Double Fatality in June 2014 (UK) - Inquest and Media Reports

serpentara said:
But what exactly makes for an old cell? For example the factory recommended cycle time for cells in rEvos is to purchase one new cell every six months, regardless of how many cells are in the unit. This means with a 3 cell setup no cell is over 18 months old. But in a 5 cell setup the last cell could be almost 2.5 years old by the time it is replaced.

They do however tell you to current limit test your cells at the end of every dive and to replace those that look bad... But still, 2.5 years?
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because this is an automated self test of the sensors
if the older sensor perfectly matches the 6-12-18 months old sensors, they are validated, and they can be used: nothing wrong with using perfectly good sensors that are over 18 months old: but you must be 100% sure they are ok
the problem is when users don't have younger sensors in their system that allow validation of the older sensors. that is clearly an accident waiting to happen

paul from london, on my way to sydney/Oztec
 
Megangel1 said:
I'd be interested on what the CCR Liberty would have made out of those cells. OK so you need known helium in the DIL but could it have at least warned that the o2 cells were defective?

Likewise with the Poseidon, would it not have alerted to the cell failure, even if both were identically current limited?

Aren't such systems better than date chips in o2 sensors?

No matter what tech you put in place, someone will find a way around it / ignore it I guess.
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The problem with the Poseidon continous evaluation system is that it's protected under a patent (created by Arne Sieber, aka Seabear who also happens to be developer of solid state sensors). I'd love to see this system as an optional addon but it's not going to happen. So, technically better - definatly yes. But available no. Unless you dive a Poseidon of course.

/nils
 
Mr Walker said:
The problem with the Poseidon continous evaluation system is that it's protected under a patent (created by Arne Sieber, aka Seabear who also happens to be developer of solid state sensors). I'd love to see this system as an optional addon but it's not going to happen. So, technically better - definatly yes. But available no. Unless you dive a Poseidon of course.

/nils
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Yet people are still ignoring its error messages and starting dives when the electronics are saying "do not dive"

At least I think recall several instances where this has happened; the results of poseiden's accident investigations are never publicized unfortunately.
 
We live in a world where we are creating a culture of protecting the stupid.

We shouldn't need to put railings round water to stop people falling in or worse be scared of legal action if we don't.

People should be free to use a unit in any condition they wish. If they have done training and understand the risks then its their life (literally, in this case, unfortunately)
 
Bobjr said:
We live in a world where we are creating a culture of protecting the stupid.

We shouldn't need to put railings round water to stop people falling in or worse be scared of legal action if we don't.

People should be free to use a unit in any condition they wish. If they have done training and understand the risks then its their life (literally, in this case, unfortunately)
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Bob, this isn't about protecting the stupid people. This is about making sure that people, all of which make mistakes because they are human, can be protected from themselves by learning about the mistakes of others. One of the first 'rules' of safety is try to engineer out the problem so that it isn't possible to make that mistake in the first place. However, in a 'small-scale industry', it isn't possible to engineer out all of the risks and still have a commercially viable project and therefore there are still residual risks which have to be managed through process (initial and continuation training) and skills. You are of course assuming that the training delivered is the same as the training detailed by the training agency as we all know how effective agency QA is...

Airline pilots aren't stupid but they still crash aircraft: shutdown wrong engine, trying to fix $12 light bulb, crashed into swamp. Surgeons aren't stupid but they still cut off the wrong leg or remove the wrong kidney.

I have just written a piece for X-Ray magazine about the challenges we face in understanding the risks, especially as the level of risk perception and acceptance is personal and we don't have an organisation that defines what is acceptable or ALARP (nor should we to all intents and purposes)

Peer pressure is something that can be used to positive effect, so why not do it in diving to stop unsafe behaviours? As someone recently said to me, we have had 30+ years of OC diving to create acceptable 'rules' or 'best practice' and so deviation is more obvious, but CCR diving is still in its infancy with companies and training organisations vying for business without clear guidance of 'right or wrong'. However, rules are not the answer, attitudes need to change for the community to determine what is acceptable or not. Those trail blazers from years ago had years of OC experience and knowledge to develop and operate the early CCRs, a number of those are no longer around and practices which were acceptable then, are not necessarily valid now.

Regards
 
Brad_Horn said:
Go to News, top right corner http://mkvi.poseidon.com/
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In fairness Brad, that isn't all of the Poseidon-related fatalities nor do they contain much data in terms of causality and lessons learned. I remember seeing Martin Parker's presentation of the Aquarius Project fatality using unit data to recreate the incident and determine what happened. That is the sort of thing that should happen but that cost money...

Regards
 
GLOC said:
Bob, this isn't about protecting the stupid people.
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It is. Please re-read the thread. It is suggested we should install a "chip" to stop people using old cells.

CCR training is not in its infancy its been going for at least 20 years (much further if we think about the electrolung) - we understand that its not good to use old cells. This is not a mistake.
 
Apologies. I hadn't realised you were referring to that.

However, given the level of standardisation in terms of units & their configuration, training materials and course content and instructor Quality Control, I would say that CCR training (as a general thing, not specific to O2 cell management) is still in its infancy when you consider other domains where life support skills are taught and equipment is developed.

Regards
 
Bobjr said:
It is. Please re-read the thread. It is suggested we should install a "chip" to stop people using old cells.

CCR training is not in its infancy its been going for at least 20 years (much further if we think about the electrolung) - we understand that its not good to use old cells. This is not a mistake.
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Yet people boast on this very board about how long they have used cells and how they are still "good" (passing all apparent performance metrics) at 24+ months or longer. And in some very recent cases instructors have died while teaching from old cells. What is it about the CCR peer culture that creates these attitudes and acceptance by at least a subset of divers? (and even instructors)
 
Bobjr said:
It is. Please re-read the thread. It is suggested we should install a "chip" to stop people using old cells.

CCR training is not in its infancy its been going for at least 20 years (much further if we think about the electrolung) - we understand that its not good to use old cells. This is not a mistake.
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And yet you still hear people explaining that their cell replacement policy is to change them when they die.

More generally, I've never heard anyone, regardless of how they actually do it, who wasn't convinced that their way was perfectly safe because cell checker, because O2 down to 6, because check at the end the dive, because this, that and the other.

People are crap at estimating their own skill and knowledge, hence the famous statistics that 90% of drivers think they're in the top 50%. They're even worse at estimating risks.

The problem is not the culture of protecting the stupid (although I do bitch about that too). The problem is that "the stupid" is everyone (no offence to anyone, I'm in there too).

Incidentally, I do agree that the idea of tagging cells (possibly with a NFC chip, they cost cents) is not a good idea. At the end of the day, the manufacturer will have to decide what happens when the machine gets put in the water with failing tests, and I'd rather it tries to keep me alive rather than it gives me the finger.

Cheers,

Matthieu
 
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emmbee said:
And yet you still hear people explaining that their cell replacement policy is to change them when they die.

More generally, I've never heard anyone, regardless of how they actually do it, who wasn't convinced that their way was perfectly safe because cell checker, because O2 down to 6, because check at the end the dive, because this, that and the other.

People are crap at estimating their own skill and knowledge, hence the famous statistics that 90% of drivers think they're in the top 50%. They're even worse at estimating risks.

The problem is not the culture of protecting the stupid (although I do bitch about that too). The problem is that "the stupid" is everyone (no offence to anyone, I'm in there too).

Incidentally, I do agree that the idea of tagging cells (possibly with a NFC chip, they cost cents) is not a good idea. At the end of the day, the manufacturer will have to decide what happens when the machine gets put in the water with failing tests, and I'd rather it tries to keep me alive rather than it gives me the finger.

Cheers,

Matthieu
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Why do they do it? I don't know.

I don't trust my cells at all - I don't believe replacing them at 12mo from manufacture will protect me. I expect them to fail and monitor my rebreather accordingly.

Most people don't need rebreathers and/or should not be diving them. We do it for fun and, that for me, is plenty enough reason for anybody to dive whatever they want. I might not choose to dive with them though.

The real problem in the world is the pencil pushing middle management. We can see them in action on forums - the internet warriors with 100s and 1000s of posts but few dives and no ccr experience telling us all how to do it. I don't trust anybody with more posts than dives.
 
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Can any one of you who have stated the incident was due to "old cels" please explain to me what diference it would have made if the cells that had failed were new cells?


A cell fails?

You deel with it

Age of the cell seems prety irelevent to me

Some would say its more likley to hapen on an old cell?

Personaly i have had far more failures on new cells than I have had on old cells, so I am strugling with this concept.


In the great cell famin of 2010 I did dive the old BUD cells till they died as it was prooving prety much impossable to find a replacement.

And when they failed they failed in exactly the same way as a new cell fails.

They stoped being accurate.

I dived theas old BUDs to death because the AI cells id tried to replace them with were all over the place streight out of the bag. Then we had the APD cells which had a life expectance measured in hours not years

I went through two dive seasion with new cells that just didn't work

100s of APD cell users experianced the same thing yet no one seemed to die? Odd that seeing as some on this thread seem to beleive a cell failure is the cause of one of the two fatalities?

I personaly think the cells had sod all to do with the death and how the diver monitored his cells, tested his cells during the dive and dealt with a cell error had everything to do with his death

But maybe thats just me.

Perhaps NickB could chime in with his o2 tox story on his unit which had new cells in it.

ATB

Mark
 
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Mark Chase said:
100s of APD cell users experianced the same thing yet no one seemed to die? Odd that seeing as some on this thread seem to beleive a cell failure is the cause of one of the two fatalities?
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The meg diver started the dive with at least 1 cell which was 4 yrs old and the youngest cell (of the 3) was 19 months old. Then he toxed.

How can this fatality be blamed on anything other than the diver's use of (failed) cells way past their recommended replacement date?
 
Megangel1 said:
I'd be interested on what the CCR Liberty would have made out of those cells. OK so you need known helium in the DIL but could it have at least warned that the o2 cells were defective?

Likewise with the Poseidon, would it not have alerted to the cell failure, even if both were identically current limited?

Aren't such systems better than date chips in o2 sensors?

No matter what tech you put in place, someone will find a way around it / ignore it I guess.
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CCR Liberty would alert the user of the bad cell(s). He should disable them and they would not be used for PPO2 control.
 
Hi Mark,

The likelyhood of 3 New cells all failing at the same time far lower than 19 months 3 and 4 cells failing, you know that...

Best regards,
Chett
 
I think Mark's point is that failures are predominately a concern when they are undetected failures, especially when you have two cells fail in the same manner when a systems uses voting logic to determine the correct cell - see the presentation from the Parks diver at Eurotek for another example of OxTox.

It boils down to the argument that IF all of the cells were reading below 1.0 before getting in the water, then the fact that they were old (or new) makes no difference because they have failed in a detectable manner.

Using 'new' cells means that you are less likely to have a double undetected current-limited failure causing the loop to be Hyperoxic. This is a different failure mode to getting in the water with cells which are 'known' to not be operating correctly.

Regards




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