<font color='black' size='2' face='arial'>
<div><font size="3">It seems that the need for sensing could be eliminated (as far as the present question goes) by positioning the handle for the pressure relief valve in such a manner that it would interfere with releasing the hatch <font face="Arial, Helvetica, sans-serif">latch</font> unless the relief valve handle was in the open position. In other words, you have to move the handle to out of the way before you can get to the hatch release. </font></div>
<div><font size="3"></font> </div>
<div><font size="3">Having a manual control handle doesn't preclude the relief valve from being automatic. It just means the manual portion leading to the auto portion was open. It seems like a good idea for the manual valve to be opened at some reasonable depth prior to surfacing so any overpressure is free to flow to the auto relief. You don't want overpressure to blow the hatch open when you're still two feet below the <font face="Arial, Helvetica, sans-serif">surface</font>. If the relief system is entirely manual, you have to wait until surfaced to open the valve unless the overpressure is particularly high.</font></div>
<div><font face="Arial, Helvetica, sans-serif" size="3"></font> </div>
<div><font size="3">Jim</font></div>
<div><font size="3"></font> </div>
<div><font face="Arial, Helvetica, sans-serif" size="3"></font> </div>
<div></div>
<div></div>
<div style="color: black; font-family: arial,helvetica; font-size: 10pt;">-----Original Message-----<br>
From: Joe Perkel <josephperkel@yahoo.com><br>
To: personal_submersibles <personal_submersibles@psubs.org><br>
Sent: Wed, Dec 11, 2013 8:54 am<br>
Subject: Re: [PSUBS-MAILIST] G.L. summary Pressure Hull<br>
<br>
<div id="AOLMsgPart_2_5be39082-9a7e-426a-8051-31d14bd36d72">
<table border="0" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top">Alan<br>
<br>
No definitive answer but we can postulate that both sensing and actuation are involved. <br>
<br>
On sensing, differential pressure on either side of the hatch is translated to a impulse to actuation.<br>
<br>
On actuation, a method of locking out the operator from physically un-dogging the hatch, is the only way to meet the standard as per your O.P.<br>
<br>
Joe<a href="http://overview.mail.yahoo.com?.src=iOS" target="_blank"><br>
<br>
Sent from Yahoo Mail for iPad</a></td></tr></tbody></table>
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<b>
<span style="font-weight: bold;">From:</span>
</b>
hank pronk <<a href="mailto:hanker_20032000@yahoo.ca">hanker_20032000@yahoo.ca</a>>; <br>
<b>
<span style="font-weight: bold;">To:</span>
</b>
Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>; <br>
<b>
<span style="font-weight: bold;">Subject:</span>
</b>
Re: [PSUBS-MAILIST] G.L. summary Pressure Hull <br>
<b>
<span style="font-weight: bold;">Sent:</span>
</b>
Wed, Dec 11, 2013 2:36:26 PM <br>
</div>
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<div><span>Alan,</span></div>
<div><span>Is this equalization from overpressure inside the hull? or external pressure. </span></div>
<div><span>Hank </span></div>
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<div class="yqt1385517701" id="yqt07881">
<div dir="ltr"> <font face="Arial" size="2"> On Wednesday, December 11, 2013 1:23:21 AM, Alan <<a href="mailto:alanlindsayjames@yahoo.com">alanlindsayjames@yahoo.com</a>> wrote:<br clear="none"> </font> </div>
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<div>Can
anyone enlighten me on what sought of mechanism</div>
<div>is used that renders the opening of the
hatch possible only after</div>
<div>equalisation, as per G.L. Requirements?</div>
<div>Thanks</div>
<div>Alan<br clear="none"><br clear="none">Sent from my iPad</div>
<div class="yiv6100496818yqt6118645076" id="yiv6100496818yqt49514">
<div><br clear="none">On 11/12/2013, at 3:01 PM, Alan James <<a rel="nofollow" shape="rect">alanlindsayjames@yahoo.com</a>> wrote:<br clear="none"><br clear="none"></div>
<blockquote type="cite">
<div>
<div style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 14pt; background-color: rgb(255, 255, 255);">
<div>Hi,</div>
<div>I'm not covering much in this section because if I started on construction</div>
<div>regulations, I would just be duplicating what was printed.</div>
<div>G.L. wants you to have manufacturer certificates for every non structural
screw.</div>
<div>Any company you contract to do your welding has to have their facilities, personal</div>
<div>& supervision approved by G.L..</div>
<div>Some points of interest are.... hatches need to be opened from both sides, they need</div>
<div>to be able to be secured open, they need to be designed in a way that opening of the</div>
<div>hatch is only possible after equalization. Two measures are required to guarantee that</div>
<div>the hatches are closed & secured before diving; one measure is to be visibly noticeable.</div>
<div>Mechanical
measures for stopping a banging of the hatch is required.</div>
<div>Any external through hulls are to be protected against damage by appendages or covers.</div>
<div>If you are doing calculations on a computer you have to prove that the program is suitable.</div>
<div>Alan</div>
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