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.
It *can* be the same. However, oxygen graded for welding, but not for medical use, isn't safe for medical use.
Wether or not a store sells medical grade oxygen to welders is up to the store and not universally true.
So the people who said it's not the same are wrong?
snipped-for-privacy@milmac.com (Doug Miller) wrote in news:hvjf4r$2e4$ snipped-for-privacy@news.eternal-september.org:
the people who said they're different said it a long time ago when they actually were different. Times have changed,they no longer actually are different.
did you not read the article cited? it was very informative.
If the other tank contained, say, acetylene.
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.
Uh-huh. Right. Welding oxygen is certified just as pure as medical oxygen, no contaminants. Suuuurrrrre it is. That's why they use welding oxygen in hospitals.
The purity standard for welding O2 is higher than the purity standard for medical O2. In reality all three normal grades you can get, welding, medical and aviator exceed all of the standards. Only the analytical grade is higher purity.
Medical 99.95% pure Welding 99.99% pure
Nope. Why don't you look it up, starting with 1) the percentage of oxygen and ending with 2) the levels of impurities.
You can't use welding O2 for medical purposes but you can use medical O2 for welding.
There is a LOT of shit done in hospitals simply because that is the way they've always done it. To suggest otherwise to them will get you a look that suggests you've lost your mind.
I deal with policies all the time that closer examination would reveal are outdated and kind of stupid if you consider the current realities. But the Powers That Be know what they know and nobody can tell them different. So we still do what we've always done.... because we've always done it that way.
A lawyer would probably make a big deal about "welding" oxygen instead of USP in much the same way the US Navy made a big deal about the captain of the USS Indianapolis not zigzaging when his ship was torpedoed. The commander of the Japanese submarine testified at his court martial that it wouldn't have mattered one way or the other; he still would have nailed him. The Navy didn't care... because policy stated you should always zigzag when submarines might be around. After all, they'd always done it that way.
Many of the folks who determine these policies are dinosaurs, and about as current.
Jay
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 inside.
Jay
That is exactly why medical oxygen thanks have to be evacuated. Rare that one would come back with any pressure at all.
They do and they aren't an unusual thing at all to find in a low-medium usage shop.
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 tanks are.
Like I just said, the presence of impurities does not necessarily equate to medical safety or have a health impact. If those impurities are nitrogen or water vapor, then what exactly are the health implications of those? We freeking breath them all the time - in concentrations several orders of magnitude higher than what could possibly exist in a tank of welding O2.
Says who?
A lawyer? Or a biochemist?
Here's the problem I have with that.
What is the compressed gas supplier doing differently that would result in that very slight (but consistent?) difference between those two products?
If he has two machines or processes for creating the two products (welding O2 and medical O2) and if the welding O2 product is more "pure", then why would he operate two processes instead of simply using a single process (the higher purity process) to create *both* of them? Especially since the welding product is retailed at a lower price to start with.
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?
TDD
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.
It wouldn't surprise me if the LOX tank is used to fill portable tanks for patient use. I'll have to ask one of my friends who works maintenance at the hospital.
TDD
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