No, never had a failure, as such. And, O-rings don't keep hatch and
mating surfaces from touching, that would be a gasket. The O-ring itself is
slightly compressed in the O-ring groove, water then squeezes in against it,
compressing the ring further against the upper, lower and inner surfaces
(looked at in cross section) of the groove, thus keeping the drips out. I've
never seen double O-rings on a certified submersible--we had 'em for the
reactor head out at the nuclear plant, but not on a temporary seal.
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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>
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