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Sealed rotating rod.

  1. Jun 28, 2009 #1
    Imagine a solid rod passing through a cylinder filled with a fluid at certain pressure -


    The yellow part inside in the fluid, the cylinder has been made transparent for ease.

    To make the fluid not leak, the sealing of the rod and cylinder should be completely sealed...this has been done, but rod cannot be rotated in this situation independent of the cylinder.

    If it has to be rotated, there should be a friction lining on the sealing which will allow the rod to rotate yet maintain the sealing; but this way is inefficient, i.e since there's friction, there will be a resistance to the rotation of the rod and the sealing with degrade with time as the rod continues to rotate.

    So is there any efficient way known to do the same as above; for example with bearing so as to reduce friction?

    Attached Files:

  2. jcsd
  3. Jun 29, 2009 #2


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    Lip seals offer very little resistance since they require being lubricated by the fluid you are sealing. I would suggest looking into them.
  4. Jun 29, 2009 #3
    Too bad we don't have a wiki article on that.

    I'll have a look.

    But it's not that much of fool proof right...I mean if the pressure is too high, like in a compressor, it's resistance will too increase.
  5. Jun 30, 2009 #4


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    Can you specify the requirements the seal will have to operate under? I have used lip seals under a lot of different applications.

    You could also look at a dynamic o-ring seal.
  6. Jun 30, 2009 #5
    Some high vacuum applications for rotating feedthroughs use a ferrofluidic seal. See
    Other solutions use dual seals on each end with a pumpout between them.
  7. Jul 3, 2009 #6
    For instance replacement of a centrifugal pump with a 'fan based' pump...just one small example.
  8. Jul 3, 2009 #7
    That ferrotec one, but it works only a magnetic fluid right?

    Can I get a bit more detail about that pumpout technique?
  9. Jul 3, 2009 #8


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    I meant in terms of pressure difference across the seal and shaft RPM.
  10. Jul 3, 2009 #9
    Any variation.

    Similar to what is in a compressor.
  11. Jul 3, 2009 #10
    So the RPM will be very high.
  12. Jul 6, 2009 #11
    'O' Rings inside the cylinder of adequate material would work.

    Last edited by a moderator: Aug 8, 2009
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