[PSUBS-MAILIST] PLCs (was Commercial Grade O2 vs. Medical)

Wed Jan 3 22:42:46 EST 2018

This summer, 5 miles offshore of Islamorada Florida, I spend 5 hours in my
psub with the hatch closed the entire time.  My life was totally in the
hands of my life support system that was on full automatic control
throughout the dive.  The system worked flawlessly.  The oxygen I used was
commercial welding oxygen I transferred from a cylinder that gets swapped
out every time I take it into the supplier.  I use a whip that connects
from the HP port of a standard welding regulator to a Swagelok connection
on an external 1/4" SS tubing manifold that connects four externally
mounted aluminum medical grade cylinders (2 D size and 2 E size).  The HP
(2,000 psig) oxygen comes through the pressure hull and then has a 1/4"
high pressure Swagelok valve for isolation.  From there the HP Oxygen
passing directly into small box I call the AMOC unit.  AMOC is an acronym
for Atmospheric Monitoring and Oxygen Control.  All life support sensors
are installed in the AMOC module.  These include the O2 pressure, O2 and CO2
concentrations, relative humidly, cabin pressure, cabin temperature and O2
flow rate in SLPM.  The purpose of the O2 and CO2 sensors are to measure
the partial pressure of oxygen and of carbon dioxide so that the
programmable logic controller (PLC) in automatic mode and the pilot in
manual mode can make the adjustments necessary to maintain the O2 and CO2
levels within acceptable limits.  Because the PLC has data logging,  after
returning from the Islamorada dive I was able to go back and study the life
support system as well as all the other systems.  Having all the life
support systems sensors in a single module makes it easy for maintenance to
pull the AMOC  box out of the R300 and install an extension cord for the
electrical signals between the AMOC unit and PLC box and fire up the system
on the bench.    To confirm the life support system was working, I had six
different volunteers over a one year period  with different metabolisms and
with body weights from 90 lbs to 240 lbs  closed up in the boat for over 50
hours with full data logging to test the system.  This enabled me tune the
PID controller for O2 makeup and give me confidence that the system was
working.  It would not be fun but I am 100% confident I could stay confined
in my boat for 80 hours and survive.

Cliff

On Wed, Jan 3, 2018 at 8:56 PM, Sean T. Stevenson via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:

> Although I have worked with some Allen-Bradley type PLCs using ladder
> logic in the distant past, I work almost exclusively now with programmable
> automation controllers (PACs), which incorporate on-board
> field-programmable gate arrays (FPGA) on the same die as a CPU running a
> deterministic real-time operating system (e.g. National Instruments
> CompactRIO platform). These units are extremely versatile, although
> considerably more expensive than a PLC. The FPGA, main real-time OS
> program, and any PC / remote interface programs are all programmed with the
> same software suite, which while accessable to beginners, is unfortunately
> not a "master it in a weekend" type of deal - I have been developing for
> these for twenty years.
>
> As for PLCs, I have been uninvolved for too long to give a useful
> recommendation. Defer to someone who has done more recent research / usage.
>
> Sean
>
>
> -------- Original Message --------
> On Jan 3, 2018, 19:38, Alan via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>
> Thanks Sean,
> good stuff, I feel more confident about using commercial O2 now.
> the ABS 23.5 % is quite restrictive. The problem is one rule fits all
> submarines.
> In a psub there is less that's likely to cause a fire than in a large
> deisel electric
> ( like Carsten's). The chances of you emptying the contents of your O2 tank
> & starting a fire at the same time are pretty slim.
> BTW have you come across the EZautomation Ezrack plc at all.
> http://www.ezautomation.net/ezrackplc/ezrackplc.htm
> I am looking seriously at it. It says it is fully American! Is that good
> or bad?
> Alan
>
>
> Sent from my iPad
>
> On 4/01/2018, at 2:58 PM, Sean T. Stevenson via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Per ABS, the inadvertent release of the contents of any single pressure
> vessel, if stored internally, must not raise the internal cabin pressure
> more than 1 atm (101.325 kPa) above the normal atmospheric pressure, nor
> raise the cabin air oxygen concentration above 23.5%. If an oxygen cylinder
> does not meet these requirements, it must be stored externally.
>
> So, you can get away with storing any amount internally, provided you use
> a greater number of smaller vessels.
>
> Sean
>
>
> -------- Original Message --------
> On Jan 3, 2018, 18:15, Brian Cox via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>
> Alan,        It's a long list !    What I need to do is make a check list
> of things I have wrong ;-)    and  then "things I have wrong but can maybe
> slide on"  !    One question, right of the bat,  with that O2 not being
> able to fill the cabin space more than one atmosphere,  I'm not
> understanding the terminology , how can it be possible to release a volume
> of air from a bottle WITHOUT raising the pressure above one atm if your are
> already at one atm ?
>
> I should go around my sub with a video camera inside and out and you could
> really get an idea of what I need !    For instance I know I need an
> additional ballast tank HP cylinder.
>
> Brian
>
>
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.
> org>
> Subject: Re: [PSUBS-MAILIST] Commercial Grade O2 vs. Medical
> Date: Thu, 4 Jan 2018 13:52:57 +1300
>
> Brian,
> fire away; there are a few people on psubs that are familiar with GL & or
> ABS.
> Alan
>
> Sent from my iPad
>
> On 4/01/2018, at 1:37 PM, Brian Cox via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Great info Alan !           BTW  I need to pick your brain on some of the
> Lloyd's or ABS regs or equivalent.
>
> Brian
>
>
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.
> org>
> Subject: Re: [PSUBS-MAILIST] Commercial Grade O2 vs. Medical
> Date: Thu, 4 Jan 2018 13:22:59 +1300
>
> Brian,
> here is a link with some info.
> https://www.padi.com/padi-courses/emergency-oxygen-provider
> The best way about it is to enquire at your local dive shop as they will
> probably run a course if they have a few interested people.
> Alan
>
>
> Sent from my iPad
>
> On 4/01/2018, at 1:04 PM, Alan via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Brian,
> I did an Emergency O2 providers course at a dive shop that sold O2.
> Now have a card with my face on it.
> I don't know if there are any regulations, but I get on well with the
> manager
> & this is what he was happy with me doing before he would fill O2.
> This was the easiest option, cheap & Only a couple of nights.
> I think if I went to any dive shop in the World & pulled out my Padi O2
> card
> they would be happy to fill. Also we are carrying O2 so are able to
> provide it
> in a diving emergency, so thats an advantage to divers.
> Medical O2 providers may also be convinced to fill for you if you have the
> card.
> The other option for me was to do a mixed gas diving course which is much
> more expensive & intense.
> Cheers Alan
>
>
> Sent from my iPad
>
> On 4/01/2018, at 12:16 PM, Brian Cox via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Alan,           What's involved with getting a O2 cert for administering
> O2 ?
>
> Brian
>
> --- personal_submersibles at psubs.org wrote:
>
> From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.
> org>
> Subject: Re: [PSUBS-MAILIST] Commercial Grade O2 vs. Medical
> Date: Thu, 4 Jan 2018 11:21:46 +1300
>
> Steve,
> not the most experienced but this is what I'm doing.
> I have 2 steel O2 cleaned tanks. ( 2 tanks as per GL for redundancy)
> I have O2 cleaned scuba regulators & get my tanks filled at a dive shop.
> Had to have an emergency O2 provider cert first.
> I believe Nuytco were using composite tanks at one stage.
> O2 tank options & fitting options here. (EMT medical)
> http://www.emtmedicalco.com/OXYGEN-CYLINDERS-ALUMINUM-
> STEEL-COMPOSITE_c64.htm
> You will need a tank fitting suitable for where you intend filling i.e.
> dive shop
> or medical O2 supplier. Then you will need a compatible regulator . If you
> were
> heading across country for a few dives maybe have interchangeable fittings
> or
> spare tanks with different fittings if you need to switch between medical
> & dive
> suppliers. ( I haven't heard this discussed before)
> I have heard people say that medical & commercial O2 tank swap people don't
> like the idea of their tanks going under the water. They also may require
> some
> sort of certificate from you before they fill.
> Have read of deaths from people using commercial rather than medical O2,
> but
> this would be 100% O2 inhaled straight in to the lungs.
> Phil offered to sell his O2 add system to Psubbers.
> I am using a paediatric flow meter set at a minimal flow & are topping up
> via
> 3 x O2 sensors wired to my PLC & operating a solenoid valve on the low
> pressure
> O2 line. The PLC will be comparing the 3 readings & going with the average
> of
> the 2 readings closest to each other. The PLC will notify me when the
> range of
> one O2 sensor is out relative to the other 2 or the reading of the nearest
> 2 differ
> by a certain amount & may need replacing. I think the life of a sensor is
> only
> a year or so depending on the heat it is stored at. Being a small one
> person sub
> I need to be a lot more careful as the O2 % can change a lot more quickly.
> Cheers Alan
>
>
>
>
> Sent from my iPad
>
> On 4/01/2018, at 7:10 AM, Steve McQueen via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> I tried to search the archives but it wasn't very friendly.  Sorry to
> again ask about something I know has probably been discussed.
>
> I wanted to double ck. my O2 strategy.  After some investigation it seems
> I will buy a new steel high pressure oxygen tank for external mounting. My
> plan is to have it refilled with "commercial grade" O2 vs. medical grade
> 02.  As long as I keep my "personal" tank and not allow the filler to swap
> tanks I should create a "chain of custody" that will help me feel good
> about not having contamination.
>
> I am wondering how others are managing.
>
> Thanks,
> Steve
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