[PSUBS-MAILIST] Electronic contents gauge

Thu Nov 3 19:30:03 EDT 2016

Hi Alan,
I think you will find that the silicone (semiconductor type rather than
rubber-like gasket type) vs ceramic is for the pressure sensing element,
which sits behind a stainless steel diaphragm, so the process fluid doesn't
see the silicone or ceramic.

The difficult bit to get the Chinese suppliers to understand is oxygen
cleaning - and that sort of thing really needs to be cleaned before
assembly, and during any subsequent testing/calibration process.  Ie. they
are likely to use water (or maybe even oil - many standard pressure gauges
are also tested on oil by default) to test, which will leave residue that
could be very scary in oxygen service.

Cheers,
Steve

On Thu, Nov 3, 2016 at 9:46 PM, Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> I have had a number of replies from businesses to an enquiry regarding a
> stainless pressure transmitter that fits a high pressure scuba port.
> 2 options are diffused silicon (or just silicon) & ceramic.
> I am wanting to use these on my O2 cylinders as well as air.
> Does anyone know whether one or the other is better for O2.
> I am guessing the ceramic is, as silicon may be combustable,
> but know nothing about this.
> Regards Alan
>
> Sent from my iPad
>
> On 3/11/2016, at 5:57 pm, Alan via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Thanks Steve,
> a really good price but the flow rate to shut looks higher than the full
> flow rate
> from my 1st stage hp port.
> I am now trying to find a pressure transmitter I can pot with 7/16 UNF,
> about 300bar
> & stainless 316. Similar to what you suggested but with the compatible
> thread.
> Have filled out a buying request on Alibaba with those details. No doubt I
> will
> get several offers including a stuffed dog that barks!
> Cheers Alan
>
> Sent from my iPad
>
> On 3/11/2016, at 5:23 pm, Stephen Fordyce via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Hi Alan,
> These also exist and are pretty cheap, although not particularly oxygen
> friendly:
> http://valvesandregulators.aquaenvironment.com/item/check-valves-and-flow-
> limiting-devices/443-flow-fuse/443?&bc=100%7C1009
>
> (I stock a couple of these for SCUBA tank filling, but they are not very
> popular)
>
> As you say, I don't think you will be able to use these with a SCUBA reg
> HP port due to the restricted flow.
>
> Cheers,
> Steve
>
>
> On Thu, Nov 3, 2016 at 7:48 AM, Alan via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Thanks Hugh,
>> I just got a price of $160 NZ for a 1/4" 316 excess flow valve.
>> A lot cheaper than I thought. However looking at the data on their
>> standard
>> XS4 series, the "trip" flow on 3000psi is 250 cubic ft per minute or 116
>> litres
>> per second. I had measured roughly 2 litres per second coming out of my
>> 1st stage high pressure port.
>> They do say they have smaller springs for tripping at a lower flow but it
>> might be a big step to get to what I want ie. tripping with virtually no
>> flow.
>> For me I am leaning toward the option of potting the electronic gauge that
>> Steve suggested & having wires through the hull to a plc. plus have
>> contents
>> gauges within view of my dome.
>> Cheers Alan
>>
>>
>> Sent from my iPad
>>
>> On 3/11/2016, at 8:34 am, Hugh Fulton via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> Hi Hank / Alan,
>>
>> There are excess flow valves available for air/gas.  We make them but
>> also Swagelok have them.  Ours are industrial for high gas flows.
>>
>> You need to make sure they are self resetting.  Hugh
>>
>>
>>
>> *From:* Personal_Submersibles [mailto:personal_submersibles-
>> bounces at psubs.org <personal_submersibles-bounces at psubs.org>] *On Behalf
>> Of *hank pronk via Personal_Submersibles
>> *Sent:* Thursday, 3 November 2016 1:16 AM
>> *To:* Personal Submersibles General Discussion
>> *Subject:* Re: [PSUBS-MAILIST] Electronic contents gauge
>>
>>
>>
>> Alan,
>>
>> There is a hydraulic component on cranes etc the allows oil to flow at a
>> set rate, but if the flow increases dramatically the component becomes a
>> shut off valve.  This is to protect people and equipment in case a hose or
>> seal blows out.  maybe there is aa air equivalent?
>>
>> Hank
>>
>>
>>
>> On Wednesday, November 2, 2016 3:43 AM, Alan James via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>
>>
>> I just experimented with the flow from the high pressure port
>>
>> on my 1st stage regulator. That's the one your pressure gauge runs off.
>>
>> Even though the hole is literally a pin prick, I was getting at least
>>
>> 2 liters a second flow out of it.
>>
>> I am building a similar sized sub to Cliff's R300 & a leak like that,
>>
>> apart from increasing the pressure massively, would be hazardous
>>
>> if it was O2. In 4 minutes I could have 70% O2 based on an air
>>
>> volume in the sub of 250 liters.
>>
>> I think I'll go for a pressure gauge outside my view port or try potting
>>
>> a digital pressure gauge & just send the wires through a penetrator.
>>
>> Alan
>>
>>
>> ------------------------------
>>
>> *From:* Alan via Personal_Submersibles <personal_submersibles at psubs.org>
>> *To:* Personal Submersibles General Discussion <
>> personal_submersibles at psubs.org>
>> *Sent:* Wednesday, November 2, 2016 12:41 AM
>> *Subject:* Re: [PSUBS-MAILIST] Electronic contents gauge
>>
>>
>>
>> Thanks for the advice Steve.
>>
>> I haven't looked in to the electronic oxygen add system too deeply.
>>
>> Bound to have some questions later on.
>>
>> Cheers Alan
>>
>>
>> Sent from my iPad
>>
>>
>> On 1/11/2016, at 9:39 pm, Stephen Fordyce via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> Thanks Alan - I should probably point out that my Watchdogs are rather
>> literally named - ie. they can sense something is wrong and do
>> something simple about it, but are limited in how complex the reaction can
>> be.  It can only handle one O2 input, and the control is limited
>> by controller settings - it's an off-the-shelf item and not fully
>> programmable like a PLC.  Good for an independent backup or alarm.  As a
>> primary system it could be made to work but would require a thoughtful
>> setup.
>>
>>
>>
>> Eventually I do plan to make a rebreather controller (for the rebreather
>> I'm designing) which would be perfect (many O2 cell inputs and a solenoid
>> or two output), but that's a while away!
>>
>>
>>
>> A key thing to consider in automatic oxygen adding is placement of
>> sensors, natural mixing of the air and sufficient time delay in the control
>> system to get meaningful feedback before the next oxygen
>> injection (Ie. rebreather controllers squirt a little bit of oxygen in,
>> wait a few seconds for it to mix, and then measure, and squirt in more
>> accordingly).
>>
>>
>>
>> Cheers,
>>
>> Steve
>>
>>
>>
>> PS: I also have some M12 plated brass Blue Globe cable glands if you find
>> yourself short a couple - very hard to get down here.
>>
>>
>>
>>
>>
>>
>>
>> On Tue, Nov 1, 2016 at 2:19 PM, Alan James via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>>
>> Steve,
>>
>> sending this again as I didn't receive it...
>>
>> Steve,
>>
>> I am wanting to build an O2 system like James Cameron had.
>>
>> An O2 valve that flows continuously with a top up from a solenoid
>>
>> valve which  triggered by a plc that is receiving signals from 3 x O2
>> sensors.
>>
>> Mainly because I want to keep everything as small as possible.
>>
>>    With your O2 unit it looks like you could have it doing similar;
>>
>> turn on a solenoid to top up the O2 beyond what is flowing in from
>>
>> a pre-set valve. A bellows add system that replaces the bellows with
>>
>> your "Oxygen Watchdog"
>>
>> Know what you mean about UK freight charges, have cancelled items
>>
>> because of ridiculous freight charges. Thanks for the offer of buying
>>
>> through your firm.
>>
>> Cheers Alan
>>
>>
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