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Re: [PSUBS-MAILIST] Life Support Test Experience
Hi Phil, the comment about the inaccurate
of the barometic method comes not from me !
Think ist comes from Emile.
And yes - also the Euronaut has two undependly LSSystems.
But I did not use the barometic methods. I use constant flow
with about 03-04 lpm per person - and two Draeger Oxygen alarms.
One gives audio siganl at 17 % and the other at 22%. Both show the o2
level also on a analog indicator.
If one reach the border we just reduce or increase the constant flow
needle vale.
Euronaut has 48 m3 inside volume - so all reaction increase and decrease
going very, very slow.
Peppers is maybe to small for the barometic method -
temperature, hunidity and air pressure can change quick in this tiny
boat.
The "boat is tight" test on Peppers is that way that the pilot brezze
out
via the snorckel on the surface and close the snorckel vale. This cretae
a lower pressure of some 20-40 mbar to press the hatch into the seal and
show that everything ist tight before dive. .
Best regards Carsten
Phil Nuytten schrieb:
>
> 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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