Extendair

DepthCharge

OMG!!!!!!!!!! you're not using the approved CO2 absorbant in your EVO........APD will have will have something to say about that!!!! Probably cut you off from supplies or something

__________________
Later,
John

It's better to beg forgiveness than ask permission

AD_ward9

We ran tests with Sofnolime hard packed into the same volume as the 5" cartridge (195mm x 124.5mm), in the same canister. The result was 50% better in ExtendAir than on lime.

We have a setup where can test scrubbers down to 1400msw completely under computer control.

What is good news, is the customers we have all agree to publish results as part of the Open Revolution Initiative. Intermediate results are also commercially valuable (costs a lot of money to do and reproduce), but there is agreement to publish the final data in full. Probably happen shortly after DEMA.

Cheers

Alex

AD_ward9

Same volume means a cylinder 195mm x 124.5mm.
I used a tube of 125.5mm internal diameter, with a thin liner fitted. The Micropore cartridges are 125mm diameter but the end wrap means it is really on average 124.5mm.
The lime is packed hard, and the test stops when there is CO2 breakthrough. The cartridge does weigh less than granules, a lot less, but it is the amount of Ca(OH)2 you need to measure. We understand from Micropore that the cartridges are 30% more heavily loaded with Ca(OH)2 than granules. However, this does not explain the result. It comes down to the gas flow.
Correct, axial scrubber. There is no ExtendAir radial. Sorry but I do agree on this one. It is all about consistent gas flow and dwell time. We can get better gas flow in an axial design than on a radial.
ExtendAir cartridges are extremely flood tolerant. Vastly better than granules: granules are simply not flood tolerant at all, whereas the ExtendAir is good enough you can put it into a bath of water for 5 minutes, then back into a rebreather and breathe it. I do this demo from time to time: I have the curves on the effect of the water. I also put some cartridge into my tea and drink it as part of the same demo, then pass it around so the other safety specialists around the table can try the same. Do not try that with granules. Again, we have the curves showing rise in pH for both ExtendAir and granules before doing this trick.

The point with the water is that the reaction absorbing CO2 generates water. In the case of granules it is mostly absorbed, which is why the granules are hard caked together, like mortar, after use. That does not happen with ExtendAir cartridges. The water runs down the cartridge and must be collected, then removed. The amount of water can be large: a litre in some tests! There is a good and bad side to this:

1. The WOB stays the same throughout the dive, instead of increasing during the dive with granules.
2. You have to have a means to get rid of the water, preferably automatically.

Cheers,

Alex

silent running

Hi Alex, but I wonder is that canister/housing actually designed to be used with granule sorb? The extendair people say that you can't use granule sorb in the Optima, is your scrubber housing the same as the Optima or is it different? Thanks, -Andy

AD_ward9

We did a setup for a test, rather than for diving by putting a liner in a Micropore canister tube to make it the right volume, clamped a spider at one end (from an Inspo: it is bigger than the tube diameter so has to be clamped), then filled it with granules and fixed in a smaller spider and mesh at the other end. OK for a test, but not to dive from.

Just on a side issue: We offered Rebreather World to re-run this test with lots of different types of granules, but nothing came of it. If you send me a tub of the granules you want tested I can run it and publish the results. We need to re-run this particular test anyway, as it was only done once, and there are some changes to the Micropore cartridges since then. So now is your chance.

The results will be done on our latest rig. Completely under computer control down to deeper than most tech divers go on helium and air.

Cheers,
Alex

NB: We will do this test in our St Petersburg facility, so please do not ship to our Glenrothes branch. I will post an address in Finland shortly, as shipping to Finland is easy, shipping to Russia is a real pain. We will handle the collection from Finland and bring it to SPB. We need a full tub for the tests, because they are performed at different depths.

silent running

Thanks for the detailed reply. But I'm not sure I understand that last bit above. What do you agree about and with whom? Do you mean that the extendaire concept works better with an axial flow? I was under the impression that it wasn't even possible to make a radial cart. I was saying that it makes sense that the WOB would be better for the axial flow carts than a standard granule axial flow. The interesting ? to me is how does the duration of an axial flow extendair compare duration and WOB wise with an 8-12 granule radial...

And I forgot to ask: which mesh size you used in your extendair canister granule test?

And I still don't understand why it's so important to get the water out of the loop if the carts. are so flood tolerant. How much water can collect before it's a problem and must be removed? Thanks again, -Andy

AD_ward9

Axial flow/Radial flow: Using granules only, the gas flow in radial is worse than for an axial, therefore for a given weight of granules, the life will be shorted. However, in a radial scrubber the gas path is shorter, so one can pack it harder than for an axial. This is what gives rise to long life radial scrubbers. If you put the same weight of granules into an axial, it would last longer than for the radial, but either the WOB would be too high or the diameter would be too large.

Due to the above facts, ExtendAir focus on axial scrubbers. The material could be moulded as radial elements, but the production process would cost a lot more.

ExtendAir scrubbers have a very low breathing resistance. 1/3rd that of a 36mm diameter breathing hose. This is both in theory and in tests, checked in air and helium to depths well beyond what anyone other than a sat diver has dived.

On the water, if you do not get rid of it, you can have a litre swishing about. If it gets into hoses, that will be enough of a gurgle-gurgle sound to drive you round the bend, and increase WOB so much you would be hallucinating from CO2 anyway.

I will have to come back on mesh size: I need to dig out the log book when this work was done.

Cheers,
Alex

mattmexico

yo

I have a Meg and I have a set of adapters that allow me to use standard Extend Air cartridges to use with my Meg. The adapter was made by ISC for the Extend Air to be used through the filming of "the Cave" movie. I did a month of diving in Romania using the Extend Air before we switched to the standard sofnolime canister for the shooting in Mexico. I do not know if ISC would fabricate adapters again but do know that any of the 10 movie units came withvbthe adapters, as I have one of them, mine came with it.

greetings
Matt

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W 87' 04.693'
www.andreaswmatthes.com

silent running

Alex, thanks for the water amount clarification, a ltr of water sounds like a good level of flood tolerance.

But the above explantion sounds a bit odd to me. The gas flow in a radial is "worse" than an axial. What do you mean by worse? If the more tightly packed radial allows for a more optimal usage of the sorb, what's worse about that? A more densely packed scrubber would increase dwell time, slowing the velocity and thus efficiency, no?

And the "If you put the same weight of granules into an axial, it would last longer than for the radial" part, I don't get it. The USN tested the MK15.5 with the 8lb axial scrubber-very large diameter/surface area-and got the same duration as the old Prism 5.5lb scrubber...

Uh Oh, I think I see Paul coming in low out of the rising sun! -Andy

silent running

Hello Matt, interested to know, how did the WOB and duration differ btw the standard Meg axial and the extendairs? Why did you switch back to granules in Mexico? Thanks, -Andy