Pick a supplier and ask for advice on various systems. Whitey and the other larger scale folks produce a line of 02 compatible bits and pieces (no flammable guts). I prefer Swagelok systems to all others, as they can be built on the bench and do not require crush cones to seal. Tubing thickness is a product of planned system pressure. 3000 psi is .035" wall. You don't need anything heavier, and the idea of going with thicker walls for extra protection is ridiculous.
There are also other problems with weld gas not mentioned so far, not the least of which is particulate contamination and gas exchange at the supplier. Small bits of argon won't make much difference in a welder, but they'll play hell with your brain pan. Medical grade oxygen is as clean and pure as it gets, and you can buy it at the local doctor's supply, or at least order it through them. The caveat about having to have a doctor's note is the short answer. You have to find out what it takes to get a license for that kind of thing, and then buy it wholesale. A friendly local dive shop might be of some help there, especially if they have some tech diving kids.
We always ended up with trucks delivering lots of T-bottles, then filled the sub with a combination of cascading to equalize and then pumping to full pressure. You won't need that, and I don't either, anymore. That said, if you are carrying oxygen outside in fixed bottles, you will need enough gas volume and pressure on deck to cascade your sub's system adequately, or you've got to pump it. One or the other. Mine is inside on Gamma, so it won't matter overmuch.
Luckily, I have medical professionals in the family, so I'm thinking there is a way to get around some of the issues. If anything comes to mind, I'll let you know.
Vance
-----Original Message-----
From: Scott Waters <swaters@waters-ks.com>
To: personal_submersibles <personal_submersibles@psubs.org>
Sent: Sun, May 6, 2012 12:31 pm
Subject: Re: [PSUBS-MAILIST] O2
Thanks Steve! That is very helpful. So really welding O2 works just fine for what we are doing. Anyone know about the fittings for SS tubing and the wall thickness?
Thanks,
Scott Waters
Sent from my U.S. Cellular BlackBerry® smartphone
Date: Sun, 6 May 2012 11:11:06 -0500
Subject: Re: [PSUBS-MAILIST] O2
The short answer is that there is no difference. The same grade of oxygen goes into both. It has to do with the way the tanks are filled. Medical oxygen tanks are emptied before they are refilled and welding tanks are not. Aviation oxygen has more moisture removed removed to prevent freezing at altitude. And of course the label is different for liability.
Sent from my iPad
I was at my local welding and gas supply the other day and they were asking me how my sub was doing and we got on the conversation about the life support system and how it works. They told me they could not sell me medical grade oxygen with out a prescription from a doctor which I thought was kind of weird. They said I might be able to use oxygen that you use for welding, but it is not as pure. Does anyone on psubs have any ideas on what to do?
Also I had asked a question a while back about the tubing in the K-350. I have decided to go with stainless steal, but was still wondering what wall thickness to go with and how do you connect them (flair fitting, compression fitting, or something else?)
Thanks,
Scott Waters
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