|
Posted by Curt Welch on July 3, 2008, 11:41 pm
Please log in for more thread options
> "Maxwell" wrote: (clip) after just a few seconds of welding, I got an
> extremely hard
> > POP from the combustion gasses on the inside. It bloated the metal pan,
> > and could have been very dangerous. (clip)
> ^^^^^^^^^^^^^^^^^^^
> I know of a welding shop that welds gas tanks after running the exhaust
> from a small engine into the tank for an hour or so. Another idea might
> be to shove in several handfulls of dry ice. The CO2 will force
> virtually all the air out. CO2 is heavier than air, so if any air
> remains, it would not be at the bottom.
Hum. Maybe you could just fill it up with Argon (heaver than air) (or
75/25) and get the same effect??? I'd trust a hose from an Argon tank to
correctly remove the O2 from the tank before I'd try a stunt like dry ice
or engine exhaust. Shit, a 2 stroke mixes the combustible fuel with the
incoming air and pumps some of it out the exhaust on every cycle. Fill
your gas tank with the exhaust from a 2 stroke and you would be asking for
trouble when you started to weld. I wouldn't try anything like that
without the correct knowledge of all the chemistry and risks and the
correct tools like maybe an O2 meter at hand to verify what was in the
tank.
Checking a page on the specific gravity of gases, I see some nice gases
like Butane, Propane, ozone and nitrous oxide are all heaver than Argon and
CO2. Yeah, that would be nice. Push out the O2 but leave the tank full of
butane, propane, ozone and nitrous oxide (close cousin to nitro in chemical
make up). I don't know if O2 in those forms can help the butane burn under
heat, but I wouldn't be the one to bet my life it couldn't.
Personally, I wouldn't go anywhere near a welding job and tanks of highly
combustible material. :) I'll let the "real" welders do that crap.
--
Curt Welch http://CurtWelch.Com/
curt@kcwc.com http://NewsReader.Com/
|
|
Posted by Leo Lichtman on July 4, 2008, 1:11 am
Please log in for more thread options
"Curt Welch" wrote: (clip) I'd trust a hose from an Argon tank to
> correctly remove the O2 from the tank before I'd try a stunt like dry ice
> or engine exhaust. Shit, a 2 stroke mixes the combustible fuel with the
> incoming air and pumps some of it out the exhaust on every cycle. (clip)
^^^^^^^^^^^^^^^^^^^^^
"Stunt?" CO2 gas is what is produced when dry ice sublimates. It is just
as non-combustible as your argon. And I never said anything about using a
2-stroke engine. Did you throw that in just so you could argue?
|
|
Posted by Curt Welch on July 4, 2008, 3:10 pm
Please log in for more thread options > "Curt Welch" wrote: (clip) I'd trust a hose from an Argon tank to
> > correctly remove the O2 from the tank before I'd try a stunt like dry
> > ice or engine exhaust. Shit, a 2 stroke mixes the combustible fuel
> > with the incoming air and pumps some of it out the exhaust on every
> > cycle. (clip)
> ^^^^^^^^^^^^^^^^^^^^^
> "Stunt?" CO2 gas is what is produced when dry ice sublimates. It is
> just as non-combustible as your argon. And I never said anything about
> using a 2-stroke engine. Did you throw that in just so you could argue?
Yeah, I love to argue. (debate ideas really).
No, the other poster talked about the idea of venting the tank with the
exhaust of a "small engine" (if I remember the wording correctly). I was
thinking and commenting about the potential risks if that "small engine"
was a 2 stroke instead of a 4 stroke. That comment had nothing to do with
your CO2 suggestion.
The problem I would see with using dry ice is not that CO2 is better or
worse than Argon, but that you would have a very hard time knowing how much
C02 you had generated by using "a few handfuls" of dry ice and have a hard
time knowing if the CO2 had evenly displaced all the O2 or if it had just
mixed with the O2 leaving a lot of the O2 in the tank. With a welding tank
of Argon or CO2, you could calculate how much gas you had pushed through
the tank by the flow rates and you could keep it flowing at a low rate to
make it slowly displace the O2 in a "plug flow" type of mix instead of the
case where the two gases would mix and dilute each other and push a lot of
the CO2 out with the O2 leaving a lot of O2 still in the tank.
There was an interesting article in the AWS welding Journal an issue or two
back (May 08 actually) about the problems of purging a welding piece with
inert gas. They had lots of good ideas about the things you have to do to
make sure the inert gas had correctly pushed out all the reactive gases.
They suggested for example to use a dew point meter instead of an oxygen
meter because many o2 meters weren't sensitive enough to detect small
amount of oxygen (they were built for safety checks for humans to breath
not for the small amounts that could mess up a weld - and probably the
small amounts to create an explosion I would guess). There was also the
problem of bubbles of O2 being stuck in high spots to look out for. And
the general issue of plug vs mixing flows that would require you to pump
large amounts of gas through before the O2 level became low enough.
The complexity of doing purging correctly to back your weld with inert gas
made me realize the complexity you can face if trying to remove the O2 to
keep it from exploding as well.
--
Curt Welch http://CurtWelch.Com/
curt@kcwc.com http://NewsReader.Com/
|
|
Posted by Jon Danniken on July 6, 2008, 10:14 pm
Please log in for more thread options "Curt Welch" wrote:
> The problem I would see with using dry ice is not that CO2 is better or
> worse than Argon, but that you would have a very hard time knowing how
> much
> C02 you had generated by using "a few handfuls" of dry ice and have a hard
> time knowing if the CO2 had evenly displaced all the O2 or if it had just
> mixed with the O2 leaving a lot of the O2 in the tank.
Actually, no, it is very easy to know how much CO2 you would have, if you
take a few seconds and look at the numbers.
The volume of gas released (at room temp and pressures) from one cubic
centimeter of dry ice is about 0.83 liter (about a fifth of a gallon). If
you assume that a handful of dry ice is about the volume of a golf ball (a
golf ball being about 30 cubic centimeters), and that "a few handfulls" is
three golf ball size chunks of dry ice, then you are looking at the amount
of CO2 liberated being about 74 liters, or about 20 gallons.
As for the mixing of the gasses, dry ice sublimates slowly enough that if
you leave the tank undisturbed with a small orifice for O2 to leave (to
minimize drafts), you can reasonably assume that a sufficient amount of 02
has been displaced.
You can give yourself an additional safety factor if you wish; dry ice is
cheap and readily available enough.
Jon
|
|
Posted by Leo Lichtman on July 7, 2008, 12:10 am
Please log in for more thread options
"Jon Danniken" wrote: The volume of gas released (at room temp and
pressures) from one cubic
> centimeter of dry ice is about 0.83 liter (about a fifth of a gallon).
> (clip)
^^^^^^^^^^^^^^^^^^^
Actually, from my drinking experience, I believe a "fifth" equals 750 cc.
As far as displacing ALL the oxygen is concerned--you don't have to. You
need to displace most of it, so the remaining content of the tank is outside
the ignition limits. AMHIKT (Ask me how I know this.) Okay, I'll tell you.
When I ws a grad student at Cal, I worked on a project for the Air Force in
which we studied what happens inside a fuel tank when an ignition source
(such as a tracer bullet) goes into a tank. The object was to fill the
vapor space in aircraft tanks with a non-combustible mix. We used spark
plugs in most of our tests, and actually fired bullets in many of the tests.
|
| Similar Threads | Posted | | rich welder - sell Welding Equipment & Machines & mask,Power Tools,Motorcycle & Welding helmet,CUT,TIG,MIG,MMA,BX welder | June 30, 2008, 2:20 am |
| No Gas Welding | March 29, 2007, 7:14 pm |
| new to mig welding | April 30, 2007, 8:29 pm |
| old welding rod | June 19, 2007, 1:35 pm |
| Welding | August 5, 2007, 6:42 pm |
| welding help | October 5, 2007, 7:28 am |
| welding weldING WELDING | September 12, 2007, 7:59 pm |
| ARC Welding: AC/DC vs AC? | September 5, 2007, 6:36 pm |
| What is Welding? | November 9, 2007, 8:03 am |
| Welding M3 HSS | March 14, 2008, 12:04 am |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap
> extremely hard