RE: [PSUBS-MAILIST] Double O-Ring On A Hatch

[Brent Hartwig <brenthartwig@hotmail.com>]

Thank you Dan, 
 
I'll put that data in my shaft seal archive for reference. For static sealing O-rings, like in a hatch, I wouldn't expect any real trouble from pressure build up between two or more O-rings, unless all the back-up seals fail as well. I think I would like to have two or more good quality seals then just one. 
 
I'll be some times taking my pet goldfish down with me, and he's like family. ; )'

Regards,
Brent Hartwig

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From: jumachine@comcast.net
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Double O-Ring On A Hatch
Date: Thu, 9 Aug 2007 07:51:50 -0400

Brent,

 

Double O-rings in a design can sometimes actually be a problem.  It's possible to get pressurized fluid, or gas, trapped between the two O rings.  Especially in high pressure dynamic sealing situations, it's always best to use a single good seal rather then two Ok ones.  If one seal weeps and pressure gets trapped between the two seals, it binds the other wise free moving shaft even when the external pressure is removed.

 

In a sub the pressures aren't high and the added safety is a plus, so their commonly used for shafts.

 

Dan H.

----- Original Message -----

From: Cliff Redus

To: personal_submersibles@psubs.org

Sent: Wednesday, August 08, 2007 10:39 PM

Subject: Re: [PSUBS-MAILIST] Double O-Ring On A Hatch

Brent,

 

 

I concur with Vance, Carsten and Peter ..., a single o-ring witht the correct hardness is the way to go.  See technical note http://www.satoriseal.com/Technical/introduction_to_o-rings.htm on how o-ring is design to move within it's machined grove under pressure to seal.  Hatch upper and lower faces need land face to face.    If you are designing a hatch, pick a standard size so that you do not have to introduce a splice.

 

Cliff
 

Great works are performed not by strength but by perseverance.
Samuel Johnson

----- Original Message ----
From: Brent Hartwig <brenthartwig@hotmail.com>
To: PSUBSorg <personal_submersibles@psubs.org>
Sent: Tuesday, August 7, 2007 11:31:47 PM
Subject: [PSUBS-MAILIST] Double O-Ring On A Hatch

 
I finally found a double o-ring on a sub hatch. The sub on ebay right now called the Great Lake's Submarine mentioned earlier, has one. Here is the picture.
 
http://www.frappr.com/?a=viewphoto&id=4001713&pid=7375620

Regards,
Brent Hartwig