On Sun, 20 Jun 2010 11:47:13 -0400, "Ed Pawlowski"
I imagine they evacuate any tank they are going to put oxygen in, just
for the reasons you mention.
It wouldn't take much of any fuel gas in there to make an oxygen
explode like a bomb.
Have you ever seen a balloon full of oxygen and acetylene go up?
One the size of a bowling ball will rattle windows blocks away and
that is just a balloon. Imagine that being a steel tank.
Why don't you do some research? I actually use O2 regularly, both for
welding / cutting as well as for breathing and nitrox blending. I'm well
aware of the fact that the welding O2 purity standard is tighter than
the standard for medical O2, as well as the fact that all grades of O2
from any of the large gas suppliers exceeds both the welding and medical
purity standards by a significant margin.
How exactly could something get into the tank in the first place?
If it's connected to a manifold system, then yes, the gas from a
higher-pressure tank could flow into it. But doesn't that
higher-pressure tank already contain known-pure O2?
If it's never connected to a manifold system or to another tank, then
how exactly could something get into it? Deliberate tampering?
Temperature changes. If you have an open tank and let the gas inside
expand, then contract, it will draw in outside air, moisture, or whatever.
Leave that tank long enough and you can get all sorts of contamination, not
all of which is harmful, but it would still not meet medical criteria.
Acetylene in an oxygen tank is a bomb.
It could get contaminated by bacteria from the "breathing" that
happens when you leave the valve open but most real welders will turn
the tank back in with a little pressure in it, Same for SCUBA folks.
On 6/19/2010 8:05 PM, email@example.com wrote:
You typically never allow the pressure to drop to zero because higher
pressure in the tank is the only way to keep ambient moisture from
entering the tank. Ultimately it's to keep the tank from rusting on the
I would think the contrary.
O2 tanks used by hospitals are more likely to be part of a manifold
system, and as such will always be maintained at some positive pressure
by virtue of the fact that at least one of their "gang-mates" is likely
to have enough excess pressure to keep them partially pressurized.
If a gang of O2 tanks at a hospital collectively fall below some
acceptible level of pressure, then they're no longer useful as an air
souce and MUST be changed out. So again the argument here is that
medical O2 tanks are MORE likely to be returned while still containing
some positive pressure charge.
If the strongest argument so far is that a "medical-grade" tank of O2
has lived it's life with minimal to zero infiltration of atmospheric
humidity (or even nitrogen) compared to a welding tank, then that's a
pretty weak argument to say that a tank of welding O2 is unhealthy to
breath. Last I checked, we all take in some some water vapor and
nitrogen when we breath standard air.
In other words, a lack of "purity" does not equal unhealthy or hazardous
for human breathing. A lack of purity (it seems) will degrade welding
performance, maybe mess up equipment, etc.
And so far, it's just been pure speculation here that tanks of welding
O2 are *not* evacuated prior to filling, just as supposedly medical
I can see a huge LOX tank next to a main traffic artery in the Southside
neighborhood of Birmingham where UAB Hospital is located. Tanker trucks
pull up next to the thing and fill it on a regular basis. The
maintenance guys who work for the complex tell me there are tunnels all
around under the place filled with all sorts of conduits and pipes that
distribute various electrons, liquids and gases that keep the hospital
alive. I imagine that LOX tank supplies O2 to the whole hospital and
perhaps a couple of different hospitals in the same general area. The
hospitals share doctors, why not oxygen?
LOX is a different situation. It requires a cryogenic storage tank, and
perhaps on-site re-compression to boost the pressure of the O2 that's
vaporized from the LOX as needed.
We're talking about the bottled O2 that's sold under variously-labelled
end-uses by the compressed gas retailer, and whether or not there's any
*real* negative health implications when using welding O2 gas instead of
"medical" O2 gas in a residential setting.
LOX tanks fill LOX tanks. They can be filled for patient use of that is
what their supplier gives them. They are a different setup that using
compressed O2 though. Different tanks, regulators, etc. They are not
usually filled at hospital though, but by independent providers.
Compressed tanks either need mechanical pumps or, most home medical
suppliers use a cascade system of tanks increasing pressure into the smaller
tanks with each on up the line.
Hummmm, so you say LOX can't be allowed to boil off into O2 gas and
be distributed all over a hospital campus or used to fill portable
O2 tanks? UAB hospital has several hospitals next door. The VA, the
county hospital, The Eye Foundation and several clinics are all on
the same street. Many are connected by skywalks so I have to believe
they share resources.
No, not what I said, It is done often for use, but not for filling tanks.
What I did was is that the oxygen coming off of the LOX is not of sufficient
pressure to fill a compressed tank, you need mechanical pumps to assist.
There are small tanks that can be filled with LOX from big tanks and that is
allowed for local use or portables. You are confusing two different forms
of O2 and the equipment used for them.
UAB hospital has several hospitals next door. The VA, the
I doubt they have a central tank to go that distance, but I've not seen it.
Post photos or drawings of the layout when you get them.
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