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Problem with propane/compressed air torch


#1

Hi all

I have been experimenting some problems when melting the metal in
the centrifuge machine crucible with the compressed air/propane
torch which practically keeps going off the whole melting process,
Sometimes when the metal is already molten and I am about to strike
the centrifuge arm the torch goes off. I thought that this problem
was mainly caused by the turbulence generated by the compressed air
inside the partially closed centrifuge crucible but I still have the
same problem with the BernsOmatic torch which is propane only . I
have never used acetylene or any other kind of combustible other
than natural,propane gas and compressed air. I would not like to
switch to oxygen and propane cause my studio is at home. I wonder if
somebody else have experimented this problem using compressed air or
even using oxygen torches . Note;This never happens in an open
crucible. Marco


#2
  I have been experimenting some problems when melting the metal
in the centrifuge machine crucible with the compressed air/propane
torch which practically keeps going off the whole melting process,
Sometimes when the metal is already molten and I am about to
strike the centrifuge arm the torch goes off. 

I’d bet that flame gasses, hitting the inside of the crucible, and
bouncing back and litterally blowing out your flame. Move your torch
tip a bit further back, and perhaps a bit to one side and down, so the
flame returning back out of the crucible is clearly well to the side
of the torch tip. That may help.

The straight propane, Bernzomatic torches, at least the ones with
the rigid torch assembly attached straight to the tank, can have the
problem where the liquified fuel doesn’t completely evaporate to a
gas before reaching the orifice of the torch, which then clogs it and
blows out the torch. One the torch if fully warmed up, this happens
less, but it can be an annoyance with some of these types.

I would not like to switch to oxygen and propane cause my studio is
at home. 

Might I mention that in general, the danger in an oxygen / propane
system is still mostly the propane tank, which you’ve already got now.
With an oxygen tank, there are generally two risks. One is that you
get an oxygen leak. When that happens, it simply means you waste
oxygen, but can breathe easier in your shop (grin). The leaky oxygen
costs you money, but that’s all, unless there is already an out of
control fire, which will then burn more fiercly with added oxygen.
But the oxy tank wont’ cause the fire. The main danger of an oxy
tank is simply that it’s at high pressure. If you knock it over and
knock off the valve stem the high pressure tank will do a lOT of
damage. For that reason, gas tanks need to be secured, chained in
place or otherwise, so they can’t tip over. Do that, and they’re
relatively safe. Your propane tank, though, if it leaks and fills a
room with enough gas, can cause a major explosion. Propane is a good
deal more dangerous to have indoors than an oxygen tank, as the risk
is a situation that’s considerably more common… a leak. Still, I
feel safe enough to have it in my own home shop, and so do many
others. Natural gas, either in a tank or through municipal service,
is considerably safer than propane, though still not totally safe.
Unfortunately, most residential gas service is not at high enough
pressure to run a torch well.

Hope that helps.
Peter Rowe


#3

Dear Friends,

Just a short note on Propane. Residential and commercial building
codes prohibit the refillable tanks be located inside. This is the
law for most of the USA. I heard of a fire in Chicago recently that
cleared out a building for a week or so. The cause was one of these
refillable tanks. Even the small ones are against the law. The way I
get around this is to use a one pound disposable propane tank with an
adaptor that screws on a ball valve to turn it on and off. I had set
this up at a camper store. I have seen the small kit available now
that has the small disposable tanks At Rio and Gesswein. The tanks
may last a shorter period of time, but I am in no code violation in
my shop or when my shop was in the house. Here’s another little tip.
DON’T ask the fire marshal to come and look at your set up. Just
find the proper way and do it. I’m not saying break any laws, just
don’t like someone snooping around my shop looking for things to cost
me money. If there is a fire in a building and a refillable propane
tank is involved you may have a problem with an insurance claim
because they may blame you for the fire and hold you liable.

Best Regards,

Todd Hawkinson
www.trhawkinson.com
TR the Teacher
www.mctc.mnscu.edu/jewelry


#4
 If there is a fire in a building and a refillable propane tank is
involved you may have a problem with an insurance claim because
they may blame you for the fire and hold you liable. 

Thanks for the tip, TR. I also use disposable propane tanks and
oxygen with a Little Torch. I also have flashback arrestors. I
chose the tanks because they seemed the safest, it’s nice to be
vindicated.

The fire in Chicago was quite a problem, the entire building in
Jeweler’s Row was closed for more than a week as I remember, and
people couldn’t go to work. Some people wondered if it was a ploy to
get the jewelers out so the building could go condo, but luckily
that’s not possible because the building is a national historic one.

Elaine Luther
Chicago area, Illinois, USA
Certified PMC Instructor
@E_Luther


#5
 e. luther said "I also use disposable propane tanks and oxygen
with a Little Torch.  I also have flashback arrestors.  " 

you can use flashback arrestors with the little torch disposable
propane/oxy set up? i had assumed that since the regulators were
preset that the flashback arrestors wouldn’t fit. assuming that the
arrestors couldn’t be used with the disposable tanks made me think
that perhaps the disposable set up was actually more dangerous than
refillable tanks…

thanks for any clarification,
jean adkins


#6

Yes you can use them (flashback arrestors on disposable tanks). Rio
used to sell them, don’t know if they still do, but I bought mine at
a local welding shop, where they were slightly cheaper. They’re
small, but they work. They work just fine with the regulators from
Rio sold for the Little Torch and disposable tanks.

Elaine Luther
Chicago area, Illinois, USA
Certified PMC Instructor
@E_Luther