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Hi Cody, I concur. Your also touching
on what the issue Alec brought up. I think the key here would be to
balance your hardness of Sekaflex with the pressure range your design is planned
to operate in. Softer makes this type of sealing arrangement seal
more easily near the surface, and harder makes it resist being damaged
and parted beyond what the urethane can recover from. This is part of
where having two upper rings basically splits up
the total load that is transferred from the outer hatch surface
that translates into downward force on the SS sealing
rings.
I suspect you can get away with a much harder
urethane in this arrangement, and still seal at the surface, since your molding
the upper SS sealing rings into the urethane, for a perfect fit to start
with. The hardest urethanes might be able to handle a lot of
pressure. I was mostly thinking of this arrangement for subs that have a
general operating depth of 500 fsw or less. It might be really nice
for subs the have a general operating depth of 250 fsw or
less.
Regards
Brent
From: Cody McMillan
Sent: Friday, September 04, 2009 1:38 PM
Subject: RE: [PSUBS-MAILIST] No Machining Hatch Sealing
Concept Cody McMillan Marine Engineer 6046573770 From: brenthartwig@hotmail.com Subject: [PSUBS-MAILIST] No Machining Hatch Sealing Concept Date: Fri, 4 Sep 2009 04:14:04 -0700 This is an idea I've been wanting to make some CAD
models and drawings of for some time now. We have this big oval or rectangle
steel plate doors for the hyperbaric chambers, and it's expensive to machine the
doors and seating flanges flat, plus cut the O-ring groove. Even then the welded
in door frame can and usually warps some. Once welded in the door frame is very
hard to machine. The concept shown in the below pictures and
drawings, is showing a K-350 type hatch and hatch land, that have two rolled
1/4" SS rod rings, that are TIG welded onto the hatch flange, and two on the
hatch land. The two on the hatch land are to form a dam for Sekaflex, that
you caulk in there and level off. Then to allow the upper SS rings to seat
down into the Sekaflex enough to take up any warp in both flanges and not stick
to the Sekaflex while it is curing, you apply mold release to the SS rings, and
then spray them with PVA mold release agent and let that dry. Then before
the Sekaflex is caulked into the lower rings, you lower the hatch and figure out
what spacers you need to keep if from going down to far into the urethane. Then
add the Sekaflex of the type of hardness you want, and lower the hatch, which is
attached at the hinge to keep every thing lined up, and set the hatch down on
your taped or clamped on spacers, and let it cure.
One could use just one upper SS sealing ring as you
can see in the drawing of a large WWII ballast tank flapper valve. But I
like the primary and secondary sealing means, and it evens out the stresses
more.
" Stand still.
The trees ahead and bush beside you are not lost." ~ Albert
Einstein
Regards Szybowski Click less, mail more: Hotmail on the new MSN homepage! |