[PSUBS-MAILIST] O-ring Question

[Alan via Personal_Submersibles]

Thanks Dan,
just read through 170 pages of the Parker O-ring handbook &
couldn't find that information.
That makes sense. I can go for a coffee in peace now!
Alan

Sent from my iPad

> On 6/02/2017, at 4:14 PM, Dan Hryhorcoff via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 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
> 
> 
> 
> 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
> 
> 
> 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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