[PSUBS-MAILIST] Electronics contents gauge

Stephen Fordyce via Personal_Submersibles personal_submersibles at psubs.org
Mon Oct 31 19:58:56 EDT 2016


Thanks Alan,
Yes much of the stuff in my catalogue is dedicated to SCUBA gas mixing and
high pressure oxygen (and there is a bunch more about to be added).  A
couple of items are from Undersea UK and if you ever want some stuff from
there let me know and we might consolidate shipping.  For the record, my HP
oxygen digital gauge is US$183 compared to US$208 for the Undersea one -
they have great stuff but getting it down here is sometimes not
cost-effective (and their standard thread is 1/4" BSPP with O ring, whereas
I prefer 1/4" NPT).

Actually while on the subject of pressure monitoring, I've nearly
finished development and production of a couple of new products that may be
of interest to psubbers - an "Oxygen Watchdog" and "Pressure Watchdog".
These are self-contained panel-mount kits with sensor, display/controller
and 2 independent relay outputs.  They read and display the O2 percent
or cylinder pressure, and the controller can be set to trigger/release the
relays under various circumstances (low setpoint, high setpoint, too far
from a middle setpoint, etc.).

They are intended for SCUBA compressors and mixing systems, but would do
well (with perhaps a few minor modifications) if you want a
standalone/PLC-independent alarm system in a PSUB.  A couple of pictures of
the prototypes are below.

If anyone is interested in a kit, (or just bits of it) then let me know.
They are light enough that shipping anywhere in the world will be pretty
reasonable.

Cheers,
Steve


[image: Inline image 2][image: Inline image 3]

On Tue, Nov 1, 2016 at 8:21 AM, Alan James via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Steve,
> just had a look at your 2016 catalogue.
> http://www.tfmengineering.com.au/TFM_Engineering_Catalogue_2016-03.pdf
> Wow, you've got a lot of gear I haven't seen before.
> Alan
>
>
>
>
>
> ------------------------------
> *From:* Stephen Fordyce via Personal_Submersibles <
> personal_submersibles at psubs.org>
> *To:* Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> *Sent:* Monday, October 31, 2016 4:53 PM
> *Subject:* Re: [PSUBS-MAILIST] Electronics contents gauge
>
> Hi Alan
> Yep, my pressure transmitter is suitable for oxygen (and is ranged
> 0-400bar).
>
> A SCUBA reg HP port usually has an orifice built-in to restrict flow in
> the event of hose failure.  But with even 100bar behind it, the tank will
> still empty in a matter of minutes - pretty significant.  Having the
> prolonged restriction of a long skinny tube will help a bit, but a total
> failure would still put out a lot of gas.
>
> Cheers,
> Steve
>
> On Mon, Oct 31, 2016 at 12:04 PM, Alan James via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Thanks Emile & Steve.
> I may combine both suggestions.
> I am wanting to put my penetrations through a removeable plate
> a la Deep Worker. It will be behind me in my 1 person submersible;
> so a pressure transmitter with wires coming from it rather than a gauge
> looks like the right option.
> I like the idea of the 1/8th tube. I couldn't find a flow rate anywhere
> for a 1st stage hp port. May have to flow it in to a plastic bag & get an
> estimate, to see if a failure would be an issue anyway.
>    Steve, are those pressure transmitters suitable for oxygen?
> Cheers Alan
>
>
>
> ------------------------------
> *From:* Stephen Fordyce via Personal_Submersibles <personal_submersibles at psubs.
> org <personal_submersibles at psubs.org>>
> *To:* Personal Submersibles General Discussion <personal_submersibles at psubs.
> org <personal_submersibles at psubs.org>>
> *Sent:* Monday, October 31, 2016 12:34 PM
> *Subject:* Re: [PSUBS-MAILIST] Electronics contents gauge
>
> Hi Alan,
> I have pressure transmitters (similar to many commonly used in
> industry) that could probably be adapted for that - see attached
> photos.  You could replace the end section with a small penetrator/cable
> gland plate.  It needs a power supply of 6-30VDC and outputs 0.5-4.5V or
> 4-20mA (both linear).  They are NPT so you'd need an adaptor for the
> SCUBA HP port - but a 1/4" Swagelok thread will fit.
>
> I imagine you're worried about leaks of HP inside, and maybe cost as
> well.  Something you may not have thought of is running 1/8" SS tube.  It's
> soft enough to bend by hand (more like stiff solid-core electrical cable
> than 1/4" tube) and can be run in a bundle with cables.  Also available in
> very small inside diameters so flow is greatly restricted.  I've had good
> success using it for remote gauge lines.
>
> I also have digital HP oxygen pressure gauges if you ever need one of
> those :).
>
> Shoot me an email at Stephen.fordyce@ tfmengineering.com.au
> <Stephen.fordyce at tfmengineering.com.au> if you're interested in one -
> list price is AU$198.
>
> Cheers,
> Steve
> (TFM Engineering Australia)
>
> On Mon, Oct 31, 2016 at 7:19 AM, emile via Personal_Submersibles <personal_submersibles at psubs.
> org <personal_submersibles at psubs.org>> wrote:
>
> The scuba pressure sensors are wireless. Most scuba divers don’t want it
> as it is unreliable.
>
> Best would be to screw a industrial pressure sensor (with ¼ “thread or so)
> into the penetrator plate and attach a HP line on the outside.
>
>
> Br, Emile
>
> *Van:* Personal_Submersibles [mailto:personal_submersibles-
> bounces at psubs.org <personal_submersibles-bounces at psubs.org>] *Namens *Alan
> James via Personal_Submersibles
> *Verzonden:* zondag 30 oktober 2016 21:02
> *Aan:* Personal Submersibles General Discussion
> *Onderwerp:* [PSUBS-MAILIST] Electronics contents gauge
>
> Is there a suitable electronic scuba tank contents gauge out there?
> I am after something that plugs in to the high pressure port of the
> 1st stage regulator & has wires off it that I can run through a through
> hull so I can display the tank contents pressure on a screen.
> Trying to avoid bringing high pressure in to the hull.
> An alternative may be to run a high pressure line to a through
> hull & have an electronic pressure gauge threaded in to this from the
> inside of the hull. However with the second method, I wouldn't have
> a shut off valve if the pressure gauge failed some how.
> Alan
>
>
>
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