[PSUBS-MAILIST] O2

Thu Jan 30 13:47:24 EST 2020

Wow, I've never had that happen. How weird, I would have been sure it would
happen only if the tank was left in strong sunlight or something like that.
Have to say that would not be a good event. I guess one would switch off
the electrical power breaker immediately and surface using only ballast to
try not to have any sparks.

On Thu, Jan 30, 2020 at 1:06 PM Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Alec,
> I have seen one tank empty out. The burst disk went on one of a bunch
> of tanks we had for a dive trip.
> It was about 8am so no heat from sunlight to increase pressure.
> A really loud hisssss for ages. Would sure get you panicking.
> Alan
>
>
> On 31/01/2020, at 3:33 AM, Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Yes, fire as in the Apollo 1 scenario. It's really a hard ABS requirement
> to meet, because you're already at 21% O2 under normal conditions so any
> one tank can't contain more than 2% of the cabin volume in O2. I think
> you'll find that implies the tanks need to be absolutely minuscule. On the
> plus side, as you say it would take a really, really unusual failure to
> empty a tank. Make sure the tank valves are readily accessible and not
> hidden behind anything, and make it a documented SOP for them all to be
> closed except the one currently discharging.
>
> On Thu, Jan 30, 2020 at 9:22 AM hank pronk via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Alec, good point, so the risk with that is fire?  In my case, with
>> separate bottles not inter-connected the tank would have to fail or the
>> regulator.  I love simple
>> Hank
>>
>> On Thursday, January 30, 2020, 7:02:22 AM MST, Alec Smyth via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>
>> Hank,
>>
>> In addition to the 1 atm rule Sean mentioned, there is a second
>> requirement. The uncontrolled release of the contents of one tank of O2
>> should not raise the cabin O2 content above 23 percent. This second
>> condition I suspect you will find more onerous than the first.
>>
>> Best,
>> Alec
>>
>>
>>
>> On Thu, Jan 30, 2020 at 8:31 AM Sean T. Stevenson via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>> Plumbing all of your oxygen cylinders into a manifold using check valves
>> should suffice. The idea being that any single failure should not empty the
>> entire bank, and the individual cylinders need to be small enough to keep
>> the total pressure increase below 1 atm if you do happen to lose one.
>>
>> Examine your entire plumbing system, identifying every connection and the
>> consequences of it failing. Either the consequences need to be acceptable,
>> or you have to have a response plan for that failure.
>>
>> As far as corrosion protection for through hull fittings, if you
>> overlooked something in design, plating or cladding with corrosion
>> resistant materials can be an option. At work, I have some vessels that I
>> designed in A105 steel (similar to A516 gr 70, but forgings), that I am
>> sending out to have the fluid exposed surfaces clad with Inconel 625 for
>> corrosion resistance. Of course, I'm dealing with much worse stuff than
>> seawater: hydrogen sulphide-saturated acidified high salt brines at
>> elevated temperature. Still, it's always worth a look at costs of such
>> processes versus the lifetime cost of maintenance. I was expecting the cost
>> of cladding to be far higher than the quote I received. On the other side
>> of the coin, I have some parts in the same system with deep holes that
>> can't possibly be clad or painted, so I had to have them machined out of
>> Hastelloy C276. One 8" end cap is worth more than my truck.
>>
>> Sean
>>
>> -------- Original Message --------
>> On Jan. 30, 2020, 06:04, hank pronk via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>>
>> Sean, okay that is where I missed the boat.  I know about the do not
>> exceed 1 atm rule but did not realize it meant a single tank.  If I lost
>> all my O2 it would be a problem.  I am using multiple tanks so all is good.
>>   I do not have room to drill out the steel plus changing an O2 tank would
>> really suck with this new body. Forget about a change if the sub is in the
>> water.
>> Hank
>>
>> On Thursday, January 30, 2020, 5:12:49 AM MST, Sean T. Stevenson via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>
>> Nothing wrong with internal tanks as long as you can prove by calculation
>> that the unintended release of the contents of any single cylinder
>> (provided they are individually valved - hard plumbed manifolded cylinders
>> where a single failure would empty them all would need to be considered
>> together as one) will not raise the pressure of the occupied space by more
>> than 1 atm.
>>
>> Through hull shouldn't be a big deal either. Drill larger if necessary,
>> and use a stainless insert.
>>
>> Sean
>> -------- Original Message --------
>> On Jan. 30, 2020, 04:58, hank pronk via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>>
>> Hi All, here is an interior picture of Limiting Factor that shows what
>> appears to be O2 tanks.  I thought it was not an approved practice to have
>> that much compressed gas onboard.  My original design in E3000 was to have
>> external O2 supply but I prefer internal.  I messed up in two ways.  First
>> off I provided a steel penetrator opening for O2.  The other screw up is
>> when I built the new body I completely neglected access to change out the
>> tank.  So I am going with internal tanks unless someone can talk me out of
>> it.
>> Hank
>> [image: Image result for deep sea limiting factor images]
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