I have just picked up a med duty Victor torch/cutting set and I had some
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,
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.
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.
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
- 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.
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
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.
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
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
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.
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.
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
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
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..
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!
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!
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.
Nice site, Andrew.
To me, it's just a personal thing that can be debated all day long with no
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.
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.