[PSUBS-MAILIST] Commercial Grade O2 vs. Medical

[Alan via Personal_Submersibles]

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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