Thermal imaging of (SW) scrubber post-dive

[ErikH]

As a new Sidewinder diver I was intrigued by the exothermic process of the sofnolime and was wondering if this could be some sort of a quick reference / sanity check for the consumption of the scrubber. Just using my (cold, post-dive in 14C water and 10C air) hands it was easily noticeable that the scrubber cannisters were not uniform in temperature. Not having the syntactic foam makes this easier to feel. Knowing that the rEvo uses a tempstick on the inside during a dive, I tried to do something similar after the dive to get at least some feeling for scrubber consumption.

I got a GuideIR thermal camera available due to other reasons (installation/inspection of heating systems), so it would be easy to get some images. The first measurement I made is after 3,5h (1+1.5+1h) of diving 13-15C water and the second measurement is after a total runtime of 5:20h.

I'm not planning on pushing the scrubber for longer using this method, however it can prove valuable to have a quick sanity check after a dive. If I'd feel/see a hot spot on the inhale scrubber after just a limited amount of use, I'd be more tempted to just bin the whole contents.

Anyway, pictures!

The first picture shows 3,5h of use. The second a closeup of the exhale cannister. The 3rd picture is after another dive with total scrubber use of 5:20h. A fairly defined hot zone is visible first on the left/exhale side and another dive (of 1:50h) later this has moved to the right/inhale side. All pictures are within 5min of exiting the water and at similar temperature conditions. After the last dive the WOB was noticeably higher and the sorb was moist almost all the way to the inhale side.


Anyone else got some experience on the usability of this method and/or has good reasons to fully ignore this? There is of course a risk of misjudging channeling along the colder outside of the cannisters as 'passive' heat, so I have no intent to use this data to push my stack time to its limits. It might however give a nice confirmation of the expected use rate of the sorb over time
(Also see: The imbalance of CO2 absorption of the rebreather scrubber)

I'll gather some more data in the next couple of months to see how the peak heating zone corresponds with visual changes in the sorb moisture lever / coloring when emptying the cannisters.

 

[DiveLikeAMuppet]

Makes me want to test it on a JJ, this is cool. The only caveat would be that it’s a cone, at least with rEvo / JJ / AP due to the stick (not temp stick) in the middle of the scrubber.

 

[davehicks]

That's really cool. Thanks for putting this together and sharing the photos.

But 5+ hours on a sidewinder?? That is really pushing the system. I've been diving the same system (Spirit LTE) for a dozen years and never do more than 4 hours. Most of the time I do a Swap&Fill method after 3-4 hours. I rotate the largely unused inhale canister to the exhale side and refill the exhausted canister and install on the inhale side. This keeps some fresh sorb available at all times and dumps out any wet and saturated exhale sorb before it causes a WOB problem.

 

[ErikH]

Absolutely. I was knowingly going close to the limit (knowing people that go hours beyond this in similar circumstances) ‘for science’ in shallow, open water conditions and staying out of deeper, colder water and not exerting myself. I prefer your runtime and method for normal diving. As visible on the picture the co2 front was at least around 75% of the total stack…

 

[dylanfromwinnipeg]

Could the heat simply be due to the heat from your breath and not necessarily the scrubber chemical reaction?

 

[davehicks]

Could the heat simply be due to the heat from your breath and not necessarily the scrubber chemical reaction?

No, because the entire loop and heads would show higher temperatures if that was the case. After a couple of minutes, when the images were taken, the heat from warm air would have dissipated and cooled. The scrubber reaction is hotter and still radiating, which is what we see.