Vision vs. Optima

diverreb · 16th July 2007, 03:55

Quote: (Originally Posted by mriopel)

I have used mine for almost 4 hours in the optima, water temp was in the 80's, there were drift divers and very little work. I took it apart and unrolled it and check it ,I say I used about 75 percent. I had also unrolled it after about 2 hours and had used about 40-50 percent. I have had others tell me they had got 4 hours with no problem. But like the book says dont be cheap. Most of the time I replace before 3 hours and not after. Better to pay the extra $25 then try to explain why they should let me in upstairs.

Mike

Just curious.... How can you tell how much you've used by unrolling the EAC?

Richie

tekdiver170 · 16th July 2007, 09:40

I dive a Vision and have now logged just over 40 dives and around 55 hours. So far I've stayed really mild on the dives as I gain experience towards taking it on deeper and longer dives. The longest I've pushed my scrubber is 4 hours (2 hours on one day and 2 hours on the next day, first dive in the 100-120' range and second dive 50-70'). Using the tempstick and color changing sorb as "guidelines" the temp stick still showed on the last dive that the whole canister was registering a warm reaction and when I dumped the sorb at the end of the 2nd day only the very top 1/2" of it had turned color showing it had been used up.

Now neither one of these observations is 100% accurate or fail proof but gives an idea that with a fresh canister you can get longer than the 3 hours AP says you can get on the Inspiration.

The Vision is a good system to dive. I know there has been a lot of people stating they wish for independent controllers and the vision does have them, the down side is they only use one display. I too wish they had 2 handsets. Anyone know if the handset can be switched in the field? Any idea what a backup handset would cost?

**Gill Envy** · 16th July 2007, 17:14

Quote: (Originally Posted by jradomski)

...
I always try and prepare for continuing a trip in the event of equipment malfunction, but thats always secondary planning.. My first concern is getting back from the dive if the failure occured underwater.. So my primary concern is what is necessary to give me the best chance of getting home, anything else after that is gravy..

there in lies a subtle and tempting argument, that one’s primary concern should be safety, that safety in eCCR’s relates to configuration and that an Evolution could be more dangerous than an Optima or HH Inspo because of it’s configuration.

Certainly safety should be concern number one. The implication that two fully independent monitors/handsets, one HUD(DIVA), sharing 3 cells as is the case with the optima is safer than one handset with two overlapping set point controllers, one HUD, One audible buzzer, 3 shared cells, as with the evolution, seems plausible. But we’d expect this to bear out statistically…there are practically more visions out there than all other eCCR’s put together and last I checked I think there were 4 fatalities associated with them...a teacher and student in a double accident that reportedly started with decompression issues and cascaded from there, a cave diver who got entrapped and ran out of O2 and I forget the 4th. That's out of how many thousands of Visions out there? ...not the trend you'd expect if what you are suggesting is true.

I see no conclusive evidence that one kind of eCCR is “safer” than another eCCR, if anything, the vision may have a bit of an edge with it's dominating volume and minimal number of fatalities. It seems that there are many potential factors effecting fatalities, but surprisingly brand and thus configuration of eCCR does not seem to have much bearing. It's likely that manual set point control versus Cruise control has the single most significant impact on fatalities, but even that is up for debate. Even with mCCR’s, the zero, or near zero fatality rate technically boils down, most likely, to style of diving and level of vigilance, and if anything, relyiance on less, not more, redundancy. Many of us are motivated by a desire to increase safety to incorporate more reduncancy, myself included, but in the end it seems more like that redundancy is about continuing to dive when you'd otherwise have to bail out on OC and possibly quite diving your rig till it gets fixed. I would suggest that redundancy may be valuable from a safety point of view if you do not simply push the envelope further in your diving style, simply because it's there.

When it comes to where to put our efforts in terms of safety and accident prevention, good training and continuous monitoring of po2 is likely the overarching influential factor in preventing fatalities, well beyond any differences in configuration between eCCR's. Therefore whichever eCCR you choose, working to counter act the tendency toward complacency that all of them seem to encourage should really be the focus premera, IMHO... Know thy po2, all the frikn' time!

I personally never felt that my life was threatened in my 100 hours on the Evolution, probably because I never had a problem with the electronics. But I don’t even feel that my wife’s repeated issues with the solenoid were truly life threatening. Between her vigilance, her trianing and the way her electronics performed, as designed, helping to quickly allert her to the droping po2, the situation was under control long before things got critical.

The issue with my wife’s Evolution was a matter of inconvenience not safety, it failed the next predive set up and was out of commision just 3 days into a 10 day trip in Indonesia... a major bummer that can happen on any brand of rebreather. Thus, avoiding inconvenience is truly the compelling reason for having on hand two completely separate ways of monitoring po2, maybe even 3 (two in use, one in the tool kit).

This sport is full of paradoxes, the issue of redundancy and safety seems to be one of the most striking. While it seems logical that more redundancy is safer, surprisingly it does not seem to be a major influencing factor in fatalities.

It does seem to be the case, that out of the box, the Optima provides more options for continuing to dive on a trip in the case of a breakdown. But to continue diving after a malfunction, one would need, with either brand, in it's stock configuration, to be willing and prepared to venture into the territory of going against manufacturers recommendations, against training protocal and make modifications or fly with a known malfunction.

Overall, whether two independent handsets really makes the Optima, out of the box, either safer or more reliable therefore depends on how you look at it.

For those of us who are willing to venture beyond the manufacturers recommendations and standard training protocal, there is less of a debate. In this case, out of the box, it sounds like the Optima's configuration lends itself more readily to modification and in field repairs. To diverge from standard protocol and dive even when there is malfunction…going against all standard training, can never really be recommended. You are on your own. for most of us who venture into this realm, we are untrained technicians, faced with learning as we go. We know full well we are taking our chances, in a school of very hard knocks. But in that case I would concure, the Optima’s configuration does appear to more readily offer options for continued diving. But that said, all the wonderful amenities of the Vision can be brought up to expedition specs relatively inexpensively and easily with the addition of a 4th cell adapter and a 3 cell capable po2 monitor.

When it comes to choosing between any two rebreathers, electronic rebreathers in particular, it really comes down to what you want and what is necessary to configure your kit to your specs but surprisingly it does not seem to be a matter of which one is safer - perhaps one of the most common misperceptions we are drawn to make. the real issue of safety boils down to weather diving electronic rebreathers is justifiable for your needs, and if so, are you willing to do what is necessary to maintain active awareness of the PO2 to avoid the ever lurking tendency toward complacency that non-active participation in po2 maintenance seems to engender.

If you are planning remote trips, I'd recommend buying whatever unit appeals to you and gradually building toward an expedition configuration with adequate contingencies plans for a variety of failure modes to avoid the added inconveniences that can come with diving with such a complex and wonderful tool in areas where there are not yet repair facilities available.

diverklondike · 16th July 2007, 23:24

Quote: (Originally Posted by diverreb)

Just curious.... How can you tell how much you've used by unrolling the EAC?

Richie

Hmmm Looking forward to that answer also....

***caveseeker7*** · 17th July 2007, 14:49

Another vote for the Hammerhead's independent set up.
Having the option of adding a backup for deco computing is the icing on the cake.
In case of the Optima or Inspo HH the ability to add either pO2 monitor or deco
computer with it's own cell adds yet another layer of independent redundancy.
Only way you could top it is by having a redundant set of sensors for primary
and secondary.

As far the Vision electronics are concerned, they are a big step in the right direction
from the original Classic electronics. Adding HUD and deco computing is great,
and the handset is as nice as they get. There is redundancy, what IMHO is missing
is the independency. Battery compartment is shared, battery power is shared,
both sets of electronics are wired together to communicate.

Even on the mighty MK-5p with three setpoint controllers in two locations powered by
multiple batteries from their own compartments and various displays Bill Stone
choose to have an independent pO2 display with it's own wiring and power supply.
I believe he had good reasons for it.

Backup is good, independent and separate backup is better.

JCdesign97 · 17th July 2007, 15:02

Quote: (Originally Posted by diverklondike)

Hmmm Looking forward to that answer also....

Shameless bump and third vote of curiosity to hear how one might divine the EAC usage visually by unrolling it ...

n2diving · 8th August 2007, 22:27

Quote: (Originally Posted by diverreb)

Just curious.... How can you tell how much you've used by unrolling the EAC?

Richie

The EAC is a long sheet of a matrix of plastic embedded with absorbent (the exact same chemistry as granular). It's rolled up into a cylinder which can be unrolled (like you would unroll paper towels). The unused material is very flexible and white... when used the portion that is consumed becomes noticably harder and discolors (a slight yellowing)... by unrolling its very easy to determine rather precisely how much has been consumed just by feel. Done repetitively, the user of the EAC can determine how much of the EAC is being consumed by their specific metabolism and specific dive conditions. This works because the EAC is extremely consistent from cartridge to cartridge (mfg says within 5%, in my experience much better than that).

Note, Dive Rite is now rating the EAC when used in the O2ptima for 240 liters of CO2. If you track your oxygen consumption, this means you can more reliably determine the life of the EAC... for many divers this means substantially more life than 3 hours (usually somewhere between 4 to 5 hours, some individuals much more or less) and still remain within mfg specifications. Again, this works because the EAC is very consistent without concern for packing varation or channelling issues.

For example: Assume the user is using al-13's (13 cu ft of o2 at 3000 psi). If you assume that the diver produces .9 liters of CO2 for every 1 liter of O2, then when 266 liters of O2 have been consumed 240 liters of CO2 have been produced. At 28.3 liters per cubic foot, 266 liters would be about 9.4 cubic feet of O2, or 9.4 / 13 * 3000 = 2170 psi of O2. So, when the diver has used about 2200 psi of O2 from their cylinder (i.e. 800 psi remaining from a full fill) they need a cartridge change. For myself, this equates to about 6 hours of non-deco diving (where I'm not doing a lot of O2 flushing on deco stops), including the O2 I used to do one calibration. [Numerous varations and refinements are possible if you like: use 1 liter of O2 consumed equals 1 liter of CO2 produced, make adjustments for calibrations, waste on ascents, O2 that came from Dil, yada... yada...]

If the EAC user does not wish to track O2 consumption (and therefore CO2 production) then they can choose to fall back on the 3 hour time duration previously recommended if they wish to remain within mfg specifications for duration.

Note this discussion applies only to the EAC EP cartridge as used in the O2ptima.

-- Mark

**Gill Envy** · 9th August 2007, 02:22

by saying you can tell the used from unused portion, are you saying that you or someone you know has tested, for chemical composition, a sample of each portion to see if you are really seeing what you think you are?

Quote: (Originally Posted by n2diving)

The EAC is a long sheet of a matrix of plastic embedded with absorbent (the exact same chemistry as granular). It's rolled up into a cylinder which can be unrolled (like you would unroll paper towels). The unused material is very flexible and white... when used the portion that is consumed becomes noticably harder and discolors (a slight yellowing)... by unrolling its very easy to determine rather precisely how much has been consumed just by feel. Done repetitively, the user of the EAC can determine how much of the EAC is being consumed by their specific metabolism and specific dive conditions. This works because the EAC is extremely consistent from cartridge to cartridge (mfg says within 5%, in my experience much better than that).

Note, Dive Rite is now rating the EAC when used in the O2ptima for 240 liters of CO2. If you track your oxygen consumption, this means you can more reliably determine the life of the EAC... for many divers this means substantially more life than 3 hours (usually somewhere between 4 to 5 hours, some individuals much more or less) and still remain within mfg specifications. Again, this works because the EAC is very consistent without concern for packing varation or channelling issues.

For example: Assume the user is using al-13's (13 cu ft of o2 at 3000 psi). If you assume that the diver produces .9 liters of CO2 for every 1 liter of O2, then when 266 liters of O2 have been consumed 240 liters of CO2 have been produced. At 28.3 liters per cubic foot, 266 liters would be about 9.4 cubic feet of O2, or 9.4 / 13 * 3000 = 2170 psi of O2. So, when the diver has used about 2200 psi of O2 from their cylinder (i.e. 800 psi remaining from a full fill) they need a cartridge change. For myself, this equates to about 6 hours of non-deco diving (where I'm not doing a lot of O2 flushing on deco stops), including the O2 I used to do one calibration. [Numerous varations and refinements are possible if you like: use 1 liter of O2 consumed equals 1 liter of CO2 produced, make adjustments for calibrations, waste on ascents, O2 that came from Dil, yada... yada...]

If the EAC user does not wish to track O2 consumption (and therefore CO2 production) then they can choose to fall back on the 3 hour time duration previously recommended if they wish to remain within mfg specifications for duration.

Note this discussion applies only to the EAC EP cartridge as used in the O2ptima.

-- Mark

n2diving · 9th August 2007, 02:41

Quote: (Originally Posted by Gill Envy)

by saying you can tell the used from unused portion, are you saying that you or someone you know has tested, for chemical composition, a sample of each portion to see if you are really seeing what you think you are?

Yes, this has been discussed at length with Tom at Micropore, the mfg of the EAC. The hardness is not entirely the result of direct consumption of the absorbent, a significant part is a result of the effect of heat of reaction. And much of the hardened area is not actually completely exhausted of absorbent capacity... but for the purposes of a conservative evaluation it's sufficient to assume so.

-- Mark

**Gill Envy** · 9th August 2007, 04:35

thanks Mark, have you found that this measuring technique matches your Co2 production calculations along the lines you would expect? eg: extrapolating the time it would take for you to produce Aprox 180 liters of CO2 more ore less results in some like 75% of scrubber spent. If those cacluations roughly match, it sounds like a promising measuring technique, making the EAC potentially more economical than previously thought without "pushing the limits".

g

Quote: (Originally Posted by n2diving)

Yes, this has been discussed at length with Tom at Micropore, the mfg of the EAC. The hardness is not entirely the result of direct consumption of the absorbent, a significant part is a result of the effect of heat of reaction. And much of the hardened area is not actually completely exhausted of absorbent capacity... but for the purposes of a conservative evaluation it's sufficient to assume so.

-- Mark

16th July 2007, 03:55	#41 (permalink)
diverreb DE/MD/NJ Wreck Diver Current Rebreather/s: Optima Other Rebreather/s: Join Date: Mar 2007 Location: Dover, DE Posts: 599	Re: Vision vs. Optima Quote: (Originally Posted by mriopel) I have used mine for almost 4 hours in the optima, water temp was in the 80's, there were drift divers and very little work. I took it apart and unrolled it and check it ,I say I used about 75 percent. I had also unrolled it after about 2 hours and had used about 40-50 percent. I have had others tell me they had got 4 hours with no problem. But like the book says dont be cheap. Most of the time I replace before 3 hours and not after. Better to pay the extra $25 then try to explain why they should let me in upstairs. Mike Just curious.... How can you tell how much you've used by unrolling the EAC? Richie
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16th July 2007, 09:40	#42 (permalink)
tekdiver170 New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Jan 2007 Location: Honolulu, HI Posts: 87	Re: Vision vs. Optima I dive a Vision and have now logged just over 40 dives and around 55 hours. So far I've stayed really mild on the dives as I gain experience towards taking it on deeper and longer dives. The longest I've pushed my scrubber is 4 hours (2 hours on one day and 2 hours on the next day, first dive in the 100-120' range and second dive 50-70'). Using the tempstick and color changing sorb as "guidelines" the temp stick still showed on the last dive that the whole canister was registering a warm reaction and when I dumped the sorb at the end of the 2nd day only the very top 1/2" of it had turned color showing it had been used up. Now neither one of these observations is 100% accurate or fail proof but gives an idea that with a fresh canister you can get longer than the 3 hours AP says you can get on the Inspiration. The Vision is a good system to dive. I know there has been a lot of people stating they wish for independent controllers and the vision does have them, the down side is they only use one display. I too wish they had 2 handsets. Anyone know if the handset can be switched in the field? Any idea what a backup handset would cost?
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16th July 2007, 17:14	#43 (permalink)
Gill Envy Shearwater Copis Divers Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,314	Re: Vision vs. Optima Quote: (Originally Posted by jradomski) ... I always try and prepare for continuing a trip in the event of equipment malfunction, but thats always secondary planning.. My first concern is getting back from the dive if the failure occured underwater.. So my primary concern is what is necessary to give me the best chance of getting home, anything else after that is gravy.. there in lies a subtle and tempting argument, that one’s primary concern should be safety, that safety in eCCR’s relates to configuration and that an Evolution could be more dangerous than an Optima or HH Inspo because of it’s configuration. Certainly safety should be concern number one. The implication that two fully independent monitors/handsets, one HUD(DIVA), sharing 3 cells as is the case with the optima is safer than one handset with two overlapping set point controllers, one HUD, One audible buzzer, 3 shared cells, as with the evolution, seems plausible. But we’d expect this to bear out statistically…there are practically more visions out there than all other eCCR’s put together and last I checked I think there were 4 fatalities associated with them...a teacher and student in a double accident that reportedly started with decompression issues and cascaded from there, a cave diver who got entrapped and ran out of O2 and I forget the 4th. That's out of how many thousands of Visions out there? ...not the trend you'd expect if what you are suggesting is true. I see no conclusive evidence that one kind of eCCR is “safer” than another eCCR, if anything, the vision may have a bit of an edge with it's dominating volume and minimal number of fatalities. It seems that there are many potential factors effecting fatalities, but surprisingly brand and thus configuration of eCCR does not seem to have much bearing. It's likely that manual set point control versus Cruise control has the single most significant impact on fatalities, but even that is up for debate. Even with mCCR’s, the zero, or near zero fatality rate technically boils down, most likely, to style of diving and level of vigilance, and if anything, relyiance on less, not more, redundancy. Many of us are motivated by a desire to increase safety to incorporate more reduncancy, myself included, but in the end it seems more like that redundancy is about continuing to dive when you'd otherwise have to bail out on OC and possibly quite diving your rig till it gets fixed. I would suggest that redundancy may be valuable from a safety point of view if you do not simply push the envelope further in your diving style, simply because it's there. When it comes to where to put our efforts in terms of safety and accident prevention, good training and continuous monitoring of po2 is likely the overarching influential factor in preventing fatalities, well beyond any differences in configuration between eCCR's. Therefore whichever eCCR you choose, working to counter act the tendency toward complacency that all of them seem to encourage should really be the focus premera, IMHO... Know thy po2, all the frikn' time! I personally never felt that my life was threatened in my 100 hours on the Evolution, probably because I never had a problem with the electronics. But I don’t even feel that my wife’s repeated issues with the solenoid were truly life threatening. Between her vigilance, her trianing and the way her electronics performed, as designed, helping to quickly allert her to the droping po2, the situation was under control long before things got critical. The issue with my wife’s Evolution was a matter of inconvenience not safety, it failed the next predive set up and was out of commision just 3 days into a 10 day trip in Indonesia... a major bummer that can happen on any brand of rebreather. Thus, avoiding inconvenience is truly the compelling reason for having on hand two completely separate ways of monitoring po2, maybe even 3 (two in use, one in the tool kit). This sport is full of paradoxes, the issue of redundancy and safety seems to be one of the most striking. While it seems logical that more redundancy is safer, surprisingly it does not seem to be a major influencing factor in fatalities. It does seem to be the case, that out of the box, the Optima provides more options for continuing to dive on a trip in the case of a breakdown. But to continue diving after a malfunction, one would need, with either brand, in it's stock configuration, to be willing and prepared to venture into the territory of going against manufacturers recommendations, against training protocal and make modifications or fly with a known malfunction. Overall, whether two independent handsets really makes the Optima, out of the box, either safer or more reliable therefore depends on how you look at it. For those of us who are willing to venture beyond the manufacturers recommendations and standard training protocal, there is less of a debate. In this case, out of the box, it sounds like the Optima's configuration lends itself more readily to modification and in field repairs. To diverge from standard protocol and dive even when there is malfunction…going against all standard training, can never really be recommended. You are on your own. for most of us who venture into this realm, we are untrained technicians, faced with learning as we go. We know full well we are taking our chances, in a school of very hard knocks. But in that case I would concure, the Optima’s configuration does appear to more readily offer options for continued diving. But that said, all the wonderful amenities of the Vision can be brought up to expedition specs relatively inexpensively and easily with the addition of a 4th cell adapter and a 3 cell capable po2 monitor. When it comes to choosing between any two rebreathers, electronic rebreathers in particular, it really comes down to what you want and what is necessary to configure your kit to your specs but surprisingly it does not seem to be a matter of which one is safer - perhaps one of the most common misperceptions we are drawn to make. the real issue of safety boils down to weather diving electronic rebreathers is justifiable for your needs, and if so, are you willing to do what is necessary to maintain active awareness of the PO2 to avoid the ever lurking tendency toward complacency that non-active participation in po2 maintenance seems to engender. If you are planning remote trips, I'd recommend buying whatever unit appeals to you and gradually building toward an expedition configuration with adequate contingencies plans for a variety of failure modes to avoid the added inconveniences that can come with diving with such a complex and wonderful tool in areas where there are not yet repair facilities available. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°> Last edited by Gill Envy : 17th July 2007 at 19:05.
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16th July 2007, 23:24	#44 (permalink)
diverklondike Just one of the Peasants Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Oct 2005 Location: Delaware, USA Posts: 1,613	Re: Vision vs. Optima Quote: (Originally Posted by diverreb) Just curious.... How can you tell how much you've used by unrolling the EAC? Richie Hmmm Looking forward to that answer also....
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17th July 2007, 14:49	#45 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,451	Re: Vision vs. Optima Another vote for the Hammerhead's independent set up. Having the option of adding a backup for deco computing is the icing on the cake. In case of the Optima or Inspo HH the ability to add either pO2 monitor or deco computer with it's own cell adds yet another layer of independent redundancy. Only way you could top it is by having a redundant set of sensors for primary and secondary. As far the Vision electronics are concerned, they are a big step in the right direction from the original Classic electronics. Adding HUD and deco computing is great, and the handset is as nice as they get. There is redundancy, what IMHO is missing is the independency. Battery compartment is shared, battery power is shared, both sets of electronics are wired together to communicate. Even on the mighty MK-5p with three setpoint controllers in two locations powered by multiple batteries from their own compartments and various displays Bill Stone choose to have an independent pO2 display with it's own wiring and power supply. I believe he had good reasons for it. Backup is good, independent and separate backup is better. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"
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17th July 2007, 15:02	#46 (permalink)
JCdesign97 My unit can beat up yours Current Rebreather/s: Optima Other Rebreather/s: Join Date: Mar 2007 Location: PA, USA Posts: 385	Re: Vision vs. Optima Quote: (Originally Posted by diverklondike) Hmmm Looking forward to that answer also.... Shameless bump and third vote of curiosity to hear how one might divine the EAC usage visually by unrolling it ... __________________ Cheers, John Cogan
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8th August 2007, 22:27	#47 (permalink)
n2diving Custom Title Allowed! Current Rebreather/s: Optima Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Feb 2005 Location: Florida, USA Posts: 272	Re: Vision vs. Optima Quote: (Originally Posted by diverreb) Just curious.... How can you tell how much you've used by unrolling the EAC? Richie The EAC is a long sheet of a matrix of plastic embedded with absorbent (the exact same chemistry as granular). It's rolled up into a cylinder which can be unrolled (like you would unroll paper towels). The unused material is very flexible and white... when used the portion that is consumed becomes noticably harder and discolors (a slight yellowing)... by unrolling its very easy to determine rather precisely how much has been consumed just by feel. Done repetitively, the user of the EAC can determine how much of the EAC is being consumed by their specific metabolism and specific dive conditions. This works because the EAC is extremely consistent from cartridge to cartridge (mfg says within 5%, in my experience much better than that). Note, Dive Rite is now rating the EAC when used in the O2ptima for 240 liters of CO2. If you track your oxygen consumption, this means you can more reliably determine the life of the EAC... for many divers this means substantially more life than 3 hours (usually somewhere between 4 to 5 hours, some individuals much more or less) and still remain within mfg specifications. Again, this works because the EAC is very consistent without concern for packing varation or channelling issues. For example: Assume the user is using al-13's (13 cu ft of o2 at 3000 psi). If you assume that the diver produces .9 liters of CO2 for every 1 liter of O2, then when 266 liters of O2 have been consumed 240 liters of CO2 have been produced. At 28.3 liters per cubic foot, 266 liters would be about 9.4 cubic feet of O2, or 9.4 / 13 * 3000 = 2170 psi of O2. So, when the diver has used about 2200 psi of O2 from their cylinder (i.e. 800 psi remaining from a full fill) they need a cartridge change. For myself, this equates to about 6 hours of non-deco diving (where I'm not doing a lot of O2 flushing on deco stops), including the O2 I used to do one calibration. [Numerous varations and refinements are possible if you like: use 1 liter of O2 consumed equals 1 liter of CO2 produced, make adjustments for calibrations, waste on ascents, O2 that came from Dil, yada... yada...] If the EAC user does not wish to track O2 consumption (and therefore CO2 production) then they can choose to fall back on the 3 hour time duration previously recommended if they wish to remain within mfg specifications for duration. Note this discussion applies only to the EAC EP cartridge as used in the O2ptima. -- Mark Last edited by n2diving : 8th August 2007 at 22:53.
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9th August 2007, 02:22	#48 (permalink)
Gill Envy Shearwater Copis Divers Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,314	Re: Vision vs. Optima by saying you can tell the used from unused portion, are you saying that you or someone you know has tested, for chemical composition, a sample of each portion to see if you are really seeing what you think you are? Quote: (Originally Posted by n2diving) The EAC is a long sheet of a matrix of plastic embedded with absorbent (the exact same chemistry as granular). It's rolled up into a cylinder which can be unrolled (like you would unroll paper towels). The unused material is very flexible and white... when used the portion that is consumed becomes noticably harder and discolors (a slight yellowing)... by unrolling its very easy to determine rather precisely how much has been consumed just by feel. Done repetitively, the user of the EAC can determine how much of the EAC is being consumed by their specific metabolism and specific dive conditions. This works because the EAC is extremely consistent from cartridge to cartridge (mfg says within 5%, in my experience much better than that). Note, Dive Rite is now rating the EAC when used in the O2ptima for 240 liters of CO2. If you track your oxygen consumption, this means you can more reliably determine the life of the EAC... for many divers this means substantially more life than 3 hours (usually somewhere between 4 to 5 hours, some individuals much more or less) and still remain within mfg specifications. Again, this works because the EAC is very consistent without concern for packing varation or channelling issues. For example: Assume the user is using al-13's (13 cu ft of o2 at 3000 psi). If you assume that the diver produces .9 liters of CO2 for every 1 liter of O2, then when 266 liters of O2 have been consumed 240 liters of CO2 have been produced. At 28.3 liters per cubic foot, 266 liters would be about 9.4 cubic feet of O2, or 9.4 / 13 * 3000 = 2170 psi of O2. So, when the diver has used about 2200 psi of O2 from their cylinder (i.e. 800 psi remaining from a full fill) they need a cartridge change. For myself, this equates to about 6 hours of non-deco diving (where I'm not doing a lot of O2 flushing on deco stops), including the O2 I used to do one calibration. [Numerous varations and refinements are possible if you like: use 1 liter of O2 consumed equals 1 liter of CO2 produced, make adjustments for calibrations, waste on ascents, O2 that came from Dil, yada... yada...] If the EAC user does not wish to track O2 consumption (and therefore CO2 production) then they can choose to fall back on the 3 hour time duration previously recommended if they wish to remain within mfg specifications for duration. Note this discussion applies only to the EAC EP cartridge as used in the O2ptima. -- Mark __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
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9th August 2007, 02:41	#49 (permalink)
n2diving Custom Title Allowed! Current Rebreather/s: Optima Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Feb 2005 Location: Florida, USA Posts: 272	Re: Vision vs. Optima Quote: (Originally Posted by Gill Envy) by saying you can tell the used from unused portion, are you saying that you or someone you know has tested, for chemical composition, a sample of each portion to see if you are really seeing what you think you are? Yes, this has been discussed at length with Tom at Micropore, the mfg of the EAC. The hardness is not entirely the result of direct consumption of the absorbent, a significant part is a result of the effect of heat of reaction. And much of the hardened area is not actually completely exhausted of absorbent capacity... but for the purposes of a conservative evaluation it's sufficient to assume so. -- Mark Last edited by n2diving : 9th August 2007 at 02:43.
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9th August 2007, 04:35	#50 (permalink)
Gill Envy Shearwater Copis Divers Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,314	Re: Vision vs. Optima thanks Mark, have you found that this measuring technique matches your Co2 production calculations along the lines you would expect? eg: extrapolating the time it would take for you to produce Aprox 180 liters of CO2 more ore less results in some like 75% of scrubber spent. If those cacluations roughly match, it sounds like a promising measuring technique, making the EAC potentially more economical than previously thought without "pushing the limits". g Quote: (Originally Posted by n2diving) Yes, this has been discussed at length with Tom at Micropore, the mfg of the EAC. The hardness is not entirely the result of direct consumption of the absorbent, a significant part is a result of the effect of heat of reaction. And much of the hardened area is not actually completely exhausted of absorbent capacity... but for the purposes of a conservative evaluation it's sufficient to assume so. -- Mark __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
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