Question 1950s WK Twinset and Navy Double Hose

[n1023]

Just wanted to share these tanks I just picked up. Had to use some paint remover to uncover these markings. Looks like they’re LP50s, never seen 1800psi service pressure that’s cool. Walter kidde is the manufacturer based on stamp and logo. US govt stamp, maybe old army tanks (guessing based on base green paint). Speaking of paint, look at all those layers! Non shatterable is an interesting stamp too. Banded with AMF Voit Snugpack and US Divers manifold. They were full of air, though it smelled pretty bad kinda like old paint. Hoping a tumble and hydro is all they need but I picked them up for $60 so not a terrible deal for decoration.

I’m hoping to throw on this double hose setup I also picked up. Parts already on the way from the scuba museum. Picked it up for $50 so again, won’t be disappointed if it’s just decoration.

Now for the questions. Anyone know where I can find a backplate that will fit these tanks? I have little experience with twin manifolds (especially vintage ones), are there parts available for this one?

Thanks

 

[Scuba Lawyer]

Great find!

I didn't see a date on the tanks but looks like 3/4" o-ring sealed neck. The valve is dated 1958. I've never seen 1800 psi LP 50's. They look like 38's (42's at 10% overpressure). Not many parts in those valves (especially with no J-valve) and those parts are standard valve innards easily obtainable. Given the Govt. markings they could be repurposed 38's that were used on the deck of aircraft carriers to pneumatically deploy/retract the arrestor cables across the flight deck. But who knows. I have a set of those. As for a backpack, if you can find an old VDH backplate that would be best. Many of us made our own DH backplates by cutting down acrylic kitchen cutting boards. The Voit Navy reg is identical on the inside to a USD AquaMaster so as you know parts are easy to find. My 2psi. Good luck! Looks like a fun project. M

 

[Luis H]

They are 1" tapered pipe thread with a bushing.
A lot of dive shops think that the use of a bushing is not legal, but that is incorrect. The bushing has to be removed to perform the hydro test, it is perfectly legal and safe to use the bushing. The bushing has to be rated for the pressure, but those bushings look like the stainless.

You should be able to find a good dive shop in your area that can deal with this set-up.


Based on the green paint and the pressure, I say they were oxygen cylinders. They could have been aviation.

The original hydro date is probably on the other side.

 

[Scuba Lawyer]

Luis is correct about the tapered pipe thread with bushings. My old eyes failed to see that is what they were especially with that manifold. I also concur that the green likely signifies former use as an oxygen tank. Luis is far more up on these things than I am.

 

[n1023]

Great find!

I didn't see a date on the tanks but looks like 3/4" o-ring sealed neck. The valve is dated 1958. I've never seen 1800 psi LP 50's. They look like 38's (42's at 10% overpressure). Not many parts in those valves (especially with no J-valve) and those parts are standard valve innards easily obtainable. Given the Govt. markings they could be repurposed 38's that were used on the deck of aircraft carriers to pneumatically deploy/retract the arrestor cables across the flight deck. But who knows. I have a set of those. As for a backpack, if you can find an old VDH backplate that would be best. Many of us made our own DH backplates by cutting down acrylic kitchen cutting boards. The Voit Navy reg is identical on the inside to a USD AquaMaster so as you know parts are easy to find. My 2psi. Good luck! Looks like a fun project. M

Ah 38s makes sense, they’re pretty light. Man I’d love to know what they were actually used for. Guess they repurposed just about anything in those days haha. Essentially the same as having an 80 but way cooler

Here’s the hydro markings, by far the oldest tanks I own now.

 

[Luis H]

I have a very strong suspicion that they are oxygen tanks. I have hydro tested and converted a few of them back in the 70's when I worked at my LDS (we had a hydro station).

One of the issues with them being so light is that they tend to float.

BTW, I can't read the original date. It is probably above the 2-70+ re-qualification date. The oldest re-qualification date I can make out is the 2-52, but the actual original date is probably from the 40's, maybe the early 40's.

 

[Luis H]

The pictures below are from a different size cylinder, but I think is a similar application.

Notice that the middle of this cylinder is tightly wrapped with a wire for protection.

The cylinders, the same size as yours, that we tested had a similar wire wound protection. We had to remove all the wire before hydro testing, it was a mess.

I tried doing a Google search, to try to find your size cylinder with this wire winding, but no luck.

 

[n1023]

1940s wow, so they might be WWI or WWII O2 tanks. Super cool. I don’t see any evidence of wire wrapping but there’s also like 5 layers of paint over everything. I’m dropping them off for hydro today at Spectrum Gas Products in Anaheim. They’ve been pretty knowledgeable about old tanks I’ve brought them in the past. We’ll see!

 

[Luis H]

They are 3AA which is the code for chrome molybdenum steel. I don't know the exact dates when chrome moly steel was introduced to ICC pressure vessels, but I think it was during WWII. They could not be WWI.

Older tanks were typically stamped 3A which is the code for carbon steel cylinders.

The regulatory agency was the Interstate Commerce Commission or ICC (as stamped on the cylinder). The ICC is the predecessor to the DOT (Department of Transportation). The documents covering the material alloys and technical cylinder specifications are the CFR (Codes of Federal Regulations). You can search and download them on line. Make sure to have a lot of coffee on hand if you want to start reading them.

You may notice the + stamp next to the 2/70 + re-qualification date. The plus ( + ) was introduced during WWII to allow the filling and transportation of 10% extra pressure gas in portable cylinders. That was a big material and cost savings during the war effort, to be able to transport an extra 10% in the same container (pressure vessel). After the war the regulations stayed unchanged.

In order to qualify for the + stamp (and the extra 10% pressure) the original hydro date has to contain the + stamp next to it. And it can be re-qualified and re-stamped with the + during any of the later hydro test.

The hydro test procedure (and test pressure) is the same. the only difference is the criteria used for passing. The typical hydro qualification (for a 3AA) cylinder uses as failing criteria that the plastic (or permanent) deformation has to be greater than 10% of the total elastic deformation. I am sure this requires a lot more explanation, but it can all be found in the CFR and there are many videos on line (some of them are accurate ).

The pass/ fail criteria for the hydro test doesn't change, but to qualify for the + stamp, the total elastic expansion has to be less then the REE (Reject-able Elastic Expansion) number for that cylinder type/ design. The REE number for older cylinders is hard or impossible to find, but it can be calculated with some data and measurements from the cylinder. I have measured and calculated REE numbers for most of my old steel cylinders, but it is not something that the casual observer would care to do...


This is probably more information than most people cared for (and more than many dive shops and even some hydro stations are aware of), but it is all in the CFR and CGA (Compress Gas Association) manuals. Just be aware that there is a lot of wrong information shared in the scuba industry. If you have any question, you can go to the source.

 

[Still Kicking]

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