On 9/11/2012 4:55, Larry Jaques wrote:
On Mon, 10 Sep 2012 20:51:05 +0300, Kristian Ukkonen
On 9/10/2012 19:49, Tim Wescott wrote: On Sun, 09 Sep 2012 21:57:01
-0500, Jon Elson wrote:
RogerN wrote:
I've seen a few of the suppliers that sell torches for glassblowing
also sell oxygen concentrators so you can run the torches without
having to buy oxygen in tanks. I'm wondering if this would be
beneficial to metalworkers that do a lot of torch work.
http://www.sundanceglass.com/oxygen-concentrator.htm
They have 7PSI 5LPM for $275. This may be OK for oxy/acetylene welding
but
not enough pressure (or volume) for cutting. So what about adapting an
oil free compressor and a tank to give you enough pressure and volume
for cutting torch operation. Seems this price is getting competitive
with the price of tank and contents, or at least by the time you have
to get a couple of refills.
Pure Oxygen is extremely dangerous. Only certain metals and plastics
are compatible with it. For instance, a fingerprint left inside an
oxygen system is enough to cause a fire that will set the metal lines on
fire.
I thought it was pure oxygen at high pressure or in liquid form that was
so very dangerous -- does this hold for oxygen at 40 psi?
Normal compressor has oxygen at about 2.1bar (30psi) if
tank is at 10bar.. 21% of air is oxygen.. Compressor with
higher tank pressure has higher oxygen partial pressure.
No, normal compressor at 10 bar tank pressure has oxygen (in the air)
at 10 bar. There is no separation in the tank, at least not that I've
ever heard of. Why would the hydrogen (and other gases) compress at a
higher pressure? That's daft, man!
I'm afraid you don't understand what partial pressure means.
http://en.wikipedia.org/wiki/Partial_pressure
http://chemistry.about.com/od/worked...alpressure.htm
If the compressor compresses normal air to 10bar in tank, there
will be partial pressures of gasses about
:
7.8bar nitrogen
2.1bar oxygen
0.09bar argon
0.0003bar CO2
.....
0.0000005bar hydrogen
etc. based on how much of each gas there is in air.
There is not much hydrogen in air, really.
If you take the nitrogen and all other gasses, except oxygen, away,
there still will be the oxygen pressure of 2.1bar left in tank.
You could achieve the same (as above compressing air) by pumping
vacuum to tank, filling 7.8bar N2, 2.1bar O2, 0.09bar Ar etc..
The end result would be exactly the same.
This doesn't take into account that the compressor propably
has a different compression ratio for different gasses, so the
partial pressures above are not very accurate, but that is
not the point here anyway.
Normal "instrument air" (synthetic air) is 21% oxygen at 200bar
in a bottle.. Nothing special required yet at partial pressure of
oxygen at 42bar. Just normal nitrogen pressure reducer etc..
This is all stated by the "safety sheet" of the product by
gas company.
Cite, please?
My documents are in Finnish so I think that wouldn't help much.
Google found these english MSDSs for synthetic air and pure oxygen:
http://www.praxair.com/praxair.nsf/AllContent/A3552DAFCB8D265685256A86008095F6/$File/p4560j.pdf
http://www.praxair.com/praxair.nsf/AllContent/E88BE35D13EF81F685256A860081E837/$File/p4638h.pdf
Notice the significant differences in precautions etc..
Kristian Ukkonen.