Re: [PSUBS-MAILIST] scrubbers

[irox <irox@ix.netcom.com>]

Hi Alan,

checkout page 419 of Manned Submersibles by Frank Busy.  This gives
some formulas which can be used to calculate the CO2 build up taking
into account the volume of the pressure hull (well, the floodable
volume per person).  You should be able to find this book a several
sources online (including psubs I think), this is a great reference
particularly aimed towards small submersibles.

Cheers,
  Ian.

-----Original Message-----

From: Alan James 

Sent: Jun 13, 2010 10:52 PM

To: personal_submersibles@psubs.org

Subject: [PSUBS-MAILIST] scrubbers










To All,
While looking at various papers on CO2 scrubbers 
from manufacturers
etc, I found that none addressed the unique 
situation found in submarines.
Most CO2 absorbent is used in anesthetic machines 
or rebreathers where
there is a closed circuit. The CO2 breathed out 
goes straight into the scrubber 
& is removed. 
In our subs the CO2 is breathed out & is 
diluted by the rest of the air in the 

hull & only air with a portion of the CO2 in 
the hull goes through the scrubber.
This means that the CO2 level & the pressure in 
the hull will progressively climb
unless the volume of air going through the scrubber 
is large enough to make an
impact. The Deep Worker 2000 has fans pushing 160 
liters per minute, I'm not 
sure whether this is per scrubber & whether 
they have 2 scrubbers working 
simultaneously. But based on 1 fan going, that's 
320 x the volume of CO2 being
produced. In the manufacturers guidelines for 
scrubbers they recommend that the flow 
is at least equal to 
the tidal volume of your breath (about 10 liters per minute) 
& low enough so that the air has at least 1/2 a second dwell time in the canister. 
This could be 32 x less than what Phil has worked out is necessary for the 
Deep Worker. I know 
the Deep Worker has a small hull & that fluctuations in O2 
& CO2 are more critical than a K250, but possibly the same volume of flow is 

necessary to achieve 
atmospheric control in larger subs.
Also because of the dwell time needed the large 
flow required would need large or
long canisters. Deep Worker has 2x 3.35 kg 
scrubbers.
On the psub site there is reference to rebreather 
cartridges as an option, but from 
what I've found you would probably need a number of 
these running simultaneously
to make head way.
What are ABS recommendations? & what are others 
thoughts / experiences with this.
I'm trying to sort this stuff out for 
myself.
Regards Alan



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