On Mon, 14 Apr 2014 20:02:24 +0000 (UTC), Cydrome Leader
wrote:

I finally dug out the $2 garage sale Craftsman (really Harris)
oxy-acetylene cutting torch. It came with a cutting head of unknown size
which I just cleaned out and #7 torch tip.

It passes the soapy leak test when pressurized, and the o-rings appear ok.

I've not used one of these before but have run into a problem.

I set the acetylene until the flame is not a smoky mess. Then I add oxygen
at the cutting attachment valve (It's wide open on the torch handle) then
I push the cutting lever and the flame gets really vicious. When let go of
the cutting lever, the thing goes BANG and the flame goes out.

What might be going on here? I've got a new set of torch side flashback
preventers to attach before I play with this more.

The welding forums go on about how this is backfire vs. backflash and that
the torch is leaking air or the O2 pressure is too low or something is
broken. It's all vague.

I had the O2 as about 10PSI at the regulator and the acetylene around 5.
Not sure if these are correct-ish.

Suggestions?

O2 should be 15+, acety is correct

Sounds indeed like you have a leak somewhere in the head.

...put your finger over the end of the torch tip, turn on the gas..o2
then Acet.....then stick the entire thing into a bucket of water and
look for the bubbles.

Harris is pretty good torch stuff, Ive got several...and they work
nicely.

Ive seen the backfire before on a torch with a bad tip and a bad seal
around the torch tip body. Check inside the torch handle for a ding
in the sealing area..and check for the same inside the head of the
torch where the tip goes in. And are you sure..sure you have the
right tip? Some are close...some of the old National Carbonic tips
look almost identical..but dont fit perfecticly

Gunner









--

"
I was once told by a “gun safety” advocate back in the Nineties
that he favored total civilian firearms confiscation.
Only the military and police should have weapons he averred and what did I think about that?

I began to give him a reasoned answer and he
cut me off with an abrupt, “Give me the short answer.”

I thought for a moment and said, “If you try to take our firearms we will kill you.”"

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