<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">If you double up the O-rings you increase the pressure it takes to open the valve. If I have it right, you want to put a second o-ring beside the original o-ring. The design is flawed from the start. Doubling the O-rings makes it worse. The original valve if I recall takes 20% more internal pressure than external pressure to open, not including any spring tension. <VAR id=yui-ie-cursor></VAR> <BR class=yui-cursor style="RIGHT: auto"></SPAN></div>
<div style="RIGHT: auto">Hank<BR style="RIGHT: auto"></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> James Frankland <jamesf@guernseysubmarine.com><BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> "personal_submersibles@psubs.org" <personal_submersibles@psubs.org> <BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B> Wednesday, July 24, 2013 9:51:24 AM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> [PSUBS-MAILIST] Double Seal?<BR></FONT></DIV>
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<div class=yiv982904078owaPara><FONT face=Constantia,Serif>Hi All,</FONT></div>
<div class=yiv982904078owaPara> </div>
<div class=yiv982904078owaPara>I have to re-machine the pop off top of my overpressure valve. I threaded the hole by hand and now i have finally attepted to fit it with its O ring, i can see that the bolt is not straight, causing mis-seating of the valve top. Im not over happy with having the bolt passing through anyway as it doesnt slide very easily. <BR><BR>So, im going to machine up a new smooth shaft which should be straight. Thats easy enough.</div>
<div class=yiv982904078owaPara> </div>
<div class=yiv982904078owaPara>BUT, at the same time, i am tempted to put in a second O ring groove and have 2 O rings on the pop off top. There is enough room for one outside the existing. <BR><BR>I seem to remember there was discussion on double O rings a while ago. Anyone have any thoughts on this idea? Seems to me to be a good idea as its got 2 seals, but ?</div>
<div class=yiv982904078owaPara> </div>
<div class=yiv982904078owaPara><FONT face=Constantia,Serif>Pic here as i was machining it.</FONT></div>
<div class=yiv982904078owaPara> </div>
<div class=yiv982904078owaPara>Kind Regards</div>
<div class=yiv982904078owaPara>James</div>
<div class=yiv982904078owaPara> </div>
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