<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_ym19_1_1470354669764_3243" dir="ltr">Alec, Well, really, we are talking about a pretty unlikely situation. Gamma has a single HP line to the valves and it is 1\8. It would not take long to shut off if it burst. Like you said, it is the pesky little leak that builds up some pressure. I actually carry a bottle of soapy water in the sub at all times and give a squirt to test for leaks often. It also smells nice ;-) I have done the same as you with Elementary 3000, the HP lines are external and just the valve is inside to the manifold and one 8 inch braided ss 1\8 line to exit the sub. Pretty safe set up. Neither of my subs have O\P valves but I do have vent valves.</div><div id="yui_3_16_0_ym19_1_1470354669764_3243" dir="ltr">Hank</div> <div class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"><font size="2" face="Arial"> On Thursday, August 4, 2016 5:18 PM, Alec Smyth via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br></font></div> <br><br> <div class="y_msg_container"><div id="yiv0325354012"><div><div dir="ltr">Yes, it's a big valve. Two and a half inches across if I remember right, with a bunch of radial holes in it. The thing is, changing the K250 hatch to take that pressure is just not feasible. You'd basically need a whole new design for the CT and hatch.</div><div class="yiv0325354012gmail_extra"><br clear="none"><div class="yiv0325354012gmail_quote">On Thu, Aug 4, 2016 at 4:43 PM, hank pronk via Personal_Submersibles <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br clear="none"><blockquote class="yiv0325354012gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="yiv0325354012yqt7826308598" id="yiv0325354012yqt18909"><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div dir="ltr"><span>I think there is an ABS rule that says you can not have more HP gases than the ports or dome can retain. An over pressure valve is fine if it is big and you can hold your depth in the water column. I think of deflating a big inner tube with the valve stem removed. If you have such a situation that requires an over pressure valve to save the day, then there is likely a lot of stuff going on that would be stressful. I say build so your sub can handle the over pressure and have an over pressure valve to boot. </span></div><div dir="ltr"><span>Can't a K250 have a stronger ring, with straps like Emile has and DW's</span></div><div dir="ltr"><span>I remember Vance saying "copy what the pro's are doing"</span></div><div dir="ltr"><span>Hank</span></div><div><div class="yiv0325354012h5"> <div><br clear="none"><br clear="none"></div><div style="display:block;"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div dir="ltr"><font size="2" face="Arial"> On Thursday, August 4, 2016 6:52 AM, Alec Smyth via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>> wrote:<br clear="none"></font></div> <br clear="none"><br clear="none"> <div><div><div><div dir="ltr">Hi Hank,<div><br clear="none"></div><div>I don't think there's any way a K boat hatch, 250 or 350, would hold that in. Tanks on the outside with shutoff valves are a mitigating solution, but an OP valve I'd argue is best because it's automatic and kicks in instantaneously. The 250 hatch is particularly hard to strengthen because the ring that receives the acrylic is pretty lightweight, meaning if you were to put enormous dogs on it the ring itself would probably bend. In short, I don't think it's feasible to harden the K250 hatch against over-pressure, so the way to protect against that is with the OP valve.</div><div><br clear="none"></div><div>Best,</div><div><br clear="none">Alec</div></div><div><br clear="none"><div>On Thu, Aug 4, 2016 at 8:22 AM, hank pronk via Personal_Submersibles <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>></span> wrote:<br clear="none"><blockquote style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div><span>Alan,</span></div><div dir="ltr">It seems to me you should have sufficient dome retaining to hold the dome in place with all Hp products fully vented into the sub. I am sure that the retainers on Snoopy's dome can do that. I prefer straps,not saying it is a must, but when in doubt, go big. </div><div dir="ltr">Hank</div><div><div> <div><br clear="none"><br clear="none"></div><div style="display:block;"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div dir="ltr"><font size="2" face="Arial"> On Wednesday, August 3, 2016 10:43 PM, Alan James via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>> wrote:<br clear="none"></font></div> <br clear="none"><br clear="none"> <div><div><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"><div><span></span></div><div>I was thinking that if air temperature was above water temperature,</div><div dir="ltr">(as you would get in Canada) then you could potentially get overpressure.</div><div dir="ltr">One guy on the internet was saying that his lake temperature was </div><div dir="ltr">26C & the air temperature was 10C. In this case the pressure in a</div><div dir="ltr">sub could increase by a couple of psi through the higher water temperature, </div><div dir="ltr">body & electrical heat. </div><div dir="ltr">Alan</div><div dir="ltr"><br clear="none"><br clear="none"></div><div style="display:block;"> <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><div dir="ltr"> <font face="Arial" size="2"> </font><hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Alan via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>><br clear="none"> <b><span style="font-weight:bold;">To:</span></b> Personal Submersibles General Discussion <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>> <br clear="none"> <b><span style="font-weight:bold;">Sent:</span></b> Thursday, August 4, 2016 4:04 PM<br clear="none"> <b><span style="font-weight:bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Overpressure on dome<br clear="none"> </div> <div><br clear="none"><div><div><div>Sorry, the air temperature in the bellows probably</div><div>wouldn't lag that far behind the air temperature in the sub & so</div><div>wouldn't increase the pressure much.</div><div>Yes there would need to be some major leak.</div><div>However there has been a couple of incidents!</div><div>Alan</div><div><br clear="none"></div><div> <br clear="none"><br clear="none">Sent from my iPad</div><div><div><br clear="none">On 4/08/2016, at 3:52 pm, Alan via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>> wrote:<br clear="none"><br clear="none"></div><blockquote type="cite"><div></div></blockquote></div></div><div><div><div>Sean,</div><div>thanks for the maths.</div><div>I was thinking that the scenario could arise where you dive with an internal</div><div>temperature of say 30C & set a bellows add system for the pressure at that</div><div>temperature. Then as you dived down to cool water the temperature in the</div><div>sub dropped to 15C. The air pressure in the sub would gradually halve but the </div><div>bellows add system would build the pressure up with added O2. If you rose</div><div> to near the surface & cruised around letting the sub warm up, you</div><div>could potentially raise the pressure by quite a bit. Hopefully you would notice</div><div>that the O2 % was high in the first place, but if you didn't & the dome retainers</div><div>weren't substantial, it could contribute to a catastrophic situation.</div><div>Hmmm think I'll put in an overpressure alarm!</div><div>Alan</div><div><br clear="none"></div><div><br clear="none"><br clear="none">Sent from my iPad</div><div><br clear="none">On 4/08/2016, at 2:49 pm, Sean T. Stevenson via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>> wrote:<br clear="none"><br clear="none"></div><blockquote type="cite"><div><div dir="ltr">The force acting on the dome from the inside is the internal pressure multiplied by the 222D projected area encapsulated by the innermost seal. For example, if your dome is 24" ID and 26" OD (1" thick), if it seats against a single o-ring at the mid diameter, the area would be A = π(12.5)^2 = 491 in. ^2 . Conversely, if the entire window thickness sits against a bearing gasket, the seal extends to the ID, so A = π(12)^2 = 452 in. ^2 .</div>
<div dir="ltr">The internal cabin pressure acts uniformly across the entire window, but the external sea pressure does not. Across a 26" OD window, the pressure at the bottom of the window is about 1 psi greater than at the top, so in the absence of proper retention, it would preferentially pull away at the top in the event of overpressure.</div>
<div dir="ltr">As far as what to expect, that number should be zero. The only way you will encounter overpressure is if something is leaking gas into the cabin, or if there is a dramatic temperature increase.</div>
<div dir="ltr">Your dome retainers need only be strong enough to hold the dome against its seal at whatever delta-P activates the OPV, or some margin above that if it is a slow valve. As a thought, I might be inclined to spring load the retainer arrangement, so if you have a full bottle dump or some other (otherwise) catastrophic event increasing cabin pressure, the dome could vent that gas until it dropped below the spring load, and then the OPV or manual equalizing arrangements would deal with the rest. Of course, you should avoid that possibility in design, but I'm just throwing that out there.</div>
<div dir="ltr">Sean<br clear="none">
</div>
<br clear="none"><br clear="none"><div>On August 3, 2016 8:10:56 PM MDT, Alan James via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs. org</a>> wrote:<blockquote style="margin:0pt 0pt 0pt 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid;">
<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 dir="ltr"> Hi all,</div><div dir="ltr">need some group input here.</div><div dir="ltr">I was looking at a picture of Snoopy's dome that Doug posted on Facebook. (below)</div><div dir="ltr">The 6 dome retainers that are made of plastic were making me nervous.</div><div dir="ltr">There have been a couple of cases of domes blowing off. I think George Kitrige</div><div dir="ltr">was one of them. So I wanted a bit of analysis on this scenario in general.</div><div dir="ltr">What sort of overpressure can you expect at a max!
imum on
a dive?</div><div dir="ltr">Doug's overpressure valve operates at .5psi but if you were 3psi overpressure</div><div dir="ltr">the valve wouldn't operate till you were 5ft from the surface & you would have a short</div><div dir="ltr">time to get the pressure down. Also wave movement would factor in & fluctuate the pressure quickly at that depth.</div><div dir="ltr">I think the K250 dome is 24" diameter. I calculated out that there would be 452lb </div><div dir="ltr">pressure on the dome retainers for every 1psi overpressure. I based this on the area </div><div dir="ltr">of a 24" disc, or should I be basing it on the area of the dome? (Sean)</div><div dir="ltr">At 3psi that would !
be 226lb
lifting force on each of those 6 plastic retainers!</div><div dir="ltr">What is a good safety factor here? (Sorry for picking on Snoopy Alec)</div><div dir="ltr">Cheers Alan</div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div></div><div style="margin-top:2.5em;margin-bottom:1em;border-bottom-color:rgb(0,0,0);border-bottom-width:1px;border-bottom-style:solid;"></div><pre></pre><hr><br clear="none">Personal_Submersibles mailing list<br clear="none"><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs. org</a><br clear="none"><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/ listinfo.cgi/personal_ submersibles</a><br clear="none"></blockquote></div></div></blockquote><blockquote type="cite"><div><span>______________________________ _________________</span><br clear="none"><span>Personal_Submersibles mailing list</span><br clear="none"><span><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs. org</a></span><br clear="none"><span><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/ listinfo.cgi/personal_ submersibles</a></span><br clear="none"></div></blockquote></div><blockquote type="cite"><div><span>______________________________ _________________</span><br clear="none"><span>Personal_Submersibles mailing list</span><br clear="none"><span><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs. org</a></span><br clear="none"><span><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/ listinfo.cgi/personal_ submersibles</a></span><br clear="none"></div></blockquote></div></div><br clear="none"><div>______________________________ _________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs. org</a><br clear="none"><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/ listinfo.cgi/personal_ submersibles</a><br clear="none"></div><br clear="none"><br clear="none"></div></div> </div> </div> </div></div></div></div><br clear="none"><div>______________________________ _________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs. org</a><br clear="none"><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/ listinfo.cgi/personal_ submersibles</a><br clear="none"></div><br clear="none"><br clear="none"></div> </div> </div> </div></div></div></div></div></div><br clear="none">______________________________ _________________<br clear="none">
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