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Would any modern burst disk fit the USD J central outlet manifold circa 1954-59

Discussion in 'Vintage Equipment Diving' started by elan, Apr 15, 2012.

  1. elan

    elan DIR Practitioner

    # of Dives: 200 - 499
    Location: Toronto, Ontario, Canada
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    I have a set of LP72s with that manifold and the gentleman I bought it from still used the lead plugs., which are not to be used on breathable gas. Would any modern multiport burst disk fit that manifold ? I remember someone here was mentioning that they need to be replaced but I cannot find any details.

    Thank in advance.
     
  2. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
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    Those are most likely the 3/8 burst disc. You can find replacements here:
    Shop Online

    They are very common.

    The issue with the lead plug is not related to the breathing gas. The issue is that when they let go, the plug becomes a bullet.
     
    elan likes this.
  3. elan

    elan DIR Practitioner

    # of Dives: 200 - 499
    Location: Toronto, Ontario, Canada
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    Thanks Luis.

    I unscrewed the plug and the guys have actually installed a copper burst disk underneath already.

    Unfortunately I had to condemn the cylinders :( as the internals were in an awful conditions, extensive rust with deep pits, some of them still seemed to have wet like areas around them. It looked like the water was constantly introduced into the cylinders over their whole life :)

    On one cylinder the 3,4 and 5 threads had about 1/3 damaged , on the other it was better but still a thread was damaged. :( But oh well. I will still keep the manifold and the bands.
     
  4. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
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    That is too bad about the cylinders.

    The copper disc below the lead plug is the way that it was supposed to be. Or at least that is the way I always found them. The entire assembly need to be replaced with the modern burst disc.
     
  5. captain

    captain Captain

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    The lead plug may have been an attempt to prevent salt water from reaching and corroding the burst disc. I can't see any other reason. I don't think it would hold 2500 psi on its own.
    I fill the burst disc retainer with silicone grease as a way to prevent corrosion of the disc.
     
    elan likes this.
  6. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
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    The story I always heard was that the lead was supposed to melt at low temperature in the case of a fire and allowed the copper burst disc to let go at a much lower pressure.

    At least in theory the design made sense, but as we know in practical terms it didn’t work very well. I have seen more than one lead plug (in service) that was partially sticking out. It is fairly scary to think about the possible outcome if it let go at the wrong time.

    Back in the 70’s I replaced many of these plugs.
     

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