Importance of CO2 and scrubber life sensors

[doctormike]

If your CO2 hit had of been as a result scrubber breakthrough the rEvo RMS would have picked it up and given you warning through rapidly dropping remaining scrubber time.

Your hit sounds like more to do with retained CO2, so the rEvo RMS or any scrubber monitoring system would not have picked it up. Maybe a CO2 monitor measuring end tidal CO2 would have given you warning but that technology is not available in rebreathers.

Exactly, that's what I was saying.... And it won't pick up breakthrough if the breakthrough is from channeling, right? Only if the sorb itself is being exhausted faster than anticipated.

So I think that if you stick to published data, it's unlikely on most dives that the temp stick will alert before you exhaust the scrubber, since that data tends to be so conservative.

 

[LFMarm]

Exactly, that's what I was saying.... And it won't pick up breakthrough if the breakthrough is from channeling, right? Only if the sorb itself is being exhausted faster than anticipated.

So I think that if you stick to published data, it's unlikely on most dives that the temp stick will alert before you exhaust the scrubber, since that data tends to be so conservative.

I think the benefit of a temp stick is to safely run beyond recommended scrubber life time not so much to alert you if you should stop diving before the recommended scrubber life (as you say it’s pretty hard to do that)

 

[doctormike]

I think the benefit of a temp stick is to safely run beyond recommended scrubber life time not so much to alert you if you should stop diving before the recommended scrubber life (as you say it’s pretty hard to do that)

Exactly. That's what I gather from people who use them...

 

[Tassi Devil Diver]

And it won't pick up breakthrough if the breakthrough is from channeling, right?

Channelling is not such an issue with the rEvo with the duel scrubbers, the rEvo RMS will pick up channelling through the first scrubber where cycle time will quickly drop when the reaction front is detected in the second scrubber, catching the channelling CO2.

 

[nadwidny]

Thanks @nadwidny. Did you enjoy Malin, think we were there 2 weeks after you.

I did. Planning to go back.

 

[tomh1972]

Channelling is not such an issue with the rEvo with the duel scrubbers, the rEvo RMS will pick up channelling through the first scrubber where cycle time will quickly drop when the reaction front is detected in the second scrubber, catching the channelling CO2.

This is really interesting to me. I am not an RB diver (not even "Tech"(yet)), but I find these discussions incredibly intriguing. In particular, I thought about looking taking AN/DP then an OC trimix course, but have been thinking that AN/DP to CCR might be more appropriate. What has been scaring me off, though, is the apparent inability to objectively determine whether a mechanical failure of the scrubber is causing/permitting increased CO2 in the loop. While I understand that one must "learn" the physiological signs of hypercapnia, the inability to back those signs up with an objective reference troubles me (the "unmeasurable" makes me nervous).

From what you're saying, though, do I understand correctly that 1) each scrubber in the Revo dual uses an independent temp stick; 2) the scrubbers flow in series (from scrubber A to Scrubber B); and thus 3) by monitoring whether "Scrubber B" is reacting to CO2 before "Scrubber A" is exhausted, one can determine if "Scrubber A" is improperly permitting CO2 to pass through the absorbent? If so, that seems to be a significant development, and might provide the extra "gut check" reference that I was hoping to see. Of course, this doesn't solve problems associated with overbreathing the loop/reg, but that problem exists on OC as well (and is somewhat self-limiting as compared to a scrubber failure).

Do I understand the science on this correctly?

Thanks
Tom

 

[Alekseolsen]

Channelling is not such an issue with the rEvo with the duel scrubbers, the rEvo RMS will pick up channelling through the first scrubber where cycle time will quickly drop when the reaction front is detected in the second scrubber, catching the channelling CO2.

As someone seriously considering a rEvo down the read, lets change that to: "Channelling is not such an issue for the first of the rEvo dual scrubbers"

 

[doctormike]

Question for the more experienced CCR divers in this thread. How common is channeling if you are compulsive about packing?

I mean, I have had mushroom valve failures (on a build check, not on a dive), and I overbreathed once as mentioned upthread. But I really spend a lot of time packing my scrubber, hitting it with a rubber mallet, tightening it, hitting it, tightening it more, etc... I rarely keep a scrubber from one weekend to the next, even if I don't have that much time on it.

Is that something that you guys worry about?

 

[formernuke]

I'm following this as I'm about to order a revo

 

[JonG1]

I would think its unit specific and environment specific to be honest.

A unit bouncing about in a rib that's prone to channeling would be at more risk than one packed at a site and then dived eg shore/cave.

I also think that too much packing can impact WOB through small dust particles created during the pack and smaller gaps between molecules.

My KISS Classic tends to be more affected by condensation in the form of clumps if its too tightly packed relative to a lighter one.