Effect of Depth on Scrubber

paulraymaekers · 30th August 2006, 09:28

Quote: (Originally Posted by silent running)

If I were to buy into your explanation of the slower radial velocity being equalized by the length of the axial scrubbers gas path, then the APD tempstick would not ever show a concentrated reaction front, just an elevated temp over the whole scrubber, not the case from what I've seen of the tempstick performance. -Andy

no matter what you see on the ADP display, the stick mesures the zone where the temperature increases in the sorb
regards
paul

paulraymaekers · 30th August 2006, 10:42

Quote: (Originally Posted by paulraymaekers)

come on andy, read the end of my mail

velocity slower: yes, but pathlengtevery short

it takes the same time (dwell) for a car to drive trough the wood (1mile deep) at 100 mph, as trough a wood 2 miles deep, at 200 mph

conc the radial, if you divide this scrubber in a lot of concentric tubes, and take the wallthickness of each tube small enough that in that part you can say that the speed is constant, you calculate the dwell to pass that thin volume, you calculate it for each 'tube' end at the and you sum all the dwell-times, you will have the total dwell-time for the scrubber, and you'll see that it equals exactly the dwelltime of an axial with the same volume! (means taking the integral over the depth of the pathlength..)

don't ask me to do the calculation for you :-)

regards
paul

ok, I could not let it, where can I upload the XLS file with the calculations:

comparison dwell time for radial and axial scubber with the same volume/shape

paul

**Steve** · 30th August 2006, 10:50

Paul,

I can't grasp why you can't see the pointlessness off looking at scrubbers in isolation when talking about dwell time. Your calculations are usless without factoring in the rest of the loop and the diver.

paulraymaekers · 30th August 2006, 10:58

Quote: (Originally Posted by Steve)

Paul,

I can't grasp why you can't see the pointlessness off looking at scrubbers in isolation when talking about dwell time. Your calculations are usless without factoring in the rest of the loop and the diver.

?????? EEEEUUUUUUHHHHHHH ???????

I think in the last posts we were only comparing radial with axial, and keep all the rest unchanged, correct??
the calculations only relate to dwell-time, not to other aspects in the loop, temp, WOB, total loop volume...

I agree perhaps this is the wrong treath, and we better start a separate one on this issue: dwelltime in axial and radial scrubber
??? how to upload files ??

paul

DanDunfee · 20th January 2007, 15:44

I'm slooowly developing a small personal recreational Rebreather rig (could also be a bailout for a larger, more aggressive tech or caving rigs) that will use a small scrubber (~1 kg of sorb). I've not seen data published anywhere, which paramaterizes the effects of depth and temp on CO2 breakthrough time, with scrubber charges of various sizes (and configuration, if that proves important)., so I'm doing some of that by comparative analysis of existing data from various sources.

I'm not ready to 'publish' anything yet, but data so far indicates something that might be important info re dive-planning guidance to many folks who usually don't adequately consider it in their pre-dive planning. It's quite a preliminary number, but I'll put it out here in case it might be helpful, to some folks and to solicit inputs from knowledgable folks who support their assertions with hard corrolary test data, vs speculation and rhetoric.

The data I've correlated so far indicate that.... as a generalization,.. over the range of scrubber charge sizes, from ~2 to ~3 kg , and based on data normlized to EC -test parameter values, .. there is a quite uniform reduction of breakthrough time , of about 14 % for each additional atmosphere of depth, down to ~100 m. I realize that the EC test parameter values are purposefully conversative re / vs 'normal use values.' However it does provide a relatively conservative (read 'Safe') basis to normalize & standardize other test results to for A vs B comparisons.

The data also indicate a much larger proportional effect of cold ambient temp on the smaller vs the larger scrubbers, This reduces the breakthrough time up to ~ 50 % at 4 vs 21 *C. I've no other no parameterization to offer on that yet.

Hope this helps some. Cheers

Dan ,

Gobfish1 · 21st January 2007, 04:46

Quote: (Originally Posted by DanDunfee)

I'm slooowly developing a small personal recreational Rebreather rig (could also be a bailout for a larger, more aggressive tech or caving rigs) that will use a small scrubber (~1 kg of sorb). I've not seen data published anywhere, which paramaterizes the effects of depth and temp on CO2 breakthrough time, with scrubber charges of various sizes (and configuration, if that proves important)., so I'm doing some of that by comparative analysis of existing data from various sources.

I'm not ready to 'publish' anything yet, but data so far indicates something that might be important info re dive-planning guidance to many folks who usually don't consider in their pre-dive planning. It's quite a preliminary number, but I'll put it out here in case it might be helpful, to some folks and to solicit inputs from knowledgable folks who support their arguments with hard corrolary test data, vs speculation and rhetoric.

The data I've correlated so far indicate that.... as a generalization,.. over the range of scrubber charge sizes, from ~2 to ~3 kg , and based on data normlized to EC -test parameter values, .. there is a quite uniform reduction of breakthrough time , of about 14 % for each additional atmosphere of depth, down to ~100 m. I realize that the EC test parameter values are purposefully conversative re / vs 'normal use values.' However it does provide a relatively conservative (read 'Safe') basis to normalize & standardize other test results to for A vs B comparisons.

The data also indicate a much larger proportional effect of cold ambient temp on the smaller vs the larger scrubbers, This reduces the breakthrough time up to ~ 50 % at 4 vs 21 *C. I've no other no parameterization to offer on that yet.

Hope this helps some. Cheers

Dan ,

100/180=.55 * 14 = 7.7, call it 8
So that 8mins * 10 ats = 80mis of my 180 min scrubber
So that would work in well with what AP say

Is that right

DrJM · 21st January 2007, 06:14

Just back from a nice dive spending 5min45 between -185m (45min to reach it) and -190m on my Ouroboros and even after 6h in the water at 18 cel deg it was still breathing perfectly

I scootered in one gallery at that depth and even swim in the other one, no scrubber issue

Lets remember Dave Shaw swimming between -240 and -270 with his Mk15.5 on his first dive in the Bushmangaft cave, no scrubber issue, even with a non original foam under the scrubber

Jerome

decoweenie · 21st January 2007, 08:16

Quote: (Originally Posted by DrJM)

Lets remember Dave Shaw swimming between -240 and -270 with his Mk15.5 on his first dive in the Bushmangaft cave, no scrubber issue, even with a non original foam under the scrubber

Also, I have kept hearing this as one of the causes of his second (and fatal) dive. Do we know if this is true ?

And was it something he learned in the course, or picked up on Internet ?

DanDunfee · 21st January 2007, 20:27

Quote: (Originally Posted by Gobfish1)

100/180=.55 * 14 = 7.7, call it 8
So that 8mins * 10 ats = 80mis of my 180 min scrubber
So that would work in well with what AP say

Is that right

Steve:

That's a correct approximation for a 14 % per ata case. . It doesn't take into account the ambient (water) temperature effects, which are assumed to be the same for both depth values. As I said, the cold temp (21 to 4 *C) effects for the smaller, uninsulated, scrubbers were surprisingly large to me....., eg The ~50 % value I quoted in my orig msg was a projected value for a 1.25 kg scrubber charge case, It was ~ 22 % for a ~ 2 kg case. The temp effect for a ~2.8 kg case was much smaller...~< 5 %. All the exact reasons for the differences remain unclear.

This also raises an interesting question of how much additional benefit may accrue to more 'insulated' scrubbers...Examples = the OMG Cstoro C 96 or Cressi ARO 57 types, where the scrubber is substantially imbedded within, and insulated by the counterlung.

Regards.....Dan

Gobfish1 · 22nd January 2007, 02:33

Quote: (Originally Posted by DanDunfee)

Steve:

That's a correct approximation for a 14 % per ata case. . It doesn't take into account the ambient (water) temperature effects, which are assumed to be the same for both depth values. As I said, the cold temp (21 to 4 *C) effects for the smaller, uninsulated, scrubbers were surprisingly large to me....., eg The ~50 % value I quoted in my orig msg was a projected value for a 1.25 kg scrubber charge case, It was ~ 22 % for a ~ 2 kg case. The temp effect for a ~2.8 kg case was much smaller...~< 5 %. All the exact reasons for the differences remain unclear.

This also raises an interesting question of how much additional benefit may accrue to more 'insulated' scrubbers...Examples = the OMG Cstoro C 96 or Cressi ARO 57 types, where the scrubber is substantially imbedded within, and insulated by the counterlung.

Regards.....Dan

thanks Dan

30th August 2006, 09:28	#61 (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: 1,494	Re: Effect of Depth on Scrubber Quote: (Originally Posted by silent running) If I were to buy into your explanation of the slower radial velocity being equalized by the length of the axial scrubbers gas path, then the APD tempstick would not ever show a concentrated reaction front, just an elevated temp over the whole scrubber, not the case from what I've seen of the tempstick performance. -Andy no matter what you see on the ADP display, the stick mesures the zone where the temperature increases in the sorb regards paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
(Online)

30th August 2006, 10:42	#62 (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: 1,494	Re: Effect of Depth on Scrubber Quote: (Originally Posted by paulraymaekers) come on andy, read the end of my mail velocity slower: yes, but pathlengtevery short it takes the same time (dwell) for a car to drive trough the wood (1mile deep) at 100 mph, as trough a wood 2 miles deep, at 200 mph conc the radial, if you divide this scrubber in a lot of concentric tubes, and take the wallthickness of each tube small enough that in that part you can say that the speed is constant, you calculate the dwell to pass that thin volume, you calculate it for each 'tube' end at the and you sum all the dwell-times, you will have the total dwell-time for the scrubber, and you'll see that it equals exactly the dwelltime of an axial with the same volume! (means taking the integral over the depth of the pathlength..) don't ask me to do the calculation for you :-) regards paul ok, I could not let it, where can I upload the XLS file with the calculations: comparison dwell time for radial and axial scubber with the same volume/shape paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
(Online)

30th August 2006, 10:50	#63 (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: 1,117	Re: Effect of Depth on Scrubber Paul, I can't grasp why you can't see the pointlessness off looking at scrubbers in isolation when talking about dwell time. Your calculations are usless without factoring in the rest of the loop and the diver. __________________ 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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30th August 2006, 10:58	#64 (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: 1,494	Re: Effect of Depth on Scrubber Quote: (Originally Posted by Steve) Paul, I can't grasp why you can't see the pointlessness off looking at scrubbers in isolation when talking about dwell time. Your calculations are usless without factoring in the rest of the loop and the diver. ?????? EEEEUUUUUUHHHHHHH ??????? I think in the last posts we were only comparing radial with axial, and keep all the rest unchanged, correct?? the calculations only relate to dwell-time, not to other aspects in the loop, temp, WOB, total loop volume... I agree perhaps this is the wrong treath, and we better start a separate one on this issue: dwelltime in axial and radial scrubber ??? how to upload files ?? paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
(Online)

20th January 2007, 15:44	#65 (permalink)
DanDunfee Custom Title Allowed! Current Rebreather/s: Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Other SCR Home Build Join Date: Sep 2005 Location: Virginia, USA Posts: 204	Re: Effect of Depth on Scrubber I'm slooowly developing a small personal recreational Rebreather rig (could also be a bailout for a larger, more aggressive tech or caving rigs) that will use a small scrubber (~1 kg of sorb). I've not seen data published anywhere, which paramaterizes the effects of depth and temp on CO2 breakthrough time, with scrubber charges of various sizes (and configuration, if that proves important)., so I'm doing some of that by comparative analysis of existing data from various sources. I'm not ready to 'publish' anything yet, but data so far indicates something that might be important info re dive-planning guidance to many folks who usually don't adequately consider it in their pre-dive planning. It's quite a preliminary number, but I'll put it out here in case it might be helpful, to some folks and to solicit inputs from knowledgable folks who support their assertions with hard corrolary test data, vs speculation and rhetoric. The data I've correlated so far indicate that.... as a generalization,.. over the range of scrubber charge sizes, from ~2 to ~3 kg , and based on data normlized to EC -test parameter values, .. there is a quite uniform reduction of breakthrough time , of about 14 % for each additional atmosphere of depth, down to ~100 m. I realize that the EC test parameter values are purposefully conversative re / vs 'normal use values.' However it does provide a relatively conservative (read 'Safe') basis to normalize & standardize other test results to for A vs B comparisons. The data also indicate a much larger proportional effect of cold ambient temp on the smaller vs the larger scrubbers, This reduces the breakthrough time up to ~ 50 % at 4 vs 21 C. I've no other no parameterization to offer on that yet. Hope this helps some. Cheers Dan , __________________ There are 'Bold' divers and old divers, but NO old, ' Bold ' divers Last edited by DanDunfee : 22nd January 2007 at 13:37.*
(Offline)

21st January 2007, 04:46	#66 (permalink)
Gobfish1 Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Join Date: Apr 2005 Location: Manchester UK Posts: 363	Re: Effect of Depth on Scrubber Quote: (Originally Posted by DanDunfee) I'm slooowly developing a small personal recreational Rebreather rig (could also be a bailout for a larger, more aggressive tech or caving rigs) that will use a small scrubber (~1 kg of sorb). I've not seen data published anywhere, which paramaterizes the effects of depth and temp on CO2 breakthrough time, with scrubber charges of various sizes (and configuration, if that proves important)., so I'm doing some of that by comparative analysis of existing data from various sources. I'm not ready to 'publish' anything yet, but data so far indicates something that might be important info re dive-planning guidance to many folks who usually don't consider in their pre-dive planning. It's quite a preliminary number, but I'll put it out here in case it might be helpful, to some folks and to solicit inputs from knowledgable folks who support their arguments with hard corrolary test data, vs speculation and rhetoric. The data I've correlated so far indicate that.... as a generalization,.. over the range of scrubber charge sizes, from ~2 to ~3 kg , and based on data normlized to EC -test parameter values, .. there is a quite uniform reduction of breakthrough time , of about 14 % for each additional atmosphere of depth, down to ~100 m. I realize that the EC test parameter values are purposefully conversative re / vs 'normal use values.' However it does provide a relatively conservative (read 'Safe') basis to normalize & standardize other test results to for A vs B comparisons. The data also indicate a much larger proportional effect of cold ambient temp on the smaller vs the larger scrubbers, This reduces the breakthrough time up to ~ 50 % at 4 vs 21 C. I've no other no parameterization to offer on that yet. Hope this helps some. Cheers Dan , 100/180=.55 14 = 7.7, call it 8 So that 8mins * 10 ats = 80mis of my 180 min scrubber So that would work in well with what AP say Is that right __________________ Steve G Apparently not the only gay diver in the village http://drinkingliberally.org/blogs/o...nzee-glock.gif http://www.scubatunes.com/audio/vol01/mp3/HiTech.mp3
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21st January 2007, 06:14	#67 (permalink)
DrJM Deep Cave Explorer Current Rebreather/s: Ouroboros Other Rebreather/s: MK 15.X Join Date: May 2005 Location: France Posts: 344	Re: Effect of Depth on Scrubber Just back from a nice dive spending 5min45 between -185m (45min to reach it) and -190m on my Ouroboros and even after 6h in the water at 18 cel deg it was still breathing perfectly I scootered in one gallery at that depth and even swim in the other one, no scrubber issue Lets remember Dave Shaw swimming between -240 and -270 with his Mk15.5 on his first dive in the Bushmangaft cave, no scrubber issue, even with a non original foam under the scrubber Jerome __________________ www.snoopyloop.com Deep Cave Exploration
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21st January 2007, 08:16	#68 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Effect of Depth on Scrubber Quote: (Originally Posted by DrJM) Lets remember Dave Shaw swimming between -240 and -270 with his Mk15.5 on his first dive in the Bushmangaft cave, no scrubber issue, even with a non original foam under the scrubber Also, I have kept hearing this as one of the causes of his second (and fatal) dive. Do we know if this is true ? And was it something he learned in the course, or picked up on Internet ? __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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21st January 2007, 20:27	#69 (permalink)
DanDunfee Custom Title Allowed! Current Rebreather/s: Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Other SCR Home Build Join Date: Sep 2005 Location: Virginia, USA Posts: 204	Re: Effect of Depth on Scrubber Quote: (Originally Posted by Gobfish1) 100/180=.55 * 14 = 7.7, call it 8 So that 8mins * 10 ats = 80mis of my 180 min scrubber So that would work in well with what AP say Is that right Steve: That's a correct approximation for a 14 % per ata case. . It doesn't take into account the ambient (water) temperature effects, which are assumed to be the same for both depth values. As I said, the cold temp (21 to 4 C) effects for the smaller, uninsulated, scrubbers were surprisingly large to me....., eg The ~50 % value I quoted in my orig msg was a projected value for a 1.25 kg scrubber charge case, It was ~ 22 % for a ~ 2 kg case. The temp effect for a ~2.8 kg case was much smaller...~< 5 %. All the exact reasons for the differences remain unclear. This also raises an interesting question of how much additional benefit may accrue to more 'insulated' scrubbers...Examples = the OMG Cstoro C 96 or Cressi ARO 57 types, where the scrubber is substantially imbedded within, and insulated by the counterlung. Regards.....Dan __________________ There are 'Bold' divers and old divers, but NO old, ' Bold ' divers Last edited by DanDunfee : 21st January 2007 at 21:43.*
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22nd January 2007, 02:33	#70 (permalink)
Gobfish1 Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Join Date: Apr 2005 Location: Manchester UK Posts: 363	Re: Effect of Depth on Scrubber Quote: (Originally Posted by DanDunfee) Steve: That's a correct approximation for a 14 % per ata case. . It doesn't take into account the ambient (water) temperature effects, which are assumed to be the same for both depth values. As I said, the cold temp (21 to 4 *C) effects for the smaller, uninsulated, scrubbers were surprisingly large to me....., eg The ~50 % value I quoted in my orig msg was a projected value for a 1.25 kg scrubber charge case, It was ~ 22 % for a ~ 2 kg case. The temp effect for a ~2.8 kg case was much smaller...~< 5 %. All the exact reasons for the differences remain unclear. This also raises an interesting question of how much additional benefit may accrue to more 'insulated' scrubbers...Examples = the OMG Cstoro C 96 or Cressi ARO 57 types, where the scrubber is substantially imbedded within, and insulated by the counterlung. Regards.....Dan thanks Dan __________________ Steve G Apparently not the only gay diver in the village http://drinkingliberally.org/blogs/o...nzee-glock.gif http://www.scubatunes.com/audio/vol01/mp3/HiTech.mp3
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