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

Thu Jan 4 05:07:59 EST 2018

 Tim and Brian,Even though I am a computer whiz, I can't seem to send the report ;-) .   It can be found on line if you google "Handbook for design of undersea pressure resistant concrete structures".  Hank
    On Wednesday, January 3, 2018, 11:28:58 PM MST, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 That is some fantastic computer control Cliff ! Brian 

--- personal_submersibles at psubs.org wrote:

From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] PLCs (was Commercial Grade O2 vs. Medical)
Date: Wed, 3 Jan 2018 21:42:46 -0600

This summer, 5 miles offshore of IslamoradaFlorida, I spend 5 hours in my psub with the hatch closed the entiretime.  My life was totally in the hands of my life support system that wason full automatic control throughout the dive.  The system workedflawlessly.  The oxygen I used was commercial welding oxygen I transferredfrom a cylinder that gets swapped out every time I take it into thesupplier.  I use a whip that connects from the HP port of a standardwelding regulator to a Swagelok connection on an external 1/4" SS tubingmanifold that connects four externally mounted aluminum medical grade cylinders(2 D size and 2 E size).  The HP (2,000 psig) oxygen comes through thepressure hull and then has a 1/4" high pressure Swagelok valve forisolation.  From there the HP Oxygen passing directly into small box Icall the AMOC unit.  AMOC is an acronym for Atmospheric Monitoringand Oxygen Control.  All life support sensors are installed inthe AMOC module.  These include the O2 pressure, O2and CO2 concentrations, relative humidly, cabin pressure, cabintemperature and O2 flow rate in SLPM.  The purpose of the O2and CO2 sensors are to measure the partial pressure of oxygen and ofcarbon dioxide so that the programmable logic controller (PLC) in automaticmode and the pilot in manual mode can make the adjustments necessary tomaintain the O2 and CO2 levels within acceptablelimits.  Because the PLC has data logging,  after returning from the Islamorada dive I was able to go back andstudy the life support system as well as all the other systems.  Havingall the life support systems sensors in a single module makes it easy formaintenance to pull the AMOC  box out of the R300 andinstall an extension cord for the electrical signals between the AMOC unit andPLC box and fire up the system on the bench.    To confirm thelife support system was working, I had six different volunteers over a one yearperiod  with different metabolisms andwith body weights from 90 lbs to 240 lbs  closed up in the boatfor over 50 hours with full data logging to test the system.  This enabledme tune the PID controller for O2 makeup and give me confidence that the systemwas working.  It would not be fun but I am 100% confident I could stayconfined 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.htmI am looking seriously at it. It says it is fully American! Is that good or bad?Alan

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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 & orABS. 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-providerThe 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 cardthey would be happy to fill. Also we are carrying O2 so are able to provide itin 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 muchmore 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.htmYou will need a tank fitting suitable for where you intend filling i.e. dive shopor 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 & divesuppliers. ( I haven't heard this discussed before) I have heard people say that medical & commercial O2 tank swap people don'tlike the idea of their tanks going under the water. They also may require somesort of certificate from you before they fill.Have read of deaths from people using commercial rather than medical O2, butthis 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 via3 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 ofthe 2 readings closest to each other. The PLC will notify me when the range ofone 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 onlya year or so depending on the heat it is stored at. Being a small one person subI 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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