Please see
below…
Thanks,
Alec
-----Original
Message-----
From: SJSVOB@aol.com [mailto:SJSVOB@aol.com]
Sent: Friday, September 05,
2003 3:24 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] question for
technical divers
I'm not a tech diver but I have
read much on the subject. Please read my words with a critical eye and
seek professional guidance!
You've posed a very open ended
question. I'd have to know more information to make my guesses to the
questions you are seeking answers. Here are some questions for
you.
How long would it take you to flood the sub and get out? Or
in other words, how long in seconds would you be breathing compressed air
before you started the ascent.
AS: I haven’t
attempted to quantify that, but it should not take long at all to equalize the
pressure, because the flood valve is a whopping 2 inches. The limit is
probably how fast I can compensate, rather than how fast the valve would fill
the sub. Lets say for calculation purposes a
minute.
Your sub can go to 1000' but
is your average depth different than this?
(My guess is that it would be
better to carry the best gas for the average depth.)
AS: Hard call, I have
no idea! Shall we say 300’?
In the event of a bailout
would emergency personnel be waiting for you at the surface with oxygen?
AS: No, probably not.
At least let’s not make the assumption.
How about a recompression
tank on a rescue ship?
AS:
Nope.
The bigger your bailout bottle
the higher your odds of survival. So to ask what size bottle you need
when space is confined is rather strange. How much space do you
have?
AS: Let me elaborate
on this one. There is actually generous storage space, but it’s tight getting
in or out. So it’s pretty much out of the question taking a traditional big
multi-tank technical rig out with me. But I could have say a permanently
installed tank to breath from during flooding and exit, and a 50 cf tank to take on the ride up.
Would it be possible to grab
one of your existing oxygen cylinders and take that with you in addition to a
bail-out bottle? This could make a huge difference if you were able to do a
decompression stop and breath pure oxygen for a
while.
AS: Yes, this is
possible. My main O2 bottle is carried outside per ABS rules, because an
accidental release in the cabin would increase O2 concentration over 23%.
However, one of the contingencies I’ve planned for is a failure of the main O2
supply (lets say a hose or an O-ring blow on the outside tank). For this
contingency, I carry a small medical O2 bottle internally, which has a flow
regulator attached and is completely independent of the automated life support
system. I could take this bottle with me and breathe from that, just by using
a proper reg. Or I can just breathe from the bottle with no
reg.
Some answers I can give
you now:
You only need oxygen cleaned equipment if your breathing gas has
more than 40% oxygen.
I do not think you would want to use
solely an oxygen enriched gas mixture as oxygen poisoning then becomes a
concern at depth. Divers use nitrox, or oxygen enriched air, not to dive
deeper but to extend their diving time. Their maximum diving depth is
actually reduced due to the risk of oxygen poisoning. Divers routinely
swtich to nitrox or pure oxygen as a breathing gas while they are
decompressing at relatively shallow depths to speed off-gassing of
nitrogen.
-Stephen
There were quite a number of
technical divers at the conference, and I have a
question
I forgot to ask you guys… I’m an air diver, but my sub should go far deeper
(1,000’) than I could on air. So the question is this; can I carry something
better in my bailout SCUBA tank to extend the bailout depth possibilities?
There are several aspects to the question:
-
On
the understanding I’m never going to use this for anything other than getting
directly out and up, do I need training beyond what decompression diving on
air would entail? I’ve been diving for over 20 years and consume less than
half the air of most divers, but I know nothing at all about gas
diving.
-
What
gas mix?
-
Does
that require an O2 proofed reg or anything else special on the HW
side?
-
What
size tank would be suitable for bailout? Bear in mind space is at a real
premium.
-
What
bailout depth would you consider realistic?