Safety of radial vs axial scrubber

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Paul Haynes said:
Gas will always take the pass of least resistance. A smooth internal wall aids the flow down the inside wall of a canister, which can result in an uneven use of the scrubber bed. 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.

Keep on thinking.

Rgds Paul
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interesting point

I remember few years back when I got my RECY'01 pSCR -it had a huge axial that could take more than 5kg if I remember right- the previous owner advised me to put in two o-rings at 1/3 and 2/3 of the height of the scrubber (these orings fitted just inside the scrubber wall) in order the "break the path " of the air flow that was coming down the smooth internall wall and avoid possible breakthrough

was never sure if this was a "urban myth" but did it any way to be sure ...
 
I would take a poorly packed LAR V over a poorly packed OMG Caimino.

It's as Paul says.. volume of the scrubber has a lot to do with the design of the scrubber canister configuration.

I have experience on both of the aforementioned machines. While the Caimino is definitely the nicer of the two in WOB. it is a very tricky scrubber to pack correctly. Which in my book makes that radial design a dangerous scrubber.

Just out of curiosity. What configuration of scrubber canister does the USN currently use in the Meg?

-Matt

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gianaameri said:
It did not specify here:

http://www.dtic.mil/dtic/tr/fulltext/u2/a549996.pdf

but there is a lot of useful information and also references to other yet to be released information.
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Great article!

Being prior service myself. I trend more towards what the navy considers "safe".

While they are in fact in the business of killing.. they don't want to have to explain to sailor chucks parents that there sons demise was met because of sub par equipment.

If the navy uses an axial scrubber in the current LAR. I'm sure it's adequate for Joe Shmoe.

I'm no expert in this subject matter.. I just dive what's been tried and true.

-Matt

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gianaameri said:
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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Wonder what percentage of these divers we're in good physical health (BMI, smokers vs non-smokers, alcoholics, etc).

Just pondering.

-Matt

Sent from my SCH-I510 using Tapatalk 2
 
I just read this entire thread. Wow: that's all I can say.

To the OP, the general consensus, and most of the figures available agree, radials are a superior scrubber design. HOWEVER, this does NOT make them safer, nor does it make an axial scrubber more risky to dive. To try to extrapolate such overarching statements based on just one aspect of a rebreather's design is simply folly.

The reaction of the individual diver WRT their radial (or axial) scrubber could well be such as to heighten risk past the point of a competing scrubber design.

A far far better question would be to ask how you relate to rebreathers, and how you will use a unit. If you are such that you need every single safety bell and whistle, as well as the biggest fudge factors, well... how is a radial scrubber going to save you?

cheers

Andy
 
Suprabones said:
Wonder what percentage of these divers we're in good physical health (BMI, smokers vs non-smokers, alcoholics, etc).

Just pondering.

-Matt

Sent from my SCH-I510 using Tapatalk 2
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Many of the British divers I observed are obese and drink a lot.

One more reason for them to chose a better performing rebreather.

Could it be a safer rebreather in their case could have resulted in a different outcome?
 
JJ Radial

Anyone have a lot of experience with the JJ CCR Radial scrubber? I have always used the axial.
The manufacturer, Jan, is very reluctant to even sell it. He believes (it seems) to be more dangerous as it is less forgiving to pack.
So anyone using the radial on the JJ that can comment on this?
 
Andy Del said:
I just read this entire thread. Wow: that's all I can say.

To the OP, the general consensus, and most of the figures available agree, radials are a superior scrubber design. HOWEVER, this does NOT make them safer, nor does it make an axial scrubber more risky to dive. To try to extrapolate such overarching statements based on just one aspect of a rebreather's design is simply folly.

The reaction of the individual diver WRT their radial (or axial) scrubber could well be such as to heighten risk past the point of a competing scrubber design.

A far far better question would be to ask how you relate to rebreathers, and how you will use a unit. If you are such that you need every single safety bell and whistle, as well as the biggest fudge factors, well... how is a radial scrubber going to save you?

cheers

Andy
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Not folly at all.

The NEDU studies are not done by crazy people or internet forum experts who get all excited and thump their chest like a Gorilla in heat, after smelling a Noob who wants to buy a rebreather.

NEDU has researched the subject having the budget to pay world renowned scientists to professionaly and objectively establish safe WOB, Hydrostatic Imbalance, and Elastance limits.

The fool is the one who disregards such published research in its dive planning and risk management.

I stick to NEDU limits until something better is researched, studied, and made available.
 
gianaameri said:
paulraymaekers said:
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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I bit like your attitude towards risk management. You've not yet given any numbers for that either.

Janos
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gianaameri said:
Many of the British divers I observed are obese and drink a lot.

One more reason for them to chose a better performing rebreather.
Click to expand...

Source please! (Ie of a link between obesity and diving risk; and also alcohol consumption and diving risk.)

Janos
 
I started diving CCR last year. I looked at most units on the market and decided in the end to go with the Inspiration Vision. The deciding factor for me was the fact that AP units have far and away the most hours.
I'm a 30 year software engineer veteran and one thing I know is that despite all of the testing you do on a product and standards that the product seeks to comply with there is nothing that replaces actual use by real users to expose the weaknesses in a product.
The club I joined last year has about a dozen AP CCR divers. We also dive with other CCR divers in our area almost all of whom are ap unit owners.
For me safety is about the whole solution including experience, training, add ons, compatibility etc etc. Not just one feature, however important.
When I looked at the market I saw a lot of nice features. I only saw one total solution for my circumstances.



BjFaeTorphins
 
BjFaeTorphins said:
I started diving CCR last year. I looked at most units on the market and decided in the end to go with the Inspiration Vision. The deciding factor for me was the fact that AP units have far and away the most hours.
I'm a 30 year software engineer veteran and one thing I know is that despite all of the testing you do on a product and standards that the product seeks to comply with there is nothing that replaces actual use by real users to expose the weaknesses in a product.
The club I joined last year has about a dozen AP CCR divers. We also dive with other CCR divers in our area almost all of whom are ap unit owners.
For me safety is about the whole solution including experience, training, add ons, compatibility etc etc. Not just one feature, however important.
When I looked at the market I saw a lot of nice features. I only saw one total solution for my circumstances.



BjFaeTorphins
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I meant to say that my comments are directed mainly to the OP. My thinking when starting out with CCR is that I want to be diving well within the understood parameters with people that know their stuff.

To me any marginal benefit from any specific feature that a niche CFR manufacturer brings to the table has to be about pushing things to the limits. I probably will never operate at the limits and certainly not till I have thousands of hours on my unit.

BjFaeTorphins
 
BjFaeTorphins said:
I meant to say that my comments are directed mainly to the OP. My thinking when starting out with CCR is that I want to be diving well within the understood parameters with people that know their stuff.

To me any marginal benefit from any specific feature that a niche CFR manufacturer brings to the table has to be about pushing things to the limits. I probably will never operate at the limits and certainly not till I have thousands of hours on my unit.

BjFaeTorphins
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It makes sense, but the reality check is that the people that know their stuff are either dead or were unable to help the dead, or undead them.

Self-sufficiency and risk reduction may be better direction, under the circumstances, than relying on diving a popular unit with popular experts.
 
gianaameri said:
Not folly at all.

The NEDU studies are not done by crazy people or internet forum experts who get all excited and thump their chest like a Gorilla in heat, after smelling a Noob who wants to buy a rebreather.

NEDU has researched the subject having the budget to pay world renowned scientists to professionaly and objectively establish safe WOB, Hydrostatic Imbalance, and Elastance limits.

The fool is the one who disregards such published research in its dive planning and risk management.

I stick to NEDU limits until something better is researched, studied, and made available.
Click to expand...

Do you still deny that the CE limit is based on science as you once previously did?

Do you accept that there is an error in Warkander's test of the Inspiration?

Do you still use 2.0 as "the number"?

Matt.
 
Andy Del said:
To the OP, the general consensus, and most of the figures available agree, radials are a superior scrubber design. HOWEVER, this does NOT make them safer, nor does it make an axial scrubber more risky to dive. To try to extrapolate such overarching statements based on just one aspect of a rebreather's design is simply folly.
Click to expand...

Agreed. It's a specific corner case and not the basis of a rebreather choice. Not for me for my diving, at least.

Matt.
 
BjFaeTorphins said:
I started diving CCR last year. I looked at most units on the market and decided in the end to go with the Inspiration Vision. The deciding factor for me was the fact that AP units have far and away the most hours.
I'm a 30 year software engineer veteran and one thing I know is that despite all of the testing you do on a product and standards that the product seeks to comply with there is nothing that replaces actual use by real users to expose the weaknesses in a product.
The club I joined last year has about a dozen AP CCR divers. We also dive with other CCR divers in our area almost all of whom are ap unit owners.
For me safety is about the whole solution including experience, training, add ons, compatibility etc etc. Not just one feature, however important.
When I looked at the market I saw a lot of nice features. I only saw one total solution for my circumstances.



BjFaeTorphins
Click to expand...

For me, this post sums up how a decision should be make - whole solution, including who will do the training and how you will absorb the information. The rest, for me, is mostly noise.

Matt.
 
gianaameri said:
... the reality check is that the people that know their stuff are either dead ...
Click to expand...

How many of those that "know their stuff" are dead and how many are alive? How many in total are there that "know their stuff". Numbers, please.
 
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