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10 cu ft O2 tank used as Pony Bottle

Discussion in 'Tanks, Valves and Bands' started by scubasteve65, Mar 18, 2009.

  1. scubasteve65

    scubasteve65 Angel Fish

    # of Dives: 200 - 499
    Location: Long Beach, New York
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    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?
     
  2. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
    2,881
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    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
     
  3. scubasteve65

    scubasteve65 Angel Fish

    # of Dives: 200 - 499
    Location: Long Beach, New York
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    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?
     
  4. captain

    captain Captain

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    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.
     
  5. WD8CDH

    WD8CDH Solo Diver

    753
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    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.
     
  6. pescador775

    pescador775 Loggerhead Turtle

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    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.
     
  7. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
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    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.
     
  8. Scared Silly

    Scared Silly Regular of the Pub

    # of Dives: 500 - 999
    Location: on the path to perdition
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    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.
     
  9. cwkline

    cwkline Divemaster

    # of Dives: 200 - 499
    Location: Kailua, HI
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    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.
     
  10. scubasteve65

    scubasteve65 Angel Fish

    # of Dives: 200 - 499
    Location: Long Beach, New York
    28
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    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.
     

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