Safety of radial vs axial scrubber

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Paul Haynes said:
One of the features of a well designed canister is rough internal walls, so yes it has and is being done, though not as far as I recall in the current range of civilian rebreather canisters.
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I know the solution in which corrugated wall of the enclosure. But it is more effective orifice (CRABE Aqua Lung). Adhesion layer wall, facilitates the mixing of gas from different zones. In one canister axial mixing is achieved. Tiering soda lime with a gap (Faser) is also the solution reduces the risk of breakdown channel. Absorber before breathing bag and a second for breathing bag, a lot of solutions.

Many are blind alleys.

rc greet
 
paulraymaekers said:
Paul Haynes said:
nice idea, but probably no measurable difference in duration when using small grain sorb...

and for general info: i have both radial and axial scrubbers, I have always at least 5 units I can pick for diving, from mCCR with radial to full rms with axial, from micro over mini to standard

the best WOB is the rEvo standard/mini configuration, with radial scrubbers, and cooper hoses

the unit I dive is a micro FT with axial scrubber and rms, and drager hoses

small compared to big also has influence on safety: less dragg in the water when diving, better 'human touch' with the unit when diving, less weight, less extra weight needed to get the unit negative..

so it is clear that nothing is just black and white!
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If you could please give us the numbers (WOB, Hydrostatic Imbalance, Elastance, Duration...) by placing them in the rEVO manual (i.e. audited by a Notified Body) or even better like JJ has done by releasing the independent test report, we could better understand what you actually mean by "best" WOB and work out what the trade-offs are between size and performance (I never suggetsed size does not matter).

Otherwise we just talk about "nice" and "best" and "belief" - and that leaves us neither here nor there.
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gianaameri said:
I got no clue what that number is, or how to calculate it (maybe RC has a Patent).
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The solution applies to Faser is oxygen generating mass in sinks with a long duration of action.

You mentioned that the use of lime Molecular slightly swells, even more problems occur in oxygen generating mass. There are a number of patents to prevent this (Reschig rings or dry soda lime mixed with KO2).

Personally, I ICED soaked with water Molecular 1025, after thawing, do not spread.
It's really a good product.
There is not related to the effect of CO2 transmission, at the start of the canister. It has a polymer to bind the appropriate amount of water to work properly.

http://rebreathers.pl/forum/download.php?id=110
Lime-known producer in the early work, pass some not related CO2.
Data from the book "Lime Soda in Military Applications," R.Klos 2009
"The study contains the author's research on the effects of the Naval Academy in Gdynia"

greet rc
 
gianaameri said:
The probability of the cave roof collapsing on me while I am diving - that is the number I am prepared to accept.

I got no clue what that number is, or how to calculate it (maybe RC has a Patent).

My argument is predicated on reducing risk as much as practicable, and in so stating, there is nothing which invalidates my argument.

If replacing an Axial scrubber with a Radial scrubber reduces risk, that I do, or I quit diving.

At the end of the day, if you can't pay, don't play... and I think the choice of an Axial scrubber is very much driven commercially to make rebreather diving more affordable, rather than safer (as much the numbers tell me).

Personal choice and life-style.

I am not a risk taker, where the risk can be reduced by paying USD 590 (I checked the number) for a safer scrubber, than the standard one, I pay-up (and yes, of course, it costs more to fill it with absorbent as it holds more absorbent than the standard Axial).

To me, it is a no brainer to pay USD 590 more for the added benefits.
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I thought you said you were a professional risk assessor? :confused:

Given that:
1) You have said the only risk you are prepared to accept is the risk of the cave collapsing
2) There are other risks in diving.

The only conclusion can be that you don't get in the water!

Janos
 
Janos said:
I thought you said you were a professional risk assessor? :confused:

Given that:
1) You have said the only risk you are prepared to accept is the risk of the cave collapsing
2) There are other risks in diving.

The only conclusion can be that you don't get in the water!

Janos
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Risk manager, not "risk assessor."

I will give the due consideration that your expert opinion deserves next time I have a bath.

Which scrubber do you use (Axial or Radial) and why (to stay on topic)?
 
Out of interest, which current units have Radial as an option? JJ, Meg, others? I've never dived one as I don't see any risk with the Axial I have.

Thanks,
Matt.
 
matthewoutram said:
No.
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So, what message are you sending or image are you portraying to the Noob who asked the question in this forum when you write that your Axial scrubber is "risk-free?"

Many buyers of rebreathers are educated people with disposable income and they are not stupid and it might put them off buying a rebreather if they perceive the "marketing" is not fair or is a bit aggressive.
 
gianaameri said:
So, what message are you sending or image are you portraying to the Noob who asked the question in this forum when you write that your Axial scrubber is "risk-free?"

Many buyers of rebreathers are educated people with disposable income and they are not stupid and it might put them off buying a rebreather if they perceive the "marketing" is not fair or is a bit aggressive.
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For the purpose of this thread axial and radial are as safe as each other.

Matt.
 
matthewoutram said:
For the purpose of this thread axial and radial are as safe as each other.

Matt.
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The numbers available to date show otherwise.

They show that available Radials when used in the same rebreather produce a lower WOB and higher Duration than available Axials.

The only exception is the JJ where the WOB, for some reason, appears to be the same between Radial and Axial, although the Radial has a longer Duration.

Some rebreathers with Axial scrubbers may be outside the NEDU limit, while the same rebreathers with Radial scrubbers are not.

Radials are superior to Axials, based on available numbers.
 
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gianaameri said:
The numbers available to date show otherwise.

They show that available Radials when used in the same rebreather produce a lower WOB and higher Duration than available Axials.

The only exception is the JJ where the WOB, for some reason, appears to be the same between Radial and Axial, although the Radial has a longer Duration.

Some rebreathers with Axials scrubbers may be outside the NEDU limit, while the same rebreathers with Radial scrubbers are not.

Radials are superior to Axials, based on available numbers.
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But, so what? They both do the same job and they both do it well enough. If there was a fundamental problem with axial scrubber we'd know about it by now. There isn't. Doesn't even the defunct-APOC have an axial scrubber?

Matt.
 
matthewoutram said:
But, so what? They both do the same job and they both do it well enough. If there was a fundamental problem with axial scrubber we'd know about it by now. There isn't. Doesn't even the defunct-APOC have an axial scrubber?

Matt.
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The APOC is live and kicking.

It uses a Micropore axial scrubber which has good WOB numbers and poor Hydrostatic Imbalance (something common with the other back-mounted counterlung rebreathers, some more, some less), but it has abysmal Duration.

Maybe this is anectodal evidence that flow velocity has to do a lot with absorption capacity.

BUT Radial and Axial although they do the same job (absorb CO2), the numbers show that they perform differently.

The numbers show that the Radials are superior to the Axials.

My experience with the Radial is that it costs more to buy and it takes longer to pack... but then again if you want a more performing rebreather, and safer giving you a lower WOB and longer Duration... then that is the price to pay.

As to the "fundamental problem" - there is one.

Experienced divers are dying including in recreational diving conditions and we do not know why exactly.

It could be WOB impairing the gas exchange in the body (some say)... others say it is O2 Cells/Electronics... others say it is lack of pre-dive checks (i.e. checklist)... other say it is human error... other say it is "something else."

We do not know.

Do you know?
 
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gianaameri said:
The numbers show that the Radials are superior to the Axials.
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Numbers show that BMW M3 is superior to BMW 318i. But the latter is not unsafe. The former is not safer. They both do the same job from A-B.

Experienced divers are dying including in recreational diving conditions and we do not know why exactly.
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Not sure how this relates to WOB, as per previous reply on same topic from other poster.

Do you know?
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No.

Matt.
 
matthewoutram said:
Numbers show that BMW M3 is superior to BMW 318i. But the latter is not unsafe. The former is not safer. They both do the same job from A-B.



Not sure how this relates to WOB, as per previous reply on same topic from other poster.



No.

Matt.
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Some rebreathers with Axial scrubbers are outside the NEDU limits, the numbers show.

Taking that as the benchmark, which I do, I would not dive them under any circumstance (although I'd happily drive any BMW).
 
gianaameri said:
Some rebreathers with Axial scrubbers are outside the NEDU limits, the numbers show.

Taking that as the benchmark, which I do, I would not dive them under any circumstance (although I'd happily drive any BMW).
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We've got it, we understand your opinion - saying the same thing over and over again does not make it more or less right.

Matt.
 
matthewoutram said:
We've got it, we understand your opinion - saying the same thing over and over again does not make it more or less right.

Matt.
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You were stating something which goes against the available evidence, the numbers.

That is why I pointed that out to you (and the Noobs that read you on CCRX), that is all.

Merry Christmas!
 
gianaameri said:
Maybe this is anectodal evidence that flow velocity has to do a lot with absorption capacity.

BUT Radial and Axial although they do the same job (absorb CO2), the numbers show that they perform differently.

The numbers show that the Radials are superior to the Axials.
It could be WOB impairing the gas exchange in the body (some say)... others say it is O2 Cells/Electronics... others say it is lack of pre-dive checks (i.e. checklist)... other say it is human error... other say it is "something else."
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I also have other material that shows that at higher load, absorber can not handle (at the end of its operations) and ppCO2 increases, the reduction in the load, decreases ppCO2. Effect of Speed on the size of the reaction zone is visible. If it did not depend on the speed of the reaction zone, it was not to such an effect.

Absorbers radial will be better than the axis, for several years.
Now can point to solve specific problems in their construction.

greet rc
 
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