[PSUBS-MAILIST] First Stage Regulator for O2 service Questions

[Alan via Personal_Submersibles]

Steve,
another factor that may influence your decision is how you want to 
set up a BIBS. If you have a divers regulator for emergency breathing they
normally operate off 130 psi. Hmmm got me thinking now; if the emergency
regulator is operating off a line directly from the  1st stage regulator external
to the hull then it will see 130 psi above ambient. So at your max depth it will 
see 255 psi.
Conversely if you had a high pressure line to your sub & a regulator  dropping
the pressure to 130psi, then if you needed to flood your sub to get out the 
regulator would only see 5 psi above ambient by the time the sub filled, if you 
were escaping from 250ft.
Alan

Sent from my iPad

> On 26/12/2017, at 8:56 AM, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hi Steve,
> 
> I use a 1st stage outside the hull. As you say the flow regulator can handle the tank pressure, so it is not strictly necessary, but I do so as an extra safety precaution to avoid bringing high pressure O2 inside. If doing it again I would the reg directly on the tank, so that way all of the tubing would see only low pressure. 
> 
> I'm using a 1st stage that is incredibly inexpensive ($60), but I'm delighted with the quality and what is a big plus for me, it's a particularly simple design. I've collected three of them by now, and not any problem at all.
> 
> https://www.piranhadivemfg.com/item/Balance-Piston-Din-First-Stage--For-Pony--Stage-Bottles--Nitrox-Ready-11738
> 
> I do my own oxygen cleaning on tubing and penetrators, but prefer to buy O2-clean regs and valves. You may notice this reg is advertised for Nitrox, not pure oxygen. I spoke to the owner of the business selling it, and he told me the cleaning and materials are identical for partial or full O2, but that they advertise it only for partial O2 use as a legal CYA. 
> 
> 
> Best,
> Alec  
> 
>> On Mon, Dec 25, 2017 at 12:50 PM, Steve McQueen via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> All, I am purchasing the system components for my K-250’s O2 system.  I am not a SCUBA diver so I lack some experience with regulators. I am considering sealed/balanced options for the first stage regulator (it will create an intermediate pressure downstream of the O2 tank (located external of the hull). These get pricey and I don’t really want to overspend for options I do not need (sealed vs. not, balanced vs. unbalanced, O2 ready vs. needing cleaned).
>> 
>>  
>> 
>> A couple of questions:
>> 
>> They sell regulators that are already suitable for 100% O2 use. How difficult to clean one that is not O2 ready?
>> The pediatric flow regulator (located in the hull) can directly handle the O2 tank pressure so I am wondering why we use the first stage regulators at all.
>> I assume to remove as many HP leak sources from within the hull especially since it is 100% O2 (safety).
>>  
>> 
>> Thoughts/recommendations?
>> 
>>  
>> 
>> Steve
>> 
>>  
>> 
>> 
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> 
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