[PSUBS-MAILIST] Gauge for outside viewport?

Mon Sep 21 08:20:16 EDT 2015

Hi James,

1) I have a bunch of oil filled gauges lying around, but if they are left
in any position other than with the rubber caps at the top, they leak all
over the place. The shelf they live on is covered with oil, so I'm just not
confident they will keep the oil inside in the field.

2) Yes, SCUBA tank gauges have a tiny orifice in their hose fittings for
just that purpose, to prevent a broken instrument from emptying your tank
too quickly. That is good and I plan to use it on the sub as well. However,
the problem still persists that SCUBA gauges can only be taken to under 500
feet. I came across tech diver accounts of gauge issues such as the plastic
faces buckling and pinning the needle, or the whole enclosure imploding at
about 400 feet.

Thanks,

Alec

On Mon, Sep 21, 2015 at 5:03 AM, James Frankland via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> 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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