<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><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 style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: medium;" class="" id="yui_3_16_0_1_1434749417686_22328"> </span><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: medium;" class="" id="yui_3_16_0_1_1434749417686_22290">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-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: medium;" class=""> No 40ft. </span></div><div id="yui_3_16_0_1_1434749417686_22281" dir="ltr"><span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: medium;" class="">Alan</span></div><br> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1434749417686_22265"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1434749417686_22264"> <div dir="ltr" id="yui_3_16_0_1_1434749417686_22263"> <hr size="1" id="yui_3_16_0_1_1434749417686_22284"> <font size="2" face="Arial" id="yui_3_16_0_1_1434749417686_22280"> <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 class="y_msg_container" id="yui_3_16_0_1_1434749417686_22428"><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 clear="none"></div>
<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 class="yiv4972348696yqt8972714691" id="yiv4972348696yqt79050"><blockquote style="PADDING-LEFT:5px;MARGIN-LEFT:5px;BORDER-LEFT:blue 2px solid;" id="yui_3_16_0_1_1434749417686_22432"><font style="BACKGROUND-COLOR:transparent;" color="#000000" size="2" face="Arial" id="yui_3_16_0_1_1434749417686_22433">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><div class="yqt8972714691" id="yqt70545">_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><br><br></div> </div> </div> </div></body></html>