<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><span>Brian,</span></div><div dir="ltr" id="yui_3_16_0_1_1456673473721_5382"><span>Where to put the relief valve, in my opinion it should stay on the store shelf lol. I have a vent valve in the hatch, it is a 1\4 inch valve. If you have a 1\2 psi relief valve and you want it to open at the surface, what is the point in having it? You want a relief valve to prevent your hatch blowing off or ports popping off. Well if your at the surface it is to late, the relief valve needs to open on the way to the </span>surface. That means you need to surface super slow and stop at just the right depth and wait for the valve to vent off pressure before you continue to the surface. So if your going to put a relief valve in you best go big, like Emile and Alec have or it will be like waiting for a giant inner tube to deflate that has one pound of air pressure in it. Your sub does not need a relief valve, can't hurt but no need in my mind, because you have small bolted ports and a good hatch securing system. It would be different if you had a big dome that was not strapped on like Gamma has. </div><div dir="ltr" id="yui_3_16_0_1_1456673473721_5382">We talked a while back about this and I remember Alec talking about rubber straps holding the hatch down. Now that is how I think it should be done. As long as there is catch so the hatch can only open an inch or two. </div><div dir="ltr" id="yui_3_16_0_1_1456673473721_5382">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 Saturday, February 27, 2016 11:20 PM, Brian Cox via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br></font></div> <br><br> <div class="y_msg_container"><div id="yiv9892165148"><div><div style="font-family:Arial, sans-serif;font-size:10pt;"><div>I guess if the relief valve is more than a couple of feet below the water line, that would be a 1/2 psi per foot, which would render the valve superfluous.</div><div> </div><div>Brian</div><div class="yiv9892165148yqt2412997698" id="yiv9892165148yqt49161"><div><br clear="none"><br clear="none">--- personal_submersibles@psubs.org wrote:<br clear="none"><br clear="none">From: Hugh Fulton via Personal_Submersibles <personal_submersibles@psubs.org><br clear="none">To: "'Personal Submersibles General Discussion'" <personal_submersibles@psubs.org><br clear="none">Subject: Re: [PSUBS-MAILIST] Acceptable cabin pressure swing<br clear="none">Date: Sun, 28 Feb 2016 17:36:06 +1300<br clear="none"><br clear="none"></div><div><div><span style="color:rgb(31, 73, 125);">I know Emile has had it working but is it possible for the O’ring to dislodge with flow. I think the the O’ring should be more captive like in a dovetail groove in Parker book. It is nice and simple but it should be tested at different pressures and flows. Comments?</span></div></div><div><div><span style="color:rgb(31, 73, 125);">Hugh</span><span lang="EN-NZ" style="color:rgb(31, 73, 125);"></span></div></div></div></div><div class="yiv9892165148yqt2412997698" id="yiv9892165148yqt98779"><div><span style="color:rgb(31, 73, 125);"></span> </div><div><div style="border-width:1pt medium medium;border-style:solid none none;border-color:rgb(181, 196, 223) currentColor currentColor;padding:3pt 0cm 0cm;"></div></div><div><b><span style="">From:</span></b><span style=""> Personal_Submersibles [mailto:personal_submersibles-bounces@psubs.org] <b>On Behalf Of </b>Alan James via Personal_Submersibles<br clear="none"><b>Sent:</b> Sunday, 28 February 2016 7:59 a.m.<br clear="none"><b>To:</b> Personal Submersibles General Discussion<br clear="none"><b>Subject:</b> Re: [PSUBS-MAILIST] Acceptable cabin pressure swing</span></div><div> </div><div></div><div><div></div></div><div style="background:white;"><span style="color:black;">I sent this attachment & a couple of pictures but I haven't seen it yet,</span></div><div></div><div style="background:white;"><span style="color:black;">so here is just the attachment only.</span></div><div></div><div style="background:white;"><span style="color:black;">This could be adapted in to some sort of snorkel for air on the surface.</span></div><div></div><div style="background:white;"><span style="color:black;">Alan</span></div><div></div><div style="background:white;margin-bottom:12pt;"><span style="color:black;"></span> </div><div><div><div><div><div align="center" style="background:white;text-align:center;"><span style="color:black;"></span><hr align="center" width="100%" size="1"></div></div></div></div></div><div style="background:white;"><b><span style="color:black;">From:</span></b><span style="color:black;"> 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>><br clear="none"><b>To:</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>Sent:</b> Sunday, February 28, 2016 7:41 AM<br clear="none"><b>Subject:</b> Re: [PSUBS-MAILIST] Acceptable cabin pressure swing</span><span style="color:black;"></span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div><div><div></div></div></div><div style="background:white;"><span style="color:black;">The problem with that valve is that it's just got a 1/4" diameter, and you really want it to handle large volumes. Emile and I as mentioned built our own and they're really easy to make. Interestingly we made them independently but what we came up with is identical. I know Emile posted his design here a while back, so it must be somewhere in the archives. I never made a drawing of mine, just made the actual valve directly since it's so straightforward. It's machined from a SS round and consists of just two parts. The main body is a cylinder with a bunch of holes drilled through it, and one central hole for the stem. This cylinder is welded into the hull. The other part is the cap, a shorter length cut from the same solid round but with an O ring groove around the edge and no holes. The stem goes through the body and screws into the cap. You put a spring on the stem and a wing nut to adjust the cracking pressure. That's it. If interior pressure is stronger that the spring, the cap lifts and in so doing opens all the holes. </span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div></div><div style="background:white;"><span style="color:black;">Best,</span></div><div></div><div style="background:white;"><span style="color:black;"><br clear="none">Alec</span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div><div></div></div><div style="background:white;"><span style="color:black;">On Sat, Feb 27, 2016 at 10:07 AM, Cliff Redus 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"></span></div><div style="background:white;"><span style="color:black;">Brian, see McMaster Carr part number 4620K41. This has a 1 psi cracking pressure, not 0.5 psi that I mentioned earlier.</span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div></div><div style="background:white;"><span style="color:black;">Cliff</span></div><div><div></div></div><div style="background:white;"><span style="color:black;"><br clear="none"><br clear="none">On Thursday, February 25, 2016, Brian Cox 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"></span></div><div><div></div></div><div style="background:white;"><span style="color:black;">Cliff, Where did you find that 1/2 psi relief valve?</span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div></div><div style="background:white;margin-bottom:12pt;"><span style="color:black;">Brian Cox<br clear="none"><br clear="none">--- <span>personal_submersibles@psubs.org</span> wrote:<br clear="none"><br clear="none">From: Cliff Redus via Personal_Submersibles <<span>personal_submersibles@psubs.org</span>><br clear="none">To: Personal Submersibles General Discussion <<span>personal_submersibles@psubs.org</span>><br clear="none">Subject: Re: [PSUBS-MAILIST] Acceptable cabin pressure swing<br clear="none">Date: Thu, 25 Feb 2016 19:05:00 -0600</span></div><div><div></div></div><div style="background:white;"><span style="color:black;">Jon for my boat, I have a pressure relief valve with a 1/2 psi cracking pressure to vent pressure while on the surface. I have a high cabin pressure alarm that triggers at 20 psia (5.3 psig) and a cabin lower pressure alarm set at 12 psia (-2.7 psig). In the PLC I also record and display the cabin pressure at the time the hatch is closed and log all alarm states every second. </span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div></div><div style="background:white;"><span style="color:black;">I have never had either a high or low cabin pressure alarm while diving. I have had elevated cabin pressure caused by accidently having the backup manual O2 value open and a leak in an air fitting on anther occasion.</span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div></div><div style="background:white;"><span style="color:black;">Cliff</span></div><div></div><div style="background:white;"><span style="color:black;"></span> </div><div></div><div style="background:white;"><span style="color:black;">On Wed, Feb 24, 2016 at 1:12 PM, Jon Wallace via Personal_Submersibles <<span>personal_submersibles@psubs.org</span>> wrote:<br clear="none"><br clear="none"></span></div><div style="background:white;"><span style="color:black;"><br clear="none">I think this is somewhat subjective but what is general consensus on maximum cabin pressure swing (higher/lower) relative to hatch closing at the start of a dive before setting off alarms? My thought is that an alarm should sound well before any point of emergency. I'm considering sounding a warning at 2psi +/- and an alarm at 4psi +/- but I'm not sure if this is too strict.<br clear="none"><br clear="none">Jon<br clear="none">_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><span>Personal_Submersibles@psubs.org</span><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></span></div><div style="background:white;"><span style="color:black;"></span> </div><div style="background:white;"><span style="color:black;">_______________________________________________ Personal_Submersibles mailing list <span>Personal_Submersibles@psubs.org</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></div><div style="background:white;margin-bottom:12pt;"><span style="color:black;"><br clear="none">_______________________________________________<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></span></div><div style="background:white;"><span style="color:black;"></span> </div><div style="background:white;"><span style="color:black;"></span> </div><div></div><div style="background:white;"><span style="color:black;">_______________________________________________<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></span></div></div><div style="background:white;margin-bottom:12pt;"><span style="color:black;"></span> _______________________________________________
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