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Re: [PSUBS-MAILIST] Ambient running on nitrox
Thanks for your responses.
I've seen Phils white paper, but that system has a bellows at 1atm that
responds to pressure changes in the cabin to release
additional O2. It won't work in an ambient.
I'll look into the fire risk a bit more. O2 doesn't combust but I'm not sure
wether the flash point of a fuel will be lower with the higher % O2
or how much more ferocious a fire would be. I have a friend who is a
dangerous goods expert that accompanies fire fighters to industrial fires as
an adviser.
I'll pick his brains & update you on that.
Re the physiology; you just stick to the Nitrox no decompression dive
tables. In general you get double the bottom time & your limits round 100ft
with no decompression limit above 40ft.
This idea was originally suggested to me by a pretty clued up guy who runs a
dive shop & instructs in rebreather & mixed gasses.
Alan
One thing is to breathe nitrox as a diver, but another would be to flood a
compartment with it. A 40% O2 concentration will combust if you do something
like flip a switch that produces an arc. I'd suggest you build the life
support for an ambient boat just like one would for a 1 atmosphere boat.
Keep the O2 concentration within a 18-23% range. See Phil's white paper.
Or for a simple solution, just have a continuous bleed air system like on
Pierre Poulin's boat.
thanks,
Alec
----- Original Message -----
From: "Jon Wallace" <jonw@psubs.org>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, August 12, 2009 4:31 AM
Subject: Re: [PSUBS-MAILIST] Ambient running on nitrox
Hi Alan,
Besides fire danger you'd also have to investigate the physiological
affects that the extended O2 intake would have on your body. Breathing O2
at 40% concentration for 5.5 hours could give you oxygen toxicity over
such a long period of time. There's quite a bit of information on the web
so you should be able to do some detailed investigation to determine
whether it's safe from a physiological standpoint. I like the concept,
but I suspect it is more dangerous than it is worth.
Jon
Alan James wrote:
Hi psub experts,
What do you guys think of the idea of running an ambient subs life
support on nitrox?
I'm building a very small fiberglass sub, almost canoe like. Eventually I
want to build it 1 atm but
thought it would be smart to try the design out as an ambient first.
There might be close to 200 liters of air space in the hull. I have 2 x
80cubic ft tanks. If I filled them with
40% O2 it would take 2hrs 40min for the air to get down to 21% O2. This
is in the worst case scenario of traveling just
under the surface. At 33ft I'd have 5hrs 20min etc. I could open a valve
& flush the system any time & in the normal
course of a dive this would happen as the air expanded on ascent & filled
on descent.
There is a dive limit of round 90ft with nitrox but longer no
decompression times. However I guess I would need
to stay inside this depth limit & keep to the air decompression tables to
stay safe.
On the plus side, I won't have to get anything 02 cleaned, & its pretty
simple.
Alan
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