[PSUBS-MAILIST] Gauge for outside viewport?

Mon Sep 21 05:03:08 EDT 2015

Hi Alec,

I have a couple of thoughts.

1.  The gauges I have are chemical protected, so they have an oil filled
diaphragm separating the inlet line from the gauge internals.  Then there
is a small vent hole at the top of the gauge.  You could attach a rubber
hose\bladder to this vent hole, top it up with glycerine or whatever the
gauge is filled with and have a fully compensated valve with a bladder.

2.  How about using just a normal scuba gauge which will probably be
perfectly fine.  But, just make a small adapter that screws onto the gauge
and has only a tiny little orifice to allow the input air.  That way if the
gauge did ever fail, it would only bleed out air slowly and you'd have time
to blow tanks.  If you are using a scuba 1st stage and piping from the HP
port (I assume your not and are plumbing straight into tanks) then the
scuba HP already has this small hole for the same reason.

Also, it would be easy enough to test a gauge.   Find somewhere deep enough
and take a fishing rod and a packed lunch!

Im fairly sure Emile has external gauges on his sub and its a 200m diver.
He could maybe advise?

Just a thought.
Kind Regards
James

On 21 September 2015 at 06:51, Brian Cox via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi Alec,    New sub ?  I must have missed that !    do you have any
> details?    BTW, I received that big gage !  It's huge !  I hope I can get
> it in through the hatch !   As it is designed for sea water I assume all I
> have to do is plumb it in, will salt water getting into the tubing cause
> any problems?
>
> Brian
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> Subject: [PSUBS-MAILIST] Gauge for outside viewport?
> Date: Sun, 20 Sep 2015 23:03:02 -0400
>
> I have an interesting thing to think about and wondered if any of the
> PSUBS brain trust might have a suggestion.
>
> One of the simplifications on my new sub is that all HP air lines are
> external, aside from the BIBS (which is normally shut off anyway). Thus,
> I'm looking for a 3,000-4,000 psi gauge to mount outside a viewport, like
> in the Pisces photo that I'll paste below. In case my paste doesn't come
> through, it is the one at the top of the following article:
> http://www.nytimes.com/2015/09/15/science/piloted-deep-sea-research-is-bottoming-out.html?_r=1
>
> The first thing that came to mind was to use a SCUBA submersible pressure
> gauge, but the problem is these are normally 1 atm dry enclosures of
> limited depth rating. There is generally little information posted about
> how deep they'll go, but what I did find was mentioned 260 feet for the
> plastic ones and 490 feet for the brass variety. This is a 1,000 foot sub.
>
> The second idea was to use oil filled gauges intended for above-water use.
> But these generally have considerable bubbles in the oil, are not very good
> at keeping the oil inside, and have other hardware not intended to live
> long in sea water.
>
> Any suggestions would be most welcome!
>
>
> Thanks,
>
> Alec
>
> [image: Inline image 1]
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