[PSUBS-MAILIST] O2

Thu Jan 30 02:37:51 EST 2020

I personally don't believe HP gas has a place inside a one atm sub. I know
ketteredge did it but still don't think it should be for three reasons. 1.
allows a lot more room in a small confined space, 2. could raise the ppo2
to a fire hazard level before you could secure the problem and 3. You are
going to increase your internal pressure much faster and greater if it is
HP rather than LP and the least internal positive pressure pushing the
wrong way against the ports and hatch seal while ascending, the better.
Reaction time is effected when something like a hose lets go so you may
increase internal pressure faster than one might think. I was being pushed
down to 700' in SAT on a job and all the condiments that are put inside
(salade dressing, ketchup, etc) is supposed to have a hole poked in the top
by the tenders and they forgot to do that on a bottle on salad dressing we
were using. We were eating dinner while being pressed and the last guy to
use it screwed the top on all the way thinking that a hole had been put in
it like normal and it imploded while it was sitting right next to me.
It took some time to get our witts about us as we thought a port had let go
but other than being covered with broken glass and thousand island
dressing, everything was ok. I am keeping all my HP gas outside.
Rick

On Thu, Jan 30, 2020 at 3:04 PM David Colombo via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi Hank, I am using 5 E size tanks (20cf) in the SeaQuestor. They sit
> right behind my pilot seat within arms reach. Each are individually valve
> controlled. Though they are tied to a manifold that holds the digital gauge
> tied to my plc, so that I only have one digital gauge. No more than one
> tank at a time would ever be open. Indivudually they have their own digital
> gauge and flow control, in addition to the digital gauge on the manifold.
> This gives me the ability to disconnect a bottle from the digital system in
> the event the plc goes down, and still control its flow and have the
> ability to read the tank level. I'm all about redundant systems.
> Best Regards,
> David Colombo
>
> On Thu, Jan 30, 2020, 12:39 PM Sean T. Stevenson via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
>> It is possible to employ burst devices in place of the standard cylinder
>> burst discs which similarly protect the cylinders, but allow for plumbing
>> the exhausting gas overboard instead of venting it into the cabin. Quieter
>> too.
>>
>> Sean
>>
>> -------- Original Message --------
>> On Jan. 30, 2020, 11:04, 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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