<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div><span>OK I got the last email back will try & send a picture.</span></div><div><span>This valve works well & Emile presses it before opening the hatch</span></div><div dir="ltr" id="yui_3_16_0_1_1456599905552_3897"><span>to equalize the last bit of pressure.</span></div><div dir="ltr" id="yui_3_16_0_1_1456599905552_3896"><span><br></span></div><div class="qtdSeparateBR" id="yui_3_16_0_1_1456599905552_3794"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_1_1456599905552_3804" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1456599905552_3803"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1456599905552_3802"> <div dir="ltr" id="yui_3_16_0_1_1456599905552_3801"> <font size="2" face="Arial" id="yui_3_16_0_1_1456599905552_3899"> <hr size="1" id="yui_3_16_0_1_1456599905552_3898"> <b><span style="font-weight:bold;">From:</span></b> Alan James 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> Sunday, February 28, 2016 7:59 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Acceptable cabin pressure swing<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1456599905552_3823"><br><div id="yiv3840282892"><div id="yui_3_16_0_1_1456599905552_3822"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;" id="yui_3_16_0_1_1456599905552_3821"><div dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_2752"><span id="yiv3840282892yui_3_16_0_1_1456599241714_2761">I sent this attachment & a couple of pictures but I haven't seen it yet,</span></div><div dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_2752"><span id="yiv3840282892yui_3_16_0_1_1456599241714_2849">so here is just the attachment only.</span></div><div dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_2752"><span>This could be adapted in to some sort of snorkel for air on the surface.</span></div><div dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_2752"><span>Alan</span></div><div class="yiv3840282892qtdSeparateBR" id="yiv3840282892yui_3_16_0_1_1456599241714_2753"><br clear="none"><br clear="none"></div><div class="yiv3840282892yahoo_quoted" id="yiv3840282892yui_3_16_0_1_1456599241714_2759" style="display:block;"> <div id="yiv3840282892yui_3_16_0_1_1456599241714_2758" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div id="yiv3840282892yui_3_16_0_1_1456599241714_2757" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div class="yiv3840282892yqt5160728320" id="yiv3840282892yqt58593"><div dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_2756"> <font id="yiv3840282892yui_3_16_0_1_1456599241714_2755" size="2" face="Arial"> </font><hr id="yiv3840282892yui_3_16_0_1_1456599241714_2754" size="1"> <b><span style="font-weight:bold;">From:</span></b> Alec Smyth via Personal_Submersibles <personal_submersibles@psubs.org><br clear="none"> <b><span style="font-weight:bold;">To:</span></b> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br clear="none"> <b><span style="font-weight:bold;">Sent:</span></b> Sunday, February 28, 2016 7:41 AM<br clear="none"> <b><span style="font-weight:bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Acceptable cabin pressure swing<br clear="none"> </div> <div class="yiv3840282892y_msg_container" id="yiv3840282892yui_3_16_0_1_1456599241714_2760"><br clear="none"><div id="yiv3840282892"><div id="yiv3840282892yui_3_16_0_1_1456599241714_2857"><div dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_2856">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. <div id="yiv3840282892yui_3_16_0_1_1456599241714_3116"><br clear="none"></div><div>Best,</div><div id="yiv3840282892yui_3_16_0_1_1456599241714_2858"><br clear="none">Alec</div></div><div class="yiv3840282892gmail_extra" id="yiv3840282892yui_3_16_0_1_1456599241714_2864"><br clear="none"><div class="yiv3840282892yqt0969569929" id="yiv3840282892yqtfd23793"><div class="yiv3840282892gmail_quote" id="yiv3840282892yui_3_16_0_1_1456599241714_2863">On Sat, Feb 27, 2016 at 10:07 AM, Cliff Redus via Personal_Submersibles <span dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_3062"><<a rel="nofollow" shape="rect" id="yiv3840282892yui_3_16_0_1_1456599241714_3061" 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="yiv3840282892gmail_quote" id="yiv3840282892yui_3_16_0_1_1456599241714_2862" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Brian, see McMaster Carr part number 4620K41. This has a 1 psi cracking pressure, not 0.5 psi that I mentioned earlier.<div id="yiv3840282892yui_3_16_0_1_1456599241714_3060"><br clear="none"></div><div id="yiv3840282892yui_3_16_0_1_1456599241714_2861">Cliff<div id="yiv3840282892yui_3_16_0_1_1456599241714_2860"><div class="yiv3840282892h5" id="yiv3840282892yui_3_16_0_1_1456599241714_2859"><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"><blockquote class="yiv3840282892gmail_quote" id="yiv3840282892yui_3_16_0_1_1456599241714_2867" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div id="yiv3840282892yui_3_16_0_1_1456599241714_2866" style="font-family:Arial, sans-serif;font-size:10pt;"><div id="yui_3_16_0_1_1456599905552_3921">Cliff, Where did you find that 1/2 psi relief valve?</div><div id="yiv3840282892yui_3_16_0_1_1456599241714_3059"> </div><div id="yiv3840282892yui_3_16_0_1_1456599241714_2865">Brian Cox<br clear="none"><br clear="none">--- <a rel="nofollow" shape="rect" id="yiv3840282892yui_3_16_0_1_1456599241714_3122" href="">personal_submersibles@psubs.org</a> wrote:<br clear="none"><br clear="none">From: Cliff Redus via Personal_Submersibles <<a rel="nofollow" shape="rect" href="">personal_submersibles@psubs.org</a>><br clear="none">To: Personal Submersibles General Discussion <<a rel="nofollow" shape="rect" href="">personal_submersibles@psubs.org</a>><br clear="none">Subject: Re: [PSUBS-MAILIST] Acceptable cabin pressure swing<br clear="none">Date: Thu, 25 Feb 2016 19:05:00 -0600<br clear="none"><br clear="none"></div><div dir="ltr" id="yiv3840282892yui_3_16_0_1_1456599241714_2869"><div id="yiv3840282892yui_3_16_0_1_1456599241714_2868">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. </div><div id="yiv3840282892yui_3_16_0_1_1456599241714_2870"><br clear="none"></div><div id="yiv3840282892yui_3_16_0_1_1456599241714_2871">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.</div><div id="yiv3840282892yui_3_16_0_1_1456599241714_2872"><br clear="none"></div><div>Cliff</div></div><div id="yiv3840282892yui_3_16_0_1_1456599241714_3020"><br clear="none"><div id="yiv3840282892yui_3_16_0_1_1456599241714_3022">On Wed, Feb 24, 2016 at 1:12 PM, Jon Wallace via Personal_Submersibles <span dir="ltr"><<a rel="nofollow" shape="rect" href="">personal_submersibles@psubs.org</a>></span> wrote:<br clear="none"><blockquote id="yiv3840282892yui_3_16_0_1_1456599241714_3021" style="margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid;"><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">
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