RE: [PSUBS-MAILIST] Life Support Test Experience

[Phil Nuytten <pnuytten@compuserve.com>]

Hi, Carsten:
        I note in your response to Cliff's testing that you feel that the
'pressure drop method' of oxygen add is 'inaccurate'. I wonder if you are
referring to the 'bellows-add' system or some other means brought into play
by metabolic O2 uptake and chemical bind of produced CO2? For information,
the bellows-add system has been used on well over 200 undersea vehicles
including 40 Newtsuits/Hardsuits, 32 Mantises,26 Wasps, 25 Newtsubs, 15
Jim/Sam ADS's. and a very large number of one and two offs. It is also
approved and accepted by the US Navy as part of their 2000' Hardsuit ADS
system, by Lloyds,ABS,DNV, and by the certifying agencies and/or Navies of
Japan,Korea,France,Russia,UK,Canada,Italy,Norway,Australia,  and, of
course, Germany.
        BTW, Carsten,I agree with you on the 0 .5 lpm O2 flow rate
producing high cabin pressures. Both our testing and field records of
thousands of hours of sub time indicate that our 'steady-flow' metered
orifice rate of 0.25 lpm will produce a slow cabin pressure drop with an
active occupant, while 0.50 will produce an increase in fairly short order.
The right number is around 0,35-0.4 - depending on what the occupant is
doing, stress level, etc., 'Course, with the bellows -add system, you don't
have to worry about it - the bellows reacts to your metabolic requirement
and the 'steady-flow' fixed orfice assures enough O2 to support life if
your bellows goes south on you . . and you are out cold. Speaking of which,
we use two completely independant LS systems in each vehicle with a
duration of about 40 hours each. That is, two HP sources, two first-stage
reductions,two hull-stop valves, two metered orifices ( 'steady-flow), two
2nd stage add-valves, two O2 bypass valves, and two adjustable, sealed
bellows systems.  The scrubber system is, like wise, split into two 40 hour
scrubbers. The O2 HP supply is cross-manifolded with a 'normally-off'
valve, so you can cross over to utilize your original supply (if the
problem is not in the HP O2 valving).
        A common question is: what happens if a pressure drop in caused by
hull cooling instead of metabolic uptake? The answer is that the bellows-
add will make up the diff and the cabin air will be slightly high in O2 for
a short period, until you push the bypass button on your air BIBS or longer
if you elect to live with 23% instead of 20%, etc.,. Note that I said
'Cabin Air' - the normal cabin gas is 80/20 -air, since that was what you
had in the cabin when you closed the hatch. The N2 is inert, of course, and
there is no pressure driving force to cause it to enter your
tissues,bloodstream etc., so it just acts as a 'filler gas'. The pure O2 is
simply to make-up the O2 that you burn up in the act of living!  All this
is undoubtedly 'old hat' to you, but may be helpful to any newbiesm.
Regards
Phil Nuytten





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