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  1. #1
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    IANTD Cell Presentation

    This is related to my earlier thread on limiting and linearity.

    It is an American presenter though. (Gobfish u have been alerted).

    https://youtu.be/x7tqnBn6XVo

  2. #2
    Sorry for being a dick jb2cool's Avatar
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    I was listening to this thinking it might have been a presentation originally recorded in the early 2000's and to my surprise it was published yesterday.

    Not impressed at all with the audio quality or presenting at all.

  3. #3
    Last of the Mohicans gobfish1's Avatar
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    Hard going m8 almost fell a sleep.
    till near the end when he started talking bollox
    About lieing to your Shearwater. ( Like my O2 cell give two feeks what my helium content is )
    Don't know of divers telling pork pies about O2 content lol no advantage to that at all

    I'd rather use a known gas to verify than all the bollox with mil volts.
    6 out of 10 for content
    5 out of 10 for comedy value .
    He's a few years to go before getting the guru badge

    Ps
    So now you can't dive your breather if your computer don't do mil volts or give you a po2 based on the dill cylinder or other gas in the list your using . Lol



    What did you take from it JonG. Maybe I missed something.
    Thanks for the link and post at least it's dive related.

    Kiven gurr interview on dirty dozen last week was ok . If you haven't seen it yet .
    Its normaly a bit of a back slapping club , but I enjoyed the KG interview.

    And spacex has keeped me entertained this week .
    Last edited by gobfish1; 04-06-2020 at 06:53 PM.
    None diver as of 2018.

  4. #4
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    Yeah watched the KG one and Richie Kohler was ok, purely for something different Kirk Krack was a crack. Great name.

    I knew pretty much all of the cell stuff as per my thread, but at the time it filled some gaps and allowed me to understand mv and po2 relationships, along with potential final loop po2 based on a measured linearity deviation.

    He lie us only relevant if you need to dil flush and verify mv as opposed to po2 at current depth.

    Not my bag lying about the he tho so was irrelevant.

    Quality was shocking tho.

  5. #5
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    Quote Originally Posted by JonG View Post
    Yeah watched the KG one and Richie Kohler was ok, purely for something different Kirk Krack was a crack. Great name.

    I knew pretty much all of the cell stuff as per my thread, but at the time it filled some gaps and allowed me to understand mv and po2 relationships, along with potential final loop po2 based on a measured linearity deviation.

    He lie us only relevant if you need to dil flush and verify mv as opposed to po2 at current depth.

    Not my bag lying about the he tho so was irrelevant.

    Quality was shocking tho.
    I didn't watch it all just skimmed it - but the presenter doesn't understand PO2 and mV if he's writing down mV on a piece of tape and checking mV on a dive...

  6. #6
    Coastal Member dwhitlow's Avatar
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    Quote Originally Posted by graham_hk View Post
    I didn't watch it all just skimmed it - but the presenter doesn't understand PO2 and mV if he's writing down mV on a piece of tape and checking mV on a dive...
    Yeah, I couldn't cope with the voice so just skimmed the slides. Nothing too exciting and I can't see the point in worrying about mV readings when calibration converts that to something I need to know. There were a few useful tips for anyone who didn't watch the John Lamb presentations at Eurotek:
    - maximum life of a cell is 12 months in unit
    - change one cell every four months
    - avoid cells from same batch
    - check cells at end of dive (O2 flush near 6m is simplest).

  7. #7
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    Quote Originally Posted by dwhitlow View Post
    Yeah, I couldn't cope with the voice so just skimmed the slides. Nothing too exciting and I can't see the point in worrying about mV readings when calibration converts that to something I need to know. There were a few useful tips for anyone who didn't watch the John Lamb presentations at Eurotek:
    - maximum life of a cell is 12 months in unit
    - change one cell every four months
    - avoid cells from same batch
    - check cells at end of dive (O2 flush near 6m is simplest).
    I replace my cells, 3 at a time, 12 months from date of manufacture and in my opinion each one of those 4 tips are flawed for following reasons

    1) I don't think there is any way to monitor shelf life of a cell - stored or in a rebreather is the same thing for me - so I replace based on manufacture date not date of first use.
    2) Changing single cells every 4months introduces a logistical issue and I find it much easier to buy cells at once. Furthermore, having cells of differing ages introduces a worse problem which is differential in response time rather than fix a perceived issue like bad batch (no 3)
    3) cells manufacture is cottage industry (there are only 3 cell manufacturers for diving (Vandagraph, NRC and AI)) and they don't follow true mass production or batch manufacture - there is no evidence that there is an increase in failures between or within different manufacture dates. If the manufacturer does not use a new and tracked batch of raw materials for each manufacturing run then there is no benefit to aim for different batches... why complicate matters with trying to get different batches which don't exist.
    4) I am least interested in the cell health at the end of the dive and in reality this introduces a false sense of security, i.e., cells were fine at end of last dive they must be fine now. Notwithstanding, it could be days/weeks (and at the moment months) in between dives - flushing at the end of the dive does very little. verifying cell function only tells you the cells are reading correctly at that time and not give you any indication of future efficacy - I therefore think its a wise strategy to not trust any cells at any time - cells can and do fail much better to monitor closely and never absolutely trust the PO2 reading to the actual loop PO2 and its better to be aware of signs the rebreather is not functioning correctly (loop volume and solenoid activity will give alot of information).

  8. #8
    Coastal Member dwhitlow's Avatar
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    Quote Originally Posted by graham_hk View Post
    I replace my cells, 3 at a time, 12 months from date of manufacture and in my opinion each one of those 4 tips are flawed for following reasons
    Your way works for you and mine works for me. We each have logic to support our different approach.
    We can agree to disagree I trust?

    In truth, your last point is the key point. Never trust an oxygen sensor!
    Quote Originally Posted by graham_hk View Post
    1) I don't think there is any way to monitor shelf life of a cell - stored or in a rebreather is the same thing for me - so I replace based on manufacture date not date of first use.
    Agreed they come with a date and I only put new cells in and it is easy to track.
    Quote Originally Posted by graham_hk View Post
    2) Changing single cells every 4months introduces a logistical issue and I find it much easier to buy cells at once. Furthermore, having cells of differing ages introduces a worse problem which is differential in response time rather than fix a perceived issue like bad batch (no 3)
    It is hardly difficult to track the serial numbers, dates and position of 4 cells! Anyone struggling with that should stick to a snorkel!

    As for response times, I've seen little variation and deem that to be a non-issue as they usually are pretty close.
    Quote Originally Posted by graham_hk View Post
    3) cells manufacture is cottage industry (there are only 3 cell manufacturers for diving (Vandagraph, NRC and AI)) and they don't follow true mass production or batch manufacture - there is no evidence that there is an increase in failures between or within different manufacture dates. If the manufacturer does not use a new and tracked batch of raw materials for each manufacturing run then there is no benefit to aim for different batches... why complicate matters with trying to get different batches which don't exist.
    I am only going by what John Lamb said. What would he know anyway? Also, I do recall a seeing quite a few folk having issues with a particular batch of AP cells (Jan18?) so maybe there is some batch consistency in the cottage industry.
    Quote Originally Posted by graham_hk View Post
    4) I am least interested in the cell health at the end of the dive and in reality this introduces a false sense of security, i.e., cells were fine at end of last dive they must be fine now.
    There is limited value in surface tests, or start of dive tests, as the conditions are pretty benign. After about 20 minutes the scrubber is at full temperature, the humity 100% and mixed gases gases in the loop make a less optimal environment and the most likely time for a cell to fail. A cell that comes home from that should be fine for another dive. However....
    Quote Originally Posted by graham_hk View Post
    Notwithstanding, it could be days/weeks (and at the moment months) in between dives - flushing at the end of the dive does very little. verifying cell function only tells you the cells are reading correctly at that time and not give you any indication of future efficacy
    these are unusual times and that test is indeed of limited value due to the extended surface intervals.
    Quote Originally Posted by graham_hk View Post
    - I therefore think its a wise strategy to not trust any cells at any time - cells can and do fail much better to monitor closely and never absolutely trust the PO2 reading to the actual loop PO2 and its better to be aware of signs the rebreather is not functioning correctly (loop volume and solenoid activity will give alot of information).
    We can agree on that.

  9. #9
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    Quote Originally Posted by dwhitlow View Post
    Your way works for you and mine works for me. We each have logic to support our different approach.
    We can agree to disagree I trust?
    We can indeed - it is after all only our opinions that we are right

    Quote Originally Posted by dwhitlow View Post
    In truth, your last point is the key point. Never trust an oxygen sensor!
    Yes absolutely. Any testing pre or post dive will only tell you that the cell read correct at the time of testing under the test conditions - if you trust cells to be correct on that basis you are on your way to an incident

  10. #10
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    Why is different response time any issue at all?
    I've never noticed it but I'm on MCCR, I'd probably not be too bothered if I did.

    Do old ones get slow and lazy?


 
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