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Date: Wed, 16 Oct 1996 14:39:14 -1000 (HST)
From: Richard Pyle <deepreef@bi*.bi*.ha*.or*>
To: "Mr. Dude" <heyydude@pi*.co*>
Cc: Mike Severns <severns@al*.ne*>, techdiver@terra.net
Subject: Re: Rebreather CO2 Channeling
> 1)  The BioMarine design (on the Mark 16 center section, which is in the
> 155 and the Mark 16) for the scrubber cannister does not use any springs
> for compressing the sofnolime. It uses 2 hydrophobic filters, and a foam
> filter to keep the scrubber medium compacted.  I can't see why the Krauts
> would come up with a spring arrangement.  Sounds like a stroke invented it.

I think the spring might have a place, but only if implemented intelligently.

> 2)  I've been using the 812 mesh scrubber sold by O.C. Lugo.  I noticed
> something that maybe you others rebreather dudes have already noted, but
> I'll mention it anyway:  After a dive, especially on a bouncing boat, and
> in a bouncing car going down the freeway on the ride home, the scrubber
> medium has a tendency to "settle" - much like your box of cornflakes does
> in transit to the supermarket.

This is *EXACTLY* the problem I'm talking about.  Now, your average diver 
isn't going to knock a rebreather around as much as your average car ride 
might, but your average boat ride might just do the trick.  If you pack 
your canister in the dry comfort of home (like I do), then pound through 
rough seas to the dive site, there's a slim chance that the absorbent 
(especially the 812 grade sofnolime) might settle enough that in certain 
body positions, you can have serious by-pass in the gas flow.  This is 
what we would generally refer to as "bad".  I spend about 20-30 minites 
"tapping" down the canister everytime I pack it.  If I just fill the 
canister to the brim, seal it up, tap it on the floor a few times, and 
open it up, I find that the absorbent has settled by as much as 10-15%, 
which is enough to do some damage.  I typically top it off, and repeat as 
necessary until futher tapping does not lead to further settling.

> That's why I think Leon's advice to check the scrubber before each dive is
> a good one.  I check mine each time, and often, have to add just a little
> bit more material to fully fill the cannister, due to settlement.  When I
> fill with fresh scrubber material, I shake the cannister, and tamp it on a
> flat table, to try and get it settled as much as possible before I seal it.

Sounds like we both do the same thing.

> Whatever happens to you when you enter the water is COMPLETELY AND TOTALLY
> Heyydude's Fault.  If you get hurt, have your family lawyer call him
> immediately for a big cash settlement.

Aloha,
Rich

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