Safety of radial vs axial scrubber

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matthewoutram said:
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.
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The CE limit is not based on any published peer-reviewed scientific research.

I have seeked a copy, but none has been proffered.

Maybe you can get me one?

As to errors in tests, I suspect there may be several.

For one thing, I do not understand how the JJ Radial performs the same as the JJ Axial in terms of WOB.

QinetiQ's report fails to clearly identify which scrubber was used for their testing, in one of the reports.

If I were JJ, I'd ask Qinetiq to amend the report and clearly state which scrubber is used for the tests, and correct the oversight (it happens).

However, I have seen no evidence of there being an error in any of the reports, including Warkander.

I am confident that if an error were to be pointed to Warkander in one of his reports, he would look into it, and correct it.

I had some questions and left a message on his answering machine, and he did return my call promptly.

I am positively impressed by the research and the man.

If some Warkander numbers are disputed, may I suggest that alternative test reports are supplied?

A QinetiQ test report same as the JJ would be great, and I could then add it to the Comparative WOB Rebreather Database.

I am just collecting data and assembling as best as I can in a spreadsheet. I will gladly correct any manifest errors which are brought to my attention, but Matt crying wolf when there is no wolf on an internet forum does not cut it.

I need and seek evidence, insofar the criteria for the inclusion in the Database are:

1. Numbers in a Notified Body audited User Manual
2. Numbers from third-party independent test house.
3. For those manufacturers who can't be bothered to test their products and produce 1. and 2. above, I'll reproduce the numbers they publish on their website, after having made a permanent record of the publication.
 
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gianaameri said:
The CE limit is not based on any published peer-reviewed scientific research.
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I am confident that if an error were to be pointed to Warkander in one of his reports, he would look into it, and correct it.
Click to expand...

If some Warkander numbers are disputed, may I suggest that alternative test reports are supplied?
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I'm not covering old ground again Gian. The answers to these questions have been given many times by several people including me. In summary the answers the the above are: wrong, wrong, provided.

You can find more out by engaging your ears rather than your tongue.

If anyone wants the references I'll provide them by PM.

Matt.
 
matthewoutram said:
I'm not covering old ground again Gian. The answers to these questions have been given many times by several people including me. In summary the answers the the above are: yes, no, yes.

You can find more out by engaging your ears rather than your tongue.

If anyone wants the references I'll provide them by PM.

Matt.
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I am all ears - but you are talking internet mumbo-jumbo as usual. It does not cut it with me and any other intelligent person on this forum.

I have requested from the EU relevant body and CEN/CENELEC the scientific peer-reviewed publications upon which the EN14143:2003 WOB and Hydrostatic Imbalance limits are predicated.

None have been supplied. My best understanding is that the EN14143 2.75 j/l limit and the Hydrostatic Imbalance limits are predicated upon a best guess and are well outside (more risky) the NEDU published limits.

In any event, it is undisputed that a rebreather with a lower WOB is better and safer than a rebretaher with a higher WOB, all other things being equal.

If you do not like the numbers, produce other numbers to refute them, and I will add them to the Database.

It is very easy!
 
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gianaameri said:
I am all ears - but you are talking internet mumbo-jumbo as usual. It does not cut it with me and any other intelligent person on this forum.
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Cut out the derogatory remarks, Gian.

To everyone else - Happy Christmas, finally I am done at work and have wine :-)

Cheers
Matt.
 
matthewoutram said:
Cut out the derogatory remarks, Gian.

To everyone else - Happy Christmas, finally I am done at work and have wine :-)

Cheers
Matt.
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You stop insinuating anything I do is less than accurate, correct, and objective.

To move things forward constructively, if you do have any scientific study setting any WOB... limit, I will add a column to the spreadsheet and include that as a further benchmark.

You wrote on CCRX you would provide what you have, and I PMed you requesting a copy of what you have in respect of WOB... studies.

Provide the information, if you have it, and I will include it in the Database.
 
gianaameri said:
You stop insinuating anything I do is less than accurate, correct, and objective.
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Not sure when I did that, but not the intention. As has become normal let's leave it there. I won't respond again to you as life is too short for such nonsense.

Thanks
Matt.
 
matthewoutram said:
Not sure when I did that, but not the intention. As has become normal let's leave it there. I won't respond again to you as life is too short for such nonsense.

Thanks
Matt.
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You will be politely ignored until you produce the documentation (i.e. "references") which you say you have below.

Until then, have a great life!

matthewoutram said:
I'm not covering old ground again Gian. The answers to these questions have been given many times by several people including me. In summary the answers the the above are: wrong, wrong, provided.

You can find more out by engaging your ears rather than your tongue.

If anyone wants the references I'll provide them by PM.

Matt.
Click to expand...
 
gianaameri said:
I am just collecting data and assembling as best as I can in a spreadsheet. I will gladly correct any manifest errors which are brought to my attention,
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I admire the tenacity to create the database, from my perspective, is useless.
A lot can be said about the pros and cons of the solution knowing his designs. It's been a long time described in the scientific literature, on how to build and evaluate how to study.

greet rc
 
GO.. said:
After thinking for a long time, I have decided that I should go over to dive ccr.
I am very cautious by nature, and now it just before I'm about to order a unit.

I wonder:
I currently live in northern Norway, and the water temperature is usual between 4 and 12 degrees Celsius.

Is axial scrubber safer than radial scrubber?

- Gerhard
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The units to look at would be a REVO 3 RMS, or Hammerhead/MEG, I own all three (and have 10 rebreathers now) and if I had to own just one rebreather it would be the REVO 3 RMS all day long with no hesitation, as far as the scrubbers go I prefer axial because they are easy to pack (generally) and if you are working VERY hard the gas has more exposure to the sorb so the chance of over breathing the scrubber is less.

Cheers,

Jon
 
JONT said:
The units to look at would be a REVO 3 RMS, or Hammerhead/MEG, I own all three (and have 10 rebreathers now) and if I had to own just one rebreather it would be the REVO 3 RMS all day long with no hesitation, as far as the scrubbers go I prefer axial because they are easy to pack (generally) and if you are working VERY hard the gas has more exposure to the sorb so the chance of over breathing the scrubber is less.

Cheers,

Jon
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Do you have or have you dived a JJ? I would think the best choice for Norway would be a European unit, but obviously not the Sentinel/Boris ;-) JJ, APD or rEvo. I think someone said he HH is made in the EU but not CE so exported to US (could be wrong)?

Cheers
Matt.
 
JONT said:
The units to look at would be a REVO 3 RMS, or Hammerhead/MEG, I own all three (and have 10 rebreathers now) and if I had to own just one rebreather it would be the REVO 3 RMS all day long with no hesitation, as far as the scrubbers go I prefer axial because they are easy to pack (generally) and if you are working VERY hard the gas has more exposure to the sorb so the chance of over breathing the scrubber is less.

Cheers,

Jon
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Before we can conclude that "the chance of over-breathing the scrubber is less" in an Axial relative to a Radial, this would require some testing.

My best guess is that in a Radial the chance of over-breathing the scrubber is not necessarily more than in an Axial because there is a greater surface area of absorbent exposed to the gas.

The surface area of the absorbent working in a Radial is massive compared to an Axial.
 
I've been following this thread for a while.
While I can understand the argument that a lower WOB decreases the chance of CO2 build-up, I must admit that one question keeps coming to mind:
Is WOB an issue at all?
I'll be the first to admit I'm a CCR novice and I'm on my first RB (rEvo 3 standard with less than 60hrs) but I can honestly say the last thing on my mind while diving is WOB. It could be I'm "special", it could be the rEvo that is fantastic for WOB, it could be I have not dived hard enough, deep enough, long enough or it could just be my lack of experience (or a combination of all of them).

Is there really a "mainstream" rebreather where WOB is so poor that it is an issue? Assuming you are in a more or less normal trim (not head up/down, on your back etc.).

I'm really hoping people will help enlighten me, because to me it seems WOB is getting a LOT of attention where perhaps there are greater and more relevant issues to discuss/develop....???

Thanks
Jacob
 
JacobT said:
Is there really a "mainstream" rebreather where WOB is so poor that it is an issue? Assuming you are in a more or less normal trim (not head up/down, on your back etc.).
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WOB's important (as is hydrostatic imbalance and elastance). Kellon (linked previously gives a decent overview). If you dig around you'll see that Warkander and others (Martin Parker posted on the topic about 6 months ago) are proposing a single measure that combined all these factors as WOB alone isn't enough. But I've not seen any actual use of this.

What is enough, IMHO, is the fact that all mainstream rebreathers are tested to CE standards. It may not be perfect, but it gives a decent baseline, including WOB and scrubber endurance.

So my stance remains that all those units are good for regular diving needs within their dive parameters (typically heliox or trimix to 100m or Air to 40m). Whilst WOB is interesting from an academic view point unless you are planning to jaunt to the bottom of Boesmansgat it's not likely that this will be of concern during your buying decision.

What I would say is of more concern (although very little information on the topic) is the WOB of your OCB (if you have one). If you consider what happens in a retained CO2 situation then moving to a super-low OC WOB could be very advantageous. But that's not for this thread.

HXM,
Matt.
 
JacobT said:
I've been following this thread for a while.
While I can understand the argument that a lower WOB decreases the chance of CO2 build-up, I must admit that one question keeps coming to mind:
Is WOB an issue at all?
I'll be the first to admit I'm a CCR novice and I'm on my first RB (rEvo 3 standard with less than 60hrs) but I can honestly say the last thing on my mind while diving is WOB. It could be I'm "special", it could be the rEvo that is fantastic for WOB, it could be I have not dived hard enough, deep enough, long enough or it could just be my lack of experience (or a combination of all of them).

Is there really a "mainstream" rebreather where WOB is so poor that it is an issue? Assuming you are in a more or less normal trim (not head up/down, on your back etc.).

I'm really hoping people will help enlighten me, because to me it seems WOB is getting a LOT of attention where perhaps there are greater and more relevant issues to discuss/develop....???

Thanks
Jacob
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That is a very important question.

It would be best for you to read some of the articles written by Dr. Mitchell (hopefully he will provide a link).

Some posters on CCRX have written that they do a 5 hour dive (presumably most of it on deco) on a Deco setpoint of 1.5 (using the CNS clock presumably calculated from their electronics as the limiting factor).

This on a rebreather - given all rebreathers have a higher WOB than modern OC regulators - is the most insane and risky thing to do, but they do not understand it, and write it here on CCRX as if it were something to be done as the norm, maybe "because they do it."

I do not even believe they do it regularly (if ever), or they would be more likely dead, and not posting on internet forums.

Now that I got the above off my chest, to answer your question in short quoting Dr. Mitchell:

"If the work of breathing increases unnaturally (which occurs in diving for a variety of reasons) the controller in the brain appears predisposed to allowing the blood CO2 to rise rather than drive the extra work involved in maintaining sufficient gas flow in and out of the lungs to keep CO2 at normal levels. Think of it as though the brain is still driving "X" amount of work by the respiratory muscles in response to a given level of CO2, but because the work required to breathe has increased, "X" amount of work now achieves less gas flow in and out of the lungs, therefore less CO2 is eliminated, and CO2 is retained. The more the work of breathing increases (eg deeper, denser gas, hard work, poor equipment), and the more CO2 that is being produced (eg because of exercise) then the more likely CO2 retention is to occur. The increase in PO2 and PN2 that are also encountered in diving can also "depress" the respiratory controller and make CO2 retention more likely."

This is the reason why the lower the WOB in your unit, the safer it is. This is the reason why you should buy a rebreather with low WOB, and stay within the limits set by best science and the latest research (i.e. NEDU limits).

The latter part ("The increase in PO2 and PN2 that are also encountered in diving can also "depress" the respiratory controller and make CO2 retention more likely") is why you do not want to boost pPO2 to 1.5 (considering as well the error/latency of electronics/O2 sensors) on any rebreather (and the higher is the WOB in your rebreather, the bigger is the reason not to boost your pPO2 to such levels).
 
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gianaameri said:
My best guess is that in a Radial the chance of over-breathing the scrubber is not necessarily more than in an Axial because there is a greater surface area of absorbent exposed to the gas.

The surface area of the absorbent working in a Radial is massive compared to an Axial.
Click to expand...

The same mass of soda lime, you have the same contact area of gas with lime. The differences are in the gas flow rates and temperature soda lime.
In radial canister harder to use known protection. against puncture channel. One strength solution used in Revo Paul (split into 2 sections) losing some of the advantages of radial absorber a large side surface and a small velocity through the bed.

greet rc
 
anarchista said:
The same mass of soda lime...

greet rc
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In existing Radial canisters (not theoretical ones), there is not the same mass of soda lime.

This is why actual numbers from test results are as important (or more important) than theoretical equations and mathematical models.
 
gianaameri said:
In existing Radial canisters (not theoretical ones), there is not the same mass of soda lime.

This is why actual numbers from test results are as important (or more important) than theoretical equations and mathematical models.
Click to expand...

To show that the problem is broad and comparison without knowing the structure, does not lead to concrete, instance have a binding capacity of CO2 according to the temperature and compare the two axial absorbers at different temperatures.
Draeger performs poorly, against Aqua Lung (variable speeds of the canister).

http://rebreathers.pl/forum/download.php?id=111

http://rebreathers.pl/forum/download.php?id=112

"Soda Limie in Military Aplications" R.Klos 2009

greet rc
 
matthewoutram said:
Do you have or have you dived a JJ? I would think the best choice for Norway would be a European unit, but obviously not the Sentinel/Boris ;-) JJ, APD or rEvo. I think someone said he HH is made in the EU but not CE so exported to US (could be wrong)?

Cheers
Matt.
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Dived yes, own no but that may change although the arrogance of the developers and the refusal of the developers to support the BOV really pissed me off and cost be money.

So thats not cool.

Jon
 
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