<html><head></head><body><p 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.</p>
<p 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.</p>
<p 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.</p>
<p dir="ltr">Just a few things to think about.</p>
<p dir="ltr">Sean</p>
<br><br><div class="gmail_quote">On November 25, 2016 5:25:47 AM MST, 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_1_1480075807070_2825">Hi All,</div><div id="yui_3_16_0_1_1480075807070_2825" dir="ltr">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 id="yui_3_16_0_1_1480075807070_2825" dir="ltr">After the oil is used up, the oil can be returned to the pressure tank by reversing the air flow.</div><div id="yui_3_16_0_1_1480075807070_2825" dir="ltr">Hank</div></div><p style="margin-top:
2.5em; margin-bottom: 1em; border-bottom: 1px solid #000"></p><pre class="k9mail"><hr /><br />Personal_Submersibles mailing list<br />Personal_Submersibles@psubs.org<br /><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br /></pre></blockquote></div></body></html>