10 cu ft O2 tank used as Pony Bottle

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scubasteve65

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Messages
28
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2
Location
Long Beach, New York
# of dives
200 - 499
A friend has a box of new O2 bottles. About 8 to 10cu ft in size and rated to at least 2000psi (can't recall exactly). They have a 1/2" thread. I am interested in converting one or more to a pony bottle. What valve can be used?
 
If it is an old tapered 1/2 pipe thread neck, you can find an old post valve. Converting old O2 tanks was commonly done at one time.

If it is a straight thread modern style O2 cylinder, you are probably out of luck unless you have the threads on a valve machined down to the correct size.

Good luck
 
These are modern straight thread O2 tanks. He has quite a few and I was hoping to make use of them. I recall reading on this forum or elsewhere about cutting new threads into a 3/4" valve. Does anyone know if this is safe? costly? Anyone know where to get it done?
 
It is safe, any machine shop should be able to do it but it won't be cheap. Shop rates can run between $50 to $100 an hour with an hour as the minimum.
 
The neck thread is most likely 0.750-16 UNF-2B. Are they aluminum or steel? What is their length and diameter? I can probably get you specs from that.
 
There are some antique valves which are threaded 1/2 NPS. These would have been sold by Sportsways and White Stag. However, the actual thread must be verified before shopping.

http://cgi.ebay.com/Sportsways-Vint...ryZ74003QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Machining the 3/4 valve to 1/2 is not difficult but it will be a lot cheaper per valve if several identical valves are in the job order. The biggest cost is setting up the work. That involves shimming, a sort of hit and miss. I suggest requesting an estimate for six Sherwood 5000 valves. Each must be disassembled. I also recommend handing over a valve which is known to fit the oxygen tank.
 
You could probably buy a 2015psi al14 for less than the cost of machining these valves.
8-10cf (and even 14cf) is a dinky sized pony bottle. 19 or 30cf is more realistic.
 
These bottles sound better suited to being used for an argon inflation system than a bail out bottle. And as said the cost of machining a valve would probably out weigh the cost of buying a new bottle and valve.
 
If the cost is right why don't you take a bottle, pick up a reg and mask/cannula rig and have your very own emergency oxygen supply. Just a thought.
 
Thanks for all the input. My idea is sounding futile. The reasons I was interested in attempting this are threefold. (Not is any particular order) The bottles are free. I like DIY/Customizing my rig. (Don't start yelling at me, I just wanted to know about valve threads remember) I solo dive off a kayak and wanted a smaller pony bottle. I am at depths were a free swimming ascent is not out of the question, but a nice compact redundant system (other than a spare air) would make life easier getting on/off a kayak.
 
https://www.shearwater.com/products/swift/

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