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I know there is a lot of ill will toward Cochran due to the problems
of their wireless products. However, the teaming of them with the
Prism folks is quite a nice match if they pull off the electronics to
the mask for the rebreather. The important part I'm going to post
about is the rebreather concepts that are coming with the design. The
electronics I'll wait and see about.
First: how do you know what you're breathing if you don't know the CO2
inspired? Answer is you don't and you're simply taking the risk you
may tox due to high CO2 with elevated O2. They are incorporating a
CO2 meter/alarm into their units. I'd like a nitrogen and helium
sensor too!
Second: the gas addition is a valve that essentially stays open all
the time. It is only adjusted by the results of the O2 sensing system
that say the O2 is low or too high. This requires energy only when an
adjustment is needed to allow more or less flow unlike the solenoid
that energizes over and over. Second thing here is that you're
getting a constant flow of O2 rich gas which gives you a flatter FiO2
than the solenoid saw-toothed addition scheme. Battery/electronics
failure results in the addition rate being the same as it was before
the electronics failed. A backup sensor/meter/deco computer gives you
what you need to live by.
Third: their scrubber material handles the water fine in a flood
(non-toxic, as in no burns). You just flush the system out and keep
using it. All of the above are proprietary developments, that in my
mind make the Prism a significant step above the rest of the crowd of
rebreathers. Target price was around $5000 as stated at the CDS
workshop.
I'm not buying anyone's SC or FC unit just now, but as I hear people
say this and that about the problems with rebreathers, I think that
the PRISM represents a leap toward solving 3 big problems with
rebreathers: gas addition (+ electronics failure), scrubber failure
due to water, CO2 warning alarm.
For those who say they'll never trust a rebreather that has
electronics, think about the evolution of the plane from a bicycle
mechanic's beast to electronic jet fighter/bomber. How about the
tank. Think our boys (and yours) don't trust their lives to
electronics in a hostile environment?
Give the industry time to turn out a better diver-$-trap and think
REALLY hard about what CO2 and mix you're breathing from that
counterlung. Try not to get your breathing rate or O2 consumption up
too high, you might over breath your constant flow breather or elevate
your CO2 levels! And don't ascend too quick on the Odyssey whilst
sucking that O2 down.
I think I'd want a backup loop altogether with a smallish canister
just for bailout and deco. Peter said that was simply too expensive
for the market. I didn't ask him how much his life was worth, but I
know how much mine is to me.
So even his breather has not met the level that should be expected for
overhead environments where you have an extended time till you can
surface: enough *KNOWN* redundant bottom, travel and deco gas to get
you home a the worst possible part of the dive if you or your bud's
primary system completely fails such as out of gas (or a loop
rupture). You could of course attach large enough exit tanks for
bottom, travel and deco gases, but then you've defeated the best part
of the rebreather (flexibility in a small package) and have all the
baggage of OC. Until you can reasonably safely get me a worry-free
known gas into my lungs and provide full redundancy w/sufficient
capacity and a donating system from my bud, listen to the point G-man
makes: "Do it right."
Note that his problem is deco time and scooter capacity not gas
shortage or anything like O2 sensor, scrubber, or solenoid failure.
All breather divers in Wakulla or any extreme diving will have the
same problems that OC divers have to contend with in addition to
rebreather worries. Of course George has a great team effort going to
get the staging done that allows him to worry about how many scooters
it'll take to go two miles one-way! Careful rigging keeps the drag
down while keeping fully separate, redundant, DONATABLE breathing
systems comfortably close at hand...
What about puking into a rebreather? Does it go on thru the exhaust
tee? Would that be considered a total system failure? I guess you
could flood and flush the PRISM, but what about the smell!? Enough to
make you puke again and again! Lay off the strong food before jumping
in and be sure you don't get that second tasting burp.
Keep in mind that I want a rebreather badly as the cold Great Lakes
water is a big problem on deco as well as getting in and out of the
boat with heavy tanks. I'd love to drop the heavy tanks off for a 50
lb. rig any day and warm gas on deco too! Man! Does it come with a
sub tube and a deco habitat? Safety above all else folks.
David Drake EDS/SATURN Infrastructure 8-320-4190 on GMnet
Spring Hill, TN USA Internet: saturn.ddrake05@gm*.co*
______________________________ Forward Header __________________________________
Subject: Re: Re:Rebreathers - Phinally, Physiology!
Author: owner-techdiver (INET.OWNERTE7) at DIAMOND
Date: 6/25/96 2:07 AM
>> 1. Is there more than one solenoid in a single breather?
>
>Yes there are two on the CCR500: one for the O2 tank and one for the
>diluent (air or the crazy gas of your choice ;-)
The CCR-155 uses a solenoid valve for O2 and a simple mechanical tilt valve
for diluent. Why did they change this for the -500, did they say?
--
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