe folks from a few hundred feet away, but not the anti-proponent himself!
As an aside, during an exchanging of cylinders, I watched a full tank of oxygen "flywheel" horizontally out through a overhead garage door and across the parking lot. It got knocked over and the valve-neck cracked. The load "whistling noise" stopped after about 2 or 3 seconds, but the bottle spun for about a minute. So,when the "old hand" at the job says " Don't take off the cap until you've got it chained in the cart.", take his advice rather than arguing that it's a whole lot easier to lift the bottle by the valve that by the cap.
Take care.
Brian Lawson, Bothwell, Ontario.
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AWN wrote:

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
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...very valid points... Thanks!
On 10/8/07 10:48 AM, in article snipped-for-privacy@mid.individual.net, "Nick

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AWN wrote:

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.
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wrote:

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.
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If anyone is interested, I gleened a little education from this link:
http://www.weldingmag.com/323/Issue/Article/False/11305/Issue
Thanks. Andrew.
On 10/9/07 10:52 AM, in article - snipped-for-privacy@pipex.net,

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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
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Mike wrote:

It has everything to do with product liability in the US.
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wrote:

Presumably because in the US common sense went out of the window years ago? :)
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Mike wrote:

Not sure about that, but certainly we've let the lawyers hopelessly corrupt our "legal" system.
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wrote:

The product liability (and general blame) culture is happening here as well and to an ever increasing extent over the past 5-10 years but significantly from a base of near zero - it's viewed as a modern acquired syndrome from the USA.
Maybe it was due to a major piece of general health and safety legislation passed in the UK during 1974 but the use of arresters was commonplace here within responsible industrial and educational premises from the late 70's/early 80's - virtually everywhere with any semblance of a safety culture used them. The cowboys still don't use them - no prizes for guessing where almost every recent acetylene related incident occurs.
That's why your comments on the reason for their requirement in the USA puzzles me especially after their extremely long period of usage over here!
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I think there are still a lot of people around with common sense. I do think the percentages are lower than they were years ago, though. Today, we have the WALK/DON'TWALK signs, instructions to tell us NOT to take our toaster with us into the shower, and lots of warnings. I am disheartened when talking to people, though, and watching their actions. Particularly the young. It seems the thing today is to find out just how far ANYTHING will go before it crashes, burns up, or otherwise destructs. The entertainment is in getting something to go boom. And there are serious consequences sometimes.
It's just when they involve me that I become livid. I watch their stupidity and lack of common sense all the time in videos. Trouble is they usually take out other people.
Darwin's Law has an overpowering counterinfluence. Stupid people with no common sense are usually very fertile.
Steve
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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.

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On Mon, 08 Oct 2007 10:00:10 -0400, AWN

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 http://www.westernenterprises.com/enterprises/PDFS/wi25.pdf that 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.
--<< Bruce >>--
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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.

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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
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