Differences in steel 72's

[CapeFearDiveGal]

I found a fella here who is getting rid of about 15 lp 72's. I've been wanting some for some time to build a couple of doubles sets and perhaps an 02 bottle. I've heard that I need to stay away from the 1/2 inch 72's and get only the 3/4 inch 72's. Is there any way to tell the difference between them with out taking off the valve?

Or maybe I should take off the valve anyway to look inside these tanks. I don't think thay have been dived for some time.

 

[FredT]

BTW if going for an O2 bottle those are the ones your WANT, not the ones to avoid.

If you want it for holding diving air the 3/4-14 SPM threads currently in use are the ones you want.

O2 valves are NOT available in 3/4-14 thread flavor.
O2 valves in 1/2"NGT are available in both CGA 870 (medical post) and CGA 540 (medical and industrial bulk low pressure) for under $20 each.

Vis any tank you get, avoid most internally coated ones. Especially avoid a light blue coating.

FT

 

[100days-a-year]

What he said and avoid tapered valves unless you have access to a machine shop to mill any replacements.I have 72s with hydros back to 1960 and they make great stages.Several members here have them as lightweight doubles.

 

[pescador775]

The necks on the old 1/2 inch pipe thread tanks are smaller than those on the modern O ring type tank neck. Only get one of the 1/2 inch type if you plan on using it for surface use where you might be attaching an oxygen regulator and mask. As was said, some oxygen type valves can screw into the 1/2" threaded neck. It requires a chain vise to clamp the tank for valve installation and so also is not as convenient to inspect. Don't get me wrong, these old tanks are also used with old style SCUBA valves but I would recommend the more convenient large neck type for scuba use. No special tools required for valve installation but a special O ring required for oxygen as well as special cleaning.

Try to find out which, if any, have internal paint jobs. That stuff is a pain and shouldn't be used with oxygen or air. Fortunately, the 1/2 inch type are not coated. The caveat applies to the large neck tank for the above and because the coating traps rust and cannot be easily repaired by tumbling, etc.

Only get galvanized tanks. The yellow ones which are paint over steel are prone to exterior rust, a real head ache.