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Thread: Cyro Valve Question

  1. #1
    Associate Engineer
    Join Date
    Feb 2014

    Cyro Valve Question

    Hello. I was just curious... Anyone have an idea of what might happen if liquid Nitrogen or Oxygen was ran trough a standard water ball valve? I would it would leak due to the shrinking of the metals, and probably be more difficult to turn... but any ideas?

  2. #2
    Lead Engineer
    Join Date
    Aug 2013
    Houston TX USA
    It would depend upon the materials of construction but the main issue would be the seat and stem seals. Any seal materials other than either teflon or PEEK will harden and shrink creating both seat and stem seal leakages.
    With the metals, then the selection of the body vs the ball materials would be the key. For example, a brass body, ball and stem assembly is acceptable, within the brasses cryogenic stress limits, since they will all have the same thermal contration; however, if a brass body is mixed with a SST316 ball and/or stem then the differential thermal contractions between the brass and SST would probably result in binding between the body and internals.

    Either way, the simple answer is that such a application of a standard water ball valve is definitely not a good idea.

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