Mailing List Archive Mailing List Archive
Subj: Re:saturation deco
Date: 97-05-12 20:17:12 EDT
From: CHK BOONE
To: techdiver@aquanaut.com
Jim,
The tanks and regulators were made by elves but they will only be using
these for descending excursions. I trained them myself in mixed gas
techniques which was not much of a problem. The real problem is getting
them to flush that little toilet, and, of course, the male always leaves the
seat up.
Tony,
They were reluctant to sign the releases till I agreed to abide by OSHA
standards and regulations. We seem to have come to a mutually benificial
agreement - I get trained cooperative subjects for our project and they get a
great adventure to tell their grandkids about instead of being fed to
someone's pet snake.
Harry,
I did some more playing around with DECOM. I was under the impression
that a body would saturate in about 24 hours (1440 min). Some time ago I
ran these scenarios through a couple of programs looking for a peak in the
deco requirements that would suggest that they recognized a point of
saturation. I did not find any such point - the deco schedule just kept
getting longer and longer as if they were just running a program bassed on a
model that became unrealistic after a certain exposure time.
Well I finaly found that point on DECOM at about 3 1/2 days at 50 feet on
air. This is the point beyond which decompression no longer changes with an
increase in bottom time so I suppose I simply did not push them far enough.
I wonder if this is physiologically realistic - 5000 hours to saturate at
50' ? (with a moderate safety factor)
Might be interesting to see where this point is on Abyss, Pro-Planner, and
Voyager. Why don't a couple of you check just for curiosity. Try it with
no safety factor just for consistency and lets compare them.
I have run a scenario on DECOM using 10% O2 / 90 % He for the bottom gas
and decompression on air that gives a very quick decompression (354 min deco
time).
N=5 He=7 (fuge factor)
50' 10/90 1440 min
40' air 55 min
30' air 70 min
20' air 108 min
10' air 121 min
no CNS no OTU Max ppO2 = .44
Heat loss covered by heating system.
Counterdiffusion should be no problem going in this direction (light gas to
heavy).
Anybody see any problems with this ?
----------------------
Egil,
I'm not an expert but here are a few thoughts:
I'm sure that beyond a certain number of repetitive dives any tables get
mushy and unreliable. We have very few mathmatical models that represent or
predict the outcome of natural systems faithfully in the extreme and when
this is added to the physiological vairables involved in diving the
uncertainty eventually becomes too great to risk.
This is called 'reciprocity failure' and it is a common problem in many
fields that deal with prediction bassed on mathmatical models !
A saturation opperation can offer economy of gas use by recycling, and
economy of time by avoiding multiple decompressions.
Since it is only one dive and one decompression there is only one opportunity
to develope decompression problems.
It is safer for the diver to enter a chamber and decompress in comfort with
attendants than to do so several times while exposed to the elements.
Treatments for problems can be immediate.
A diver decompressing in an onboard chamber allows the ship to get underway
if desired instead of being trapped on station.
A housing provides a point of refuge close at hand for a diver in trouble and
more reliable communications.
A greater variety of tools can be brought to the worksite without encumbering
the diver.
Chuck
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