Dive Talk Go Rebreather

[Wibble]

The testing was performed with extendair cartridges as it takes the diver packing it out of the equation. Loose sorb allows for packing differences which influence useful life. The estimates are conservative to account for this. I have probably used less than a dozen cartridges in my last 10 years diving the Optima. I pack with whatever granular sorb is available. Generally Intersorb 812 but sometime Sofnolime 797 depending on what is available locally.
Optima/Choptima scrubber holds 5.5 pounds.

We all know that you were eluding to the EACs, I was being flippant.

Being ABLE to use a proprietary scrubber is not the same as being REQUIRED to use a proprietary scrubber.

As others have pointed out, granular sorb works just fine.

Extendair cartridges are not used in other SCUBA rebreathers and are unheard of outside of DiveRite. There's a lot of people saying good things about the ChOptima, with a lot of enthusiasm too.

What isn't acceptable is pushing the proprietary Extendair cartridges which are just not available around the globe (without paying $$$$$ for them to be imported from the USA). In comparison, Sofnolime is commonly available, even in far off places such as Truc/Chuuk/Truk.

My issue, as someone researching chestmount rebreathers for a potential purchase, is that I need to know the simple specification: what is the official scrubber time for normal, i.e. widely available, Sofnolime? This should be the same measure as used by all other CCR manufacturers, preferably the CE approval standard. Agreed, there's 2.2kg of scrubber, but it needs to be measured by an ANSTI machine to prove the scrubber efficiency and WOB numbers.

Reviewing the ChOptima manual again, I cannot find a specification for the ChOptima scrubber duration. I genuinely thought I'd read in that manual about the 4h limit for Extendair cartridges, obviously not.

Point taken about "required" vs "able" to use the Extendair. As said, they're not (easily) available outside of the US and therefore need the numbers for normal scrubber material.


TL;DR
Has anyone got the tested scrubber duration for the ChOptima using normal Sofnolime?

 

[Capt Jim Wyatt]

@Wibble
The scrubber endurance time varies greatly due to many factors, primarily the diver’s workload and the water temperature. The scrubber endurance time is given during conditions where the absorbent efficiency is expected to be low, i.e. at a moderate workload, in cold water and at the maximum depth that the rebreather will be approved for.

For every liter of O2 metabolized you make .92 liters of CO2.
For a 19FT3 O2 bottle - it has 537 liters of O2 (19 X 28.3 = 537.7) so 537 X .92 = 494 liters CO2 produced from a full 19FT3 bottle of O2.

An Extendaire cartridge will scrub 300 liters of CO2. So if you produce 1 LPM of CO2 an Extendaire cartridge will last 326 minutes, or 5.4 hours. If you use the .92 production rate.

There is more on Choptima Scrubber here.

 

[Wibble]

@Wibble
The scrubber endurance time varies greatly due to many factors, primarily the diver’s workload and the water temperature. The scrubber endurance time is given during conditions where the absorbent efficiency is expected to be low, i.e. at a moderate workload, in cold water and at the maximum depth that the rebreather will be approved for.

For every liter of O2 metabolized you make .92 liters of CO2.
For a 19FT3 O2 bottle - it has 537 liters of O2 (19 X 28.3 = 537.7) so 537 X .92 = 494 liters CO2 produced from a full 19FT3 bottle of O2.

An Extendaire cartridge will scrub 300 liters of CO2. So if you produce 1 LPM of CO2 an Extendaire cartridge will last 326 minutes, or 5.4 hours. If you use the .92 production rate.

There is more on Choptima Scrubber here.

There's a little more to scrubber durations than just the overall absorbent capabilities of the scrubber material.

There is a scrubber front where the CO2 is absorbed. Common teaching practice is to consider this to be rather "pointed" cone where the exhaust gas moves through the middle of the scrubber. The size of this cone varies with depth (pressure), temperature (scrubbers are inefficient when cold), CO2 content (e.g. workload), exhaust gas volumes (breathing hard) and the design of the scrubber (e.g. are there unused "corners" where the scrubber remains unused in the gas path).

This is probably why all rebreathers are subjected to a standardised test as per the CE certifications. This requires measurement at 40m/5ATA and 100m/11ATA; at high workloads (crazy hypercapnic levels!); low temperatures; all using the ANSTI machine to measure the WOB (work of breathing) and post-scrubber CO2 content.


Important: I'm absolutely not bashing the ChOptima; I just want to compare like with like. The ChOptima seems to be a great unit and is particularly lightweight. Alas it's not available in Europe so committing to a ChOptima means effectively buying one from the US and getting trained there (as it's illegal for someone to train you on, or sell you, a non-CE certified machine in the EU and UK -- who never properly left the EU).

Found this fascinating paper and IndepthMag article.

 

[missionmtb]

Extendair cartridges are not used in other SCUBA rebreathers and are unheard of outside of DiveRite. There's a lot of people saying good things about the ChOptima, with a lot of enthusiasm too.

What isn't acceptable is pushing the proprietary Extendair cartridges which are just not available around the globe (without paying $$$$$ for them to be imported from the USA). In comparison, Sofnolime is commonly available, even in far off places such as Truc/Chuuk/Truk.

My issue, as someone researching chestmount rebreathers for a potential purchase, is that I need to know the simple specification: what is the official scrubber time for normal, i.e. widely available, Sofnolime? This should be the same measure as used by all other CCR manufacturers, preferably the CE approval standard. Agreed, there's 2.2kg of scrubber, but it needs to be measured by an ANSTI machine to prove the scrubber efficiency and WOB numbers.

Reviewing the ChOptima manual again, I cannot find a specification for the ChOptima scrubber duration. I genuinely thought I'd read in that manual about the 4h limit for Extendair cartridges, obviously not.

Point taken about "required" vs "able" to use the Extendair. As said, they're not (easily) available outside of the US and therefore need the numbers for normal scrubber material.


TL;DR
Has anyone got the tested scrubber duration for the ChOptima using normal Sofnolime?

@Capt Jim Wyatt is 100% right, the spec. is just a starting point. Common and frequently encountered variables such as water temperature, profile, workload, moisture etc. can all significantly affect scrubber duration.

For me, I've figured out across 4 different rebreathers that I typically get an hour per pound on my scrubber regardless of unit. This, I think, is a common experience. This can move by as much as 20% with water temperature for me. I never use my rebreather with workloads (read CO2 generation rates) approaching the Navy test so those numbers are super conservative for me (see ISC testing for example @ 4C and like 2.5X basal O2 consumption). I've also found that for "big dives" where having a 5 hour duration matters, the CO2 loading is at the front end, down deep in cold water with a lot of workload while the remaining scrubber is used above the thermocline on deco. In this scenario you come up gently against your scrubber limit. I know of no scrubber test that simulates this typical scenario.

I often dive with a tiny female rebreather diver who can routinely exceed my scrubber duration by more than 30% and even has to use a different CMF because the 0.7lpm is way too much.

I hope if you're really interested that you read Dr. John R. Clarke's Breakthrough: Revealing the Secrets of Rebreather Scrubber Canisters.

For the Dive Talk Go I would approach it like any other rebreather by using the hour/lb rule of thumb then adjusting for factors such as water temp, workload etc. to add/remove conservatism.

At the end of the day getting to the end of your scrubber is unpleasant, especially if you hit it hard. Better to just bring enough sorb so you have plenty of margin and factor in the cost of the buffer. At today's prices an extra hour of lime is $5. Tossing a pound on a 3 pound vs 8 pound scrubber hurts more, but...

Also, extendair was not the only cartridge available for rebreathers. I had the sofnodive and it had the same downsides but with both units the repackable was an option so, meh.

 

[h2o_hamilton]

Marketing is a wonderful thing. You think your Helly Hansen coat is anything more than their logo on a Chinese product.. ?

 

[EE-JIT]

That difficult to obtain and expensive disposable scrubber cartridge - ExpendAir? Imagine flying somewhere for long dives and having to bring those cartridges with you; adds to the travel weight.

The ExtendAir cartridges are 3x the price of Sofnolime (£300 for 8 plus tax, import duties, delivery compared with £100 for one 20kg/44lb tub of Sofnolime)

Or fill it with sorb but have an undefined but far shorter scrubber duration, 2h30?

Will it ever be CE approved? If it were, we'd know the scrubber duration like the FX-CCR and Triton.

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@EE-JIT -- are you specifically interested in a chestmount rebreather?

I like the travel charactoristics of the CM rebreathers, as i travel to dive ,Choptima as an ECCR seems preferential over a Triton and will hopefully help in managing PO2 whilst im getting to grips with things. I havent tried yet im still building knowledge and reading, and view this as a long term project.

 

[Fat old english bloke]

(as it's illegal for someone to train you on, or sell you, a non-CE certified machine in the EU and UK -- who never properly left the EU).

Well we’re no longer part of the EU, so we have in fact properly ‘left’; it’s just that we’ve managed to maintain a fair few of the negatives, introduced a load more, whilst at the same time cunningly managing to ditch many/most of the positives. So we’ve really got quite a lot to thank the dullards who voted ‘leave’ for.

 

[Wibble]

Well we’re no longer part of the EU, so we have in fact properly ‘left’; it’s just that we’ve managed to maintain a fair few of the negatives, introduced a load more, whilst at the same time cunningly managing to ditch many/most of the positives. So we’ve really got quite a lot to thank the dullards who voted ‘leave’ for.

Or…. The Remainer cultists fail to implement the wishes of the majority and simply waive through to maintain the existing rules. Hence the “new” UKCA marking is just the CE marking crossed out with crayon

 

[makar0n]

Well we’re no longer part of the EU, so we have in fact properly ‘left’; it’s just that we’ve managed to maintain a fair few of the negatives, introduced a load more, whilst at the same time cunningly managing to ditch many/most of the positives. So we’ve really got quite a lot to thank the dullards who voted ‘leave’ for.

Best Brexit summary I have heard in years.
Still remember those "350 million a week for NHS" slogans. I mean seriously, who in their sane mind would fall for that. Or so I thought...

 

[Fat old english bloke]

Or…. The Remainer cultists fail to implement the wishes of the majority and simply waive through to maintain the existing rules. Hence the “new” UKCA marking is just the CE marking crossed out with crayon

I think there’s a massively incorrect assumption on your part that the architects of brexit & c*nts at the helm actually gave a sh*t about undoing EU ‘red-tape’.

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A ScubaBoard Staff Message...

Gently...
On topic, s'il vous plait.

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