Rebreather Comparison Chart

jiseson

Optima duration as per diverite:
http://www.diveriteexpress.com/libra...aph300cold.pdf

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Jonathan D Iseson

Dsix36

This chart is what I learned from in my course. It makes a lot more sense to me than the comparison chart at the begining of this thread.
It is almost like they were trying to make the Optima look bad for the comparison. All of my research and training never showed the canister as performing that badly.

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jradomski

I don't think they set out to make the optima look bad, they set out to test it using similair parameters that CE units are tested at.. The test data Kevin released is fairly close to what I have heard in the past..

The test shows that the extendair does not do well at high flow rates with high co2 production..

If you are comparing scrubbers the worse case is a good starting point, high flow rates quickly show flaws in a scrubber.. Anyone can choose test parameters that make their units look good..

We all knew ahead of time that the sport kiss did not do well at high flow rates due to its shape but had reasonable performance when flow rates were kept in usual dive parameters.. The all out tests have their uses, since it is possible to reeach these flow rates for short periods of time.. Scrubbers with longer beds will do better at high flow rates but will usually also have a higher wob (unless the diameter is increased as well)

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Joe Radomski
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All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

Dsix36

That makes sense, Thanks for the reply.

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schford

I have updated the picture in the first post if you want to grab hold of it.

cheers

Stuart

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Ben Field

Thanks Stuart.

I wonder how the next crop of units will fair against this chart?

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Padowan

On the WOB issue - does the ANSTI test rig, actually test units under water, or just in a pressurised pot? If it's the former, then the orientation will have an effect as the differential pressure under water between mouthpiece and C/L will be considerably greater than the pressure differential not underwater.

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caveseeker7

Also remember that C2R is planning on offering the Sentinel for use with the cartridge. I'm quite sure they would have liked to get good performance out of that combo. But as Alex and Joe said, the cartridge/cannister design is difficult and has it's limitations. I was told the same by Pete Ready who experimented with solid state (cartridge like, but pre-Micropore) scrubbers for both annular axial MK15.5 and early axial PRISM years ago.

I also remember a CO2 spike in one of the tests posted a DRE. I questioned it as it looked like a brief, early breakthrough, but was assured that it was due to a mistake made during testing. That's pretty much how I envision the scrubber being overbreathed during a strenious situation, with some resting getting the scrubber to fully absorb again, as per Alex's suggestion. But taking 5 for an OC break so the scrubber can relax is less than an ideal option, more so at 300 fsw. Time to add a "scrubber relieve tank" to you gear, or ask for free DR snorkel? Apologies for the sarcasm, but for a rebreather aimed at deep technical diving that seems rather ridiculous. 2 1/2 years ago I wrote "Personally I find it a curious combiantion as the Hammerhead screams 'technical diving' with its trimix deco capabilities and myriad of adjustment choices. The Micropore scrubber on the other hand shouts 'recreational' just as loud."

In tests performed here the Optima was certainly very disappointing. Not just the scrubber's duration, but also the breathing resistance. The short loop, the advantage of the cartridge and o-t-s counterlungs, all highly touted by the manufacturer(s), yet the unit doesn't come in anywhere near the top.

IMHO, if the price and availabilty or the scrubber medium aren't good arguments for other units, the lack of performance certainly is. To paraphrase the Australian poet and aesthete McHatten from his OzTek article, Dive Rite is great and I love their products, but the Optima just isn't Dive Rite.

IMHO, Lamar and Kevin can do better.

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paulraymaekers

sorry, can not get the data from exell here..

anyone can help???

paul

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AD_ward9

Both.

The pot is filled with water, and ice to get 4C (our version has a refrigerator as well!), then equipment is put in, and the whole lot is pressurised.

Orientation does not make a difference so long as the counterlungs are above the centroid being measured, because the loop is pressured to counteract that offset: in the parlance of the standard, the "loop pressure is optimised". However, if the CL centroid is below the measurement centroid, then it is impossible to do this and the effect is the hydrostatic imbalance is added to the result.

Alex