Re: [PSUBS-MAILIST] Scuba tank hook up

Vance

-----Original Message-----
From: Alan James <alanjames@xtra.co.nz>
To: personal_submersibles@psubs.org
Sent: Fri, Aug 20, 2010 10:09 pm
Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

The first question is..... What is the internal volume of a K250 ?

The second is..... What happened to Sean Stevenson; he seemed to

be able to give flow calculations off the top of his head.

Alan

----- Original Message -----

From: vbra676539@aol.com

To: personal_submersibles@psubs.org

Sent: Saturday, August 21, 2010 1:24 PM

Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

It shouldn't be that hard to figure. Some tank manufacturer or supplier probably has a gallons to level chart of some kind. George called for a 2" ball valve for flooding, Flow rates should be available from a valve manufacturer, maybe on an x-y plot with flow versus pressure. I'll bet flooding will be faster than you think.
Vance

-----Original Message-----
From: Alan James <alanjames@xtra.co.nz>
To: personal_submersibles@psubs.org
Sent: Fri, Aug 20, 2010 7:58 pm
Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

Hi Vance,

Below is a quote from a 1970s paper Phil presented on sub escape.

It agrees with what you are saying about differing scenarios & " one

size doesn't fit all". I'd like to see a white paper on K250 escape covering

best proceedure for different depths maybe from 100 to 250ft & for 1, 2 or 3

people. However I couldn't find a flow calculator so I don't know how long

a K250 would take to flood to various internal levels.

Alan

There are at least five major factors to

consider in programming emergency procedures:

A) Nature of the problem (e.g. is the SDC entrapped?)

B) Depth of water (e.g. possible to use standby

diver?)

C) Umbilical condition (e.g. severed or intact?)

D) Load line condition ( e.g. severed or intact?)

E) SDC pressure condition (e.g. pressurized

or unpressurized?)

If one fixed case is assumed for question

"A" - the SDC is entrapped - the critical examination

of the possible combinations of other

factors will require a detailed analysis of at

least sixteen possible situations and the calculation

of the most effective emergency procedures

to use in each case.

Some time ago, our firm undertook the task

of reviewing SDC emergency procedures and we

were, frankly, astonished at the number of

possible situations that had simply not been

considered previously. The procedures to cope

were equally obscure and detailed searching of

existing literature confirmed this general lack

of specific consideration. We have since been

continuously involved in compiling emergency

procedures and running field tests on various

safety devices, both SDC internal and external.

The length of this discussion is not sufficient

to describe, in detail, the total findings, but

some highlights are presented for consideration.

It should be heavily stressed that the described

approaches should in no way be considered

universal panacea's to the problems, but

merely as potentially useful alternates to current

practises.

----- Original Message -----

From: vbra676539@aol.com

To: personal_submersibles@psubs.org

Sent: Saturday, August 21, 2010 10:35 AM

Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

I see what he's talking about. A controlled flood and then equalization with your onboard air supply. Good stuff, especially with the dome/elevator arrangement--sort of a rigid steinke hood. Very clever, but only useful when you've got the dome blown, the straps tight and are ready to haul-ass for the surface. I was thinking about a flooded or flooding boat in an unassisted blow and go scenario with possibly two people to deal with.
Vance

-----Original Message-----
From: Alan James <alanjames@xtra.co.nz>
To: personal_submersibles@psubs.org
Sent: Fri, Aug 20, 2010 6:05 pm
Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

Hi Vance,

Filling the last 15% was from Phil Nuytens reply to my question about escaping from a K250 at 200ft.( rest of my email continued below)

Also Jay had mentioned this.

Hi, Alan

Yeah, we ran the 'pressure up and escape' numbers for the micro sub 'Sea Urchin' some years ago. As I recall, escape from the rated depth (350') was quite practical. As a rule of thumb, you save your ballast air (and 02) for the final blow. The speed of initial filling is not as critical as the last few minutes before the entry dome/hatch comes off. You have to remember that when your sub is half -full of water, you are only at 33 feet of pressure (29.4 PSI), when it's 3 quarters full, you're only at 66' and so on. My plan on the Sea-Urchin was to have the hinge on the inside with the ability to pull the hinge pin out so that the entry dome is held on only by water pressure - we planned to have two 'armpit slings' stowed in a small package that is easily opened - and the sling ends were to be affixed to the inside of the dome seat ring. The procedure for bail out was to get a reading on the volume of the ballast air (by supply gauge) left, flood up with water until either the time was beginning to exceed the no-decom table (the depth IN the sub, not ambient depth) or you had flooded right up. Probably, you'd blow the last 10 or 15 % by air, Make sure the slings are firmly attached and blast in the air! The dome/hatch achieves lift-off with your head and shoulders in the gas bubble of the dome, your body acts as the drogue to keep the dome from tipping, you are breathing constantly-refreshed air (and avoiding embolism, therby) as the gas expands and bubbles out - you hit the surface and duck out and then yank on your Mae West cord to inflate your life-jacket and await pick-up by your chase boat (or commence floundering towards shore if you were subbing with no surface craft in attendance).

The numbers indicated that the likelihood of bends was very low - since your exposure to full depth is extremely brief. We were more concerned about the instant hit of hp nitrogen to those not accustomed to deep gas change-overs. It can be quite . . ..err. . ..'startling'! Hence the snugged-up slings- rather than internal handles ( my first thought) - even if you're narked out of your skull at the onset the slings will hold you in position until your calm. cool thoughts return. Actually, though, those stalwart psubbers who are also tech -divers will recognize that the likelihood of bad narcosis trip from this very brief 'deep air dive' is even less than the bends (according to the work done by researchers Overton and Mayer on the oil/water solubility ratios and the time required for the combination of Co2 and N2 to act.

I had developed a bubble stage called the 'Newt-Chute' as a safety refuge and self-rescue/self-decom vehicle for deep Heo2 bounce diving - which we (OII/Can-Dive) were doing a lot of at that time (in the early 70's) I gave a paper at the Offshore Technology Conference titled "Diving Bell escape systems - some observations and test results) Perry started building and selling these bubble stages shortly after that and then COMEX after them- and they became known in the industry as 'Class 2 bells'). While testing the Newt -Chute, the dome-lift to the surface occurred to me and we tried it in several different configurations and it worked fine. More than a decade later we re-purposed the idea to sub escape.

Sorry for such a long answer, Alan.

Phil Nuytten

With regard to filling the sub completely with water; wouldn't it be slower & slower as you approach the point where the sub was equalized

& the hatch could be opened. Initially at a 200ft depth the water would be coming in at 100 psi, then when the hull was at half full the air inside

would be compressed to half its volume so the water would be coming in at 85 psi. At 3/4 full it would be coming in at 60 psi, but eventially to

get the last bit of equalization it would be flowing in at round 1 psi.

If you were deep enough the slow fill may cause you to get the bends or prolong a session of nitrogen narcosis.

Maybe someone that's good on flow calculations could do the numbers for a K250 boat so everyone with one will know exactly

where they stand in an emergency at different depths.

Regards Alan

----- Original Message -----

----- Original Message -----

From: vbra676539@aol.com

To: personal_submersibles@psubs.org

Sent: Saturday, August 21, 2010 1:25 AM

Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

Alan,

I must be missing something here. What is the last 15% of the volume in a flooding scenario? I've never had to do it, but flooding the boat equalizes pressure inside and out. The volume of air compresses in a high point to that same pressure. All you would need was a BIBS and a face mask or something. No increase of pressure inside would be necessary unless your intent is to maintain a larger air bubble inside the boat, which would be dangerous unless you happened to have a bottom hatch (assuming the boat is in an attitude where it could even be used).

One caveat about air in the boat that I do know about is the violence of that bubble's release when the hatch is opened. In the Nekton Beta accident, the bubble shot Rick Slater out of the boat like a cork out of a champagne bottle, and the sudden movement of water flooding in to replace that air is probably what caused the other passenger to bang his head, which either caused directly or contributed to his drowning at depth. Based on that, it seems that a larger bubble might very well cause proportionally larger problems.

Mind you, flooding the boat is a pretty big problem all by itself. It gives me the shivers just thinking about it.

Vance

-----Original Message-----
From: Recon1st@aol.com
To: personal_submersibles@psubs.org
Sent: Fri, Aug 20, 2010 8:53 am
Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

Alan I would not use air to equalize in an emergency. I would simply open my flood

valve and let the incoming water do the job. This would allow time to equalize your

ears and such. And the volume of air exploding from the tower is much less violent.

Personally I prefer to have full pressure to the hull and regulate it inside. In all scenarios

I can think of, a high flow is not needed. Filling tanks and such, a slow fill seems to be

much more controllable.

Dean

In a message dated 8/19/2010 6:52:01 P.M. Central Daylight Time, alanjames@xtra.co.nz writes:

Hi Dean,

I've got more questions than answers here.

If we use air to pressurize the last 15% of the sub volume in an emergency escape,

wouldn't it be better to have the full pressure of the tank coming in through the hull?

I googled but couldn't find anything on the flow rate of air coming straight out of a

scuba tank compared to what it might be coming out of a first stage regulator or

your 250 psi regulator. ( I guess hose width figures in the equation.)

I did open up my dive tank into a rubbish bag & it blew it up about 4 x faster straight from

the tank at 3000 psi than from the 2nd stage purge valve.

In the case of a 200ft deep escape your 250 psi regulator would be operating at 150 psi

above the ambient pressure required in the hull to do the final equalization. Having a faster

fill might make the difference between getting the bends or not.

Alan

----- Original Message -----

From: Recon1st@aol.com

To: personal_submersibles@psubs.org

Sent: Friday, August 20, 2010 6:55 AM

Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

Sorry for the omission. The Tanks will be external and all I would need is HP. I have

regulators inside and the ability to crank em up to 250 psi. I guess what I am looking for

is yoke type with out the regulator.

Dean

In a message dated 8/19/2010 11:26:37 A.M. Central Daylight Time, vbra676539@aol.com writes:

External or internal? And are you set up for high pressure or not? HP air can be had with a simple yoke (like a first stage without the regulator). If you need lower pressure, then the first stage will work fine. George carried his internally, which was an issue at depth because scuba first stages can only be cranked up to about 150-160 pounds. Externally, you get that over ambient, which gives you full flow. The only other issue is flow. The 1st stage arrangement is pretty slow.
Vance

-----Original Message-----
From: Recon1st@aol.com
To: personal_submersibles@psubs.org
Sent: Thu, Aug 19, 2010 12:03 pm
Subject: Re: [PSUBS-MAILIST] Scuba tank hook up

What have any of you done to hook up standard SCUBA tanks for HP air source.

Originally I was using a large steel tank. It is just too heavy to handle and I am

switching to twin Aluminum 100 tanks.

I am thinking a scuba first stage regulator is used with an adaptor at the thru hull

connection.

Appreciate any help

Dean