What do you guys know about CO2 tanks?

[elmer fudd]

I know they're rated at 1800 psi and folks used to use them for scuba back in the day. Why not now?

This link has 5 lb, (5" diameter X 17" tall), steel bottles for $50 each. The 10 lb. steel bottles measure 6"X22" and go for $55 each.
5 pound steel CO2 tank - Gehm & Sons, Inc.

That sounds to me like something that could be used to make an affordable set of triples. Is there a problem with the valve size on them or getting fills or what?

 

[Luis H]

I am not sure of the neck size, but since they are tapered pipe thread, you should be able to use a bushing to the 1/2" tapered type of valve (if they are not already 1/2" NPT).
That may or may not be a problem with your LDS. It is not a problem from the DOT or CGA stand point, but many LDS (lacking knowledge) make there own rules.

One issue is that they are not going to be galvanized. That in itself is basically a deal breaker for me since I dive a lot in salt water.

Another issue they could have is internal pitting if they ever had any moisture inside.

In the 70’s I worked in a dive shop with our own hydro station and we did hydros for other gas industries. I saw a lot of CO2 tanks with a lot of pits in the bottom. We condemned a lot, but I think the CO2 industry is a bit more tolerant to some pitting. They have to meet the same CGA steel tank inspection standards, but there is a bit of judgment call when measuring pit size at the bottom of a tank.

I am not a chemist, but my understanding is that CO2 and moisture will create carbonic acid. This is what will cause the pitting with just minimal amount of moisture. Completely emptying a gas tank is not uncommon on other industries like it is in Scuba, therefore small amounts of moisture can find there way into an empty CO2 tank much easier than into a tank with some air pressure in it.


Good luck

 

[oldmossback]

Those 22 x 6 inch tanks look interesting.....my 38's are about 20 inches tall without the manifold............these are close to the old 72 height, but not quite......

Anyway, I did a quick calculation and each bottle is about 198 inches vol r2xpixL......how one converts that to cu ft is beyond my limited math skills...........

But I'd say you could make a nice set of double 50's or 55's with these.......

If I remember correctly, ScubaPro came out with a set of twins that were about the size of the other 17 inch tank.............way back in the late 60's

Oldmossback

 

[elmer fudd]

Those 22 x 6 inch tanks look interesting.....my 38's are about 20 inches tall without the manifold............these are close to the old 72 height, but not quite......

Anyway, I did a quick calculation and each bottle is about 198 inches vol r2xpixL......how one converts that to cu ft is beyond my limited math skills...........

But I'd say you could make a nice set of double 50's or 55's with these.......

If I remember correctly, ScubaPro came out with a set of twins that were about the size of the other 17 inch tank.............way back in the late 60's

Oldmossback

I'm not exactly sure on the volume myself. I've got an aluminum 20 lb CO2 tank that I use for bulk filling airguns and it's about the same size as an AL80. Since it's only rated to 1800 though, I suspect that the walls are thinner and it's interior volume is larger. So I'm guessing those 10 lb. bottles would be about the same as 38's.

I'd personally be more interested in rigging them up as triples. Vintage doubles still seem to be fairly common and affordable, but triples are like hen's teeth and even making a modern set out of AL30's or AL40's is going to be a pricey venture.

 

[Akimbo]

I had three sets of them in the 60s. We had to use NPT bushings… 1 or 1¼" to ½" I think. The problem now is getting a manifold and the bands to fit for less than just buying a new single ~80. They are comfortable and not very heavy. I think they were 38 Ft³ each.

Here is an old photo with some behind the triple 72s:

 

[Scared Silly]

I like those cylinders cause they are easy to handle and transport. The are also great for mix. I can always get a good fill. I prefer a 30/70 mix. I typically run a single reg although on my 10 pounder I run a dual reg each having a splitter. That keeps everything flow smoothly. We are talking beer aren't we???

 

[elmer fudd]

I like those cylinders cause they are easy to handle and transport. The are also great for mix. I can always get a good fill. I prefer a 30/70 mix. I typically run a single reg although on my 10 pounder I run a dual reg each having a splitter. That keeps everything flow smoothly. We are talking beer aren't we???

Beer and diving are a natural combination just like beer and explosives. Alcohol's just an all around fun multiplier!

Since you appear to have at least one cylinder, do you have any idea what kind of thread they use on the necks?

 

[captain]

Beer and diving are a natural combination just like beer and explosives. Alcohol's just an all around fun multiplier!

Since you appear to have at least one cylinder, do you have any idea what kind of thread they use on the necks?

Usually 1" NPT on steel cylinders.

 

[adriano210]

guys some of 8liters alu co2 cylinders have a m25 thread, we have 30 of them at work