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?