[PSUBS-MAILIST] Conning tower hatch O-Ring

[Sean T. Stevenson via Personal_Submersibles]

With regard to O-ring sizing, be aware that an O-ring / groove pair is typically designed for a specific limited amount of compression in service, such that the O-ring meets its design fatigue life and tolerance to compression set. Using an O-ring which is larger in cross-section so that it doesn't fall out of an ordinary rectangular groove may, in service, deform the O-ring beyond its elastic deformation limit. So-called "crush" installations are perfectly valid, and are used often in static seals, but any increased compression set as a result of such a design must be accommodated by more stringent maintenance and O-ring changes.

The Parker O-ring Handbook is an excellent design resource, and includes information about typical O-ring failure modes.

Sean


On October 19, 2014 9:38:49 PM MDT, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Hi Mark,
>I have heard of people with the square grove having trouble with the
>O-ring falling out, & having
>to stick them in with copious amounts of grease. That could be a sizing
>issue though.
>I think it's a 1/2 dove tail grove they have on the K boats with the
>angled edge to the outside so that
>the O-ring is squashed by external pressure against the flat side of
>the grove.
>(someone correct me if I'm wrong)
>I vaguely remember Phil saying the Deep Workers have the 1/2 dove tail
>grove.
>Alan
>
>
>
>
>
>________________________________
> From: via Personal_Submersibles <personal_submersibles at psubs.org>
>To: personal_submersibles at psubs.org 
>Sent: Monday, October 20, 2014 1:03 PM
>Subject: [PSUBS-MAILIST] Conning tower hatch O-Ring
> 
>
>Hello Psubs group,
>
>I would like to ask the group where I can purchase an O-Ring for a 24"
>conning tower hatch ring.  I also need to mill the slot in the hatch
>ring and would like to know the width and depth of the slot.  I've
>heard some folks recommend a dove tail slot for the O-ring. 
>
>Many thanks for your advise.
>
>Mark...
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