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Dynamic o ring seals

  1. Aug 5, 2009 #1
    Is it a huge daunting engineering task to create a very large dynamic o ring water seal (sliding up and down a shaft with ring on a mating surface) say about 50 or 100 meters in diamter? Would it be a good idea to make the ring and moving part a cube like shape so as to have a square seal (versus round ring seal) to make it easier to manufacture?

    It would be used in the sea down as far as say 200 to 300 meters so the water pressure would be around 3000 Kpa. It would be slightly acceptable for a little bit of water (lubricator) to enter past the seal and mating surface (no hard to internal object)
     
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  3. Aug 6, 2009 #2

    FredGarvin

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    Dynamic o-ring seals are very well understood. I see no reason to not use a standard o-ring design unless the speed or pressure are faster than a o-ring can handle. The challenge in a seal that size will definitely be the manufacture. That's a big gland to machine. I can't say I know of how it can be done in a single operation. This would definitely be a custom application that would require someone who works in the sealing industry to look at. I highly doubt you could just make a gland and then stick an o-ring in there for something that large.

    Is this a reciprocating or rotary seal?
     
  4. Aug 6, 2009 #3
    The pressure is about at about 100 or 200 meteres max and the speed is quite slow. The seal would be reciprocating (up and down on a mating surface). Would water be lubricating enough?
     
  5. Aug 6, 2009 #4
    Wow. What does the lathe for making the O ring groove look like? My major concern with a round O ring is its tendency to roll in the groove as the shaft moves up and down, especially if the 100-m diameter shaft surface is not well lubricated. A square seal in a square groove in my opinion would have less of a tendency to roll. But a square ring does not have as good a compression compliance for tolerance in the shaft diameter variations as does a round O ring. Perhaps you should look into the O ring composition; teflon vs. viton etc. for its suitability for water lubrication.
     
  6. Aug 6, 2009 #5

    FredGarvin

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    Water at slow speeds should be fine. The issue of rolling is accounted for in the gland design as well as the possibility of using back up rings.

    At that size, the "lathe" would have to be some kind of autonomous robot that traveled the circumference making the cuts.

    There's no doubt a seal that size would be a challenge.
     
  7. Aug 8, 2009 #6
    so as long as the speed at which the mating surface slids is slow, the object can slid back and forth with no significant effect on friction and still keep the water out at a depth of 200 to 300 meters?
     
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