Sensors: which gas shall I have in the loop when not in use?
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lermontov
Contributor
if your prepared to use the cell youve taken out as a 'spare' surely it good enough to leave in
The driver was Teledyne. Teledyne where the largest manufacturers of O2 cells, and had been designing and manufacturing cells for rebreathers for the Navies of the world.
They decided that the 'risk' [1] of supplying cells for the general consumer market was far to high. They switched to only supplying cells for the medical and military use. Which left all the CCR manufactures (and users) with a problem.
AP, like a number of other manufacturers where forced into the position that they need to produce their own cells. It was carnage as a number of companies attempted to learn how to produce cells, and scale up the manufacturing. During that period, some cells where only last one or two days before they failed.
I was buying cells from a number of suppliers. I have to say AP where the best in terms of support, occasionally shipping cells to the address where I would be for a week/weekends diving.
broncobowsher
Contributor
Yes, but I don't run my cells until they have failed either. So it costs a little more. I have good cells. The ones that come out are near end of life. The last bit of life is being a spare. Better than a new cell be tossed because it aged out being a spare that was never used.
Is your suggestion to run cells until they fail and hope the spare you bought long ago is good?
Usind a cell untill it fails is no option for me at all. In the past I used them for 18 month in the rebreather, that worked fine until 2018. Then I switched from Inspiration to Liberty. Until then I had some cells failing after 1-12 month and now I had 2 cells failing after 15 month. Well "failing" is perhaps wrong. They past all the tests including 3.5 bar pO2 test but Liberty often kicks them out during dive. Sometimes one of them, sometimes both. So in my eyes they must be exchanged, you don't want to have 2 cells excluded and 2 working cells.
From now on I will exchange after 12 month working in the rebreather or earlier if necessary.
I will keep on changing all the sensors together, this makes a bit more sense for me, even if there are pros and cons.
From now on I will exchange after 12 month working in the rebreather or earlier if necessary.
I will keep on changing all the sensors together, this makes a bit more sense for me, even if there are pros and cons.
lermontov
Contributor
As mentioned earlier i change my cell when it shows a) current limiting b) 10% linearity variation c) its noticeably slow to respond d) it unexpectedly fails
Cells do wear out over time but if your using a cell lets say 4 times a week with higher po2 then it will deteriorate faster than if you are diving once every 2 months and is sitting around at .21 for most of that time so the date stamp on a cell means what ? its indicative. So i use the criteria as mentioned above, after 18 months is when i get nervous -I throw them out
Given you have a revo with 5 cells the chance of mutiple cells failing to the point you miss a dive is practically zero especially when you can replace a wayward cell by taking a good out of your nerd/dreams and put it in your controller even without replacing it with a spare and you still have one more cell than most CCRs - but im sure you know this
Worrying about having an unopened new cell not working is way too stressful for me, sure it does happen but id speculate of the millions of cells produced each year -on a percentage basis a dead new one is rare. In fact some retailers/distributors do not recommended to keep an old cell as a spare due it rattling around in a box somewhere getting knocked around- but thats another discussion.
Here we see why testing up to 3.5 bar makes much more sense then 1.0 bar only. Between 0 and 1 bar the green cell seems to be worst of them, lower voltage. But from 1 to 3.5 bar the green cell works perfectly linear. The yellow cell seems to be perfect when testing from 0 to 1 bar but becomes weak at 1.5 bar.
Testing up to 1 bar only: perhaps you kick out the green cell, definitely not the yello one.
Testing up to 3.5 bar: you keep the green one, you kick out the yellow one.
By the way testing was not perfectly made, in the beginning (first measuring point) there was not air in there but some nitrox, therefor wrong reading at 0.21 bar. My fault.
Testing up to 1 bar only: perhaps you kick out the green cell, definitely not the yello one.
Testing up to 3.5 bar: you keep the green one, you kick out the yellow one.
By the way testing was not perfectly made, in the beginning (first measuring point) there was not air in there but some nitrox, therefor wrong reading at 0.21 bar. My fault.
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Heat Miser
Contributor
@tbone1004 I read on you other posts that you tend to run a lower set point @ 1.2 on your CCR. Are you proposing for a 30 m dive to run a rich dil higher than your high setpoint and breathe it down? I was taught to target a dil mix with 1.1 PpO2 at max depth, when I asked why not 1.0 or 1.2 I never really got an answer? Feel free to move to new post if not relevant to O2 cell longevity strategies of the OP.
EDIT
moved question here at @broncobowsher encouragemet
What is your selection process for rich versus lean Dil mixes?
Incidentally I think that argues for using pretty rich dil mixes that are in line with what you are using for a setpoint. I.e. EAN32 at 30m/100ft instead of air where your dil flush validates function at 1.3 instead of 0.8. @tbone1004 I read on you other posts that you tend to run a lower set...
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