The Pelagian Way

Jonathan · 4th September 2007, 13:16

I like this question from Steve:

A simple question. You are at 50m and your displays read 1.333 and 1.666. You flush with dil and the displays agree and both display 1.222. Which cell is the bad one?

Commenting *generaly* on the replies supporting running on 2 sensors, at 50m do I really want to be figuring in my head cell failure rates, electonics, chemistry, temperature, did I leave the head of between dives for condensation to evaporate off membranes, if I did - was it raining, which carpet cleaner is the best product on the market(*!) etc., or look at three gauges and have it clear infront of me which one is off kilt and, more importantly, what my PO2 is?

There's enough intersting stuff going on to have attention on than a growing niggle over 2 disagreeing gauges and having to cut a dive & bail out.

J.

jaap · 4th September 2007, 13:17

Quote: (Originally Posted by Steve)

A simple question. You are at 50m and your displays read 1.333 and 1.666. You flush with dil and the displays agree and both display 1.222. Which cell is the bad one?

My very simple newbie approach is to not use some standard extra lean diluent but rather so that the bottom dil pO2 is something close to the diving pO2. If the cells start to disagree a dil flush gives a hint which one is right. Turn the dive and go home.

Even if a dil flush shallower than bottom depth would yield a testing pO2 far under the "setpoint" another way of seeing it could be: Why abandon loop as long as the max/min readings are acceptable? That is, not way high and not so low that say your bailout is far richer.

I have not done Rebreather dives with more than around 30 min ascent time yet but if I did I would definately prefer 3 cells to reduce the guesswork when the cells start to play around.

Drmike · 4th September 2007, 13:25

Quote: (Originally Posted by Rebreatherlab)

Seems you're missing the point. The point is that the ability to quickly and easily put some DIL across the cells is safer than not being able to do it.

what units dont allow this?? Does the Palagian have an dil inject right next to the cells (I designed my BOB in same way) to enable fast verification?

Quote:

Sure it is better to have 3 than 2 cells and sure it is better to have 5 than 4 cells.
The Pelagian can use 3 cells, but they are split up in order to not share common ground or battery. The Pelagian is not sold with a third read out in its a basic package as many divers would prefer to run a live deco computer from one cell. If not an additional display can be added.

this was my understanding when we talked at adex and I fully agree with that philophosy. Indeed a 2 cell display and a seperate 1 cell display is safer than a single 3 cell display and this is how I dived my BOB previously.

Quote:

If one argues that simply adding a third cell would be a better solution and think that you are safe just because 2 cells read one thing and ONLY one cell reads another you are just trying to improve your luck.

that statement makes little sense to me and to me is contradictory to your earlier one (the more the safer). Having had 2 cells fail together several times a 3rd cell is definately going to help as it may (in my cases did) show a variance.

Quote:

the corner stones are checking cells in air (or any other known gas) at 1 ATA, then in pure O2 at 1 ATA, then pure O2 at 6m, then reference the readouts frequently with DIL during the dive.

yes I agree those are good methods but how practical is doing dil flushes at depth? How often will people really do them (damn we cant even check our displays often enough) With 3 cells I dont think theres such a need to do dil verifications. I also dont want to (and quite frankly probably couldnt) calculate the dil ppo2 at all depths on deep dives anyway

Quote:

Sorry I am tired...

Sorry for what?

Drmike · 4th September 2007, 13:44

Quote: (Originally Posted by OceanOpportunity)

not to split hairs or start a pissing match, BUT your electronics could fail and leave you not noticing until its too late as well.

you could also get hit by a truck crossing the road on the way to the dive site.

but that doesnt change anything either.

Quote:

I'm not convinced that there is enough hard evidence on failure mode analysis to say one method is better than another.

there is - read up on cell failure modes.

Quote:

Yes, doing a dil check every few minutes may be distracting during a dive, but practically speaking it will work, which is my point.

yes it will work - but that doesnt make it the safest method. Lets be clear here Im not slagging off the Pelagian as it was previously mu understanding (and now confirmed by Andy) that the idea is to run 2 cells and a 3rd independant one from say a VR3 - and I like the dil verification stuff. What Im against was your comment that 'hey we only need 1 cell'

Quote:

mCCR is constantly trickling O2 at or close to your metablic rate anyway, so it'd be next to impossible to go so long as to not notice the PO2 drop on a dead sensor...you'd notice right away. You should be looking at your display more often that that if you are manually adding O2 now and then.

hyperoxia is the concern not hipoxia

dantheman · 4th September 2007, 13:47

Quote: (Originally Posted by Jonathan)

. . . or look at three gauges and have it clear infront of me which one is off kilt and, more importantly, what my PO2 is?

You have neither with certainty under any system.

DrMike is closest when he proposes a system with 4000 cells of varying characteristics . . .
even then the best we can say is that the odds are much better.

--dan

dantheman · 4th September 2007, 13:50

Quote: (Originally Posted by jaap)

If the cells start to disagree a dil flush gives a hint which one is right.

This is Steve's point: you won't know (even with 3 cells).
If cells fail high as well as low, there is no way to get a handle
on which one is correct, ever, unless it fails the dil flush test.

The best you have is a statistical approach.

--dan

dantheman · 4th September 2007, 14:00

Quote: (Originally Posted by Steve)

Where is Alex D when we need him?

. . . he had had a sensor fail high on a dive whilst in PNG. Scared the hell out of him as he firmly believed that it couldn't happen. He changed the design of his stingray on the spot.

I agree: I am very curious what Mr Wizard (Alex) has to say

I'm very interested in any information about cells failing high, especially on a dive . . .
Anyone else?

--dan

Drmike · 4th September 2007, 14:03

I do like the idea of reg dil flushes to verify cells indeed i recall proposing such a thing years ago when my inspiration cells were trying to get me killed (temp comp faulty) but it does remind me of my experiences back then..

...flush
...i should get 1.2
....i got 1.2

cool

but i was subconciously stopping flushing when i got the ppo2 i was expecting to see

flushing longer may/did at times change the results.

i found myself doing similar when analysing gas

my point is only that the flush needs to be thorough (but i am guessing this has been designed into the unit making it easier) and not to stop flushing as soon as the expectant ppo2 is displayed. the trick to me was to not calculate the expected ppo2 before the flush.

Drmike · 4th September 2007, 14:12

Quote: (Originally Posted by dantheman)

I agree: I am very curious what Mr Wizard (Alex) has to say

I'm very interested in any information about cells failing high, especially on a dive . . .
Anyone else?

--dan

its not only about the cells. Get salt water intrusion into the wiring and you can have high cell readings too. Another reason why independant displays are important and why I like the old KISS display concept, seperate wires, seperate cells, seperate batteries

**wedivebc** · 4th September 2007, 14:14

Quote: (Originally Posted by DeepBlueInnovation)

Not necessarily, I believe cells can read high just as easily as they can low when they fail.

Yes I agree but I would be very surprised if a cell that was failing in this manner gave a sensible reading when flushed with dil then took a crap.
The only time I have seen a cell fail high the air reading was way high and it was a R22d used in a miniox.

4th September 2007, 13:16	#31 (permalink)
Jonathan New Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Sep 2005 Location: Ireland Posts: 28	Re: The Pelagian Way I like this question from Steve: A simple question. You are at 50m and your displays read 1.333 and 1.666. You flush with dil and the displays agree and both display 1.222. Which cell is the bad one? Commenting generaly on the replies supporting running on 2 sensors, at 50m do I really want to be figuring in my head cell failure rates, electonics, chemistry, temperature, did I leave the head of between dives for condensation to evaporate off membranes, if I did - was it raining, which carpet cleaner is the best product on the market(*!) etc., or look at three gauges and have it clear infront of me which one is off kilt and, more importantly, what my PO2 is? There's enough intersting stuff going on to have attention on than a growing niggle over 2 disagreeing gauges and having to cut a dive & bail out. J.
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4th September 2007, 13:17	#32 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 438	Re: The Pelagian Way Quote: (Originally Posted by Steve) A simple question. You are at 50m and your displays read 1.333 and 1.666. You flush with dil and the displays agree and both display 1.222. Which cell is the bad one? My very simple newbie approach is to not use some standard extra lean diluent but rather so that the bottom dil pO2 is something close to the diving pO2. If the cells start to disagree a dil flush gives a hint which one is right. Turn the dive and go home. Even if a dil flush shallower than bottom depth would yield a testing pO2 far under the "setpoint" another way of seeing it could be: Why abandon loop as long as the max/min readings are acceptable? That is, not way high and not so low that say your bailout is far richer. I have not done Rebreather dives with more than around 30 min ascent time yet but if I did I would definately prefer 3 cells to reduce the guesswork when the cells start to play around. __________________ My initials: JAAP Last edited by jaap : 4th September 2007 at 13:20.
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4th September 2007, 13:25	#33 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: The Pelagian Way Quote: (Originally Posted by Rebreatherlab) Seems you're missing the point. The point is that the ability to quickly and easily put some DIL across the cells is safer than not being able to do it. what units dont allow this?? Does the Palagian have an dil inject right next to the cells (I designed my BOB in same way) to enable fast verification? Quote: Sure it is better to have 3 than 2 cells and sure it is better to have 5 than 4 cells. The Pelagian can use 3 cells, but they are split up in order to not share common ground or battery. The Pelagian is not sold with a third read out in its a basic package as many divers would prefer to run a live deco computer from one cell. If not an additional display can be added. this was my understanding when we talked at adex and I fully agree with that philophosy. Indeed a 2 cell display and a seperate 1 cell display is safer than a single 3 cell display and this is how I dived my BOB previously. Quote: If one argues that simply adding a third cell would be a better solution and think that you are safe just because 2 cells read one thing and ONLY one cell reads another you are just trying to improve your luck. that statement makes little sense to me and to me is contradictory to your earlier one (the more the safer). Having had 2 cells fail together several times a 3rd cell is definately going to help as it may (in my cases did) show a variance. Quote: the corner stones are checking cells in air (or any other known gas) at 1 ATA, then in pure O2 at 1 ATA, then pure O2 at 6m, then reference the readouts frequently with DIL during the dive. yes I agree those are good methods but how practical is doing dil flushes at depth? How often will people really do them (damn we cant even check our displays often enough) With 3 cells I dont think theres such a need to do dil verifications. I also dont want to (and quite frankly probably couldnt) calculate the dil ppo2 at all depths on deep dives anyway Quote: Sorry I am tired... Sorry for what? __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you Last edited by Drmike : 4th September 2007 at 13:33.
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4th September 2007, 13:44	#34 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: The Pelagian Way Quote: (Originally Posted by OceanOpportunity) not to split hairs or start a pissing match, BUT your electronics could fail and leave you not noticing until its too late as well. you could also get hit by a truck crossing the road on the way to the dive site. but that doesnt change anything either. Quote: I'm not convinced that there is enough hard evidence on failure mode analysis to say one method is better than another. there is - read up on cell failure modes. Quote: Yes, doing a dil check every few minutes may be distracting during a dive, but practically speaking it will work, which is my point. yes it will work - but that doesnt make it the safest method. Lets be clear here Im not slagging off the Pelagian as it was previously mu understanding (and now confirmed by Andy) that the idea is to run 2 cells and a 3rd independant one from say a VR3 - and I like the dil verification stuff. What Im against was your comment that 'hey we only need 1 cell' Quote: mCCR is constantly trickling O2 at or close to your metablic rate anyway, so it'd be next to impossible to go so long as to not notice the PO2 drop on a dead sensor...you'd notice right away. You should be looking at your display more often that that if you are manually adding O2 now and then. hyperoxia is the concern not hipoxia __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you Last edited by Drmike : 4th September 2007 at 13:47.
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4th September 2007, 13:47	#35 (permalink)
dantheman Emoticonoclast Current Rebreather/s: Sport Kiss rEvo Other Rebreather/s: Classic Kiss rEvo Join Date: May 2005 Location: NorthEast USA Posts: 393	Re: The Pelagian Way Quote: (Originally Posted by Jonathan) . . . or look at three gauges and have it clear infront of me which one is off kilt and, more importantly, what my PO2 is? You have neither with certainty under any system. DrMike is closest when he proposes a system with 4000 cells of varying characteristics . . . even then the best we can say is that the odds are much better. --dan
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4th September 2007, 13:50	#36 (permalink)
dantheman Emoticonoclast Current Rebreather/s: Sport Kiss rEvo Other Rebreather/s: Classic Kiss rEvo Join Date: May 2005 Location: NorthEast USA Posts: 393	Re: The Pelagian Way Quote: (Originally Posted by jaap) If the cells start to disagree a dil flush gives a hint which one is right. This is Steve's point: you won't know (even with 3 cells). If cells fail high as well as low, there is no way to get a handle on which one is correct, ever, unless it fails the dil flush test. The best you have is a statistical approach. --dan
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4th September 2007, 14:00	#37 (permalink)
dantheman Emoticonoclast Current Rebreather/s: Sport Kiss rEvo Other Rebreather/s: Classic Kiss rEvo Join Date: May 2005 Location: NorthEast USA Posts: 393	Re: The Pelagian Way Quote: (Originally Posted by Steve) Where is Alex D when we need him? . . . he had had a sensor fail high on a dive whilst in PNG. Scared the hell out of him as he firmly believed that it couldn't happen. He changed the design of his stingray on the spot. I agree: I am very curious what Mr Wizard (Alex) has to say I'm very interested in any information about cells failing high, especially on a dive . . . Anyone else? --dan
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4th September 2007, 14:03	#38 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: The Pelagian Way I do like the idea of reg dil flushes to verify cells indeed i recall proposing such a thing years ago when my inspiration cells were trying to get me killed (temp comp faulty) but it does remind me of my experiences back then.. ...flush ...i should get 1.2 ....i got 1.2 cool but i was subconciously stopping flushing when i got the ppo2 i was expecting to see flushing longer may/did at times change the results. i found myself doing similar when analysing gas my point is only that the flush needs to be thorough (but i am guessing this has been designed into the unit making it easier) and not to stop flushing as soon as the expectant ppo2 is displayed. the trick to me was to not calculate the expected ppo2 before the flush. __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you
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4th September 2007, 14:12	#39 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: The Pelagian Way Quote: (Originally Posted by dantheman) I agree: I am very curious what Mr Wizard (Alex) has to say I'm very interested in any information about cells failing high, especially on a dive . . . Anyone else? --dan its not only about the cells. Get salt water intrusion into the wiring and you can have high cell readings too. Another reason why independant displays are important and why I like the old KISS display concept, seperate wires, seperate cells, seperate batteries __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you
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4th September 2007, 14:14	#40 (permalink)
wedivebc FIGJAM Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,358	Re: The Pelagian Way Quote: (Originally Posted by DeepBlueInnovation) Not necessarily, I believe cells can read high just as easily as they can low when they fail. Yes I agree but I would be very surprised if a cell that was failing in this manner gave a sensible reading when flushed with dil then took a crap. The only time I have seen a cell fail high the air reading was way high and it was a R22d used in a miniox. __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
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