[TheForge] cutting propane cylinders

[Clyde]

There was a thread going around here a few months ago on cutting the propane
tanks. Here is part of it:

Yup you got it, simply pull the valve, and start cutting, obviously you stay
away from the cut zone until the residual propane burn out of the tank, as
it is capable of squeezing out a 16" or so flame.  Typically the guys just
use the torch at arms length to cut a few inches till all the full is
burned, or the tank "pops".  Popping refers to when the air/fuel mixture in
the tank is right and it burn like a jet engine for a few seconds.   Propane
has a very tight band for its fuel/air ratio to burn correctly.  Even things
like gasoline take a very specific ratio to burn.  I design and build
Valveless rocket engines for fun "Pulsejets"  I use propane as one of the
fuels for them, and have yet to explode a rocket body, and they are very
thin material sometimes.  I have one body that's made from Hastaloy, that's
only .010 thick, since it is started with an Air/Propane mixture you
sometimes get a fairly good KABOOM as it is started.  Because Propane burns
so slowly it does not have any real percussive power.

If your worried about getting burnt by a tank while cutting it open, simply
get out a jig saw or a sawzall, drill a hole and start cutting.  Another
process, is to take a CO2 tank put a hose on stick the hose in the bottom of
the tank, and bleed CO2 into the old cylinder for about 1 minute evacuating
all of the fuel.  Just because you smell garlic oil doesn't mean there is
still fuel in the tank.  Generally you will find  a few ounces of the stuff
left over in the bottom of the tank.  Its rude stuff, we keep a few bottles
of it laying around, it seems to turn up in peoples trunks and under
toolboxes in Ziploc bags full of paper towels left open for everyone to
smell.....

Awhile back I was reading the article on Freon tank forges.  While they are
very cool, I am not about to go cutting on a freon tank, the hazardous
gasses generated by burning freon are as terrible as some of the chemicals
we used to work around in he silicon wafer fabs.  One of the gasses that can
be generated is Silane, its deadly in only a few micrograms per cubic meter
concentration.  Hydrofluoric acid is also generated this material if inhaled
in enough quantity will basically drown you as it damages your lungs while
you sleep This is also generated by burning PVC, and Teflon.  There are
thousands of varieties of propane tanks that can be used for the same
purpose and as we all Know propane is safe to burn.  If anyone needs tanks
of any particular size, with the holes pre cut, simply drop me a note, the
tank is free you pay the shipping.

Paul

----- Original Message -----
From: "Peter Fels And Phoebe Palmer" <artgawk at thegrid.net>
To: <theforge at mailman.qth.net>
Sent: Sunday, June 01, 2003 12:25 AM
Subject: Re: [TheForge] [OT] Pyro-boom (Re: Thanks for the info...)


> Paul;
> A while back we had a discussion about cutting open old propane tanks
> and several of us had fairly elaborate precautions we took first.
> Clearly you are the expert here...
> The text below infers that you just jerk the valves and plugs and cut
> them open straight off...is that right?........Pete
>
> Paul Hewitt wrote:
>
> >While O/A has an awesome power to exceed the sound barrier making small
> >sonic booms, I am failed to be impressed by the percussive powers.  For a
> >small experiment about 8 years ago, we made a "blast container"   I own a
> >propane tank disposal buisness, so we are always coming by 1000 gallon
tanks
> >that are damaged or out of service that must be burned down.  We cut one
to
> >about 8 feet long, and buried the bottom 4' in the ground.  We then set
up a
> >20# (5 US GAL) propane tank with a 3/4 plug instead of a valve, and a
> >detonator mounted in the plug.  We filed the tank with a perfect mixture
> >then plugged it and placed it in the bottom of the tank, and set it off.
> >Much to our dismay it went PING, and then proceeded to suck air back into
> >the container as the burnt O/A takes up less space creating a vacuum and
> >sucking the small wire back into the container from the detonator through
> >the epoxy.   We devalve about 500 to 1000 tanks a day, and typically then
> >cut holes in them.  The guys with torches usually pride themselves on the
> >tanks that become "jet engines"  when a tank sits open long enough they
get
> >a perfect mixture and then will burn inside the tanks emitting the hot
> >exhaust gasses out the hole that's been cut.  After about a 2 to 3 second
> >interval they burn out, but do not explode the tank.
> >

-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net]On Behalf Of Gladish Family
Sent: Thursday, March 24, 2005 12:16 PM
To: Sponsored by ABANA
Subject: Re: [TheForge] cutting propane cylinders


I don't mind cutting the little ones with the valve removed, but the big
ones are spooky, since my sawzall (great metalworking tool, btw) also
throws sparks sometimes.
I think I will remove the valve, wash it, then burn a candle inside just
before cutting.
andy g

JOHN CHOBRDA wrote:

>	Someone correct me if I am wrong, but I under stand the only SAFE
>way to cut an old propane tank is with a hacksaw or sawzall. I have been
>told that the steel absorbs molecules of propane so that no mater how many
>times you wash and air it out there is still danger of explosion if you use
>a torch or spark producing cut off saw. About 3 years ago I was working in
a
>shop in Trenton when a young fellow cut into a "purged" tank with a cut off
>saw and lost his life.
>
>
>
>
>
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