<html><body><div style="color:#000; background-color:#fff; font-family:tahoma, new york, times, serif;font-size:12pt"><div style="RIGHT: auto"><SPAN style="RIGHT: auto">Hi Jim,</SPAN></div>
<div style="FONT-SIZE: 16px; FONT-FAMILY: tahoma, new york, times, serif; RIGHT: auto; COLOR: rgb(0,0,0); FONT-STYLE: normal; BACKGROUND-COLOR: transparent"><SPAN style="RIGHT: auto">I am no expert on the subject, but I do a test with as much vacuum as possible. When you dive the hatch is secured tight so there is always pressure on the seal. Before I converted my k350 hatch to open from both sides, I did the vacuum test without securing the hatch. I does not take much vacuum to suck the hatch down tight. Honestly I am not sure about a low vacuum test, you could be right. <VAR id=yui-ie-cursor></VAR> I just assumed it should be more than less. Before I tested my last sub in the lake, I did a vacuum test and I did loose vacuum overnight. It was very minor, so I went anyways. Sure enough I had a leak, I took on a couple of litres of water at 200 feet for an hr. I think my connection
point from the acrylic cylinder to the hatch land was the problem. There is no seal, it is cast in place. </SPAN></div>
<div style="FONT-SIZE: 16px; FONT-FAMILY: tahoma, new york, times, serif; RIGHT: auto; COLOR: rgb(0,0,0); FONT-STYLE: normal; BACKGROUND-COLOR: transparent"><SPAN style="RIGHT: auto">Hank</SPAN></div>
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<DIV class=hr style="FONT-SIZE: 0px; BORDER-TOP: #ccc 1px solid; HEIGHT: 0px; BORDER-RIGHT: #ccc 1px solid; BORDER-BOTTOM: #ccc 1px solid; PADDING-BOTTOM: 0px; PADDING-TOP: 0px; PADDING-LEFT: 0px; MARGIN: 5px 0px; BORDER-LEFT: #ccc 1px solid; LINE-HEIGHT: 0; PADDING-RIGHT: 0px" readonly="true" contenteditable="false"></DIV><FONT size=2 face=Arial><B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> "JimToddPsub@aol.com" <JimToddPsub@aol.com><BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> personal_submersibles@psubs.org <BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B> Monday, September 2, 2013 8:57:18 AM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: [PSUBS-MAILIST] Leak, pressure and life support test<BR></FONT></DIV>
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<DIV><FONT size=3>Hi Hank,</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>See if you agree with my line of thinking: At a hatch depth of 20 feet you'll have about 9 psi differential on your hatch and your other penetrations as well. At a hatch depth of 1 foot you have about .445 psi differential.</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>For many things, the greater the pressure differential, the greater the chance of a leak or seepage. However on the hatch in particular (and possibly on some other things), the greater the pressure forcing the hatch against the landing, the more tightly it will seal. So the hatch might seal well at depth, but leak when barely submerged</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>It seems it would be good to do both a high vacuum and a low vacuum test. If the hatch seals well at high vacuum, but leaks down at low vacuum, more work is needed on the latches or the mating surfaces.</FONT></DIV>
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<DIV><FONT size=3>Best regards,</FONT></DIV>
<DIV><FONT size=3>Jim</FONT></DIV>
<DIV> </DIV>
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<DIV>In a message dated 9/2/2013 9:21:58 A.M. Central Daylight Time, hanker_20032000@yahoo.ca writes:</DIV>
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<DIV><SPAN>Hi James,</SPAN></DIV>
<DIV style="FONT-SIZE: 16px; FONT-FAMILY: tahoma, new york, times, serif; COLOR: rgb(0,0,0); FONT-STYLE: normal; BACKGROUND-COLOR: transparent"><SPAN>I always do a vacuum test before my test dives. I use a compressor as a vacuum pump and draw out as much air as possible. Then I have a valve on the hull and a vacuum gauge. I let it sit for 24 hr. If it holds the vacuum your set. </SPAN></DIV>
<DIV style="FONT-SIZE: 16px; FONT-FAMILY: tahoma, new york, times, serif; COLOR: rgb(0,0,0); FONT-STYLE: normal; BACKGROUND-COLOR: transparent"><SPAN>Hank<VAR id=yiv1137719860yui-ie-cursor></VAR></SPAN></DIV>
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<DIV class=yiv1137719860hr style="FONT-SIZE: 0px; BORDER-TOP: #ccc 1px solid; HEIGHT: 0px; BORDER-RIGHT: #ccc 1px solid; BORDER-BOTTOM: #ccc 1px solid; PADDING-BOTTOM: 0px; PADDING-TOP: 0px; PADDING-LEFT: 0px; MARGIN: 5px 0px; BORDER-LEFT: #ccc 1px solid; LINE-HEIGHT: 0; PADDING-RIGHT: 0px"></DIV><FONT size=2 face=Arial><B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> James Frankland <jamesf@guernseysubmarine.com><BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> personal_submersibles@psubs.org <BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B> Monday, September 2, 2013 3:45:27 AM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> [PSUBS-MAILIST] Leak, pressure and life support test<BR></FONT></DIV>
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<DIV>Hi All,</DIV>
<DIV> </DIV>
<DIV>I did some tests at the weekend. Very small pics attached as i havent updated my site yet.</DIV>
<DIV> </DIV>
<DIV>First i tested the battery pods and seals with old inner tubes. Managed to pump them to about 5psi. Not much but i think it was ok to indicate any leaks. I couldnt see or hear anything and pressure remained steady.</DIV>
<DIV> </DIV>
<DIV>Then i did the very sophisticated "saucepan test" over the hatch viewport. I was just a bit suspicious of this one as it has no gasket, the lense seats directly to the face. No leak, but agreed, not much test pressure although the saucepan was full despite the spillage out the sides.</DIV>
<DIV> </DIV>
<DIV>Next i did a life support test. I filled and ran the scrubber and then sat inside for an hour with the hatch sealed. CO2 seemed to level out at about 5500ppm and i topped up O2 when it got to 19%. </DIV>
<DIV> </DIV>
<DIV>i also dropped half a psi of internal pressure and that seemed to hold, so i am hoping the boat is tight.</DIV>
<DIV> </DIV>
<DIV>I was going to do a leak test in a local fresh water resovoir, but as im a bit more confident its not going to leak now and its such a logistical fuss, im going to go straight in the sea. Next week.</DIV>
<DIV>Kind Regards</DIV>
<DIV>James</DIV>
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