[PSUBS-MAILIST] O-ring Question

[Dan Hryhorcoff via Personal_Submersibles]

Alan

Don’t worry about stretch or no stretch.  What’s more important is the squeeze of the O-ring and the clearance between your two mating parts.  

As long as you get 15-20 % squeeze of the O-ring when assembled and the gap between the two parts your sealing isn’t so great that the pressure your operating at isn’t going to allow the O-ring to be extruded out, you’ll be fine.  

Normally, for an external O-ring groove the O-ring is stretched on with a bit of stretch when its in it’s groove and when an O-ring is used in an internal groove application, as yours is, it’s actually a little bit larger then the groove when it’s inserted in place to help it stays there while the mating part is inserted.  

For your application forget about stretch.  Use a ring that’s to size if it stays in place good, or one size larger if you have a problem getting the lens in place without pinching the O-ring.

Dan H.

From: Alan James via Personal_Submersibles 
Sent: Sunday, February 05, 2017 9:13 PM
To: Personal Submersibles General Discussion 
Subject: Re: [PSUBS-MAILIST] O-ring Question

Thanks Hank,
I have 4 O-rings in my light design & had gone through the calculations
before designing. However one of these O-rings is in the bore groove  & I'm
having a re-think about this one, but can't find any specific advice for
this application.
Alan






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From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Monday, February 6, 2017 2:59 PM
Subject: Re: [PSUBS-MAILIST] O-ring Question


Alan,
If your glass is say 2 inces diameter then use a 2 inch o-ring with a groove design from the o-ring groove chart.  You will also find a spec for the clearance between the glass and housing.



On Sunday, February 5, 2017 6:52 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:




Hi Sean,
yes had a quick look through that, along with other material.
Spent a couple of hours & still haven't come up with an answer to
what seemed a simple question!
Maybe I'll have to read through it slowly!
Cheers Alan




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From: Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Monday, February 6, 2017 2:39 PM
Subject: Re: [PSUBS-MAILIST] O-ring Question


Alan, do you have a copy of the Parker O-ring handbook? Best free resource out there for designing O-ring seals. ORD5700.pdf  Download it from the Parker website.
Sean




On February 5, 2017 6:32:51 PM MST, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote: 
  Hi,
  am having trouble Googling an answer to this question.
     I have an O-ring groove in the bore of my light housing, sealing
  between the bore & the side of my acrylic lens as per attached diagram.
  On a piston O-ring groove it calls for an optimal 2% stretch & not more than 5%.
  I can't find any reference to what stretch if any should be, if any, for an o-ring
  in a bore groove. I did see that in a! rotary application they don't advice that
  their should be any pressure on the rotating rod.
  Should I be designing so that the o-ring will have a 2% stretch around the lens?
  Thanks, Alan

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