<div dir="ltr">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><br></div><div>Best,</div><div><br>Alec</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Feb 27, 2016 at 10:07 AM, Cliff Redus via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span> wrote:<br><blockquote class="gmail_quote" 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><br></div><div>Cliff<div><div class="h5"><br><br>On Thursday, February 25, 2016, Brian Cox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="font-family:Arial,sans-serif;font-size:10pt"><div>Cliff, Where did you find that 1/2 psi relief valve?</div><div> </div><div>Brian Cox<br><br>--- <a>personal_submersibles@psubs.org</a> wrote:<br><br>From: Cliff Redus via Personal_Submersibles <<a>personal_submersibles@psubs.org</a>><br>To: Personal Submersibles General Discussion <<a>personal_submersibles@psubs.org</a>><br>Subject: Re: [PSUBS-MAILIST] Acceptable cabin pressure swing<br>Date: Thu, 25 Feb 2016 19:05:00 -0600<br><br></div><div dir="ltr"><div>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><br></div><div>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><br></div><div>Cliff</div></div><div><br><div>On Wed, Feb 24, 2016 at 1:12 PM, Jon Wallace via Personal_Submersibles <span dir="ltr"><<a>personal_submersibles@psubs.org</a>></span> wrote:<br><blockquote 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>
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>
<br>
Jon<br>
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