New Meg Radial Scrubber

paulraymaekers · 16th May 2008, 16:36

Quote: (Originally Posted by Gill Envy)

I have to say that after my second trip with a prism diver, that radial scrubbers seem to be worth their weight in gold in terms of sorb use and airline overage getting too a remote destination. Our friend with the prism consistently uses about 50% less sorb than we did, in part because starting a second day of diving with the deepest dive first was plausible on a radial that still had half it's duration left while the axial was consistently too far gone to feel safe taking it on a additional demanding dive.

the two things I want to add to my copis are a needle valve and a ISC's radial scrubber.

Hi Gill, how do you know that the axial was to far gone compared to the radial??

IMHO, the advantage of radials lies in (perhaps) longer duration in cold water, and/or lesser WOB if you want a lot of sorb in your system

but in warm water, you don't need the radial for longer duration, because in warm water duration is more depending on amount of sorb you take with you, and much less the thermal system (radials compared to axials)

paul

**Gill Envy** · 16th May 2008, 18:36

well, I guess since we don't have objective data I can't be sure, and I screwed up the math to boot, it was more like 30% less, but still substantial. My understanding of the theory behind radial scrubbers is that they essentially have a much larger surface area of exposed sorb to exhalled air, increasing the dwell time and therefore allowing the sorb to be used more completely with less chance of breakthrough. My understanding is that there is less chance of the reactant front migrating substantially during increased work loads. My understanding of an axial scrubber is that because dwell time can diminish exponentially with increased respiration that a much more substantial buffer needs to be calculated in terms of the migrating of the reactant front... like 50%, in order to prevent breakthrough co2, so we theoretically are throwing away roughly 50% of our scrubber each time on an axial scrubber.

I realize that the rEvo takes another aproach to addressing this issue and i'm also intrigued with it as well... it's my understanding that that 50% buffer is only occasionally used and likely for short durations and as the theory goes, splitting the scrubber in two and replacing half each time, advancing the second half the scrubber to the front of the line in the loop on the rEvo has a similar potential for sorb efficiency while maintaining a good safety margine. I get that theory and I think it's plausable as long as the margines aren't pushed too much.

In any case, I realize this is a hotly debated subject and there are diverging opinions about it and i'm only a little bit knowledgable about it, but given the dives and durations we were witnessing on the Prism, it seems only explainable by a dramatic difference in design efficiency of the scrubber. I"m guessing the meg version will have similar if not better performance and luckinly it will fit in my Copis!

g

Quote: (Originally Posted by paulraymaekers)

Hi Gill, how do you know that the axial was to far gone compared to the radial??

IMHO, the advantage of radials lies in (perhaps) longer duration in cold water, and/or lesser WOB if you want a lot of sorb in your system

but in warm water, you don't need the radial for longer duration, because in warm water duration is more depending on amount of sorb you take with you, and much less the thermal system (radials compared to axials)

paul

paulraymaekers · 16th May 2008, 18:51

Quote: (Originally Posted by Gill Envy)

My understanding of the theory behind radial scrubbers is that they essentially have a much larger surface area of exposed sorb to exhalled air, increasing the dwell time and therefore allowing the sorb to be used more completely with less chance of breakthrough. My understanding is that there is less chance of the reactant front migrating substantially during increased work loads. My understanding of an axial scrubber is that because dwell time can diminish exponentially with increased respiration that a much more substantial buffer needs to be calculated in terms of the migrating of the reactant front... like 50%, in order to prevent breakthrough co2, so we theoretically are throwing away roughly 50% of our scrubber each time on an axial scrubber.

hello Gill, sorry to put is quite blunt, but this is, hm, hm, complete nonsense...... dwell time, well, we already spent some time about it, is ONLY dependant on the amount of sorb you have in your system, XX kg, and NOTHING else, not the shape, not the form, nor axial or radial, just kilo's..
the more kilo's, the more dwell time...(if kept all the rest equal, RMV, ..)

the difference between radial and axial is mainly the thermal behaviour, how to keep the warmth in your system, how to prevent part of the sorb beiing cooled down, and in that way making a path of less efficient sorb, and faster breaktrough.

IF, and only IF, sorb efficiency, or absorbant capabilities, would be not lineair with gasspeed through the sorb, in that case slow flow would eventually increase efficiency, but the dwell time itself would still be the same...

with best regards
paul

fin · 16th May 2008, 19:50

Quote: (Originally Posted by Outlaw)

Thanks a lot mate. any links to a website that i can get the my hands on those same black tanks like Tom Jaspers?

Thanks

Spyros

Sorry to break in Spyros, but I wrote that in another thread (about your meg configuration I think). I don't understand the reason you dont paint the 3l tanks yourself. Its easier than searching and paying shipping and no rocket science after all.
Ive been painting my club's tanks for decades to protect them from corosion using high quality marine paint.
Another think is that black may be a sexy colour indeed (I would follow using my zero free time), but does not stand strict EU industrial gas legislations (colour code). You must be sure that you will never meet a very strict Rebreather friendly club in the future

.

Outlaw · 16th May 2008, 19:56

Quote: (Originally Posted by fin)

Sorry to break in Spyros, but I wrote that in another thread (about your meg configuration I think). I don't understand the reason you dont paint the 3l tanks yourself. Its easier than searching and paying shipping and no rocket science after all.
Ive been painting my club's tanks for decades to protect them from corosion using high quality marine paint.
Another think is that black may be a sexy colour indeed (I would follow using my zero free time), but does not stand strict EU industrial gas legislations (colour code). You must be sure that you will never meet a very strict Rebreather friendly club in the future

.

hey fin,

thanks for that, but the reason i got wild about this is that the ones Tom Jaspers is using are much thinner than the catalina blacks i got now. and i dont like the steel ones to paint them...

that's all. if the price is right, then great. besides, i got the tanks valves upright, so these are perfect fit for my meg.

Spyros

01RMB · 16th May 2008, 21:41

Quote: (Originally Posted by Gill Envy)

...given the dives and durations we were witnessing on the Prism, it seems only explainable by a dramatic difference in design efficiency of the scrubber....

g

or that you are being more conservative on the meg than the prism diver.

What scientific evidence is there to prove your statement? As I understand it with a number of tests done on both axial and radial found there was not a lot of difference and in fact other issues may cause problems with radial scrubbers. Channelling...

When I spoke to Gordon Smith some years back he said the most efficient scrubber design was a long thin axial scrubber tube - but it was impossible to breath through. Ignoring the thermal design issues - A radial scrubber simply provides a means to shorten the length of sorb you need to breath through for the same mass than in a longer axial scrubber. All things being equal I would think the life of a scrubber will be dictated by the mass of sorb.

I accept with my Evolution scrubber than I do not get the same dive time per kg of sorb because I lose the efficiency of mass but I win in other areas such as being able to have a fresh fill more often. Swings and roundabouts and in general it does not cause much of an issue.

Must go - got a plane to catch to the South China Sea with my axial scrubber...

silent running · 16th May 2008, 23:09

Hi Paul, I know we have been over this stuff many times, but I'm not sure I understand what you're saying below.

Quote: (Originally Posted by paulraymaekers)

dwell time, well, we already spent some time about it, is ONLY dependant on the amount of sorb you have in your system, XX kg, and NOTHING else, not the shape, not the form, nor axial or radial, just kilo's..
the more kilo's, the more dwell time...(if kept all the rest equal, RMV, ..)

If this were somehow true, then are you also saying that the shape/form of the scrubbers doesn't matter at all and that the different scrubber types used by various manufacturers are just aesthetic choices? How can you seperate dwell time from the gas flow characteristics of different shapes? I don't see how what happens inside the sorb can be isolated from the gas flow characteristics of the inlet and outlet of a scrubber and it's shape.

Quote: (Originally Posted by paulraymaekers)

the difference between radial and axial is mainly the thermal behaviour, how to keep the warmth in your system, how to prevent part of the sorb beiing cooled down, and in that way making a path of less efficient sorb, and faster breaktrough.

No, the main difference between axial and radial is a physical one-the length of grain boundary, the surface area of the inlet and outlet and the shape of the scrubber. In other words, the gas path. Insulating characteristics very from design to design and include variables such as flow direction and material types used in the scrubber itself and the housing.

Quote: (Originally Posted by paulraymaekers)

IF, and only IF, sorb efficiency, or absorbant capabilities, would be not lineair with gasspeed through the sorb, in that case slow flow would eventually increase efficiency, but the dwell time itself would still be the same...with best regards
paul

OK Paul, but aren't "absorbant capabilities" increasing and "non linear" given the expanding sorb area and reaction front found in an in-out radial with surface area increasing as the gas moves radially outward? -Andy

silent running · 17th May 2008, 00:23

Quote: (Originally Posted by 01RMB)

or that you are being more conservative on the meg than the prism diver.

Hello 01RMB, how about the considering the idea that the radial does have additional duration and GE is also a little more conservative than myself?

Quote: (Originally Posted by 01RMB)

What scientific evidence is there to prove your statement? As I understand it with a number of tests done on both axial and radial found there was not a lot of difference and in fact other issues may cause problems with radial scrubbers. Channelling...

Channeling? I think you have this backwards as channeling in a properly packed scrubber is more likely in the scrubber that has the most sorb in contact with a solid material. The surface area of the walls of a standard axial scrubber is far greater than any in a radial, where there is almost no contact with solid material in the gas path. And given that plastic has no capacity to absorb CO2, which seems more likely to facilitate channeling, sorb granuals against plastic, or sorb granuals against other sorb granuals?

As for scientific tests, that depends what standard you mean by scientific. The USN did extensive controlled tests on the 6lb Prism radial and found that it was able to perform equally to or possibly better than the MK16 scrubber which holds 8+lbs. So no, I don't think there is no difference between the 2 designs. Do you know any Inspo divers that have gotten 11 hrs out of their axial scrubbers in 10C water? This has been done on the Prism. I have had no issues getting 10 hours on mine in warm water after several hundred hours, even with lots of time spent working hard in current.

And what tests on which axial and radial scrubbers are you referring to above and where they done with known scrubbers from actual production units? -Andy

paulraymaekers · 17th May 2008, 03:47

Quote: (Originally Posted by silent running)

Hi Paul, I know we have been over this stuff many times, but I'm not sure I understand what you're saying below.

If this were somehow true, then are you also saying that the shape/form of the scrubbers doesn't matter at all and that the different scrubber types used by various manufacturers are just aesthetic choices? How can you seperate dwell time from the gas flow characteristics of different shapes? I don't see how what happens inside the sorb can be isolated from the gas flow characteristics of the inlet and outlet of a scrubber and it's shape.

No, the main difference between axial and radial is a physical one-the length of grain boundary, the surface area of the inlet and outlet and the shape of the scrubber. In other words, the gas path. Insulating characteristics very from design to design and include variables such as flow direction and material types used in the scrubber itself and the housing.

OK Paul, but aren't "absorbant capabilities" increasing and "non linear" given the expanding sorb area and reaction front found in an in-out radial with surface area increasing as the gas moves radially outward? -Andy

Andy, I will not start the whole issue again, I have debated it more then enough..

If this were somehow true, then are you also saying that the shape/form of the scrubbers doesn't matter at all and that the different scrubber types used by various manufacturers are just aesthetic choices?

I'm not saying that at all, but I do say that if they contain the same XXkg of sorb, then the well time is the same. There are huge differences in performance, partly because of the size (=kilo's), partly because of shape (thermal), partly because of what happens OUTSIDE the scrubber (thermal, flowcurve)

see what happens with the new sentinel: a small axial scrubber, performing better then any other (under specific conditions: the CE, not under other conditions..)

please remember: a radial is nothing more then a large surface, thin, axial, that has been curved in the shape of a tube (bent so that the sides touches)

regards
paul

**Steve** · 17th May 2008, 05:40

Quote: (Originally Posted by paulraymaekers)

hello Gill, sorry to put is quite blunt, but this is, hm, hm, complete nonsense...... dwell time, well, we already spent some time about it, is ONLY dependant on the amount of sorb you have in your system, XX kg, and NOTHING else, not the shape, not the form, nor axial or radial, just kilo's..
the more kilo's, the more dwell time...(if kept all the rest equal, RMV, ..)

Paul, This is your opinion, it isn't a fact, and I for one don't share it. I believe the following to be the case.

A rebreather's scrubber's dwell time is due "primarily" to 2 things. The ratio between the divers lung size and the loop volume, and the length of the gas path in the scrubber. Your way of looking at dwell time ignores these 2 key factors and looks at a simplistic linear gas path which ignores the reality of the system as a whole.

What you say is of course very true if the gas flow is constant and the scrubber isn't in a rebreather, but that isn't how we use rebreathers and is therefore of passing simplistic interest.

The gas moves through a CCR in steps directly related to the breaths of the diver. There is some further gas movement due to pressure equalisation but it is a smaller amount. The length of these steps and the length of the sorb bed are very important in determining dwell time. I find it usefull to focus on a single molecule of CO2. It is moving through the system and can only be scrubbed when in the sorb bed. A smaller tidal volume to scrubber bed length increase the dwell time and ovbiously the converse is true.

16th May 2008, 16:36	#21 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,384	Re: New Meg Radial Scrubber Quote: (Originally Posted by Gill Envy) I have to say that after my second trip with a prism diver, that radial scrubbers seem to be worth their weight in gold in terms of sorb use and airline overage getting too a remote destination. Our friend with the prism consistently uses about 50% less sorb than we did, in part because starting a second day of diving with the deepest dive first was plausible on a radial that still had half it's duration left while the axial was consistently too far gone to feel safe taking it on a additional demanding dive. the two things I want to add to my copis are a needle valve and a ISC's radial scrubber. Hi Gill, how do you know that the axial was to far gone compared to the radial?? IMHO, the advantage of radials lies in (perhaps) longer duration in cold water, and/or lesser WOB if you want a lot of sorb in your system but in warm water, you don't need the radial for longer duration, because in warm water duration is more depending on amount of sorb you take with you, and much less the thermal system (radials compared to axials) paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
(Online)

16th May 2008, 18:36	#22 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,253	Re: New Meg Radial Scrubber well, I guess since we don't have objective data I can't be sure, and I screwed up the math to boot, it was more like 30% less, but still substantial. My understanding of the theory behind radial scrubbers is that they essentially have a much larger surface area of exposed sorb to exhalled air, increasing the dwell time and therefore allowing the sorb to be used more completely with less chance of breakthrough. My understanding is that there is less chance of the reactant front migrating substantially during increased work loads. My understanding of an axial scrubber is that because dwell time can diminish exponentially with increased respiration that a much more substantial buffer needs to be calculated in terms of the migrating of the reactant front... like 50%, in order to prevent breakthrough co2, so we theoretically are throwing away roughly 50% of our scrubber each time on an axial scrubber. I realize that the rEvo takes another aproach to addressing this issue and i'm also intrigued with it as well... it's my understanding that that 50% buffer is only occasionally used and likely for short durations and as the theory goes, splitting the scrubber in two and replacing half each time, advancing the second half the scrubber to the front of the line in the loop on the rEvo has a similar potential for sorb efficiency while maintaining a good safety margine. I get that theory and I think it's plausable as long as the margines aren't pushed too much. In any case, I realize this is a hotly debated subject and there are diverging opinions about it and i'm only a little bit knowledgable about it, but given the dives and durations we were witnessing on the Prism, it seems only explainable by a dramatic difference in design efficiency of the scrubber. I"m guessing the meg version will have similar if not better performance and luckinly it will fit in my Copis! g Quote: (Originally Posted by paulraymaekers) Hi Gill, how do you know that the axial was to far gone compared to the radial?? IMHO, the advantage of radials lies in (perhaps) longer duration in cold water, and/or lesser WOB if you want a lot of sorb in your system but in warm water, you don't need the radial for longer duration, because in warm water duration is more depending on amount of sorb you take with you, and much less the thermal system (radials compared to axials) paul __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
(Online)

16th May 2008, 18:51	#23 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,384	Re: New Meg Radial Scrubber Quote: (Originally Posted by Gill Envy) My understanding of the theory behind radial scrubbers is that they essentially have a much larger surface area of exposed sorb to exhalled air, increasing the dwell time and therefore allowing the sorb to be used more completely with less chance of breakthrough. My understanding is that there is less chance of the reactant front migrating substantially during increased work loads. My understanding of an axial scrubber is that because dwell time can diminish exponentially with increased respiration that a much more substantial buffer needs to be calculated in terms of the migrating of the reactant front... like 50%, in order to prevent breakthrough co2, so we theoretically are throwing away roughly 50% of our scrubber each time on an axial scrubber. hello Gill, sorry to put is quite blunt, but this is, hm, hm, complete nonsense...... dwell time, well, we already spent some time about it, is ONLY dependant on the amount of sorb you have in your system, XX kg, and NOTHING else, not the shape, not the form, nor axial or radial, just kilo's.. the more kilo's, the more dwell time...(if kept all the rest equal, RMV, ..) the difference between radial and axial is mainly the thermal behaviour, how to keep the warmth in your system, how to prevent part of the sorb beiing cooled down, and in that way making a path of less efficient sorb, and faster breaktrough. IF, and only IF, sorb efficiency, or absorbant capabilities, would be not lineair with gasspeed through the sorb, in that case slow flow would eventually increase efficiency, but the dwell time itself would still be the same... with best regards paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials... Last edited by paulraymaekers : 16th May 2008 at 18:54.
(Online)

16th May 2008, 19:50	#24 (permalink)
fin New Member Current Rebreather/s: Megalodon Dolphin Other Rebreather/s: Megalodon Dolphin Join Date: Jul 2006 Location: Thessaloniki, Hellas (Greece) Posts: 47	Re: New Meg Radial Scrubber Quote: (Originally Posted by Outlaw) Thanks a lot mate. any links to a website that i can get the my hands on those same black tanks like Tom Jaspers? Thanks Spyros Sorry to break in Spyros, but I wrote that in another thread (about your meg configuration I think). I don't understand the reason you dont paint the 3l tanks yourself. Its easier than searching and paying shipping and no rocket science after all. Ive been painting my club's tanks for decades to protect them from corosion using high quality marine paint. Another think is that black may be a sexy colour indeed (I would follow using my zero free time), but does not stand strict EU industrial gas legislations (colour code). You must be sure that you will never meet a very strict Rebreather friendly club in the future .
(Offline)

16th May 2008, 19:56	#25 (permalink)
Outlaw In search of Law breaking Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Aug 2006 Location: Cyprus, Nicosia Posts: 627	Re: New Meg Radial Scrubber Quote: (Originally Posted by fin) Sorry to break in Spyros, but I wrote that in another thread (about your meg configuration I think). I don't understand the reason you dont paint the 3l tanks yourself. Its easier than searching and paying shipping and no rocket science after all. Ive been painting my club's tanks for decades to protect them from corosion using high quality marine paint. Another think is that black may be a sexy colour indeed (I would follow using my zero free time), but does not stand strict EU industrial gas legislations (colour code). You must be sure that you will never meet a very strict Rebreather friendly club in the future . hey fin, thanks for that, but the reason i got wild about this is that the ones Tom Jaspers is using are much thinner than the catalina blacks i got now. and i dont like the steel ones to paint them... that's all. if the price is right, then great. besides, i got the tanks valves upright, so these are perfect fit for my meg. Spyros __________________ CMAS - IANTD - TDI Kamikazi Instrustor Trainer DIRRebreather Team Member ---------------------------- "Once an Outlaw, always an Outlaw"
(Offline)

16th May 2008, 21:41	#26 (permalink)
01RMB Evolving Current Rebreather/s: Evolution Other Rebreather/s: Join Date: May 2005 Location: Brisbane, Australia Posts: 191	Re: New Meg Radial Scrubber Quote: (Originally Posted by Gill Envy) ...given the dives and durations we were witnessing on the Prism, it seems only explainable by a dramatic difference in design efficiency of the scrubber.... g or that you are being more conservative on the meg than the prism diver. What scientific evidence is there to prove your statement? As I understand it with a number of tests done on both axial and radial found there was not a lot of difference and in fact other issues may cause problems with radial scrubbers. Channelling... When I spoke to Gordon Smith some years back he said the most efficient scrubber design was a long thin axial scrubber tube - but it was impossible to breath through. Ignoring the thermal design issues - A radial scrubber simply provides a means to shorten the length of sorb you need to breath through for the same mass than in a longer axial scrubber. All things being equal I would think the life of a scrubber will be dictated by the mass of sorb. I accept with my Evolution scrubber than I do not get the same dive time per kg of sorb because I lose the efficiency of mass but I win in other areas such as being able to have a fresh fill more often. Swings and roundabouts and in general it does not cause much of an issue. Must go - got a plane to catch to the South China Sea with my axial scrubber... __________________ Cheers Rod
(Offline)

16th May 2008, 23:09	#27 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,777	Re: New Meg Radial Scrubber Hi Paul, I know we have been over this stuff many times, but I'm not sure I understand what you're saying below. Quote: (Originally Posted by paulraymaekers) dwell time, well, we already spent some time about it, is ONLY dependant on the amount of sorb you have in your system, XX kg, and NOTHING else, not the shape, not the form, nor axial or radial, just kilo's.. the more kilo's, the more dwell time...(if kept all the rest equal, RMV, ..) If this were somehow true, then are you also saying that the shape/form of the scrubbers doesn't matter at all and that the different scrubber types used by various manufacturers are just aesthetic choices? How can you seperate dwell time from the gas flow characteristics of different shapes? I don't see how what happens inside the sorb can be isolated from the gas flow characteristics of the inlet and outlet of a scrubber and it's shape. Quote: (Originally Posted by paulraymaekers) the difference between radial and axial is mainly the thermal behaviour, how to keep the warmth in your system, how to prevent part of the sorb beiing cooled down, and in that way making a path of less efficient sorb, and faster breaktrough. No, the main difference between axial and radial is a physical one-the length of grain boundary, the surface area of the inlet and outlet and the shape of the scrubber. In other words, the gas path. Insulating characteristics very from design to design and include variables such as flow direction and material types used in the scrubber itself and the housing. Quote: (Originally Posted by paulraymaekers) IF, and only IF, sorb efficiency, or absorbant capabilities, would be not lineair with gasspeed through the sorb, in that case slow flow would eventually increase efficiency, but the dwell time itself would still be the same...with best regards paul OK Paul, but aren't "absorbant capabilities" increasing and "non linear" given the expanding sorb area and reaction front found in an in-out radial with surface area increasing as the gas moves radially outward? -Andy
(Online)

17th May 2008, 00:23	#28 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,777	Re: New Meg Radial Scrubber Quote: (Originally Posted by 01RMB) or that you are being more conservative on the meg than the prism diver. Hello 01RMB, how about the considering the idea that the radial does have additional duration and GE is also a little more conservative than myself? Quote: (Originally Posted by 01RMB) What scientific evidence is there to prove your statement? As I understand it with a number of tests done on both axial and radial found there was not a lot of difference and in fact other issues may cause problems with radial scrubbers. Channelling... Channeling? I think you have this backwards as channeling in a properly packed scrubber is more likely in the scrubber that has the most sorb in contact with a solid material. The surface area of the walls of a standard axial scrubber is far greater than any in a radial, where there is almost no contact with solid material in the gas path. And given that plastic has no capacity to absorb CO2, which seems more likely to facilitate channeling, sorb granuals against plastic, or sorb granuals against other sorb granuals? As for scientific tests, that depends what standard you mean by scientific. The USN did extensive controlled tests on the 6lb Prism radial and found that it was able to perform equally to or possibly better than the MK16 scrubber which holds 8+lbs. So no, I don't think there is no difference between the 2 designs. Do you know any Inspo divers that have gotten 11 hrs out of their axial scrubbers in 10C water? This has been done on the Prism. I have had no issues getting 10 hours on mine in warm water after several hundred hours, even with lots of time spent working hard in current. And what tests on which axial and radial scrubbers are you referring to above and where they done with known scrubbers from actual production units? -Andy
(Online)

17th May 2008, 03:47	#29 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,384	Re: New Meg Radial Scrubber Quote: (Originally Posted by silent running) Hi Paul, I know we have been over this stuff many times, but I'm not sure I understand what you're saying below. If this were somehow true, then are you also saying that the shape/form of the scrubbers doesn't matter at all and that the different scrubber types used by various manufacturers are just aesthetic choices? How can you seperate dwell time from the gas flow characteristics of different shapes? I don't see how what happens inside the sorb can be isolated from the gas flow characteristics of the inlet and outlet of a scrubber and it's shape. No, the main difference between axial and radial is a physical one-the length of grain boundary, the surface area of the inlet and outlet and the shape of the scrubber. In other words, the gas path. Insulating characteristics very from design to design and include variables such as flow direction and material types used in the scrubber itself and the housing. OK Paul, but aren't "absorbant capabilities" increasing and "non linear" given the expanding sorb area and reaction front found in an in-out radial with surface area increasing as the gas moves radially outward? -Andy Andy, I will not start the whole issue again, I have debated it more then enough.. If this were somehow true, then are you also saying that the shape/form of the scrubbers doesn't matter at all and that the different scrubber types used by various manufacturers are just aesthetic choices? I'm not saying that at all, but I do say that if they contain the same XXkg of sorb, then the well time is the same. There are huge differences in performance, partly because of the size (=kilo's), partly because of shape (thermal), partly because of what happens OUTSIDE the scrubber (thermal, flowcurve) see what happens with the new sentinel: a small axial scrubber, performing better then any other (under specific conditions: the CE, not under other conditions..) please remember: a radial is nothing more then a large surface, thin, axial, that has been curved in the shape of a tube (bent so that the sides touches) regards paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
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17th May 2008, 05:40	#30 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,070	Re: New Meg Radial Scrubber Quote: (Originally Posted by paulraymaekers) hello Gill, sorry to put is quite blunt, but this is, hm, hm, complete nonsense...... dwell time, well, we already spent some time about it, is ONLY dependant on the amount of sorb you have in your system, XX kg, and NOTHING else, not the shape, not the form, nor axial or radial, just kilo's.. the more kilo's, the more dwell time...(if kept all the rest equal, RMV, ..) Paul, This is your opinion, it isn't a fact, and I for one don't share it. I believe the following to be the case. A rebreather's scrubber's dwell time is due "primarily" to 2 things. The ratio between the divers lung size and the loop volume, and the length of the gas path in the scrubber. Your way of looking at dwell time ignores these 2 key factors and looks at a simplistic linear gas path which ignores the reality of the system as a whole. What you say is of course very true if the gas flow is constant and the scrubber isn't in a rebreather, but that isn't how we use rebreathers and is therefore of passing simplistic interest. The gas moves through a CCR in steps directly related to the breaths of the diver. There is some further gas movement due to pressure equalisation but it is a smaller amount. The length of these steps and the length of the sorb bed are very important in determining dwell time. I find it usefull to focus on a single molecule of CO2. It is moving through the system and can only be scrubbed when in the sorb bed. A smaller tidal volume to scrubber bed length increase the dwell time and ovbiously the converse is true. __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
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