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Thread: Burst disks

  1. #1

    Default Burst disks

    Where do you get yours? What burst pressures?

    Thanks in advance,

    Tim

    Why yes that was me in shorts and a t-shirt @ the 700' marker

  2. #2

    Default

    Is this you starting stuff like you said on FB, Tim?


    Safe diving,


    Rich

    Education, enjoyment and exploration.....
    http://divecaves.com
    https://www.facebook.com/divecaves

  3. #3

    Default

    I get mine from John at Northeast Scuba.
    Of note. Burst discs are technically supposed to be 90% of test pressure.
    AL80's ~4500psi
    3442/3500psi ~4650
    3aa 2400+ bottles ~3600

    I put the same ~4500psi burst discs in everything though I have been slowly switching over to blanking plugs as they've needed them


  4. #4

    Default

    Quote Originally Posted by tbone1004 View Post
    I get mine from John at Northeast Scuba.
    Of note. Burst discs are technically supposed to be 90% of test pressure.
    AL80's ~4500psi
    3442/3500psi ~4650
    3aa 2400+ bottles ~3600

    I put the same ~4500psi burst discs in everything though I have been slowly switching over to blanking plugs as they've needed them
    I'm afraid that isn't completely accurate. The 90% rule is for DOT 3HT cylinders. 3AA or 3AL are 100% of test pressure with a tolerance of 0 psi over and 10% under.

    https://www.law.cornell.edu/cfr/text/49/173.302

    I use 5250 burst discs everywhere also. I wouldn't even know where to find a 4500 psi burst disc.


  5. #5

    Default

    Quote Originally Posted by chrpai View Post
    I'm afraid that isn't completely accurate. The 90% rule is for DOT 3HT cylinders. 3AA or 3AL are 100% of test pressure with a tolerance of 0 psi over and 10% under.

    https://www.law.cornell.edu/cfr/text/49/173.302

    I use 5250 burst discs everywhere also. I wouldn't even know where to find a 4500 psi burst disc.
    plus 0 to minus 10% is still 90% of test pressure, the 3hl's are 90% minus 10%.

    They are spec'd at 5250, but I ran a couple of them up one day for shits and giggles and they both blew around 4700 or so. In either instance, if you are rebuilding your own valves, just use the SS plugs. They're invisible from the outside if you have someone actually paying attention, and never have to worry about them. Couple of bucks more, but worth it imo


  6. #6
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    Default

    Dive gear express. Quick shipping and if you get some other stuff shipping is free. NE supply is good. I get things I cant get elsewhere from them, but much slower to receive.


    Sent from my iPhone using Tapatalk


  7. #7

    Default

    Quote Originally Posted by tbone1004 View Post
    plus 0 to minus 10% is still 90% of test pressure, the 3hl's are 90% minus 10%.

    They are spec'd at 5250, but I ran a couple of them up one day for shits and giggles and they both blew around 4700 or so. In either instance, if you are rebuilding your own valves, just use the SS plugs. They're invisible from the outside if you have someone actually paying attention, and never have to worry about them. Couple of bucks more, but worth it imo
    That's really not the same thing. It's similar but not the same. It's still a 5250 burst disc.

    The only burst disc I ever have blow was a 4000 psi disc on an LP95 that had about 3800 in it. Man that valve was frosty as #### when it got done. About as frosty as my wife was to me when she called me up and chewed my ass out for the "explosion" that just happened in the garage. I replaced it with a 5250 and I've had no problems since.


  8. #8

    Default

    Quote Originally Posted by chrpai View Post
    That's really not the same thing. It's similar but not the same. It's still a 5250 burst disc.

    The only burst disc I ever have blow was a 4000 psi disc on an LP95 that had about 3800 in it. Man that valve was frosty as #### when it got done. About as frosty as my wife was to me when she called me up and chewed my ass out for the "explosion" that just happened in the garage. I replaced it with a 5250 and I've had no problems since.
    Of course you can do what you want, but the burst disc did what its supposed to do. it is to protect the cyl from a catastrophic failure and blowing your home to pieces. In a fire using a disc higher than hydrotest pressure could cause it to explode.
    Bottom line is that in the US it is a federal offense to use a disc higher than the cyls hydrotest pressure.

    You can never have enough dive gear!

  9. #9

    Default

    Tim don't make me come up there!
    Hydro Dave

    You can never have enough dive gear!

  10. #10

    Default

    Quote Originally Posted by kvdivr View Post
    Of course you can do what you want, but the burst disc did what its supposed to do. it is to protect the cyl from a catastrophic failure and blowing your home to pieces. In a fire using a disc higher than hydrotest pressure could cause it to explode.
    Bottom line is that in the US it is a federal offense to use a disc higher than the cyls hydrotest pressure.
    Yes it is true that it's a violation of federal DOT regulations to use an incorrect burst disc in the tank. On the other hand the DOT only has jurisdiction over tanks used in interstate commerce.

    It's also unlikely that a cave filled 2400 psi tank with a 5000 psi burst disc (test pressure and an appropriate burst disc pressure for an AL 80) installed would rupture before either a) the burst disc still ruptured, or b) the o-ring in the neck melted or burned and released the contents of the tank. In Europe burst discs are not required as they recognize the o-ring will fail before the tank.

    After some use that 5000 psi burst disc will fail at around 4500 psi, but with 3600-3800 psi fills that is still plenty of margin, so I see no need to install 5250 psi burst discs.

    It also simplifies the logistics as almost everything (3AA 2400 psi steels and 3AL 3000 psi tanks) all get the same 5000 psi burst discs. I just need to stock 5000 psi burst discs, plus a few 3375 psi discs for my steel 72s.

    NACD Cave DPV Cert # 666: Cave DPV Anti-christ


 

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