Preserving cell life?

jcolley · 1st May 2007, 20:38

So, as I'm looking at my Meg tonight, it occurs to me that there is an awful large volume of air (and therefore oxygen) that the cells are exposed to when the unit is not in use.

If the voltage produced by the cells is a function of oxygen percentage in air, would it makes sense that more useful life could be obtained by not exposing the cells to oxygen all the time? Sort of a lay-up condition comes to mind where the cells are left in the head, but using caps on the head to seal it. I'm not talking about making it pressure tight more than a couple of PSI, but just enough that you could purge the head and the surface the cells are exposed to by using a nitrogen blanket.

Any thoughts? Left field?

Jim

n2diving · 2nd May 2007, 01:02

This edited version from my post on a similar discussion on TDS, it's got some unneeded explanation for RBW readers but it answers the question...

I sell lots of oxygen sensors for use in analyzers and rebreathers, and I also sell some of the analyzers and rebreathers those sensors are used in... I've had very lengthy discussions with the manufacturers over these issues.... here is some information for your consideration...

The oxygen sensors in analyzers and rebreathers are complex devices, but fundamentally it's helpful to think of them as oxygen powered fuel cells. They operate on a chemical reaction, -- an oxygen sensor is a lead-oxygen battery consisting of a lead anode, an oxygen cathode made up of gold and a weak acid electrolyte, usually a 'secret formula' that is mostly potassium hydroxide. A great many factors affect this chemical reaction, some of the most important being pressure, temperature, humidity and of course the presence of oxygen. However, the factors that affect the chemical reaction as much, or more, are those factors inherent in the manufacturing process itself. The chemical reaction began the moment the cell was assembled, continued at predictable pace while the new cell sat in the special bag, and vigorously accelerates when the bag is opened and the cell is exposed to normal atmosphere.

How rebreather divers use and maintain their oxygen sensors and how divers analyzing their Nitrox mix for content use and maintain their oxygen sensors are two completely different situations.

Cells used in rebreathers are exposed to pressures of oxygen much greater than normally encountered in analyzing gas. As they age they become 'non-linear', meaning they are perfectly accurate for some conditions and very inaccurate for certain other conditions and this can have serious consequences for rebreather divers. Rebreather manufacturers recommend replacing the cells annually, long before they can become non-linear. The widely accepted absolute maximum lifespan of cells in rebreather applications is 18 months. No manufacturer recommends doing things to cells like vacuum packing, freezing, refrigerating, storing in inert gas because they have not tested what happens to cells when these things are done. They can tell you that based on their expert knowledge of the cells, these life-extending steps can and probably will cause minor improvements in the life of some components in the cell while damaging or having no effect on other components in the cell. They are almost certain to cause the cell to go non-linear faster than normal, to become unstable, affect the cell response time curves, and on and on.

So real world for a rebreather diver....

Case one: take three cells, install them in the rebreather, and leave them there. Treat the rebreather with respect, keep it at temperatures you are comfortable in (if you are too hot or too cold, so are the sensors).... at the end of 12 months, throw the perfectly good sensors away and install new ones. (BTW, these things are not precision devices, they are high failure items that have a long history of quality control issues with amazing variations from lot to lot... the really paranoid rebreather divers install three sensors from three different lots and stagger the installation over a period of time such as two or three months). IMO, and those of the manufacturers, this is the best course of action to follow.

Case two: another rebreather diver installs and removes the cells after each dive trip... carefully doing their favorite ritual to store the sensors to extend their life. At the end of twelve months the rebreather diver removes the sensors that have been handled in a manner that scares the crap out of the rebreather manufacturers, producing at best a perfectly good sensor or at worst a sensor that has any number of bizarre and unknown or unpredictable behaviors, and having removed them throws them away. Hopefully the diver survives case two, there have been a few accidents where handling of the cells have been implicated or even declared the proximate cause of the accident.

Case Three: See case one or two, except the rebreather manufacturers extremely strong warnings regarding cell replacement times are further ignored and the cells are continued to be used until failure. Hopefully the diver survives case three; even more fatalities are directly linked to old cells.

The experiences of the rebreather community have proven time and again that the life of the '36 month in air 10mv oxygen sensor' in rebreather applications is 12 to 18 months and with heavy use it's probably less.... (I do 200 hours a year and replace my perfectly good sensors every 6 to 8 months). It would seem most reasonable rebreather divers at this point would just follow manufacturer’s recommendations, but there are always those who feel the manufacturers have a 'hidden agenda' in the frequent replacement of oxygen sensors and choose their own path.

Now let’s visit a completely different situation, the use of oxygen sensors in analyzers. In this situation, we are almost always analyzing a known gas, i.e. we have an expectation regarding what's in the cylinder and are using the analyzer to confirm it. In this case do whatever you like to the sensor; if you think it will extend the life of the sensor that's fine... it's harmless. As long as you understand that the moment the analysis of the contents varies from expected by more than 1% you realize you do NOT know what's in the cylinder and take appropriate action. Oh, and don't use a sensor that’s been mishandled (i.e. vacuum packed, frozen, refrigerated, stored in inert gas, older than 36 months, over heated, desiccated, etc) to determine the oxygen content of an unknown gas, ever.

So how would I feel about using some kind of unproven life extension technique on oxygen sensors in cylinder contents analyzers? (I'll include 'sensor saver caps' and the like.) Well, recall the previous remarks about the huge number of factors that affect sensors? Many of the most important ones have nothing to do with environmental factors, they have to do with variations in the manufacturing process... two important factors being the cleanliness of the lead anode and the exact composition of electrolyte; these vary significantly from batch to batch and sensor to sensor.... so much so that the sensors have a little electronic circuit in them that factory calibrates in each sensor to produce the final target output mv range. These factors have FAR more effect on the life of the sensor than any dubious benefit from aftermarket sensor life extension techniques. Just because some one used some life extension technique on the sensor and that sensor 'lasted longer' is meaningless... too many factors at work to have any chance of knowing what effect, if any, the life extension technique had on the life of the sensor. To be frank, a harmless waste of time if you are using the analyzer to confirm cylinder contents are as expected and otherwise a risky practice.

vacuum pack your sensor? No. Rupture membrane, create bubbles in electrolyte.

freeze your sensor? NO!

refrigerate your sensor? Depends on the brand, but no for the Teledyne brand (10C min) and no would be best practice for all brands.

store your sensor in inert gas? Maybe, but best practice would be no due to risk of affecting moisture content (i.e. drying out) of sensor.

Seal it in bag or with cap? Harmless, but probably would not make a significant difference in practice. Remember, some components are aging regardless of being deprived of oxygen.

One final thought, extending the life of an oxygen sensor is a 'risk vs. reward' decision. Typical life of an analyzer sensor is somewhere between 24 and 48 months (I've seen plenty of them last 60 months and longer) and it costs about $70. If you assume the aftermarket processes add one year to the life, you saved a few dollars and at an unknown but significant risk.

teksimple · 2nd May 2007, 01:34

WoW. Well put, Mark.

***ScubaDadMiami*** · 2nd May 2007, 04:24

Excellent information, Mark. If I may quote Kevin Juergensen (HeyYDude) (as stated in the Juergensen manual, and written by Joe Radomski (JRadomski)):

"Some divers believe sensors should be disconnected and store in containers flooded with Nitrogen or Helium. In practice, these divers get about a year of service out of the sensors. Others believe that the sensors should be removed and stored in the refrigerator. In practice, these divers get 12 months of service out of the sensors. It would not be difficult to imagine [that] flushing the sensors with Nitrogen or Helium, packing them in an airtight container, and storing in the refrigerator, the expected service life would be as much as 365 days."

Combining this with what Mark said above, I leave my sensors in my unit, opening up the head to dry out between uses. I stagger replacement in month 10, 11 and 12, and I use sensors recommended by the manufacturer.

I am no expert. I just follow the directions. I don't take any chances beyond the recommendations of the manufacturer of my unit.

***Decodiver*** · 2nd May 2007, 07:15

This subject & peoples ideas always amazes me.

You spend $$$$$$$$$$$$ on a Closed Circuit Rebreather and then want to prolong the life of your consumables?

These things, to a certain degree, decide whether you live or die.

If you have any doubts whatsoever about your cells, ditch them.

There are more and more outlets offering cells at a reasonable price now.

It's like watching someone take a cell out of the sealed packet on a boat, fit it & go diving.

Cells need to wake up from inert gas.

Cheers,

Dave Cooper.

jcolley · 2nd May 2007, 12:32

Perhaps I should clarify my intent. There is no way I would ever consider using a cell beyond one year of service life.

I think most people would find it hard to argue that the performance of a cell will degrade over time. As a person with an engineering mindset from many years in the world of nuclear power, one of the things I am always looking to do is minimize unnecessary stresses on equipment if for no other reason than good engineering practice. This most certainly applies to anything which I might consider to be life support equipment.

It does make sense to me however that if there is some way I could contribute to getting the best possible performance from a batch of cells during that year of service life, it would be worth at least discussing. If a cell continues to degrade as a result of reaction with oxygen, then it would make sense not to expose it to oxygen when not int use. Would there be any noticeable improvement? Probably not, then it's just a matter of perceived increase in mean time between failure of the cell versus effort required to purge them. Not something you could easily measure without years of testing...

Again, I have no experience in this area and felt sure that someone on the board would, so that's why I brought it up. :D Thanks for the input n2diving and ScubaDadMiami, very useful information.

I can't imagine that people would actually disconnect the cells after every use, the mechanical stress on the molex contacts from unnecessary operation and the increased risk of tugging too hard and pulling a wire off seem too high for me...

n2diving · 2nd May 2007, 13:28

Quote: (Originally Posted by jcolley)

If a cell continues to degrade as a result of reaction with oxygen, then it would make sense not to expose it to oxygen when not int use.

The answer I had from one of the experts regarding the effects of storage in inert gas was a definate 'not sure'. The cells are manufactured and sealed in ordinary air in a somewhat gas permeable bag... the cell will deplete most but not all of the oxygen in the bag. As many here can attest, the cell can and does degrade in an unopened bag and the vendors say that the shelf life is two years. Thus there are several factors at work determining the life of the cell, not just the exposure to oxygen.

If you were to store them in inert gas, what would happen? As mentioned earlier, storage in inert gas would introduce issue of the 'wake up' time on the cell and if the inert gas is other than nitrogen what effect does this have? Certainly some aging processes would continue even in inert gas, but if some components age differently than others on a cell previous exposed to oxygen how does it affect the cell behavior or performance? Another concern mentioned is that pure inert gas contains no moisture, would this have a dessicating affect on the cells? The expert I talked to was most concerned about drying of the electrolyte. Since no testing has been performed to answer these questions, it seems like best practice not to store your sensors in inert gas.

The recommended way to get the 'best' performance from your sensors: store them at cool room temperatures in ordinary air.... this was what they were designed for.

I had not considered the mechanical stresses of unneccessary removal/replacement of cells. But one broken wire in a harness requiring a replacement is going to cost more money than you might have saved from trying to extend the life of the cell.

curt · 2nd May 2007, 16:14

Many thanks, n2diving. Good info.

have some green...

n2diving · 17th June 2007, 13:30

I've become aware of a practice that probably will significantly shorten life of oxygen sensors in rebreather use. I've noticed that it's not unusual for divers to leave an elevated level of oxygen in their loop with their sensors. This can happen when the unit is left overnight (or longer) before cleaning, or following a calibration when precedes the dive by a signficant amount of time, or any number of other circumstances.

Best practice for maintaining sensor life would be to flush the loop with dil or expose to air when practical.

-- Mark

Skipbreather · 17th June 2007, 17:08

Quote: (Originally Posted by jcolley)

So, as I'm looking at my Meg tonight, it occurs to me that there is an awful large volume of air (and therefore oxygen) that the cells are exposed to when the unit is not in use.

If the voltage produced by the cells is a function of oxygen percentage in air, would it makes sense that more useful life could be obtained by not exposing the cells to oxygen all the time? Sort of a lay-up condition comes to mind where the cells are left in the head, but using caps on the head to seal it. I'm not talking about making it pressure tight more than a couple of PSI, but just enough that you could purge the head and the surface the cells are exposed to by using a nitrogen blanket.

Any thoughts? Left field?

Jim

Just a little photo essay of how I attempt to preserve cells. Change out still done on schedule, but attempt is to minimize degradation in the mean time. Might help, might not, but figure it can't hurt.

Material is 1/2 inch ~ 13 mm moderately dense closed cell foam cut from a back packer's sleeping pad.

1st May 2007, 20:38	#1 (permalink)
jcolley New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Megalodon Not Bought Yet Join Date: Oct 2006 Location: Port Orchard, WA Posts: 57	Preserving cell life? So, as I'm looking at my Meg tonight, it occurs to me that there is an awful large volume of air (and therefore oxygen) that the cells are exposed to when the unit is not in use. If the voltage produced by the cells is a function of oxygen percentage in air, would it makes sense that more useful life could be obtained by not exposing the cells to oxygen all the time? Sort of a lay-up condition comes to mind where the cells are left in the head, but using caps on the head to seal it. I'm not talking about making it pressure tight more than a couple of PSI, but just enough that you could purge the head and the surface the cells are exposed to by using a nitrogen blanket. Any thoughts? Left field? Jim
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2nd May 2007, 01:02	#2 (permalink)
n2diving www.RebreatherExpress.com Current Rebreather/s: Optima Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Florida, USA Posts: 283	Re: Preserving cell life? This edited version from my post on a similar discussion on TDS, it's got some unneeded explanation for RBW readers but it answers the question... I sell lots of oxygen sensors for use in analyzers and rebreathers, and I also sell some of the analyzers and rebreathers those sensors are used in... I've had very lengthy discussions with the manufacturers over these issues.... here is some information for your consideration... The oxygen sensors in analyzers and rebreathers are complex devices, but fundamentally it's helpful to think of them as oxygen powered fuel cells. They operate on a chemical reaction, -- an oxygen sensor is a lead-oxygen battery consisting of a lead anode, an oxygen cathode made up of gold and a weak acid electrolyte, usually a 'secret formula' that is mostly potassium hydroxide. A great many factors affect this chemical reaction, some of the most important being pressure, temperature, humidity and of course the presence of oxygen. However, the factors that affect the chemical reaction as much, or more, are those factors inherent in the manufacturing process itself. The chemical reaction began the moment the cell was assembled, continued at predictable pace while the new cell sat in the special bag, and vigorously accelerates when the bag is opened and the cell is exposed to normal atmosphere. How rebreather divers use and maintain their oxygen sensors and how divers analyzing their Nitrox mix for content use and maintain their oxygen sensors are two completely different situations. Cells used in rebreathers are exposed to pressures of oxygen much greater than normally encountered in analyzing gas. As they age they become 'non-linear', meaning they are perfectly accurate for some conditions and very inaccurate for certain other conditions and this can have serious consequences for rebreather divers. Rebreather manufacturers recommend replacing the cells annually, long before they can become non-linear. The widely accepted absolute maximum lifespan of cells in rebreather applications is 18 months. No manufacturer recommends doing things to cells like vacuum packing, freezing, refrigerating, storing in inert gas because they have not tested what happens to cells when these things are done. They can tell you that based on their expert knowledge of the cells, these life-extending steps can and probably will cause minor improvements in the life of some components in the cell while damaging or having no effect on other components in the cell. They are almost certain to cause the cell to go non-linear faster than normal, to become unstable, affect the cell response time curves, and on and on. So real world for a rebreather diver.... Case one: take three cells, install them in the rebreather, and leave them there. Treat the rebreather with respect, keep it at temperatures you are comfortable in (if you are too hot or too cold, so are the sensors).... at the end of 12 months, throw the perfectly good sensors away and install new ones. (BTW, these things are not precision devices, they are high failure items that have a long history of quality control issues with amazing variations from lot to lot... the really paranoid rebreather divers install three sensors from three different lots and stagger the installation over a period of time such as two or three months). IMO, and those of the manufacturers, this is the best course of action to follow. Case two: another rebreather diver installs and removes the cells after each dive trip... carefully doing their favorite ritual to store the sensors to extend their life. At the end of twelve months the rebreather diver removes the sensors that have been handled in a manner that scares the crap out of the rebreather manufacturers, producing at best a perfectly good sensor or at worst a sensor that has any number of bizarre and unknown or unpredictable behaviors, and having removed them throws them away. Hopefully the diver survives case two, there have been a few accidents where handling of the cells have been implicated or even declared the proximate cause of the accident. Case Three: See case one or two, except the rebreather manufacturers extremely strong warnings regarding cell replacement times are further ignored and the cells are continued to be used until failure. Hopefully the diver survives case three; even more fatalities are directly linked to old cells. The experiences of the rebreather community have proven time and again that the life of the '36 month in air 10mv oxygen sensor' in rebreather applications is 12 to 18 months and with heavy use it's probably less.... (I do 200 hours a year and replace my perfectly good sensors every 6 to 8 months). It would seem most reasonable rebreather divers at this point would just follow manufacturer’s recommendations, but there are always those who feel the manufacturers have a 'hidden agenda' in the frequent replacement of oxygen sensors and choose their own path. Now let’s visit a completely different situation, the use of oxygen sensors in analyzers. In this situation, we are almost always analyzing a known gas, i.e. we have an expectation regarding what's in the cylinder and are using the analyzer to confirm it. In this case do whatever you like to the sensor; if you think it will extend the life of the sensor that's fine... it's harmless. As long as you understand that the moment the analysis of the contents varies from expected by more than 1% you realize you do NOT know what's in the cylinder and take appropriate action. Oh, and don't use a sensor that’s been mishandled (i.e. vacuum packed, frozen, refrigerated, stored in inert gas, older than 36 months, over heated, desiccated, etc) to determine the oxygen content of an unknown gas, ever. So how would I feel about using some kind of unproven life extension technique on oxygen sensors in cylinder contents analyzers? (I'll include 'sensor saver caps' and the like.) Well, recall the previous remarks about the huge number of factors that affect sensors? Many of the most important ones have nothing to do with environmental factors, they have to do with variations in the manufacturing process... two important factors being the cleanliness of the lead anode and the exact composition of electrolyte; these vary significantly from batch to batch and sensor to sensor.... so much so that the sensors have a little electronic circuit in them that factory calibrates in each sensor to produce the final target output mv range. These factors have FAR more effect on the life of the sensor than any dubious benefit from aftermarket sensor life extension techniques. Just because some one used some life extension technique on the sensor and that sensor 'lasted longer' is meaningless... too many factors at work to have any chance of knowing what effect, if any, the life extension technique had on the life of the sensor. To be frank, a harmless waste of time if you are using the analyzer to confirm cylinder contents are as expected and otherwise a risky practice. vacuum pack your sensor? No. Rupture membrane, create bubbles in electrolyte. freeze your sensor? NO! refrigerate your sensor? Depends on the brand, but no for the Teledyne brand (10C min) and no would be best practice for all brands. store your sensor in inert gas? Maybe, but best practice would be no due to risk of affecting moisture content (i.e. drying out) of sensor. Seal it in bag or with cap? Harmless, but probably would not make a significant difference in practice. Remember, some components are aging regardless of being deprived of oxygen. One final thought, extending the life of an oxygen sensor is a 'risk vs. reward' decision. Typical life of an analyzer sensor is somewhere between 24 and 48 months (I've seen plenty of them last 60 months and longer) and it costs about $70. If you assume the aftermarket processes add one year to the life, you saved a few dollars and at an unknown but significant risk. Last edited by n2diving : 2nd May 2007 at 02:01.
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2nd May 2007, 01:34	#3 (permalink)
teksimple RBW Member Current Rebreather/s: MK 15.X Other Rebreather/s: Sport Kiss Classic Kiss Join Date: Apr 2005 Location: Hawaii Posts: 589	Re: Preserving cell life? WoW. Well put, Mark.
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2nd May 2007, 04:24	#4 (permalink)
*ScubaDadMiami* Moderator Current Rebreather/s: Optima Other Rebreather/s: Join Date: Sep 2005 Location: Florida, USA Posts: 2,421	Re: Preserving cell life? Excellent information, Mark. If I may quote Kevin Juergensen (HeyYDude) (as stated in the Juergensen manual, and written by Joe Radomski (JRadomski)): "Some divers believe sensors should be disconnected and store in containers flooded with Nitrogen or Helium. In practice, these divers get about a year of service out of the sensors. Others believe that the sensors should be removed and stored in the refrigerator. In practice, these divers get 12 months of service out of the sensors. It would not be difficult to imagine [that] flushing the sensors with Nitrogen or Helium, packing them in an airtight container, and storing in the refrigerator, the expected service life would be as much as 365 days." Combining this with what Mark said above, I leave my sensors in my unit, opening up the head to dry out between uses. I stagger replacement in month 10, 11 and 12, and I use sensors recommended by the manufacturer. I am no expert. I just follow the directions. I don't take any chances beyond the recommendations of the manufacturer of my unit. __________________ Howard Packer IANTD CCR Instructor Miami Beach, Florida CCRDiveTraining.com
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2nd May 2007, 07:15	#5 (permalink)
*Decodiver* Administrator Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jan 2005 Location: Geneva Posts: 2,260	Re: Preserving cell life? This subject & peoples ideas always amazes me. You spend $$$$$$$$$$$$ on a Closed Circuit Rebreather and then want to prolong the life of your consumables? These things, to a certain degree, decide whether you live or die. If you have any doubts whatsoever about your cells, ditch them. There are more and more outlets offering cells at a reasonable price now. It's like watching someone take a cell out of the sealed packet on a boat, fit it & go diving. Cells need to wake up from inert gas. Cheers, Dave Cooper. __________________ CCR/OC Trimix Instructor Trainer CCR Training to Mixed Gas in Switzerland, France, UK & Germany on Megalodon/COPIS-Megalodon/KISS/Sport KISS/Ouroboros/rEvo/Inspiration/Evolution/Sentinel www.zerogravitydiving.com Rebreather World Terms & Conditions
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2nd May 2007, 12:32	#6 (permalink)
jcolley New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Megalodon Not Bought Yet Join Date: Oct 2006 Location: Port Orchard, WA Posts: 57	Re: Preserving cell life? Perhaps I should clarify my intent. There is no way I would ever consider using a cell beyond one year of service life. I think most people would find it hard to argue that the performance of a cell will degrade over time. As a person with an engineering mindset from many years in the world of nuclear power, one of the things I am always looking to do is minimize unnecessary stresses on equipment if for no other reason than good engineering practice. This most certainly applies to anything which I might consider to be life support equipment. It does make sense to me however that if there is some way I could contribute to getting the best possible performance from a batch of cells during that year of service life, it would be worth at least discussing. If a cell continues to degrade as a result of reaction with oxygen, then it would make sense not to expose it to oxygen when not int use. Would there be any noticeable improvement? Probably not, then it's just a matter of perceived increase in mean time between failure of the cell versus effort required to purge them. Not something you could easily measure without years of testing... Again, I have no experience in this area and felt sure that someone on the board would, so that's why I brought it up. :D Thanks for the input n2diving and ScubaDadMiami, very useful information. I can't imagine that people would actually disconnect the cells after every use, the mechanical stress on the molex contacts from unnecessary operation and the increased risk of tugging too hard and pulling a wire off seem too high for me...
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2nd May 2007, 13:28	#7 (permalink)
n2diving www.RebreatherExpress.com Current Rebreather/s: Optima Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Florida, USA Posts: 283	Re: Preserving cell life? Quote: (Originally Posted by jcolley) If a cell continues to degrade as a result of reaction with oxygen, then it would make sense not to expose it to oxygen when not int use. The answer I had from one of the experts regarding the effects of storage in inert gas was a definate 'not sure'. The cells are manufactured and sealed in ordinary air in a somewhat gas permeable bag... the cell will deplete most but not all of the oxygen in the bag. As many here can attest, the cell can and does degrade in an unopened bag and the vendors say that the shelf life is two years. Thus there are several factors at work determining the life of the cell, not just the exposure to oxygen. If you were to store them in inert gas, what would happen? As mentioned earlier, storage in inert gas would introduce issue of the 'wake up' time on the cell and if the inert gas is other than nitrogen what effect does this have? Certainly some aging processes would continue even in inert gas, but if some components age differently than others on a cell previous exposed to oxygen how does it affect the cell behavior or performance? Another concern mentioned is that pure inert gas contains no moisture, would this have a dessicating affect on the cells? The expert I talked to was most concerned about drying of the electrolyte. Since no testing has been performed to answer these questions, it seems like best practice not to store your sensors in inert gas. The recommended way to get the 'best' performance from your sensors: store them at cool room temperatures in ordinary air.... this was what they were designed for. I had not considered the mechanical stresses of unneccessary removal/replacement of cells. But one broken wire in a harness requiring a replacement is going to cost more money than you might have saved from trying to extend the life of the cell.
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2nd May 2007, 16:14	#8 (permalink)
curt RBW Member Current Rebreather/s: Other CCR Dolphin Other Rebreather/s: Not Bought Yet Inspiration Classic Classic Kiss MK 15.X Other CCR Dolphin Join Date: Jul 2006 Location: Rockville, MD USA Posts: 112	Re: Preserving cell life? Many thanks, n2diving. Good info. have some green...
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17th June 2007, 13:30	#9 (permalink)
n2diving www.RebreatherExpress.com Current Rebreather/s: Optima Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Florida, USA Posts: 283	Re: Preserving cell life? -- an addendum I've become aware of a practice that probably will significantly shorten life of oxygen sensors in rebreather use. I've noticed that it's not unusual for divers to leave an elevated level of oxygen in their loop with their sensors. This can happen when the unit is left overnight (or longer) before cleaning, or following a calibration when precedes the dive by a signficant amount of time, or any number of other circumstances. Best practice for maintaining sensor life would be to flush the loop with dil or expose to air when practical. -- Mark
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