<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1433884861179_20061"><span>Hi Alec,</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20474">that one is also showing 40psi.</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20475">This is a Sean type problem.</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20821">I guess it's a bit like snapping a match stick. Anyone can do it, but try breaking it by</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20820">crushing it from end to end. In this case you can squeeze the tube & bend it but try </span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20819">crushing it cross sectionally with even pressure all around.</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20271">A solution may be to just squeeze up a section of the hose with a hose crimp</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20476">so that a point of weakness is created for the water pressure to continue crushing the</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span id="yui_3_16_0_1_1433884861179_20561">tube from there along it's length.</span></div><div id="yui_3_16_0_1_1433884861179_20061" dir="ltr"><span>Alan</span></div><br> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1433884861179_20065"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1433884861179_20064"> <div dir="ltr" id="yui_3_16_0_1_1433884861179_20063"> <hr size="1" id="yui_3_16_0_1_1433884861179_20062"> <font size="2" face="Arial" id="yui_3_16_0_1_1433884861179_20066"> <b><span style="font-weight:bold;">From:</span></b> Alec Smyth via Personal_Submersibles <personal_submersibles@psubs.org><br> <b><span style="font-weight: bold;">To:</span></b> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Wednesday, June 10, 2015 10:55 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1433884861179_20067"><br><div id="yiv9937101574"><div id="yui_3_16_0_1_1433884861179_20069"><div dir="ltr" id="yui_3_16_0_1_1433884861179_20068">Wow. If there is no mistake that is really counter intuitive, because the hose feels super pliable in your fingers - almost like those yellowish rubber lab hoses if you know what I mean. The size I'm using is half the wall thickness of what you calculated with, if that makes a difference. It's 1/4" ID X 3/8" OD X 1/16" thickness.<div id="yui_3_16_0_1_1433884861179_20070"><br clear="none"></div><div id="yui_3_16_0_1_1433884861179_20071">Alec</div></div><div class="yiv9937101574gmail_extra" id="yui_3_16_0_1_1433884861179_20072"><br clear="none"><div class="yiv9937101574gmail_quote" id="yui_3_16_0_1_1433884861179_20257">On Tue, Jun 9, 2015 at 6:46 PM, Alan James via Personal_Submersibles <span dir="ltr" id="yui_3_16_0_1_1433884861179_20308"><<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br clear="none"><blockquote class="yiv9937101574gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;" id="yui_3_16_0_1_1433884861179_20256"><div class="qtdSeparateBR"><br><br></div><div class="yiv9937101574yqt8200860419" id="yiv9937101574yqt51777"><div id="yui_3_16_0_1_1433884861179_20255"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;" id="yui_3_16_0_1_1433884861179_20254"><div id="yui_3_16_0_1_1433884861179_20302"><span>Alec,</span></div><div id="yui_3_16_0_1_1433884861179_20270"><span id="yui_3_16_0_1_1433884861179_20269">I had a look at the specs on that link. Thanks.</span></div><div id="yui_3_16_0_1_1433884861179_20303"><span id="yui_3_16_0_1_1433884861179_20360">The 3/8" ID x 5/8" OD X 1/8" tube is rated for 40psi internal pressure.</span></div><div id="yui_3_16_0_1_1433884861179_20268"><span id="yui_3_16_0_1_1433884861179_20267">As this is for fuel there could be a safety margin of 4x, so 160 psi burst pressure.</span></div><div dir="ltr" id="yui_3_16_0_1_1433884861179_20307"><span id="yui_3_16_0_1_1433884861179_20359">I ran a couple of plastics I have in my pressure program through internal and then</span></div><div dir="ltr" id="yui_3_16_0_1_1433884861179_20304"><span id="yui_3_16_0_1_1433884861179_20309">external pressure, & the maximum external pressure was 2/3rds the internal in both cases.</span></div><div dir="ltr" id="yui_3_16_0_1_1433884861179_20305"><span id="yui_3_16_0_1_1433884861179_20310">This could mean that it would take 106 psi before the hose would equalize significantly.</span></div><div dir="ltr" id="yui_3_16_0_1_1433884861179_20266"><span id="yui_3_16_0_1_1433884861179_20265">The diameter would maybe shrink a bit before collapsing.</span></div><div dir="ltr" id="yui_3_16_0_1_1433884861179_20264"><span id="yui_3_16_0_1_1433884861179_20904">Cheers Alan</span></div><div dir="ltr" id="yui_3_16_0_1_1433884861179_20306"><span><br clear="none"></span></div><br clear="none"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;" id="yui_3_16_0_1_1433884861179_20253"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;" id="yui_3_16_0_1_1433884861179_20252"> <div dir="ltr" id="yui_3_16_0_1_1433884861179_20262"> <hr size="1" id="yui_3_16_0_1_1433884861179_20905"> <font size="2" face="Arial" id="yui_3_16_0_1_1433884861179_20263"> <b id="yui_3_16_0_1_1433884861179_20312"><span style="font-weight:bold;" id="yui_3_16_0_1_1433884861179_20311">From:</span></b> Alec Smyth via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org" id="yui_3_16_0_1_1433884861179_20319">personal_submersibles@psubs.org</a>><span class="yiv9937101574" id="yui_3_16_0_1_1433884861179_20315"><br clear="none"> <b id="yui_3_16_0_1_1433884861179_20314"><span style="font-weight:bold;" id="yui_3_16_0_1_1433884861179_20313">To:</span></b> Personal Submersibles General Discussion <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> <br clear="none"> </span><b id="yui_3_16_0_1_1433884861179_20907"><span style="font-weight:bold;" id="yui_3_16_0_1_1433884861179_20906">Sent:</span></b> Wednesday, June 10, 2015 10:11 AM</font><div id="yui_3_16_0_1_1433884861179_20261"><div class="yiv9937101574h5" id="yui_3_16_0_1_1433884861179_20260"><br clear="none"> <b id="yui_3_16_0_1_1433884861179_20259"><span style="font-weight:bold;" id="yui_3_16_0_1_1433884861179_20258">Subject:</span></b> Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca<br clear="none"> </div></div> </div><div id="yui_3_16_0_1_1433884861179_20251"><div class="yiv9937101574h5" id="yui_3_16_0_1_1433884861179_20250"> <div id="yui_3_16_0_1_1433884861179_20249"><br clear="none"><div id="yui_3_16_0_1_1433884861179_20248"><div id="yui_3_16_0_1_1433884861179_20247"><div dir="ltr" id="yui_3_16_0_1_1433884861179_20246">The stuff I'm using is really flexible, and has a wall thickness of only 1/16". I'm having trouble imagining that the seal could offer less resistance than this, it's very soft. See McMaster item #<span style="color:rgb(51,51,51);font-family:arial, helvetica, sans-serif;font-size:12px;line-height:15.6000003814697px;" id="yui_3_16_0_1_1433884861179_20908">5552K25.</span><div id="yui_3_16_0_1_1433884861179_20245"><span style="color:rgb(51,51,51);font-family:arial, helvetica, sans-serif;font-size:12px;line-height:15.6000003814697px;"><br clear="none"></span></div><div><span style="color:rgb(51,51,51);font-family:arial, helvetica, sans-serif;font-size:12px;line-height:15.6000003814697px;">Best,</span></div><div id="yui_3_16_0_1_1433884861179_20358"><span style="color:rgb(51,51,51);font-family:arial, helvetica, sans-serif;font-size:12px;line-height:15.6000003814697px;"><br clear="none">Alec</span></div></div><div id="yui_3_16_0_1_1433884861179_20318"><br clear="none"><div>On Tue, Jun 9, 2015 at 5:29 PM, Alan James via Personal_Submersibles <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br clear="none"><blockquote style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><br clear="none"><br clear="none"></div><div><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"><div><span>Does anyone (Sean) have the material specifications in their</span></div><div dir="ltr"><span>pressure programs for the soft pvc that we would be using in</span></div><div dir="ltr"><span>our flexible compensation hoses?</span></div><div dir="ltr"><span>The nearest I had was nylon, & that had a crush depth of 8,000ft</span></div><div dir="ltr"><span>for a 1 meter long tube, 10mm diameter & 2mm wall thickness.</span></div><div dir="ltr"><span>I was thinking of using oil filled light housings with the wiring</span></div><div dir="ltr"><span>running through flexible hose as compensation, but are having second thoughts.</span></div><div dir="ltr"><span>Alan</span></div><br clear="none"> <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"> <hr size="1"> <font size="2" face="Arial"> <b><span style="font-weight:bold;">From:</span></b> Sean T. Stevenson via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><span><br clear="none"> <b><span style="font-weight:bold;">To:</span></b> Personal Submersibles General Discussion <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> <br clear="none"> </span><b><span style="font-weight:bold;">Sent:</span></b> Wednesday, June 10, 2015 6:11 AM<span><br clear="none"> <b><span style="font-weight:bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca<br clear="none"> </span></font> </div> <div><span><br clear="none"></span><div><div><div dir="ltr">I have always been a fan of oil compensation at higher than ambient pressure, for a variety of reasons. The only real downside is the environmental impact of potentially losing oil to the surrounding water in the event of a leak, but that impact can be mitigated with oil selection. Positive pressure allows you to compensate for volumetric changes in your compensated volumes due to the exterior pressure, as well as for thermal expansion of the oil, and if you have any leakage at all, you leak oil out, rather than water in, which can be an expensive lesson. Additionally, if you provide the bias with something like a spring loaded cylinder or elastomeric bladder, you can instrument its displacement for accurate monitoring of demanded compensation volume, and potentially detect leaks well in advance of when they actually become a problem. Ambient-only compensation has the disadvantage of not compensating for boundary-layer viscosity effects on rotating shafts,!
density
differences (gravity induced exchange and/or centripetally accelerated fluid) and other small but cumulative effects that can contribute to water ingress. </div>
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