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<DIV><FONT size=3>Hi Alan,</FONT></DIV>
<DIV><FONT size=3>I'm speaking in terms of absolute pressure. That is,
pressure at the surface being 14.7 psi or 1 atm and water pressure at 33
feet deep being 2 atm. I think you're speaking comparatively as
though air pressure at the surface were 0.0 psi. Right?</FONT></DIV>
<DIV><FONT size=3>Jim</FONT> </DIV>
<DIV> </DIV>
<DIV>
<DIV>In a message dated 6/19/2015 4:46:04 P.M. Central Daylight Time,
personal_submersibles@psubs.org writes:</DIV>
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<DIV id=yui_3_16_0_1_1434749417686_22281 dir=ltr><SPAN
id=yui_3_16_0_1_1434749417686_22291>Jim,</SPAN></DIV>
<DIV id=yui_3_16_0_1_1434749417686_22281 dir=ltr><SPAN
id=yui_3_16_0_1_1434749417686_22327>>>></SPAN><SPAN
id=yui_3_16_0_1_1434749417686_22328
style="FONT-SIZE: medium; FONT-FAMILY: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif"> </SPAN><SPAN
id=yui_3_16_0_1_1434749417686_22290
style="FONT-SIZE: medium; FONT-FAMILY: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif">If
the air pressure inside your sub rose to 20 psi or about 1.33 atm,
you would reach equal pressure when you got within 11 feet of the
surface. </SPAN></DIV>
<DIV id=yui_3_16_0_1_1434749417686_22281 dir=ltr><SPAN
style="FONT-SIZE: medium; FONT-FAMILY: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif">
No 40ft. </SPAN></DIV>
<DIV id=yui_3_16_0_1_1434749417686_22281 dir=ltr><SPAN
style="FONT-SIZE: medium; FONT-FAMILY: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif">Alan</SPAN></DIV><BR>
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style="FONT-SIZE: 16px; FONT-FAMILY: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif">
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<FONT id=yui_3_16_0_1_1434749417686_22280 size=2 face=Arial><B><SPAN
style="FONT-WEIGHT: bold">From:</SPAN></B> via Personal_Submersibles
<personal_submersibles@psubs.org><BR><B><SPAN
style="FONT-WEIGHT: bold">To:</SPAN></B> personal_submersibles@psubs.org
<BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B> Saturday, June 20,
2015 7:58 AM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re:
[PSUBS-MAILIST] Over Pressure Valve<BR></FONT></DIV>
<DIV id=yui_3_16_0_1_1434749417686_22428 class=y_msg_container><BR>
<DIV id=yiv4972348696>
<DIV id=yui_3_16_0_1_1434749417686_22427><FONT id=yiv4972348696role_document
color=#000000 size=2 face=Arial></FONT>
<DIV><FONT size=3>John, </FONT><FONT size=3>I hadn't given much thought lately
to how the Big Boys handle it. I've planned to have a small,
onboard compressor, but its purpose is to create under-pressure to seal the
domes prior to diving. It's not large enough to charge the tanks.
I'm depending on a portable compressor dockside or on the support boat for
that. A snorkel would be nice even if it extends just two feet
above the hatch or dome. Looking forward to the update on your 65-footer
at the convention.</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>Hank, that's definitely a sweet setup you have on
Gamma. The compressor recharged the tanks much more quickly than I
expected. I don't recall how low you let them get before
recharging. I don't expect to have room onboard, and the heat generated
would be something of a negative in semitropical conditions.</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>I wish I knew what the pressure differential was that
Captain K. experienced. Apparently it was small enough that he wasn't
aware of it and yet significant enough to convert his coming tower into a
personnel launch tube. If the air pressure inside your sub
rose to 20 psi or about 1.33 atm, you would reach equal pressure when you got
within 11 feet of the surface. Any depth greater than that and the
outside pressure would still be greater than the inside pressure (no
OP). The point being that you would have to have a lot of excess
interior pressure to experience OP at a significant depth. Wouldn't your
ears tell you if you got as high as 20 psi? Monitoring and alarm systems
are a must.</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>Jim</FONT></DIV>
<DIV> </DIV>
<DIV id=yui_3_16_0_1_1434749417686_22426> </DIV>
<DIV id=yui_3_16_0_1_1434749417686_22429>Personally I think an onboard
compressor is a much safer option than an over pressure valve. There are
multiple safety benefits to an onboard compressor, over pressure being the
biggy. With a compressor you can get rid of the pressure without
surfacing and trying to control a perfect ascent. With the OPV you have
to surface a bit and let air out and wait then surface more and wait and so
on. You can't just surface and hope the valve keeps up with the demand. This
is more important for subs with large domes.<BR clear=none>The next benefit to
a compressor is, if you lost all your air, you surface by dropping your
weight. In my case the weight is small and I would also drop the
thruster and tail assembly. Still, not much sub out of the water.
With the compressor, I can open my vent valve in the hatch and use the
compressor to fill the ballast tanks.<BR clear=none>Hank<BR
clear=none>_______________________________________________<BR
clear=none>Personal_Submersibles mailing list<BR
clear=none>Personal_Submersibles@psubs.org<BR
clear=none>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles<BR
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<DIV id=yui_3_16_0_1_1434749417686_22430> </DIV>
<DIV id=yui_3_16_0_1_1434749417686_22431>
<DIV>In a message dated 6/19/2015 12:35:49 P.M. Central Daylight Time,
personal_submersibles@psubs.org writes:</DIV>
<DIV class=qtdSeparateBR><BR><BR></DIV>
<DIV id=yiv4972348696yqt79050 class=yiv4972348696yqt8972714691>
<BLOCKQUOTE id=yui_3_16_0_1_1434749417686_22432
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id=yui_3_16_0_1_1434749417686_22433 style="BACKGROUND-COLOR: transparent"
color=#000000 size=2 face=Arial>Hi Jim:<BR clear=none><BR clear=none>On the
boat if their was an positive pressure while submerged at depth we started
the air compressor and charge the air banks. The other option was to raise
the snorkel to equalize before opening the hatch.<BR clear=none><BR
clear=none><BR clear=none>John K.<BR clear=none>(203) 414-1000<BR
clear=none><BR clear=none>Sent from my iPhone<BR clear=none><BR
clear=none>> On Jun 19, 2015, at 3:07 AM, via Personal_Submersibles
<personal_submersibles@psubs.org> wrote:<BR clear=none>> <BR
clear=none>> Jim,<BR clear=none>> <BR clear=none>> Thanks for the
mental diagram, that helps imensely. Does any one know how the big boys,
navy subs, deal with over pressure? Has any one had their OP valve open at
depth and if so how much water came in?<BR clear=none>> <BR
clear=none>> Keith T<BR clear=none>> <BR clear=none>> via
Personal_Submersibles <personal_submersibles@psubs.org> wrote:<BR
clear=none>> <BR clear=none>>> Keith,<BR clear=none>>> <BR
clear=none>>> Sorry, I just got home. I was hoping Alec and
some others with more <BR clear=none>>> experience than I have
would chime in as I see has now happened. There have <BR
clear=none>>> been some good discussions on OP valves in the
past. I think some have <BR clear=none>>> installed a T (on its
side) inside the sub so the air enters the horizontal <BR
clear=none>>> portion, and any water that comes in goes down to
a small trap or into a tube <BR clear=none>>> that leads to a
reservoir. Others just use a rag to catch the small amount <BR
clear=none>>> of water.<BR clear=none>>> <BR clear=none>>>
Alec, does the OP on the exterior of Snoopy point downward after it
exits <BR clear=none>>> at the top?<BR clear=none>>> <BR
clear=none>>> We've also discussed having an air pressure gauge or
altimeter set to zero <BR clear=none>>> (1 atm) before
diving. If it indicates any pressure above that level at <BR
clear=none>>> anytime during your dive, you'll know you'll have an
over pressure situation <BR clear=none>>> to deal with as you
surface and you'll have an indication of how severe <BR
clear=none>>> that will be. We've also discussed various things
that could cause an over <BR clear=none>>> pressure
condition.<BR clear=none>>> <BR clear=none>>> Best regards,<BR
clear=none>>> Jim<BR clear=none>>> <BR clear=none>>> <BR
clear=none>>> In a message dated 6/18/2015 7:09:19 P.M. Central
Daylight Time, <BR clear=none>>> personal_submersibles@psubs.org
writes:<BR clear=none>>> <BR clear=none>>> If it opens when
submerged, it is because air is on the way out, and that <BR
clear=none>>> prevents water from coming in. Its like blowing through
your nose <BR clear=none>>> underwater, your nose is open but if
you're blowing, you don't get water in your <BR clear=none>>>
lungs. <BR clear=none>>> <BR clear=none>>> <BR
clear=none>>> Certainly you do get a little water in if you push the
valve open manually <BR clear=none>>> while submerged, as a
test. Or a few drops if you do so when surfaced to <BR
clear=none>>> equalize, as the valve is all wet. But its nothing
much.<BR clear=none>>> <BR clear=none>>> <BR clear=none>>>
<BR clear=none>>> Best,<BR clear=none>>> <BR clear=none>>>
Alec<BR clear=none>>> <BR clear=none>>> <BR clear=none>>>
<BR clear=none>>> On Thu, Jun 18, 2015 at 7:19 PM, Ken Martindale
via Personal_Submersibles <BR clear=none>>>
<_personal_submersibles@psubs.org_
(mailto:personal_submersibles@psubs.org) <BR clear=none>>>>
wrote:<BR clear=none>>> <BR clear=none>>> TEST!!!<BR
clear=none>>> <BR clear=none>>> -----Original
Message-----<BR clear=none>>> From: Personal_Submersibles <BR
clear=none>>> [mailto:_personal_submersibles-bounces@psubs.org_
(mailto:personal_submersibles-bounces@psubs.org) ] On Behalf Of via
<BR clear=none>>> Personal_Submersib<BR
clear=none>_______________________________________________<BR
clear=none>Personal_Submersibles mailing list<BR
clear=none>Personal_Submersibles@psubs.org<BR
clear=none>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles<BR
clear=none></FONT></BLOCKQUOTE></DIV></DIV></DIV></DIV><BR>
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