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Acetylene fumes, could it be a flashback?

#1

Today I was working in my Studio and left for 5 minutes to grab a
sandwich. Came back and the place reeked of acetylene fumes. Quickly
turned the tank off…got my dog outa the Studio… and went to
bleed the line but couldn’t touch the torch handle as it was too hot
to touch. I am very careful about turning the torch off when I put
it in the holder, so don’t think it was left on. No flame was coming
out of the torch…so if it was inadvertently left on, it shouldn’t
have been hot, right??? The hose looks fine…

Called the welding shop and they said ‘it could be flashback’ but
aren’t used to dealing with a Smith torch so weren’t sure if that
even occured in a non-welding situation. This has never happened and
of course frightened me.? Would appreciate any input on why this may
have happened…

Thanks…
Liane

#2

Forgot to mention the following when I wrote…

Wanted to mention that when the torch cooled down, that it had
indeed been turned off.?? The handle of the torch, the hose where it
connects to the torch, and my floor are covered in something very
sticky which wasn’t there prior.

Phoned Rio to see if they knew what may have happened and they
thought ‘flashback with a now burned hose.’ ? Hose looks okay…so
does the torch. I tested for any leaks and everything seems to be
okay…

I am really stumped.

Liane

Liane Redpath Worlund

#3 
Wanted to mention that when the torch cooled down, that it had
indeed been turned off.? The handle of the torch, the hose where
it connects to the torch, and my floor are covered in something
very sticky which wasn't there prior.

Sometimes, the valves on a torch can leak. What colour is the sticky
stuff? There’s a small possibility of acetone getting out of the
tank under certain situations, and acetone being a fine solvent - it
may be a case of the floor being dissolved by acetone. Hard to say
without knowing what the residue looks like.

Phoned Rio to see if they knew what may have happened and they
thought 'flashback with a now burned hose.' ? Hose looks okay...so
does the torch. I tested for any leaks and everything seems to be
okay....

Was it whistling when this happened? What can happen sometimes, the
flame can receed into the torch, and end up burning inside. This can
make the torch very hot, and end up melting it - leading to a very
large fire indeed. Are you shutting down the torch properly? It’s
important to turn off the oxygen valve, then the acetylene. That
way, if the oxygen is leaking, when you shut off the acetylene you’ll
get a pop, and if the acetylene is leaking, the flame won’t
completely go out.

Paul Anderson

#4

Dear Liane,

Phoned Rio to see if they knew what may have happened and they
thought 'flashback with a now burned hose.

I wish I’d have taken that call. Sometimes on fuel AIR torches the
valve on the control knob gets a little worn and hard to turn all the
way off. Like an old water facet it will, very slowly, leak and if
the flame is not extinguished it will continue to burn back inside of
the handle eventually heating it up, such as you experienced. It is
important to hear that “POP” when turning off an acetylene (fuel) air
torch, this tells you the flame has been completely extinguished.
Many people are frightened by this POP but it is a reassurance of the
flame being extinguished. If you leave your work area you should be
turning off your tank - period.

Flash backs are rare, if ever, on a fuel/AIR systems (one tank).
They are a very real concern on fuel/OXYGEN torch systems (two
tanks).

Sincerely,

Thackeray Taylor
Rio Grande Technical Support
505-839-3000 ex13903
800-545-6566
technical@tbg.riogrande.com

#5

Yes it sounds like a flash back which is combustion inside the torch
and or hoses, and or regulators. I would guess you either did not
fully turn off the torch or the seals on the torch are leaking and
when you turned it off the flow of gas through the bad seals allowed
enough gas to supply a small flame inside the torch itself. This is
why it was hot and it probably did not have enough oxygen to burn
for long and the flame went out but the acetylene was still leaking
out of the torch.

You need to get your whole rig (torch, hoses, regulators) to a
service tech to have them inspected and replace or repair anything
that was damaged by the flashback.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550

#6

Hi

One possibility is that some of the liquid (acetone maybe) that
stabilizes acetylene leaked out. Did you tank get tipped over at any
point? That would let acetone get out which might dissolve
plastic-Becoming your sticky substance. Without the acetone the tank
is extremely dangerous. One thing I hate about acetylene (among
others) is that it can be set off by shock. So, they stabilize it
with acetone. At least that is what I was taught in school! Could be
wrong but if in doubt call your supplier and just replace the
cylinder.

Daniel Ballard

Here is a link to a picture of the design on the inside

http://www.motorera.com/dictionary/pics/a/acetylene.jpg

Quoting from a web source

http://www.hobartwelders.com/weldtalk/showthread.php?p=269788

Exclamationacetylene storage - now for the facts... 

There is nothing inherently unsafe with STORING an acetylene
tank on its side, just as there't nothing wrong with putting a
bottle of soda on its side in the refrigerator. The acetylene
molecules don't really care what orientation the tank is in. 

The problem comes with using an acetylene tank that has been on
its side. The acetone filler needs time re-absorb back into the
filler completely or you risk drawing some of it out of the tank
when you open it. I have heard people in the gas industry
recommend leaving the tank upright for 24 hours to allow the
acetone time to completely re-absorb. Other people have told me
that you can get away with leaving the tank upright for a couple
hours before using it, but I always going with the 24 hour time
period. 

Reading some of the various acetylene threads on this website
could lead you to believe that a Hiroshima explosion in your
workshop is more than likely if you look at your acetylene
cylinder wrong! 

And, in case you don't believe me (aw shucks, you'll hurt my
delicate feelings), here's a quote from the US Dept. of Labor
website: 

"WHILE STORAGE IN A HORIZONTAL POSITION DOES NOT MAKE THE
ACETYLENE LESS STABLE OR SAFE, IT DOES INCREASE THE LIKELIHOOD OF
SOLVENT LOSS, WHICH WILL RESULT IN A LOWER FLAME QUALITY WHEN THE
CYLINDER IS USED. THEREFORE IT IS ALWAYS PREFERABLE TO STORE AN
ACETYLENE CYLINDER IN AN UPRIGHT POSITION." -

http://www.msha.gov/alerts/hazardsofacetylene.htm

#7 
went to bleed the line but couldn't touch the torch handle as it
was too hot to touch.

This has happened where I teach. It appears to me that it can happen
that the torch doesn’t get quite shut off, and the flame is somehow
burning down in the handle. I have only seen this happen when using
a very large tip. The solution would seem to be to be extra careful
turning the knob fully off.

Noel

#8 
One possibility is that some of the liquid (acetone maybe) that
stabilizes acetylene leaked out.

It’s dissolved in the acetone, much like the way carbon dioxide is
dissolved in a bottle of coke.

Paul Anderson

#9

I guess I should get the flashback arresters for my Little Torch
(oxy/propane). I don’t understand why they were not simply included
in the kit (caddy, tanks, torch, regulators, but no FAs). Any
preference among the experts over “torch end” or “regulator end” and
why?

Chris (beginner)

#10

You’ve gotten some very useful and on-target responses on this. Just
wanted to add that when I’ve seen this happen (or suspected it) on
an acetylene/AIR rig, you can actually SEE the flame or black soot in
the little holes at the base of the torch handle (where the ambient
air intake is) if you look through them against a lighter surface.

This seems more prevalent with the really small tips (0, 00) as they
don’t necessarily have enough oomph (the technical term) to blow
themselves out completely with a “pop” when you turn them off.

The fix is simple if you catch it immediately - turn the gas back on
to light it, then turn it off more fully. OR blow through the holes
in the base of the torch like you’re blowing out birthday candles.

Hope this helps!

Karen Goeller
No Limitations Designs
Hand-made, one-of-a-kind jewelry

#11 
I guess I should get the flashback arresters for my Little Torch
(oxy/propane). I don't understand why they were not simply
included in the kit (caddy, tanks, torch, regulators, but no FAs).
Any preference among the experts over "torch end" or "regulator
end" and why?

This should be simple…if you use a torch that mixes a fuel gas
(acetylene, propane, MAPP, natural gas, etc.) with high pressure
oxygen then you should have flashback arrestors on both the fuel gas
line and the oxygen line, all the time, one every torch.

UL Listed flashback arrestors usually combine a flashback arrestor
with a check valve and come in two types - regulator mount and torch
mount. They both do the same thing - the difference is which
direction gas flows through them and where they are installed on the
gas and oxygen lines. Putting the wrong type in the wrong place
blocks gas flow to the torch.

Regulator mount flashback arrestors screw right onto the regulator
on your cylinder or gas line. Torch mount flashback arrestors are
attached to your torch. Many jewelry torches do not have the fittings
for flashback arrestors to be attached so regulator mount flashback
arrestors can be installed in the gas line itself.

New York City has recently changed its Fire Code to require
flashback arrestor checkvalves on all jewelers’ torches and my
company has prepared a brochure with photos and text explaining the
diference in regulator-mount and torch-mount flashback arrestors, and
how to install them. If you would like a PDF of this brochure please
contact me off-line at @ehoward and I will e-mail a copy
to you.

Ed Howard
G-TEC Natural Gas Systems

#12

Hello Chris,

I guess I should get the flashback arresters for my Little Torch
(oxy/propane). I don't understand why they were not simply
included in the kit (caddy, tanks, torch, regulators, but no FAs).

I would like Smith to package kits like this myself, I’ve been
meaning to ask them why they don’t and this is motivation to do so.

Any preference among the experts over "torch end" or "regulator
end" and why?

As for the type of flashback arrestor for the Little Torch systems,
the only one that will work with it is the regulator mount. Torch
body (handle) mount flashback arrestors are designed for large
torches that have long wide hoses. These types of torch systems carry
lots of fuel and oxygen so it is best to catch the flashback at the
source. The difference between the two flashback kits is the
direction they allow the flow of gas, so they are not
interchangeable.

Hope this helps,

Sincerely,

Thackeray Taylor
Rio Grande Technical Support
505-839-3000 ex13903
800-545-6566
technical@tbg.riogrande.com

#13 
I guess I should get the flashback arresters for my Little Torch
(oxy/propane). I don't understand why they were not simply
included in the kit (caddy, tanks, torch, regulators, but no FAs).
Any preference among the experts over "torch end" or "regulator
end" and why?

Chris, I agonized over that when I was making my first torch
decisions. And I can’t speak for the oxy-propane Little Torch setup,
it may or may not be different from the oxy-acetylene version, but
it’s not possible to add flashback arrestors to the oxy-acetylene
version of the Smith Little Torch – where you add flashback
arrestors is between the torch handle and the hose, and on that
torch, it’s got a permanent connection there already.

I also later decided that I wasn’t ready for the oxy-acetylene
version of the Smith Little Torch, and it sits unused while I use an
air-acetylene ordinary Smith torch, and I’m loving it. No more
acetylene soot floating through the air, only one knob to adjust,
much easier to light… Of course, with a propane torch, you won’t
have to worry about the acetylene soot. :slight_smile:

#14

Hi Chris,

Any preference among the experts over "torch end" or "regulator
end" and why?

I think you’ll find that you can’t put arrestors on the torch end on
the Smith Little Torch. The hoses are attached directly to the hard
lines inside the handle. I don’t think they make them to fit in
between, but I could be wrong. Even if they do, if they are the size
of normal arrestors, they will somewhat defeat the purpose of the
Little Torch by about doubling it’s weight. FWIW, I have them on the
hose ends where the Little Torch hoses join the main lines (between
the regulators and the Little Torch lines). I’m not sure how
effective they are there, but I’ve got them. I always put them on
bigger torches at the torch though. I don’t think propane presents as
much of a danger of flashback as acetylene, but again, I could be
wrong, and I’m not taking any chances. The Youtube video of the
exploding LP tank made a believer out of me.

Dave

#15 
I guess I should get the flashback arresters for my Little Torch
(oxy/propane).

When I set up my Propane/O2 torch, I was horribly confused by the
directions. I wanted to set it up properly, but didn’t quite get it.
Finally, I took the whole pile of parts to the local company that
sells oxygen and welding supplies. It turned out that I had some
incorrect parts (can’t remember now what they were). They sold me
the correct parts and told me how to assemble it (although they
wouldn’t assemble it themselves). They really cleared my brain.
Highly recommended to get the experts involved in such an important
task!!

Jamie

#16 
but it's not possible to add flashback arrestors to the
oxy-acetylene version of the Smith Little Torch -- where you add
flashback arrestors is between the torch handle and the hose, and
on that torch, it's got a permanent connection there already.

Yes it is possible, there are two types of flash back arrestors
torch mount and regulator mount. For the little torch setup use the
regulator mount type.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550

#17

Lauren…There really should not be any problem with the oxy-acet
system. You are missing out on some real good activities by
foresaking it. To keep from getting the soot (we calll them
parachutes) just crack the oxy knob open a tad and then add the acety
and light er up. No soot, just beautiful blue flame ready to work.
Adjustment? Yes, there is some but then there are times one might
want a reducing flame and other times an oxidizing flame. Muuuuchhh
more flexible than the air/acet torch. More precise heat, better
adjusted flame, etc. etc. Try it. I use my air/acet torch for the big
stuff where I want large soft flame and the lil-torch where I want
real heat.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry!

#18

My sincere thanks to everybody and their assistance with my torch
scenario of this past week.

We are still stumped as everything looks good and checks out. We are
assuming there was a fire in the torch but it wasn’t bad enough to
burn the hose…nor the ‘o’ rings in the tip…nor any of the
connections. Perhaps I was just extremely lucky and caught it early.
My only other thought is my torch ‘stand’ doesn’t fit my torch
perfectly and may have knocked the shut off valve a little.

Since I am so careful about turning the torch off, I really
appreciated the comment about how this Smith one tank set up must
have the torch ‘pop’ when you shut it off. (I do not have a two tank,
oxy/acetylene system) Either the pop happens and I no longer hear
it…or it isn’t happening. It’s my next thing to check.

Been busy with having our home painted all week so haven’t gotten
into my Studio…

Liane
Liane Redpath Worlund

#19 
there are two types of flash back arrestors torch mount and
regulator mount. For the little torch setup use the regulator mount
type.

Thanks James and everyone for your help on this. I’ll stop by my
welding supplier next week and pick up the FAs for the regulator end
of my Little Torch.

Chris

#20

Thanks, Jamie. I had no trouble setting up my Little Torch oxy/pro,
the single advantage of having bought a kit from Frei (disadvantages:
price, 6-week delay, $35 for shipping). The LT directions were well
written and in ENGLISH which always helps (not ESL English, either).
I’ll also say this about the LT user it is complete. I
keep it handy to refresh my memory about their recommendations for
gas pressure. At first I just kept it near to remind me of the
sequence of things for activating and shutting down the system, until
I was comfortable with it and better understood what was happening
with the gas and the regulators.

To take this back to the topic, it was reading the user info and
Karen C’s torch recommendations that I determined I needed flashback
arrestors.

Thanks again, all.