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O-ring Query

  1. Jan 19, 2012 #1
    Hi guys

    I have a general query regarding Rubber O-rings.

    For an application , say seal between 2 mating flanges of pipes ,with water pressure say about 10bars,

    How exactly does the hardness of rubber effect the the sealing?

    Is there a direct relation between hardness & strength ?

    Can some one give me equations for the stress in O-rings when in compression?

    A decent link would help, I have looked through stuff online , but still haven't found what I was looking for .

    And how over tightening of the bolts on Flanges would effect the O-ring
  2. jcsd
  3. Jan 19, 2012 #2
    Get a catalogue for Orings.

    James Walker
    busak + shamban


    Look for your pressure, look for the environment. It even shows you how to design the grooves that it sits in.

    Hardness and strength are kind of related, but also not. Rubbers are odd like that. I realise this isn't a massively helpful answer, but the exact chemistry used to make the polymers means properties can be tailored.

    O-rings sit in grooves, designed to give a certain operating compression. A correctly designed groove means that overtightening shouldnt affect the sealing at all. If you are overtighening to the point of the flanges (or whatever) deforming, then obviously there will be a sealign issue.
  4. Jan 19, 2012 #3


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    Gold Member

    RDK89, During over 20 years experience with sonar systems I dealt with lots of "O" rings. xxChrisxx above is exactly correct...contact the manufacturer. They will answer all your questions. One tip: learn the recommended torque to apply and NEVER overtighten!
  5. Jan 20, 2012 #4
    Thanks guys.........I have found design Handbooks on O-rings...........and now I understand why such a simple thing is a bit complicated to design
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