<DIV style="font-family:Arial, sans-serif; font-size:10pt;"><DIV>I would think the biggest worry would be if you had a large over pressure in the cabin and when you get to the surface you force a viewport to leak air outside, but that shouldn't happen unless you sheared off a retaining ring or something.</DIV><DIV> </DIV><DIV>Brian<BR><BR>--- personal_submersibles@psubs.org wrote:<BR><BR>From: Private via Personal_Submersibles <personal_submersibles@psubs.org><BR>To: Personal Submersibles General Discussion <personal_submersibles@psubs.org><BR>Subject: Re: [PSUBS-MAILIST] Snorkel<BR>Date: Wed, 14 Jan 2015 19:02:45 -0500<BR><BR></DIV><DIV>Hi Sean,</DIV><DIV><BR></DIV><DIV>It's extremely easy to relieve negative pressure... You just press the plunger and can do it with one finger. I do this almost every time before opening the hatch, as a small negative pressure is SOP.</DIV><DIV><BR></DIV><DIV>Best,</DIV><DIV><BR></DIV><DIV>Alec<BR><BR><DIV><BR></DIV></DIV><DIV><BR>On Jan 14, 2015, at 6:57 PM, Sean T Stevenson via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>> wrote:<BR><BR></DIV><BLOCKQUOTE><DIV><P dir="ltr">Is it always possible to manually actuate the valve if you have a negative differential pressure?  I always presumed that a ball or needle valve would be necessary to equalize pressure on either side of a hatch before opening, because such a valve accommodates pressure differences in either direction.  With the overpressure valve, in such a situation you need to overcome this difference in addition to the spring preload. That, or I guess you could just bleed some air or oxygen into the cabin.</P></DIV>
<P dir="ltr">Sean<BR>

<BR><BR><DIV>On January 14, 2015 12:36:36 PM MST, Alan James via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>> wrote:<BLOCKQUOTE style="margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;">
<DIV style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);"><DIV dir="ltr"><SPAN>Brian,</SPAN></DIV><DIV dir="ltr"><SPAN>I seem to remember you can manually operate Emile's</SPAN></DIV><DIV dir="ltr"><SPAN>overpressure valve; and it is operating procedure to press</SPAN></DIV><DIV dir="ltr"><SPAN>it to relieve the remaining pressure before opening the hatch.</SPAN></DIV><DIV dir="ltr"><SPAN>If you are looking for an off the shelf solution, make sure</SPAN></DIV><DIV dir="ltr"><SPAN>you can do that.</SPAN></DIV><DIV dir="ltr"><SPAN>Alan</SPAN></DIV><BR>  <DIV style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <DIV style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <DIV dir="ltr"> </DIV></DIV></DIV></DIV></BLOCKQUOTE></DIV></P><HR size="1">  <FONT face="Arial" size="2"> <B><SPAN style="font-weight: bold;">From:</SPAN></B> Brian Cox via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</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;">Sent:</SPAN></B> Thursday, January 15, 2015 6:11 AM<BR> <B><SPAN style="font-weight: bold;">Subject:</SPAN></B> Re: [PSUBS-MAILIST] Snorkel<BR> </FONT>  <DIV><BR><DIV><DIV><DIV style="font-family: Arial, sans-serif; font-size: 10pt;"><DIV>I don't see where they list the pressure limit on it.</DIV><DIV> </DIV><DIV>Brian<BR><BR>--- <A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A> wrote:<BR><BR>From: James Frankland via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR>To: Personal Submersibles General Discussion <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR>Subject: Re: [PSUBS-MAILIST] Snorkel<BR>Date: Wed, 14 Jan 2015 16:31:56 +0000<BR><BR></DIV><DIV dir="ltr"><DIV>what about something like
this?  I only just googled it so would need research.  Don't quote me on it!</DIV><DIV> </DIV><DIV><A href="http://www.haitima.com.tw/valve/check-valve/check-valve-2026.htm">http://www.haitima.com.tw/valve/check-valve/check-valve-2026.htm</A></DIV></DIV><DIV><BR><DIV>On 14 January 2015 at 15:55, Brian Cox via Personal_Submersibles <SPAN dir="ltr"><<A href="mailto:personal_submersibles@psubs.org">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;"><DIV><BR><BR></DIV><DIV><DIV style="font-family: Arial, sans-serif; font-size: 10pt;"><DIV>Is there an off the shelf over pressure valve that I can get?</DIV><DIV> </DIV><DIV>Brian<BR><BR>--- <A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A> wrote:<BR><BR>From: James Frankland via Personal_Submersibles <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><SPAN><BR>To: Personal Submersibles General Discussion <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR></SPAN>Subject: Re: [PSUBS-MAILIS!
 T]
Snorkel<BR>Date: Wed, 14 Jan 2015 13:58:24 +0000<BR><BR></DIV><DIV><DIV><DIV dir="ltr">Yes, my OP valve does not have enough holes.  I have a job over the winter to add more or drill existing holes bigger.  </DIV><DIV><BR><DIV>On 14 January 2015 at 13:04, Emile van Essen via Personal_Submersibles <SPAN dir="ltr"><<A href="mailto:personal_submersibles@psubs.org">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;">Mark, All.<BR>
<BR>
Mind the area is big enough. The valve in the attachment is designed for a<BR>
3000 Kg sub. But even then it is to small if you surface too quick in case<BR>
of massive overpressure.<BR>
Cracking pressure: 25-75 mBar.<BR>
<BR>
<BR>
Best regards, Emile<BR>
<BR>
-----Oorspronkelijk bericht-----<BR>
Van: Personal_Submersibles [mailto:<A href="mailto:personal_submersibles-bounces@psubs.org">personal_submersibles-bounces@psubs.org</A>]<BR>
Namens Mark via Personal_Submersibles<BR>
Verzonden: dinsdag 13 januari 2015 13:12<BR>
Aan: Personal Submersibles General Discussion<BR>
Onderwerp: Re: [PSUBS-MAILIST] Snorkel<BR>
<DIV><DIV><BR>
Since we are discussing over-pressure valves, can you recommend a make and<BR>
model, or describe its specifications?<BR>
<BR>
Regards,<BR>
<BR>
Mark...<BR>
<BR>
Sent from iPhone.<BR>
<BR>
> On Jan 12, 2015, at 7:06 PM, Pete Niedermayr via Personal_Submersibles<BR>
<<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>> wrote:<BR>
><BR>
> Scott, I see you have an overpressure valve in place of the snorkel .<BR>
Whats that on the other side ?<BR>
><BR>
> Pete ?<BR>
> --------------------------------------------<BR>
> On Mon, 1/12/15, via Personal_Submersibles<BR>
<<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>> wrote:<BR>
><BR>
> Subject: Re: [PSUBS-MAILIST] Snorkel<BR>
> To: "Personal Submersibles General Discussion"<BR>
<<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR>
> Date: Monday, January 12, 2015, 5:09 PM<BR>
><BR>
> I<BR>
> would recommend a cabin overpressure valve instead. It is a<BR>
> mushroom valve. You can see pics on my sub page. Alec<BR>
> did the same thing.<BR>
><BR>
> Thanks,<BR>
> Scott Waters<BR>
><BR>
><BR>
> -------- Original<BR>
> Message --------<BR>
> Subject: [PSUBS-MAILIST] Snorkel<BR>
> From: Pete Niedermayr via Personal_Submersibles<BR>
> <<A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A>><BR>
> Date: Mon, January 12, 2015 3:58 pm<BR>
> To: <A href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</A><BR>
><BR>
> I have a set of K 350 plans that I'm using as a<BR>
> reference for my own design. I'm using the conning tower<BR>
> plans pretty much as per. The question I do have is. Snorkel<BR>
> or no snorkel ? On the one hand I can see how it would be<BR>
> useful have. On the other hand no other design seems to have<BR>
> one. What are your opinions? Snorkel or no snorkel?<BR>
><BR>
> Pete<BR>
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