[PSUBS-MAILIST] O2

Thu Jan 30 22:42:33 EST 2020

I agree with you Vance but that doesn't apply to the majority of the subs
the Psubs group are building. I just don't like HP gas in a one atm sub if
it can be helped, that's all.
Rick

On Thu, Jan 30, 2020 at 4:17 PM via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Okay for shallow subs, Rick, not for deep. HP bottles don't much care for
> external pressure--will collapse at 3000 psi external (once empty). Alvin,
> Nautile, and others of the deep diving community (including P4, 5 & 6) all
> carry their primary HP oxygen storage internally. They have to. Not a psubs
> issue, obviously, unless your name is Scott Waters. the secondary O2 bank
> is external on P6 but if these bottles were ever depleted at depth, they
> would probably have to be replaced after the fact. HP air is different, as
> they can't be depleted beyond whatever the external pressure is. Oxygen
> bottles? Not so much.
> Vance
>
>
> -----Original Message-----
> From: Rick Patton via Personal_Submersibles <
> personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> Sent: Thu, Jan 30, 2020 8:41 pm
> Subject: Re: [PSUBS-MAILIST] O2
>
> 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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