[PSUBS-MAILIST] Commercial Grade O2 vs. Medical

Thu Jan 4 14:26:10 EST 2018

Yes that is the scenario. I also agree with your evaluation.  I will try the unsupported cylinder calc. if I get the tank thickness. Thanks for sharing.

Thanks,
Steve

---- Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote: 
> Steve, to me this failure mode is only possible with an empty O2 cylinder
> at max design depth.  My experience is that the O2 tank pressures remains
> high almost all the time as typically dive durations are small.   So what
> you are really asking is if you got stuck on the bottom for 72 hours at
> your maximum design depth would the aluminum cylinders collapse due to out
> of roundness as you pulled the O2 pressure down to a  pressure below
> ambient.  To me this scenario has a very low probability of occurring.  To
> answer your question, no I did not do the calc. Would be easy to take the
> ABS hull spreadsheet and do the calc as an unsupported cylinder.
> 
> Cliff
> 
> On Thu, Jan 4, 2018 at 8:36 AM, Steve McQueen via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
> 
> > Cliff, I bought an M60 aluminum O2 tank for external mounting (this was my
> > "perfect" size but couldn't find in steel).  However I am thinking about
> > returning it because I have no "math" yet to support it can withstand say
> > 180psi of external pressure (I do not know the wall thickness (yet, asked
> > and am waiting, probably won't get)and the bottom is not rounded etc.).
> > Probably being over concerned here but wanted to be able to defend my
> > designs with data.
> >
> > Did you have enough data on your aluminum tanks to do calculations?
> >
> >
> > Thanks,
> > Steve
> >
> > ---- Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.
> > org> wrote:
> > > 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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