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

[Brent Hartwig <brenthartwig@hotmail.com>]

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 diameter 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
> >> >
> >> >
> >> >
> >> >
> >> >
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> > --
> > Best Regards
> > Øystein Skarholm
> > www.ubat.no
> >
> 
> 
> 
> 
> 
> 
> 
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