Was given a "working air" tank... can I convert to SCUBA?

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It looks to me that this is just a standard AL 80.

IMO, It probably has the standard scuba thread (3/4" NPSM) just because it is a lot easier and less expensive to produce a valve that fit a standard scuba cylinder than it is to have a custom tank for a limited application.

Most of the industrial gas cylinders are steel, and AFAIK they all tend to use tapered neck threads.

Aluminum cylinders in the US are not allowed to use tapered neck threads so most of the ones that I have seen, AFAIK use either 3/4" NPSM or 1/2"NPSM.

Aluminum cylinders are used for portable O2 medical and for SCBA (fire fighting, mining, HAZMAT, etc.). I think those tend to use the 1/2"NPSM threads (similar to the old Sportsways or White Stag scuba valves), but I am not positive about all of them.

The new composite very high pressure (4500psi) SCBA cylinders probably use the 7/8”UNF neck threads to make sure they can’t use the older valves, but this is just a guess.

The 7/8” UNF thread is a relatively new neck thread that was introduced for very high pressure cylinders so that older valves cannot be installed in high pressure cylinders.



None of the pictures show the actual neck of the cylinder. Sometimes you can tell from the outside, by the size of the neck, what type of threads it probably has. There is no guaranties by just looking at the neck, but the sizes are so different that it is sometime obvious.

A picture of the neck may show if it is just a standard scuba AL 80 that was just re-purposed. Everything about it looks like it is.


BTW, that is a cool sticker. I wish scuba cylinders were provided with that much information.
 
CGA 346 only refers to the outlet connection of the current valve that is screwed onto the tank. The tank is still a luxfer s80 with standard 3/4 NPS threads. you can put any modern 3/4 threaded valve onto it. you may want to pop the current valve off and take a look inside first though. if it has been filled with a shop compressor, there may be residue you will want to rinse out with some simple green. else the LDS will charge you for cleaning.

I would recommend a convertible pro valve if you are buying a new one though as they don't cost much more than a yoke only valve. you can get a new one off ebay for 30 dollars. or see if DGX puts the thermo valves on clearance again.
 
Drain the air and take the valve out, check the threads if scuba they should be 3/4 NPS
 
Luxfer makes 80's with either 0.750-14 NPSM, or M25 x 2.0. Could not find any reference to an industrial type valve that would fit a Luxfer 80 so whoever has the tank may have jury rigged a valve on it.


http://www.rmiorder.com/pdf/34A-16.pdf
 
It looks like the first hydro was 6-97, well after the discontinuation of the 6351 alloy. However, you still might find a dive shop that won't fill it due to it's age. There is no reason for this other than ignorance.
 
https://www.shearwater.com/products/peregrine/

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