Vintage Double Hose

These look like CO2 tanks converted to scuba? Im trying to decide if I want to spend the money on hydros. They are shorter and a bit lighter than my double 72's, but looks to only have an 1800psi rating. Which means I will only get 1500psi hot fills or 1700 if I leave it. Anyone know what size they are by my picture of the numbers?

Basically a DIY homemade SCUBA rig. Those are probably 53's. The valves are not that unusual, I have a set of old 38's set up with same valves & USD manifold, and very similar harness attachments at the tank necks. I believe the valves have standard CGA-540 attachment (normally used for Oxygen), and the USD manifold used the same standard 540. Odd that the tanks are marked for "C O Two", which would be fire extinguisher use, but have what must be Oxygen valves. I originally thought they were surplus aviation Oxygen tanks due to valves, but maybe those were changed out to make an easy adaptation to Scuba with the USD piece.

The valves are capped off, with no individual shut off installed, but same valve body was also available with the typical bonnet, stem, seat, etc.
I'll check mine to see if they are 540's, and post update if not.

Look a bit closer, they are labeled C-O-TWO FE CO which I bet means " CO2 Fire Equipment Company " so CO2 bottle would be my bet.

Herman wrote: ↑

Tue Mar 05, 2019 11:23 am

Look a bit closer, they are labeled C-O-TWO FE CO which I bet means " CO2 Fire Equipment Company " so CO2 bottle would be my bet.

Hi Herman... you must have read my initial post before I noticed those markings. I quickly edited it, and you probably missed that. Sorry I messed up the first post, which was only up for just a few minutes.

Please read my edited version where I acknowledged the "C O TWO" stamp and suggested they were for fire extinguisher use... but had Oxygen connection CGA-540 valves in them.

I checked my identical valves and confirmed they had the 540 valve connection. Otherwise the USD manifold would not have fit anyway. The 540 is typically used for Oxygen and I'm pretty sure the original valves in those tanks would have been different for the normal precaution to prevent someone from using the CO2 in place of O2. Gasp... choke...

I think I will stop buy the welding shop and see if I can exchange them for a newer O2 tanks with the same thread size and a higher psi rating. Use the o2 in my torch, have the vissed (if the lds will), and put the manifold on.

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Maybe newer co2 tanks still use that thread size.

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So I called the NLDS (not local), and asked if they pass hydro if they will fill them. The tank guy told the phone guy "it was an astounding no." I said "even they were being used for scuba back then?", to which he replied "they didnt wear seat belts back then either". So I guess using a CO2 tank is as dangerous as shooting through your windshield.

tripplec wrote: ↑

Tue Mar 05, 2019 3:42 pm

So I called the NLDS (not local), and asked if they pass hydro if they will fill them. The tank guy told the phone guy "it was an astounding no." I said "even they were being used for scuba back then?", to which he replied "they didnt wear seat belts back then either". So I guess using a CO2 tank is as dangerous as shooting through your windshield.

Yeah, don't you know that all those vintage (and therefore even more dangerous) CO2 molecules are hiding in the the internal rust pits, just waiting for some unsuspecting ignorant diver to suck them in and snuff his fire out ?

This is exactly why you need a compressor.

If stuf from the 70's and 80's was as dangerous as they teach us in the 2000's, none of you guys would have been alive to teach me how to dive.

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Its actually a pretty slick alternative to using bushings and 1/2" tapered thread manifolds. I was wondering if this was possible when I discovered that the center section of my USD manifold fit the connection on an old O2 tank. But I only had a single tank to try it on. It looked like it might position the tanks too close together... And they ARE close... But it obviously works. I was thinking the tanks would have to retain the big valve knobs but here again, they are cleverly capped off.

If I were you, I would get the tanks hydrotested. Then clean up the manifold and re-paint the tanks. They just might be beautiful and fun to dive with. I think those would be somewhere around 48 cf at 1800 psi and maybe 53 at 10% over.

I restored a set of similar tanks and posted it here: viewtopic.php?f=41&t=9070&p=73144&hilit=twin+48#p73144

Not sure what I will do with them. If I had my own compressor, I would hydro and use. For now they will just look good in my garage.