Half-packing sorb -- Possible, or deadly?

[J-Vo]

Expanding on this, someone could only fill 1 canister of the sidewinder and do a 3hr dive no? or rotate exhale to inhale side and get 9hrs from 1.5 fills!

I rotate mine somewhat revo style, but I would never only pack one canister.

 

[rjack321]

The recent thread about the Dive Talk GO got me thinking... One of that unit's features is a small scrubber. Its limited sorb capacity makes this particular rebreather only suitable for non-expedition-type dives, but for that particular use case, the small scrubber seems reasonable.

Let's assume, then, that a diver has a rebreather with a standard-capacity scrubber (say four or five hours' worth of sorb). This diver has a use case in which they'll be doing a 1.5-hour one-off dive, or maybe two relatively quick dives. The diver doesn't want to go OC, and storing the partially used sorb for later is either impossible or impractical.

Could this diver half-pack the scrubber in their full-size rebreather? And if so, would it necessarily be a bad idea?

NOTE: I'm not gonna do it; I'm just curious.

Just buy a unit that supports varying scrubber canisters. Depending on the unit some have up to 4 different supported scrubber sizes. 3,5,6 and 9 lbs for instance.

 

[davehicks]

You have no way to actually know this and it's dangerous to promulgate fallacies like this. Nevermind that scrubber duration is highly dependent on water temperature, and even if you were using indicating sorb you can't see the actual reaction front.

I have years of experience using this unit that tells me it does work.

And even with non-indicating sorb you can observe the color, clumping, and texture to distinguish between fresh and spent sorb - again with experience. When you dump that inhale canister after 3 hours runtime, it is obviously not significantly used. Finally I can report on the success of actually using this rotation process.

The revo units have a similar design and the rotation of canister is widely accepted.

I fail to understand your knee jerk reaction in this case.

 

[Wibble]

Before we go off on one here; can we confirm that the Kiss Spirit and the Kiss Sidewinder, both with two serial scrubber canister designs, do not have removable scrubber baskets and therefore cannot be swapped around?

The Fathom Gemin has removable baskets and can be swapped around as per the Revo.

 

[davehicks]

Before we go off on one here; can we confirm that the Kiss Spirit and the Kiss Sidewinder, both with two serial scrubber canister designs, do not have removable scrubber baskets and therefore cannot be swapped around?

The Fathom Gemin has removable baskets and can be swapped around as per the Revo.

There is no removable basket, but the two KISS canisters are identical and interchangeable. So swapping is no problem.

 

[rjack321]

Before we go off on one here; can we confirm that the Kiss Spirit and the Kiss Sidewinder, both with two serial scrubber canister designs, do not have removable scrubber baskets and therefore cannot be swapped around?

The Fathom Gemin has removable baskets and can be swapped around as per the Revo.

You can swap the sidewinder cans around in theory. but the rigging/clips will be off. It's more hassle than it's worth. But somewhat related, I have replaced the exhale side can after a shorter dive and used the otherwise unused inhale can for a 2nd dive along with a fresh exhale side can.

 

[J-Vo]

You can swap the sidewinder cans around in theory. but the rigging/clips will be off. It's more hassle than it's worth. But somewhat related, I have replaced the exhale side can after a shorter dive and used the otherwise unused inhale can for a 2nd dive along with a fresh exhale side can.

It is pretty easy to rig symmetrically and just swap heads. I do it all the time. There is something about having the fresh sorb on the inhale side that makes me feel more confident.

 

[rjack321]

It is pretty easy to rig symmetrically and just swap heads. I do it all the time. There is something about having the fresh sorb on the inhale side that makes me feel more confident.

Mine are not symmetrical. I would only refill the exhale side and leave the inhale as is if the dive was so short I was confident that side was basically unused.

 

[211ratsbud]

Mine are not symmetrical. I would only refill the exhale side and leave the inhale as is if the dive was so short I was confident that side was basically unused.

When you exhale into a sidewinder type system. Does your tidal volume send some of your exhale through the first scrubber forcefully or and short enough fashion so that the dwell time is insufficient? The bag is after the first scrubber. Just about every other unit I can think of has an accumulator or a bag before the scrubber that absorbs the pulse of exhale. no doubt the accumulator being after the bag absorb some of that load and then allows the inhale scrubber to wipe it again.

I'm not speaking from the end of experience fwiw

I just happen to be talking to someone else about this prior to this thread popping up and they directed me to the Navy pulsatile flow chart for efficiency. This is meant to add constructive dialogue just reiterating that.

I did attach it here:

 

[rjack321]

When you exhale into a sidewinder type system. Does your tidal volume send some of your exhale through the first scrubber forcefully or and short enough fashion so that the dwell time is insufficient? The bag is after the first scrubber. Just about every other unit I can think of has an accumulator or a bag before the scrubber that absorbs the pulse of exhale. no doubt the accumulator being after the bag absorb some of that load and then allows the inhale scrubber to wipe it again.

I'm not speaking from the end of experience fwiw

I just happen to be talking to someone else about this prior to this thread popping up and they directed me to the Navy pulsatile flow chart for efficiency. This is meant to add constructive dialogue just reiterating that.

I did attach it here:
View attachment 888015

I'm sure some of the 2nd can is getting leftover CO2 cause the dwell time in the exhale can isn't that long. Plus the exhale side gets soaked pretty fast and I am skeptical it's as efficient as claimed when over-wet.

That's why I said "basically unused". Don't know the extent the 2nd canister does any work on a 30min dive, perhaps its aborted/short or just to demo some new gear, or check something (we do this a lot). Like do my new dry glove rings leak, or is the new ADV stem all good, or are those freshly serviced BO regs in order.

Basically if only 30mins and the next dive isn't a big one depth or time wise I will reuse the whole scrubber.
After a 60-90mins dive and if the next one is gonna be short and not especially deep, I will swap out the exhale side.
>90-120min dive1 I will just dump both and start over. Or if not within a few weeks.

This is in 7-10C water so not the greatest absorptive capacity in the first place. If significantly colder (2-3C water) I don't reuse any scrubber even if the dive was short. I don't think I would extend my personal 60-90 guideline for swapping the exhale scrubber only any longer than that even in MX. Sorb is cheap.

The OP was asking about only half packing a scrubber and that could in theory be done on the sidewinder. Kiss sold a single canister version as a pendulum rebreather to select folks - it was never marketed commercially. I forget the name of that beta unit. There were a few CO2 hits on that. Was it due to the limited sorb or the pendulum design with the excessive dead space in the hose? I don't know, but you could fill only 1/2 your sidewinder and see what happens. Could end very badly if your extertion goes up, or it's cold, or the axial reaction front is not even (which we know they aren't). But would be a nice despite dumb experiment for someone braver than me.