+ Reply to Thread
Page 2 of 5 FirstFirst 1 2 3 4 5 LastLast
Results 11 to 20 of 43

Thread: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

  1. #11
    RBW Member Apeturbo is an unknown quantity at this point Apeturbo's Avatar
    Join Date
    Jun 2010
    Location
    Italy - Toscana - Versilia
    Posts
    30
    Custom Dolphin mCCR

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    It's seems like a friend of mine...
    40 meters dive, 90 minutes; during all dive a cell wasn't ok, displaying much less (about 0,90). At about 70 minutes (18m depth) warning beep starts and solenoid flushed o2.
    He took EAN50 bailout gas and went out.
    The day after i've checked the 3 cells at 0.21, 1.00 and 1.50 of ppo2.
    one of them was compleately gone, 9 mv @ 0.21, 30mv max reading.
    The two others were very unlinear.
    They were dated Jan 2012, but used for less than 10 dives.
    Just for courious, i've tested an old AP cell dated 2007 and used on a spare analyzer and still works very good.
    I think that sensors are the worst friend of a reb diver... they are unstable, fragile and EXPENSIVE.

    Daniele from Italy

  2. #12
    Capt/ Instructor
    tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1's Avatar
    Join Date
    Mar 2006
    Location
    Long Island, NY
    Posts
    406
    SF2 | rEvo

    PRISM Topaz

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    Quote Originally Posted by jaksel  View Original Post
    Cell 1 was rising, but the others were still fair to me. Here I made my great misjudgment and thought that no 1 was the wrong cell and the other worked fine... So I just checked that I felt OK and continued the dive.
    Scary on so many levels.

    This is the Open Circuit equivelent of saying, "I reached bottom, manifold exploded and raging torrents of gas continued to escape over my shoulder. Luckily the explosion didn't kill me so I shrugged it off. I then saw a turtle and decided to chase it."

  3. #13
    Jakob Selbing jaksel will become famous soon enough jaksel will become famous soon enough jaksel will become famous soon enough jaksel's Avatar
    Join Date
    Oct 2008
    Location
    Stockholm
    Posts
    178
    AP Evolution+

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    Quote Originally Posted by qazwsx  View Original Post
    It's not in the story so I was curious how the predive cell calibration went with O2?

    Also not in the story, did your friend do a 6m O2 flush at the start of the dive to check for limited cells?
    As far as I know, the pre-dive calibration was successful.

    If you look at the image I attached, you'll see that no O2 flush was made at the start of the dive.

    Quote Originally Posted by PatB  View Original Post
    How old and what brand cells?
    I was told the cells were about 1 year old each, and I think they were bought from APD.

    Quote Originally Posted by paca_mike  View Original Post
    Do you think , it's possible to know the diluant gas and bail out gas during the dives
    Yes, the diluent used was trimix 17/35.

  4. #14
    Jakob Selbing jaksel will become famous soon enough jaksel will become famous soon enough jaksel will become famous soon enough jaksel's Avatar
    Join Date
    Oct 2008
    Location
    Stockholm
    Posts
    178
    AP Evolution+

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    Quote Originally Posted by Paul S  View Original Post
    Also, through it all I wonder why controllers (All controllers, not just APD) don't notice they're injecting O2, and we're descending, but the readings aren't rising. Surely that's a detectable cause for concern.
    It has crossed my mind more than once that it would be quite possible to build a smarter controller that does more than just injecting any amount of O2 to keep the measured ppO2 close to the setpoint.

    E.g. a controller could report the current O2 injection rate to the diver, and trigger a warning if it drifts beyond reasonable limits, perhaps also taking into account changes in depth.

    Or as you suggested, the depth changes but the ppO2 does not change accordingly.

  5. #15
    Capt/ Instructor
    tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1's Avatar
    Join Date
    Mar 2006
    Location
    Long Island, NY
    Posts
    406
    SF2 | rEvo

    PRISM Topaz

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    Quote Originally Posted by jaksel  View Original Post
    It has crossed my mind more than once that it would be quite possible to build a smarter controller that does more than just injecting any amount of O2 to keep the measured ppO2 close to the setpoint.

    E.g. a controller could report the current O2 injection rate to the diver, and trigger a warning if it drifts beyond reasonable limits, perhaps also taking into account changes in depth.

    Or as you suggested, the depth changes but the ppO2 does not change accordingly.
    It would be incredibly hard to calculate an expected O2 addition rate with a dive computer.

    You would need ways to monitor depth, O2 injection volume rates (which could change if you're solenoid is having issues or clogged even a little), real time physical O2 metabolism in the diver, diluent addition volume, exhausted gas volumes (from OPV, diver's nose, lips, mask clearing), loop volume, etc. These are all factors outside of the unit's control that would have to be monitored to do it correctly.

    Or you could buy an MCCR where you're brain is the computer and you know definitively how often your finger has been hitting the add button and have a decent idea about all of the above.

  6. #16
    RBW Member Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe is a glorious beacon of light Joe's Avatar
    Join Date
    Oct 2005
    Location
    Florida, USA
    Posts
    485
    Megaladon

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    That is exactly why I dive my unit manually and use the electronics as a fail safe. I also keep my setpoint at 1.0 because that is what I have calibrated to so the possibility of cells being linear within that range is reduced.

    Quote Originally Posted by tmccar1  View Original Post
    ......Or you could buy an MCCR where you're brain is the computer and you know definitively how often your finger has been hitting the add button and have a decent idea about all of the above.

  7. #17
    When In Doubt - Bail Out Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E is a glorious beacon of light Jeppe_E's Avatar
    Join Date
    Nov 2011
    Location
    Sweden
    Posts
    1,391
    Poseidon 7 - 100M Tech

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    Quote Originally Posted by jaksel  View Original Post
    E.g. a controller could report the current O2 injection rate to the diver, and trigger a warning if it drifts beyond reasonable limits, perhaps also taking into account changes in depth.
    Probably gonna get flamed for this, but the Poseidon MkVI sort of does this. It tracks the O2 consumption and add more if the workload suddenly increases or lay off on the O2 if the workload decreases.

    It also happens to be a discussion right now, about just the 3 cell approach vs the MkVI ASV. But lets keep that there and not here.

    Glad that he is alright Jakob.

  8. #18
    Capt/ Instructor
    tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1 is a jewel in the rough tmccar1's Avatar
    Join Date
    Mar 2006
    Location
    Long Island, NY
    Posts
    406
    SF2 | rEvo

    PRISM Topaz

    Quote Originally Posted by Jeppe_E  View Original Post
    Probably gonna get flamed for this, but the Poseidon MkVI sort of does this. It tracks the O2 consumption and add more if the workload suddenly increases or lay off on the O2 if the workload decreases.

    It also happens to be a discussion right now, about just the 3 cell approach vs the MkVI ASV. But lets keep that there and not here.

    Glad that he is alright Jakob.
    It has a backup method outside of cell readings to tell if its adding too much O2? Does it do something above other eccr's and the add o2/ check ppo2 with cells/ add o2 or is it just a way to make it sound good for marketing? Not flaming, it's just that too many companies are using fancy wording for things to make it sound new an its hard to tell if its an actual significant improvement to technology or if someone used a thesaurus.
    -Capt Tom McCarthy
    Stone Rust | East Coast Wreck Diving
    SF2 | rEvo
    Training | Charters | Equipment

  9. #19
    Jakob Selbing jaksel will become famous soon enough jaksel will become famous soon enough jaksel will become famous soon enough jaksel's Avatar
    Join Date
    Oct 2008
    Location
    Stockholm
    Posts
    178
    AP Evolution+

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    Quote Originally Posted by tmccar1  View Original Post
    You would need ways to monitor depth...
    Don't most dive computers monitor depth?
    Quote Originally Posted by tmccar1  View Original Post
    ... O2 injection volume rates (which could change if you're solenoid is having issues or clogged even a little), real time physical O2 metabolism in the diver, diluent addition volume, exhausted gas volumes (from OPV, diver's nose, lips, mask clearing), loop volume, etc. These are all factors outside of the unit's control that would have to be monitored to do it correctly.
    I don't see why a warning given due to a clogged/failing solenoid would be bad?

    Further, diluent addition (or manual O2 addition) will change the ppO2 -- but not gas exhaustion itself.

    The metabolism changes of course, but the upper and lower limit would be fairly easy to figure out. At least we know that the rate is larger than 0.5 L/min and probably less than 5 L/min or so.

    Figuring out how the flow rate changes while descending and ascending is not too difficult either (only a few simple equations to solve).

    Or, one could just accept that the controller will give a warning also in those cases when O2 injection rate changes due to "natural causes" (not because cells are current-limited). After all, if we're at constant depth and not doing random dil flushes, we would expect a constant O2 injection rate.

    Quote Originally Posted by tmccar1  View Original Post
    Or you could buy an MCCR where you're brain is the computer and you know definitively how often your finger has been hitting the add button and have a decent idea about all of the above.
    That is definitely an advantage for mCCRs, but I am talking about eCCR now. A properly designed eCCR could, (just as your finger does with an mCCR, tell you the approximate O2 injection rate.

  10. #20
    Jakob Selbing jaksel will become famous soon enough jaksel will become famous soon enough jaksel will become famous soon enough jaksel's Avatar
    Join Date
    Oct 2008
    Location
    Stockholm
    Posts
    178
    AP Evolution+

    Re: Serious incident (hyperoxia) when 2 cells fail simulatenously and identically

    Quote Originally Posted by Jeppe_E  View Original Post
    Probably gonna get flamed for this, but the Poseidon MkVI sort of does this. It tracks the O2 consumption and add more if the workload suddenly increases or lay off on the O2 if the workload decreases.

    It also happens to be a discussion right now, about just the 3 cell approach vs the MkVI ASV. But lets keep that there and not here.
    It was actually that discussion about the MKIV that made me think about this particular incident, and subsequently start this thread!

+ Reply to Thread
Page 2 of 5 FirstFirst 1 2 3 4 5 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts