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Thread: Keep Me Alive... The cost of being cheap on sensors

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    Re: Keep Me Alive... The cost of being cheap on sensors

    Quote Originally Posted by rjack  View Original Post
    Same thing different unit happened here to Ron Akeson. 2 low failing cells led to hyperoxic loop and O2 tox fatality, with students in a class.
    I remember Jeff's thread on CCRX. Did anyone ever discover the age of his cells?

    Matt.

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    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
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    Re: Keep Me Alive... The cost of being cheap on sensors

    Quote Originally Posted by matthewoutram  View Original Post
    I remember Jeff's thread on CCRX. Did anyone ever discover the age of his cells?

    Matt.
    At least some were over 18 months and one in the 20-24 month window. I don't think that was written down anywhere, I heard that from another local WA instructor during my mod1 which was a few months after his death.

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    Re: Keep Me Alive... The cost of being cheap on sensors

    Quote Originally Posted by rjack  View Original Post
    At least some were over 18 months and one in the 20-24 month window. I don't think that was written down anywhere, I heard that from another local WA instructor during my mod1 which was a few months after his death.
    It's a pity that people truly don't understand how a sensor can fool you into thinking it is working fine when it is not. This is why I never use old-cells and don't use a pressure-pot. Both lure me into a false-sense of security.

    RIP to these guys, I'm sure we all learn from them.

    Matt.

  4. #14
    So many CCR So little etc Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase's Avatar
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    Re: Keep Me Alive... The cost of being cheap on sensors

    Quote Originally Posted by Chett.L  View Original Post
    Hi Mark,

    Wasn't there a case where (2) sensors died at the same time in a unit that had 3 sensors and it screwed up the voting logic.

    Best regards,

    I am strugling to see why this would cause anyone a problem if they dive their CCR properly


    I bet you he didnt spike his cells to 1.8ish on decent?

    I bet you he didnt manual add a bit of 02 during the dive to make sure his cells were reading OK above 1.3

    I bet you he totaly ignored the third cell error (or corect reading in this case) and didnt dill flush on low setpoint to confirm cell output against a known dill PP02 and bring the unit manualy slowly back to just past set point.


    THATS why he / she died, no other reasion


    Brand new fresh out of the bag cells can have exactly the same issue

    Cells less than 12 months old can have the same issue

    Age of cells is not a valid excuse IMHO

    However its obvious to me that somone who dives such old cells without proper cell management, was an accident waiting to happen


    I am not advocating diveing old cells

    But I am cirtainly not suporting ANY claim that regular cell replacement makes you safer

    12 years on CCR now and I have had new cell fail, new cells be current limited and cells fail after a few short months

    Complacency is the killer, not the cells

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    Re: Keep Me Alive... The cost of being cheap on sensors

    I'm curious if the cost of cells was much cheaper, say $25 a pop instead of $75-$100, if people would be more willing to change them at short intervals, of if they'd still use them beyond the expiration dates.

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    So many CCR So little etc Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase's Avatar
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    Re: Keep Me Alive... The cost of being cheap on sensors

    Quote Originally Posted by rjack  View Original Post
    At least some were over 18 months and one in the 20-24 month window. I don't think that was written down anywhere, I heard that from another local WA instructor during my mod1 which was a few months after his death.


    In about April every year ill buy three new cells. These are my new spare cells

    Then I remove my old cells one at a time over three dives and replace them with the new cells I baught LAST april (assuming I havent used any)

    Those cells could have been 8 months old the day I baught them and 20 months old the day i opened the pac and put them in my CCR

    Then I dive them for a year

    So by manufacture date, the cells could be getting on for three years old when i bin them but less than 1 year in use

    Done this for at least the last 8 years

    I have still suffered more cell failures on new cells than I have on old ones

    God forbid I cop it, please remember that I screwed up and got complacent about cell monitoring and testing and dont make excuses for me about the age of my cells. The chances of all three going out of range in such a way as id not notice had i been paying attention, is so slim as to be not worth bothering with

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    Re: Keep Me Alive... The cost of being cheap on sensors

    Quote Originally Posted by Mark Chase  View Original Post
    In about April every year ill buy three new cells. These are my new spare cells

    Then I remove my old cells one at a time over three dives and replace them with the new cells I baught LAST april (assuming I havent used any)

    Those cells could have been 8 months old the day I baught them and 20 months old the day i opened the pac and put them in my CCR

    Then I dive them for a year

    So by manufacture date, the cells could be getting on for three years old when i bin them but less than 1 year in use

    Done this for at least the last 8 years

    I have still suffered more cell failures on new cells than I have on old ones

    God forbid I cop it, please remember that I screwed up and got complacent about cell monitoring and testing and dont make excuses for me about the age of my cells. The chances of all three going out of range in such a way as id not notice had i been paying attention, is so slim as to be not worth bothering with

    You have more cell failures on new vs old cause you aren't diving with 2yo cells!


    I don't know the manufacture date on the cells vs the install date. I was told the youngest was about 18 months. We dive year round here and its easy for a professional do have several hours of bottom time a week. 100+ hours a year isn't hard or extreme. How many hours were on those cells? Who knows, but its unlikely they were on the shelf all winter.


    There was some confusion on the previous day and these 3 cells were rotated on the supposition that there was a wiring problem. In retrospect, there was one bad cell that day and another one went bad overnight or early in the next dive.


    Minus the rotating/bullet dodge, the whole incident is nearly identical to the instructor diving several year old cells in Oz, having 2 bad ones and toxing. I thought that was an AP unit but don't have time to confirm that incident.

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    Re: Keep Me Alive... The cost of being cheap on sensors

    Thankfully the AI cells are marked with a "Do not use after" date, that is 15 months after the manufacturing date. If you follow the rules you will never end up using cells that are 1 1/2 years or older. Since I have had heavily used cells fail just around the "do not use after" date, I don't keep old cells even if I could get another years use out of them in my O2 analysers.

    Yeah, 6-7 cells every year for 2 RBs is money, but have you looked into the cost of creamation and the obligitory mourners wake anytime in the last few years?

    Michael

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    Re: Keep Me Alive... The cost of being cheap on sensors

    Quote Originally Posted by michael-fisch  View Original Post
    Thankfully the AI cells are marked with a "Do not use after" date, that is 15 months after the manufacturing date. If you follow the rules you will never end up using cells that are 1 1/2 years or older. Since I have had heavily used cells fail just around the "do not use after" date, I don't keep old cells even if I could get another years use out of them in my O2 analysers.

    Yeah, 6-7 cells every year for 2 RBs is money, but have you looked into the cost of creamation and the obligitory mourners wake anytime in the last few years?

    Michael

    The ISC/Teledyne/vandergraph cells that Leon keeps in stock are marked with their test/pack date. Not sure how long the might be there for as they are rebadged, on the plus side they test every one before re-shrink wrapping and sealing. They are usually available within a few days of ordering.

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    Re: Keep Me Alive... The cost of being cheap on sensors

    I also quite like that AII cells come with a use by date and test reports. From talking to them, civilian Mk15x cells are made to order so it's a reasonable assumption they are not sitting on a shelf in god knows what kind of environment for a few months before installation. Reliability has been as good as if not better than TAI sensors. Interestingly AII rate their cells at 42 months expected life.

    I made my own cell checker. I don't think it is a £3-400 worth of uesful bit of kit. For 40 quid it is interesting to blow the cells once in a while and watch them as they age. I doubt they give any useful instantaneous info but cumulatively I've seen the high end linearity creep downwards over time and that rate of change is generally indicative of cell health. I change one out every 6 months so it's more an awareness exercise than anything. I used to think a pot was essential, now not so much. I certainly wouldn't recommend buying one.

    I also dive a low setpoint, 1.0 which on a HH is more like 0.93-0.96. I like knowing that the front of the linearity curve is just that little bit further away. For the diving I do, generally 50-85m, the difference in deco is minimal.

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