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

[irox <irox@ix.netcom.com>]

If both O-rings are the same, whatever causes the failure on the
outer ring could also cause the failure on the inner ring (and you
have two O-rings to replace instead of one).  If the inner ring
was stronger/bigger than the outer, then maybe, but what would be
the point - unless you had a leak detector fitter between the two
to let you know when the outer ring failed?

The O-ring only keeps the water out when you are near the surface.
Once the sub is at a certain depth, the water pressure will keep
the metal on metal (metal on plastic on metal if you use a gasket)
surfaces well sealed.

If things are failing before their scheduled replace period, it's
probably a good idea to inspect/over-haul the sub before using it
again (rather than having a system that allows you to continue
to operate the sub when components are knowingly or unknowningly
failing).

Ian.

-----Original Message-----
>From: Brent Hartwig <brenthartwig@hotmail.com>
>Sent: Aug 8, 2007 1:37 PM
>To: personal_submersibles@psubs.org
>Subject: RE: [PSUBS-MAILIST] Double O-Ring On A Hatch
>
>
> 
>I have no doubte that single O-Rings are successful in sub hatches, as well as numerous other applications. One item I was thinking about, was that if you have two O-Rings in your hatch flange, of the same thickness as the same hatch with a single O-Ring, wouldn't you have twice the resistance in the double O-Ring hatch in keeping the mating flanges from touching (bottoming out). Also some custom O-Rings are spliced together, and if that outer O-Ring splice fails, you would have a back-up O-Ring to protect you. If your hatches are machined correctly, and the outer O-Ring fails by extrusion or cracking from very cold or hot tempertures, old age and/or manufactures inconsistency in material or process, then the second O-Ring might work perfectly. Many subs are left out in the hot sun, which can get the steel hulls very hot. This can be hard on plastic and rubber products.
> 
>I've seen a number of double O-Ring designs used in aquarium pump connections and covers. Perhaps this is better for stopping leaks in lower pressure system, like is used in most aquaria.
> 
>Does anyone here have a story of a hatch O-Ring failing?
>
>Regards,
>Brent Hartwig> Date: Wed, 8 Aug 2007 09:09:02 -0700> From: clientes@tolimared.com> To: personal_submersibles@psubs.org> Subject: Re: [PSUBS-MAILIST] Double O-Ring On A Hatch> > Hello Oystein,> > Very good link - thanks,> > I see your point what concerns difference to normal hatches - in fact > i am considering the model of the scuba gear seal as a model for a > deep diver - hatch i have in mind - could go to ocean bottom - based > on concrete spheres...> > In any case the point seems to be that the mecanism that makes a > o-ring fail is extrusion trough a gap. As long as you avoid this > properly a o-ring will hold hundereds of bar = thousands of meter of > waterdepth...> > If you have several rings and a big gap due to deficient machining - > ALL of them will fail at the same depth.> > In hydraulics that normally work at that kind of pressure you have all > kind of single o-rings...> > > Cheers, Wil> > > Quoting Øystein Skarholm <skarholm@gmail.com>:> > > In scubagear the seat for connenction between tank and the 1st stage is> > spesial in that manner that the oring is in a deep groove and the 1st stage> > seat goes into this groove, unlike one on a hatch. Having said that there> > are plenty off hi pressure applications seald off using single o-ring.> >> > http://o-ring.info/en/technical%20manual/ERIKS%20-%20Technical%20Manual%20-%20O-Ring%20Sealing%20Principles.pdf> >> >> >> >> > On 8/8/07, clientes@tolimared.com <clientes@tolimared.com> wrote:> >>> >> In a scuba gear the first stage - is attached to the tank with a> >> single O- ring this single o-ring takes some 200bar in this> >> configuration - or i am wrong on this? - So i also see no need of> >> double ring in any application in a submarine.> >> Cheers, Wil> >>> >> Quoting MerlinSub@t-online.de:> >>> >> > No idear why they make that.. one is just fine with lower> >> > cost for rings, trench and paint maintance issue.> >> >> >> > I just pressuries my diverchamber with a> >> > singel o-ring to 32 atmosp..> >> >> >> > Think better one with bigger!
  diamete
r than two smalls.> >> >> >> > best regards Carsten> >> >> >> > "Brent Hartwig" <brenthartwig@hotmail.com> schrieb:> >> >>> >> >>> >> >> 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> >> >> >> >> >> >> >> >> >> >> >> > ************************************************************************> >> > ************************************************************************> >> > ************************************************************************> >> > The personal submersibles mailing list complies with the US Federal> >> > CAN-SPAM Act of 2003. Your email address appears in our database> >> > because either you, or someone you know, requested you receive messages> >> > from our organization.> >> >> >> > If you want to be removed from this mailing list simply click on the> >> > link below or send a blank email message to:> >> > removeme-personal_submersibles@psubs.org> >> >> >> > Removal of your email address from this mailing list occurs by an> >> > automated process and should be complete within five minutes of> >> > our server receiving your request.> >> >> >> > PSUBS.ORG> >> > PO Box 53> >> > Weare, NH 03281> >> > 603-529-1100> >> > ************************************************************************> >> > ************************************************************************> >> > ************************************************************************> >> >> >> >> >>> >>> >>> >>> >>> >>> >>> >> ************************************************************************> >> ************************************************************************> >> ************************************************************************> >> The personal submersibles mailing list complies with the US Federal> >> CAN-SPAM Act of 2003. Your email address appears in our da!
 tabase> 
>> because either you, or someone you know, requested you receive messages> >> from our organization.> >>> >> If you want to be removed from this mailing list simply click on the> >> link below or send a blank email message to:> >> removeme-personal_submersibles@psubs.org> >>> >> Removal of your email address from this mailing list occurs by an> >> automated process and should be complete within five minutes of> >> our server receiving your request.> >>> >> PSUBS.ORG> >> PO Box 53> >> Weare, NH 03281> >> 603-529-1100> >> ************************************************************************> >> ************************************************************************> >> ************************************************************************> >>> >>> >> >> > --> > Best Regards> > Øystein Skarholm> > www.ubat.no> >> > > > > > > > ************************************************************************> ************************************************************************> ************************************************************************> The personal submersibles mailing list complies with the US Federal> CAN-SPAM Act of 2003. Your email address appears in our database> because either you, or someone you know, requested you receive messages> from our organization.> > If you want to be removed from this mailing list simply click on the> link below or send a blank email message to:> removeme-personal_submersibles@psubs.org> > Removal of your email address from this mailing list occurs by an> automated process and should be complete within five minutes of> our server receiving your request.> > PSUBS.ORG> PO Box 53> Weare, NH 03281> 603-529-1100> ************************************************************************> ************************************************************************> ************************************************************************> 





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