<DIV style="font-family:Arial, sans-serif; font-size:10pt;"><DIV>Alan, </DIV><DIV> This is just an off the shelf everyday check valve ( rated to 510 psi). I had an idea ! What about making a short stand pipe that would hold a small amount of water so that when you are at the surface there would still be enough positive pressure on the check valve to keep it closed. This might mess up those who would like a slight bit of negative pressure on the inside however.</DIV><DIV> </DIV><DIV>Brian<BR><BR>--- personal_submersibles@psubs.org wrote:<BR><BR>From: Alan James via Personal_Submersibles <personal_submersibles@psubs.org><BR>To: Personal Submersibles General Discussion <personal_submersibles@psubs.org><BR>Subject: Re: [PSUBS-MAILIST] over pressure valve<BR>Date: Sat, 20 Jun 2015 00:03:55 +0000 (UTC)<BR><BR></DIV><DIV style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);"><DIV><SPAN>Any link to it Brian?</SPAN></DIV><DIV><SPAN>I think Emile posted his over pressure valve design at one time.</SPAN></DIV><DIV><SPAN>It has a plunger for manually releasing the last bit of pressure.</SPAN></DIV><DIV><SPAN>With a bit of thought you could incorporate a snorkel system &</SPAN></DIV><DIV dir="ltr">circulate air around the hull through it.</DIV><DIV dir="ltr">Another thought is to use Vance's Top Hat valve design for ballast tanks,</DIV><DIV dir="ltr">& use a weak spring.</DIV><DIV dir="ltr">Alan</DIV><BR> <DIV style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <DIV style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <DIV dir="ltr"> <HR size="1"> <FONT face="Arial" size="2"> <B><SPAN style="font-weight: bold;">From:</SPAN></B> Brian Cox via Personal_Submersibles <personal_submersibles@psubs.org><BR> <B><SPAN style="font-weight: bold;">To:</SPAN></B> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <BR> <B><SPAN style="font-weight: bold;">Sent:</SPAN></B> Saturday, June 20, 2015 11:15 AM<BR> <B><SPAN style="font-weight: bold;">Subject:</SPAN></B> Re: [PSUBS-MAILIST] over pressure valve<BR> </FONT> </DIV> <DIV><BR>I found a really nice 1" SS spring check valve that I think would work really nicely as an OP valve, the spring is so light that the differential would be next to nothing. I also looked at an interesting ball bearing check valve that works on just gravity, which would work as well, but it wasn't SS.<BR><BR>Brian<BR><BR>--- <A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A> wrote:<BR><BR>From: hank pronk via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR>To: Personal Submersibles General Discussion <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR>Subject: Re: [PSUBS-MAILIST] over pressure valve<BR>Date: Fri, 19 Jun 2015 14:28:43 -0700<BR><BR><BR>Alec,<BR>At first I resisted the notion of thermal expansion, but I was thinking in terms of heat generated from motor use. I didn't consider the temperature change from the sun on a black motor until the light went on :-)<BR>I have changed my p trap ss tube to a larger hose so there is more air volume to work with. I am ready to test that part. Now I have to fix my bent up rudder :-(<BR>Hank--------------------------------------------<BR>On Fri, 6/19/15, Alec Smyth via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>> wrote:<BR><BR> Subject: Re: [PSUBS-MAILIST] over pressure valve<BR> To: "Personal Submersibles General Discussion" <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> Received: Friday, June 19, 2015, 5:03 PM<BR> <BR> Oh! Well I<BR> suppose it just depends on the volume the valve can handle.<BR> This is an interesting calculation, which I have not done<BR> but should. In general, these valves should handle pretty<BR> huge flow rates. But you're right, its basic to surface<BR> very slowly when there's any over-pressure - normally we<BR> dive with under-pressure. For a K-boat sized hatch, an<BR> over-pressure of 1/4 psi translates to a force of 95lbs<BR> trying to pull the dome out of the hatch ring. I know<BR> Snoopy's dome stays put at 1/4 psi, but I wouldn't<BR> take it any further than that just in case. <BR> BTW, on the subject of calculations<BR> and changing topics back to the recent thruster compensation<BR> thread, you were right about the temperature change. The<BR> volume I had to compensate was a combination of thermal<BR> contraction and air bubble. The air bubble was of unknown<BR> size, but I ran the numbers on the thermal contraction alone<BR> and it is enough to cause the problem. The little hose only<BR> has a an internal volume of 10ml. The thermal contraction of<BR> the oil turned out to be 16ml - add to that the volume of<BR> the unknown bubble, and you can see the hose was inadequate<BR> even if it squashed to zero internal volume. I am now<BR> installing bellows bottles in place of the little hoses,<BR> with a capacity of 60ml. And a better filling method that<BR> should eliminate the bubble. You'd think I wasn't an<BR> engineer, assuming the effect of thermal contraction to be<BR> negligible. Its easy to focus the calculations on big items<BR> like hull strength or stability and make assumptions about<BR> the little stuff.<BR> Best,<BR> Alec<BR> On Fri, Jun 19, 2015 at<BR> 4:19 PM, hank pronk via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> wrote:<BR> <BR> <BR> You have to be experienced to surface slowly and hover while<BR> the valve leaks out the<BR> air.--------------------------------------------<BR> <BR> On Fri, 6/19/15, Alec Smyth via<BR> Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> wrote:<BR> <BR> <BR> <BR> Subject: Re: [PSUBS-MAILIST] over pressure valve<BR> <BR> To: "Personal Submersibles General Discussion"<BR> <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> <BR> Received: Friday, June 19, 2015, 4:16 PM<BR> <BR> <BR> <BR> I<BR> <BR> don't get the "in the hands" part... its<BR> <BR> completely automatic.<BR> <BR> On Fri, Jun 19, 2015 at<BR> <BR> 4:09 PM, hank pronk via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> <BR> wrote:<BR> <BR> <BR> <BR> <BR> <BR> Agreed,<BR> <BR> <BR> <BR> In the hands of an experienced submarine operator an<BR> over<BR> <BR> pressure valve is safe, providing it is large enough. <BR> I<BR> <BR> have not seen an example of a large enough OPV. A<BR> simple<BR> <BR> valve in the hatch will do the same job, just need an<BR> <BR> umbrella :-)<BR> <BR> <BR> <BR> The noise of a compressor is a welcome sound if it<BR> means<BR> <BR> keeping the dome on the sub :-)<BR> <BR> <BR> <BR> Hank--------------------------------------------<BR> <BR> <BR> <BR> On Fri, 6/19/15, Carsten Standfuß" via<BR> <BR> Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> <BR> wrote:<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> Subject: Re: [PSUBS-MAILIST] over pressure valve<BR> <BR> <BR> <BR> To: "Personal Submersibles General<BR> Discussion"<BR> <BR> <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> <BR> <BR> <BR> Received: Friday, June 19, 2015, 2:47 PM<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> But a overpressure vale works<BR> <BR> <BR> <BR> full auto. A compressor<BR> <BR> <BR> <BR> not. <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> A OPV needs<BR> <BR> <BR> <BR> no energy - but a compressor did.<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> A OPV needs no room - but<BR> <BR> <BR> <BR> a compressor did.<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> And a<BR> <BR> <BR> <BR> compressor is<BR> <BR> <BR> <BR> a noisy solution..<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> vbr<BR> <BR> <BR> <BR> Carsten<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> "hank<BR> <BR> <BR> <BR> pronk via Personal_Submersibles" <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR> <BR> <BR> <BR> schrieb:<BR> <BR> <BR> <BR> > Personally I think an onboard<BR> <BR> <BR> <BR> compressor is a much safer option than an over<BR> pressure<BR> <BR> <BR> <BR> valve. There are multiple safety benefits to an<BR> <BR> onboard<BR> <BR> <BR> <BR> compressor, over pressure being the biggy. With a<BR> <BR> <BR> <BR> compressor you can get rid of the pressure without<BR> <BR> surfacing<BR> <BR> <BR> <BR> and trying to control a perfect ascent. With the<BR> OPV<BR> <BR> you<BR> <BR> <BR> <BR> have to surface a bit and let air out and wait then<BR> <BR> surface<BR> <BR> <BR> <BR> more and wait and so on. You can't just surface<BR> and<BR> <BR> hope<BR> <BR> <BR> <BR> the valve keeps up with the demand. This is more<BR> <BR> important<BR> <BR> <BR> <BR> for subs with large domes.<BR> <BR> <BR> <BR> > The next<BR> <BR> <BR> <BR> benefit to a compressor is, if you lost all your air,<BR> <BR> you<BR> <BR> <BR> <BR> surface by dropping your weight. In my case the<BR> weight<BR> <BR> is<BR> <BR> <BR> <BR> small and I would also drop the thruster and tail<BR> <BR> assembly.<BR> <BR> <BR> <BR> Still, not much sub out of the water. With the<BR> <BR> compressor,<BR> <BR> <BR> <BR> I can open my vent valve in the hatch and use the<BR> <BR> compressor<BR> <BR> <BR> <BR> to fill the ballast tanks.<BR> <BR> <BR> <BR> > Hank<BR> <BR> <BR> <BR> ><BR> <BR> <BR> <BR> _______________________________________________<BR> <BR> <BR> <BR> > Personal_Submersibles mailing list<BR> <BR> <BR> <BR> > <A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR> <BR> <BR> <BR> > <A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR> <BR> <BR> <BR> ><BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> -----Inline Attachment Follows-----<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> _______________________________________________<BR> <BR> <BR> <BR> Personal_Submersibles mailing list<BR> <BR> <BR> <BR> <A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR> <BR> <BR> <BR> <A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> _______________________________________________<BR> <BR> <BR> <BR> Personal_Submersibles mailing list<BR> <BR> <BR> <BR> <A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR> <BR> <BR> <BR> <A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> -----Inline Attachment Follows-----<BR> <BR> <BR> <BR> _______________________________________________<BR> <BR> Personal_Submersibles mailing list<BR> <BR> <A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR> <BR> <A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR> <BR> <BR> <BR> <BR> <BR> _______________________________________________<BR> <BR> Personal_Submersibles mailing list<BR> <BR> <A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR> <BR> <A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR> <BR> <BR> <BR> -----Inline Attachment Follows-----<BR> <BR> _______________________________________________<BR> Personal_Submersibles mailing list<BR> <A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR> <A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR> <BR><BR>_______________________________________________<BR>Personal_Submersibles mailing list<BR><A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR><A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR><BR><BR><BR>_______________________________________________<BR>Personal_Submersibles mailing list<BR><A href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR><A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR><BR><BR></DIV> </DIV> </DIV> </DIV>_______________________________________________
Personal_Submersibles mailing list
<A href="/eonapps/ft/wm/page/compose?send_to=Personal_Submersibles%40psubs.org">Personal_Submersibles@psubs.org</A>
<A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A>
</DIV>