[PSUBS-MAILIST] Fw:

[Sean T. Stevenson via Personal_Submersibles]

A water expansion tank will be wholly insufficient for this. They simply are not designed for the pressure you need, nor for submerged service.  That said, it may not be as complicated as you think. If you can find or build a vessel that will take a higher pressure (pipe with end caps or SCUBA tank?), and an appropriate bladder to fit inside, connect the bladders through a directional valve such that at any given time, one side is connected to your regulated high pressure gas source, and one side is vented through a check valve to sea. Then do the same thing on the oil side (switching pressure supply and reservoir return). This way, when you exhaust your oil supply, you need only switch the valves and you're good to go again, provided you have sufficient HP gas. You can fill your HP gas between dives, or have spare bottles on hand to swap out. Venting the bladder in the receive tank to sea takes care of pressure compensation (at ambient + check valve back pressure), giving you
constant delta-P as long as your HP gas supply holds out.

Short of purchasing a commercial accumulator, I like the SCUBA tank as a vessel because of the known pressure capability and the smooth interior and rounded ends, which are likely to permit a bladder to expand against it without damage. The downside is of course that everything has to fit through the neck opening, unless you cut and customize the end opening with a flange or new end cap of some sort. I second Alan's concern about DIY high pressure vessels.

Sean


On November 27, 2016 1:05:16 PM MST, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Sean,This was my original idea for an accumulator but  the tank needs
>to handle  the work pressure of the cylinder (130 lbs)  plus ambient
>pressure, plus rod dia pressure, plus pressure against receiving tank.
> Not a big challenge but but getting more complicated.  Hank
>
>  On Sunday, November 27, 2016 1:01 PM, xxx xxxxx <mp13 at live.ca> wrote:
> 
>
>http://www.ebay.com/itm/FLEXCON-PH5-2-GAL-FLEX-2-PRO-POTABLE-WATER-THERMAL-EXPANSION-VFD-PRESSURE-TANK-/272224750856?hash=item3f61dc0d08:g:tD0AAOSwaZdXH46l
>
>
>
>   
>
>------------------------------------------------------------------------
>
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