Reading the Tea Leaves/Sodasorb Grains

jkaterenchuk

I have two seperate examples that indicate a similar distribution pattern in the scrubber. I will look at the next scrubber to see if it represents a third consistent pattern. If so its likely not random and is an indication of something. What I am trying to do is find out what the "something" is and if it is significant from a diving perspective.

John

se2schul

I'm finding this thread interesting. I wish that my scrubber were clear so that I could instantly see how wet, used and well packed my scrubber is.

Ben Field

Oh yes it must mean something.... I was only trying to suggest it might mean alot more or even less than it is supposed to mean in its proper application when used in a diving rebreather, while its a curiosity I'm not sure it can be used as a guide (not that I'm suggestion you where/are)

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Underwaterbear

Here is the MSDS for Ethyl Violet : Link

After reading Alex's "warm air rises" thought, I have an unclear hypothesis swirling in my brain that the pattern we're seeing is a two act play; temperature zones in the scrubber and reversion of the indicator dye in the time between use and inspection. I'm thinking that perhaps the top of the scrubber (when horizontal) is more active due to higher temperature, this means more moisture generated from the reaction and that in turn leads to more complete use of each grain of sorb. Then I think reversion of the indicator - as moisture penetrates the grains of sorb and allows the removal of H2CO3 from solution, the saturated sorb goes basic again and turns white (or a lighter shade at least) - has something of a role.

Then there's also "wall effect" to consider.

Hey John, what do you normally do with your rig when you are dekitting after the dive - stand the rig up or lay it down on it's front or back? I'm trying to understand whether the scrubber would be vertical or horizontal as it cools.

Finally for those that are enjoying this thread, Sodasorbs' absorbents manual is interesting reading.

jkaterenchuk

In both sets of pictures the scrubber was removed and photographed within 5 minutes of surfacing from the dive. Its a shore dive site with the tables being about 30ft/10M from the shore. I walked over to the table. Took of my BO tanks, gloves, hood, mask etc. Took the rig off while it is in a upright position and then immediately took the scrubber out and photographed it.

I normally leave the rig sitting in the upright position when not in use, between dives, before dives, after dives and when transporting.

From what I have seen the violet colour does not fade away all that quickly once the scrubber is opened.

John

jkaterenchuk

Here is the explantion from ISC.....I am still trying to reconcile this explanation in my mind...

John


"From the pictures it appears the change in hue is probably related to the moisture content of the sorb, an axial consumes the sorb from primarily bottom to top in the Meg, hence more moisture is produced towards the bottom of the scrubber as it is a by product of the chemical reaction. The unevenness of the pattern could have something to do with packing but may be due to other factors such as attitude of the scrubber during the dive having some influence on the migration of moisture."

jkaterenchuk

Here is the third scrubber in which I have taken pictures. Same pattern is evident. I think something else might be going on here then has been suggested so far.

To ensure correct packing this time I filled 1/4 then tapped about ten minutes, then another 1/4 and tapped 10 minutes, another 1/4 and so forth until full.

1st picture is looking at divers left side
2nd looking at divers right side
3rd looking down on top of diver
4th looking up from under diver.

John

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Hanssing

Very nice investigation and pictures you have taken.

If its not due to packing (it was transported standing up) and sorb being loose on the top part, then the thermals inside is still a good explanation.

Ie. hot air rises, adn cold a descens and condensates, This effect could be self-amplifying if relative moisture in the scrubber is inverse to the coloring, since the moisture would inhibit gasflow due to clumping.

Hmm, very interesting.....
.... Wonder if a axial-granualr scrubber-front can be come "unstable" and "flicker". Ie if you had a wide and vary long scrubber would it then have the expected front through its burn-time or would it become so uneven that it would leave whole parts unused...

I allways considered clumped sorb as a self-regulating part (feedback) ensuring evenly spread reaction-front. But perhaps that is not so if the axial is lying down and has realtively low flow-rates?

Still like the pictures!

Nicolai

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Its going to be bitchin' tricked out piece of gear

jkaterenchuk

Some of the observations are:

1) More purple evident on the part of the scrubber closest to the surface. Less purple on the bottom. The dives were in normal prone position.

2) Less purple evident on the lower part of the scrubber that is closest to the area in which the exhale side of the loop enters the cannister.

Still not sure about the theory that explains this....if i assume that the purple represents the reaction front and therefore is representative of the volume of gas flowing thru that section of the absorbent.....then what is causing the volume flow to be smaller/lower/restricted on the lower left divers side quadrant of the canister when in dive position?

More tests and pictures needed over the next coming weeks.

John

zzzzzzzz

Hi John,

Do you wear stages or piece of gear on a particular side?

The pictures are interesting indeed. The dye would turn purple in the active front and apparently dissappear once the humidity level increases in the sorb(?)

The purple coloration has left me puzzled in designs with unconventional scrubber beds. At least yours may lead to some insight.

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