Canister Insulation

[doctormike]

I was intrigued by this concept - the insulation of the scrubber canister on KISS rebreathers. If this really does increase scrubber duration (seems like it should), I imagine that it would be something theoretically applicable to any rebreather with a relatively exposed canister (for example, my JJ).

This material was apparently chosen to add minimal buoyancy, to have little inherent compressibility, and to keep the heat generated by the sorb reaction in the loop.

I wonder if there would be any interest in adding that as an aftermarket option?

Anyone know anything about this stuff?

 

[KevinNM]

I was intrigued by this concept - the insulation of the scrubber canister on KISS rebreathers. If this really does increase scrubber duration (seems like it should), I imagine that it would be something theoretically applicable to any rebreather with a relatively exposed canister (for example, my JJ).

This material was apparently chosen to add minimal buoyancy, to have little inherent compressibility, and to keep the heat generated by the sorb reaction in the loop.

I wonder if there would be any interest in adding that as an aftermarket option?

Anyone know anything about this stuff?

There is a bunch of stuff by a scientist with NEDU on rebreathers and I think he vaguely discussed that. But I can’t remember his web site off hand and I’m on my phone.

 

[Akimbo]

NEDU has been doing R&D work on insulating the loop for decades; both for diver heat conservation and absorbent efficiency. I'm not sure how much actually ended up in unclassified research papers rather than buried in engineering notes though. I'm a little skeptical over the reliability of the method described in the KISS link because the risk of water leakage is high, hard to detect, and miserable to repair.

I would look into the insulation used on saturation diving bells. Trelleborg's syntactic PU foam is one example. For more, just Google: diving bell insulation.

It is probably more complicated than it is worth but the idea of installing the loop inside your drysuit keeps coming to mind. The weirdest part is keeping the harness from crushing the bags. It sure reduces the potential for water leaking into the scrubber. Some of the European commercial dive gear manufacturers played with the idea in the 1970s before hot water suits and surface-based closed circuit recycling systems made it pointless.

 

[tbone1004]

Rhino lining works as well, apparently it gives a roughly 10*F boost to scrubber temps on the Meg so it should be similar on the JJ

 

[wedivebc]

The problem with using add-ons to increase scrubber duration or any rebreather performance items is how much does it improve duration? Who's testing besides the random reports of "I got 6 hours with no headache"

 

[Akimbo]

The problem with using add-ons to increase scrubber duration or any rebreather performance items is how much does it improve duration? Who's testing besides the random reports of "I got 6 hours with no headache"

The absorbent efficiency at different temperatures is available. I wonder if there are any small temperature recording devices that you could put in the canister? It would reduce absorbent capacity a little but would give you real numbers without adding a penetrator to the canister for a thermistor.

 

[tbone1004]

The absorbent efficiency at different temperatures is available. I wonder if there are any small temperature recording devices that you could put in the canister? It would reduce absorbent capacity a little but would give you real numbers without adding a penetrator to the canister for a thermistor.

megs have a loop temp sensor in them, several others also have scrubber temperature monitors

 

[doctormike]

The problem with using add-ons to increase scrubber duration or any rebreather performance items is how much does it improve duration? Who's testing besides the random reports of "I got 6 hours with no headache"

Right, exactly. I had started a thread about a similar topic a while ago... Since what I was envisioning was an aftermarket third party product to use on a variety of CCRs, there would be no one company to put the funds into calculating scrubber times at different temperatures, and any benefit would vary from unit to unit, so any company making the aftermarket kit couldn't do it either, even if it was financially viable.

I was thinking more along the lines of diving nitrox but using air tables in OC. Sort of a safety buffer that you don't explicitly calculate for, to compensate for unanticipated inefficiencies / breakthrough / channeling / etc... in the scrubber.

 

[doctormike]

Rhino lining works as well, apparently it gives a roughly 10*F boost to scrubber temps on the Meg so it should be similar on the JJ

Right, but I have read that this is an improvement over that - the KISS website says that this is bonded to uncoated scrubber tubes, which are then covered with Rhino Guard. This thread points out that if you wanted to upgrade an existing Sprit LTE you would first need to take off the Rhino Guard (which doesn't sound very easy!)

 

[tbone1004]

Right, but I have read that this is an improvement over that - the KISS website says that this is bonded to uncoated scrubber tubes, which are then covered with Rhino Guard. This thread points out that if you wanted to upgrade an existing Sprit LTE you would first need to take off the Rhino Guard (which doesn't sound very easy!)

yeah, it's just whether it's worthwhile and how much the can temp comes up vs. how much it drops from the loop/you breathing. Should be fairly easy to do on something like a meg/HH/JJ type canister and run some tests. Meg would probably be easiest since it has the thermocouple in the head already