<html><head></head><body><p dir="ltr">What is off? O-ring groove / seat parallelism (hatch angle)? Or radial position (concentricity)? Are you dogging it first? Dogging is intended to create the initial recommended O-ring squeeze to create an effective seal at low pressure differentials, before increased external pressure takes over at depth and squeezes them down to the maximum design squeeze when you have metal-to-metal contact at the face seal, loosening your dogs in the process. With a hinged hatch, the part of the O-ring that is radially closest to the hinge will make contact first, and begin to squeeze and support the weight of the hatch from that side first. It is possible that the entire weight of your hatch is fully supported by the force developed by less than the entire o-ring, such that the hinge side is squeezed and the far side is only just making contact. You can even that out by switching to a softer durometer ring, or simply dog the hatch to ensure the minimum
necessary squeeze on the far side of the ring. You can test if it lines up under increased pressure by piling a bunch of weight on it.</p>
<p dir="ltr">You want the hatch to go metal-to-metal as soon as possible, as this eliminates any possible extrusion path for the O-ring (face seals are zero clearance). A softer ring will make this easier, but is also more prone to extrusion before the gap can be closed. What is your design squeeze at fully closed?</p>
<p dir="ltr">Sean<br>
</p>
<br><br><div class="gmail_quote">On March 22, 2016 11:15:56 AM MDT, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_ym18_1_1458666726266_8718"><span id="yui_3_16_0_ym18_1_1458666726266_8717">Oops, I cut off my e mail. The amount it is off is maybe 2 thousandths.</span></div><div id="yui_3_16_0_ym18_1_1458666726266_8705"><span>Hank</span></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 Tuesday, March 22, 2016 11:13 AM, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br /></font></div> <br /><br /> <div class="y_msg_container"><div
id="yiv8781309021"><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div id="yiv8781309021"><div id="yiv8781309021yui_3_16_0_ym18_1_1458664884172_10416"><div id="yiv8781309021yui_3_16_0_ym18_1_1458664884172_10415" style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div id="yiv8781309021yui_3_16_0_ym18_1_1458664884172_3019"><span id="yiv8781309021yui_3_16_0_ym18_1_1458664884172_3020">Sean yes it is conical, but when I close it with the o-ring, it does not close tight metal to metal and with the play in the hinge I feel like it is not closing evenly when I do the vacuum test. I am probably worrying about nothing, likely the hatch is not </span>completely seated metal to metal under vacuum. I am talking</div> <div class="yiv8781309021qtdSeparateBR"
id="yiv8781309021yui_3_16_0_ym18_1_1458664884172_10417"><br clear="none" /><br clear="none" /></div></div></div></div><div> <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 class="yiv8781309021qtdSeparateBR"><br clear="none" /><br clear="none" /></div><div class="yiv8781309021yqt7943374468" id="yiv8781309021yqt64945"><div class="yiv8781309021yqt9433575184" id="yiv8781309021yqt16859"><div dir="ltr"><font size="2" face="Arial"> On Tuesday, March 22, 2016 10:18 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br clear="none" /></font></div> <br clear="none" /><br clear="none" /> <div class="yiv8781309021y_msg_container"><div id="yiv8781309021"><div><div dir="ltr">What type of misalignment exists? Aren't you using a conical bearing face on your hatch?
That should be self-centering.</div>
<div dir="ltr">Sean<br clear="none" />
</div>
<br clear="none" /><br clear="none" /><div class="yiv8781309021gmail_quote">On March 22, 2016 9:03:59 AM MDT, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="yiv8781309021gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex;">
<div class="yiv8781309021yqt7690350165" id="yiv8781309021yqt20545"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div id="yiv8781309021yui_3_16_0_ym18_1_1458658465670_2557">Hi All,</div><div id="yiv8781309021yui_3_16_0_ym18_1_1458658465670_2557">When I built my hatch system, I built it so the hinge pin has moment in it so the o-ring would have full contact before the hatch was fully closed metal to metal.</div><div id="yiv8781309021yui_3_16_0_ym18_1_1458658465670_2557">When I vacuum test it, the hatch is not perfectly even in the seat, or at least it seems like it. I am wondering if I should close the hatch with the o-ring out and the hatch perfectly positioned and then weld bushings to the hinge so the pin has no movement. Or should I leave it alone and expect that the external pressure will push the hatch into place? </div><div
id="yiv8781309021yui_3_16_0_ym18_1_1458658465670_2557">Hank</div><div id="yiv8781309021yui_3_16_0_ym18_1_1458658465670_2557"><br clear="none" /></div><div id="yiv8781309021yui_3_16_0_ym18_1_1458658465670_2557">Scott, did you notice if your hatch hinge has play?</div></div></div><div style="margin-top:2.5em;margin-bottom:1em;border-bottom:1px solid #000;"></div><pre class="yiv8781309021k9mail"></pre><hr /><br clear="none" />Personal_Submersibles mailing list<br clear="none" />Personal_Submersibles@psubs.org<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><br clear="none" /></blockquote></div></div></div><br clear="none" /><div class="yiv8781309021yqt7690350165" id="yiv8781309021yqt20336">_______________________________________________<br clear="none" />Personal_Submersibles mailing list<br clear="none" /><a rel="nofollow"
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