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Re: [PSUBS-MAILIST] PSUB Fatalities...
----- Original Message -----
From: "Phil Nuytten" <72020.572@compuserve.com>
To: <personal_submersibles@psubs.org>
Sent: Thursday, March 09, 2000 7:05 AM
Subject: Re: [PSUBS-MAILIST] PSUB Fatalities...
> Hi, Pat:
> The choice of escape mix would depend on the proposed depth of
> operations. .I'd use air down to a depth that I was comfortable with . .
> probably 350 feet or so . .then ( for depths greater) add the minumum
> helium consistent with maintaing an equivalent air depth of 350 and a
> relative oxygen depth of about 90 feet. The idea is to use a gas that is
> slower on the uptake than He . .the bottom exposure time will be short,
but
> the driving pressure is high . .so you want to both keep the inert gas at
> the lowest tissue level possible and get the highest ratio of blood gas
> pressure to ambient pressure without triggering bubble formation. I
pick
> these numbers because they are real ones to me. I have breathed pure O2 at
> ninety feet for 15 minutes on a number of occasions ( during O2 tolerence
> tests/ decom table trials) and can tolerate deep air quite well ( during
> the HeO2 surface bounce era it was critical to switch back to air as deep
> as possible - to shorten bottom time on Heo2 and increase O2
> percentage/pressure - some guys handle it well, some do not. - A deep
> swithch-back really rattles your cage!) More important than precise
> designer gas mixtures is the ability to flood fast and to have ballast
air
> and O2 plumbed in a manner that you can dump everything you've got into
> the cabin if you have to hit the road. All of this consistent with the
> certifying agency requirement for O2 hull stops, - separation of O2 supply
> containers to ensure that you cant accidentally dump a large HP cylinder
of
> O2 in to the cabin- etc.etc.
> Get out quick! - then streak to the light! A good time to shoot
> for ( from start of pressurization to start of ascent ) would be 3 minutes
> or less. This means large flood valves or other flood means and lots of
> blow-down gas. All of this is relative to depth. It's an easy matter to
> figure out the best escape options for a 300 foot-rated sub compared to a
> 1000 feet. Past a thousand?? Hmmm . .Ascent rates: figure 200 to 300 feet
> per minute for buoyant ascent. Please note usual disclaimer on the
> foregoing:. These are my own opinions and I do not suggest that you use
> them as a basis for your own decisions.
> Phil Nuytten
Thanks, Phil. We're all exchanging ideas in trying to better understand how
we can improve safety here, but your input is based on state-of-the-art
industrial experience us homebuilt guys don't usually have access to, and so
is really appreciated. I hope everyone will read your post.
Pat Regan