[PSUBS-MAILIST] psi

[Alec Smyth via Personal_Submersibles]

Hi Rick,

Your understanding is correct, but I'm curious about the flow meter. The
ones I use are designed to work with medical O2 tanks (although I don't
have those tanks in the sub.) Like you, I drop the pressure to 150 over
ambient outside the hull. It is a safety measure, to avoid bringing HP
oxygen inside. If I were using the flow meters as designed, directly on a
tank, they would see variable pressure as the tank empties, so as long as
my outside regulator is supplying O2 at a pressure that is within the range
of a medical tank, they are happy. What I use are pediatric flow
regulators, with a dial to adjust liters per minute. Pediatric ones are
good because they have lower scale flow rates, which are well suited for
the ranges we need in a sub.

Thanks,
Alec



On Tue, Aug 3, 2021 at 11:15 PM Rick Patton via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Having a brain fart,,,,,, I am knocking down my HP - 02 on the outside of
> the sub with an 02 cleaned 1st stage reg which I understand will bring it
> into the sub at around 150 psi + - on the surface.  As I understand it,
> this 1st stage will always give me around 150 psi over ambient? so is it
> safe to assume that at the max operating depth of my K-350, will it be
> trying to push in around 320 psi absolute?
>
> everything tells me that it will but the part that I am having a hard time
> with is that the 150 psi over bottom is pushing it into a 14.7 psi scenario
> so does that change things up? My flow meter is calibrated for a 50 psi
> inlet psi. I also have run new rubber 02 hose that I seperated from an
> acetylene hose for a burning torch and will have to see if that hose is
> rated for that pressure.
>
>  I chose to go that way as I am not a good tube bender. Another scenario I
> was thinking of doing if the 1st stage keeps pushing more and more is to
> attach a shop 02 regulator just inside the sub that has both the HP and LP
> gauges on it and dial down the LP side to put out no more than 50 psi?
>
> Rick
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