<html><head></head><body><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_1_1480175087437_3060"><span>Sean,</span></div><div id="yui_3_16_0_1_1480175087437_3060"><span id="yui_3_16_0_1_1480175087437_3181">The receiving tank will take the full depth pressure and be large </span>enough to take all the oil without building up excess air pressure, no need to vent off, since it is only receiving oil and displacing air. I need a balance with two tanks to maintain neutral buoyancy.</div><div id="yui_3_16_0_1_1480175087437_3060" dir="ltr">I am not worried about oxidation of the oil because the oil is not going through a pump and the flow rate is so small. I ordered air cylinders for the manipulator with a 5\8 rod to reduce the back pressure. Gamma's manipulator operated at 1,100 psi when the sub was at 1,000 feed of depth. The arm will loose power, but I don't expect that to be an issue, because the oil tank will be powered from a separate bottle of air. </div><div id="yui_3_16_0_1_1480175087437_3060" dir="ltr">I have to work with what I have to keep the cost in check, so I can modify an open centre valve by blocking the final pressure port drain. I also have some HP tanks. If it does not work out easily, I have a few electric pumps I can use. </div><div id="yui_3_16_0_1_1480175087437_3060" dir="ltr"><br></div><div id="yui_3_16_0_1_1480175087437_3060" dir="ltr">If I go electric, I intend to submerge the motor pump unit in the oil reservoir with a bladder top to compensate. That means I will use WD40 as hydraulic fluid.</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 Saturday, November 26, 2016 6:25 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br></font></div> <br><br> <div class="y_msg_container"><div id="yiv9148892080"><div><div dir="ltr">How do you intend to control the pressure on the receive tank? Just vent it through a check valve to the water? You need to design carefully to prevent contamination in either direction.</div>
<div dir="ltr">I wouldn't use air as the drive gas under high pressures, in order to prevent oxidation of the oil. Charge with nitrogen if you intend to do this.</div>
<div dir="ltr">To generate the same drive capability as a hydraulic pump, you are talking about very high precharge pressure - approaching the pressure at which HP bottled gas is supplied, unless you can source e.g. 6000 psi nitrogen and regulate it down to 2500-5000 depending on your manipulator requirements. In any case, if your cylinders are single acting, or even dual acting with a single rod, you have to contend with the force from the ambient water pressure, so your receive tank pressure needs to be this at minimum, and with a pressure reservoir source instead of a pump, that available delta-P is further reduced the moment you demand any fluid from the system (i.e. HP bottle pressure will drop), so your manipulator becomes weaker over time.</div>
<div dir="ltr">Just a few things to think about.</div>
<div dir="ltr">Sean</div>
<br clear="none"><br clear="none"><div class="yiv9148892080gmail_quote">On November 25, 2016 5:25:47 AM MST, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="yiv9148892080gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex;">
<div class="yiv9148892080yqt2885590970" id="yiv9148892080yqt95748"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div id="yiv9148892080yui_3_16_0_1_1480075807070_2825">Hi All,</div><div dir="ltr" id="yiv9148892080yui_3_16_0_1_1480075807070_2825">I have an idea to replace the hydraulic pump for my new manipulator with a air over hydraulic system. It is quite simple, the hydraulic oil reservoir is a hp tank that can be pressurized from a designated HP supply. The oil return goes to another HP tank to receive the oil. This eliminates the pump completely and that is a dream. The manipulator can go through 54 complete extensions and retractions, that is 54 complete movements of all functions. </div><div dir="ltr" id="yiv9148892080yui_3_16_0_1_1480075807070_2825">After the oil is used up, the oil can be returned to the pressure tank by reversing the air flow.</div><div dir="ltr" id="yiv9148892080yui_3_16_0_1_1480075807070_2825">Hank</div></div></div><div style="margin-bottom:1em;border-bottom:1px solid #000;"></div><pre class="yiv9148892080k9mail"></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><div class="yqt2885590970" id="yqt00964">_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><br><br></div> </div> </div> </div></div></body></html>