Are rebreathers getting safer over time?

[rjack321]

What extra automation does a Poseidon have over say a JJ or a Vision?

It has continuous cell validation of 2 cells and no voting logic just one primary validated cell. Cells are validated by the O2 injection blowing across their face before its mixed in the loop. The electronics know how the cell is supposed to behave during an injection and compares the primary cell against those parameters. If the primary cell fails specifications it switches to the secondary and says "abort". If there's some other problem it tell you to bail out (don't quote me on this, I have never even seen a Poseiden).

The rest of this thread sure could use a massive editing...

 

[Dr. Lecter]

the ascent phase can be the time where there is an awful lot going on.

Irrelevant. As a CC diver, you either keep your priorities straight or you suffer the consequences.

 

[KenGordon]

Regarding blowing O2 overs the two cells on the mk6/7.

That isn't what I was thinking of as automation, that I would say is part of how the ppo2 is measured.

My point really was that the supposedly nannying, soft and fluffy rec rebreathers are not actually more automated but less manual. They take away manual adds for example, rather than adding more automatic stuff compared to a 'normal' eCCR.

 

[steady1570]

Irrelevant. As a CC diver, you either keep your priorities straight or you suffer the consequences.

Sure, but that doesn’t preclude it being a good idea (or alternatively not a bad idea) to have some automation assist you. You still have to be on top of the situation, monitor and understand what the unit is doing. The ascent does have more going on and so letting the computer inject for example does free up capacity for unexpected events. I don’t argue that a fully automated ccr where the diver is a passenger is a good idea (submarine anyone?), but in a very loose analogy, I don’t think too many people believe that having automatic gears in a car makes terribly unsafe drivers.

One of the most common complaints I have heard about rebreathers is that they are so unforgiving of mistakes. I don’t know the answer, but having some form of safety net without introducing a dependency on said net has got to be a good thing. (Maybe the computer on a low set-point but running 1.3 manually is a good compromise…?)

 

[Dr. Lecter]

Sure, but that doesn’t preclude it being a good idea (or alternatively not a bad idea) to have some automation assist you. You still have to be on top of the situation, monitor and understand what the unit is doing. The ascent does have more going on and so letting the computer inject for example does free up capacity for unexpected events.

You're forgetting the fact that the unit's automation is itself something one must monitor, to ensure it is not doing something counter to what the situation calls for. I agree that running a low set-point solenoid driven safety net with manual addition to the actual set-point is probably a good balance, to the extent that's an option on the unit, but anytime you have a solenoid in play you need to devote some of your attention to ensuring it's doing what you want.

 

[steady1570]

Yes I agree, you still have to monitor and be in control of the unit, and so perhaps the automation doesn't so much reduce the amount that you have to do but rather change the focus, moving from a physical task (hitting the MAV) to a cerebral one (watching what the ppO2 is telling you vs what you expect). You are watching the ppO2 whether manually adding or not, so now maybe you can spend a bit more grey matter analysing rather than just reading.

Perhaps this is moving a little OT though. I think what my original point was is that I trust the electronics to do what they are supposed to be doing, albeit that may not be what they should be doing in any given situation, and so you can’t abrogate responsibility but must still control the system yourself.

 

[rjack321]

Regarding blowing O2 overs the two cells on the mk6/7.

That isn't what I was thinking of as automation, that I would say is part of how the ppo2 is measured.

My point really was that the supposedly nannying, soft and fluffy rec rebreathers are not actually more automated but less manual. They take away manual adds for example, rather than adding more automatic stuff compared to a 'normal' eCCR.

Actually the cell is validated before its allowed to measure ppO2. I.e. if the cell doesn't spike the appropriate number of mV during an inject its failed and not used to report loop ppO2. The backup cell is used instead, assuming it passes.

Vs. a JJ, vison or meg where cells are calibrated before the dive and assumed to behave linearly for the rest of the dive (assumed by the unit's calibration that is).

Based on the number of Poseidon serious injuries/fatalities so far (5 I think?). The unit doesn't appear to be any safer than any other CCR.

 

[ajduplessis]

We had a se7ven fatality here a month or so ago in a local quarry. This did not even make the news here or anywhere else, so the figure indicate is actually higher. This is the second poseidon rec ccr fatality in 14 months here.The victim (experienced) procured 10 se7ven units as part of his new diving business and dream in becoming a se7ven instructor. I never liked the idea of rebreathers being available to rec divers as the complexity and nature of these units is unforgiving in a hostile environment.

 

[allianceidc]

Definitely yes, rebreather are getting safer. As a Poseidon Trainer and enthusiast of new technologies rebreather are the future of Tec diving, as well will be part of recreational diving market.
But we have to consider some points.
Equipment - units like Poseidon MK VI and Se7en have uniques features like automatic pre dive test that ensure the unit is able to dive and fully operational, at the same time you have a gain of time to perform this test. In the other side, even an automatic test requires total attention for the diver during the procedure. Software and firmware development are crucial too, to ensure the safety of diving and new capacities. Constant investments are required to ensure the latest updates to maintain the safety record.
Recognitions like CE requirements should be considered.
Training – new technologies requires new approaches to train the divers. Divers are trained to dive the unit , but points like software updates, dive planning , equipment maintenance and the constant train to use the unit are more important , even for experienced divers. Poseidon units are approved for Rec and Tec courses , basically using the same rig (battery and counterlungs are different for each level) but the training differs.
Procedure – most of the problems with rebreathers happen for diver actions: ignore alarms, inappropriate scrubber use, exceed limits or lack of training. An interesting point about the Poseidon unit is the data record unit (red box) that allows have access about unit function and alarms after the diving, With this type of information, in case of accident we can know if the diver received/ignore an alert/alarm during the dive , as well the entire dive profile including depth, time, tank pressures. This feature can be use for safety record and accident report and analyses.
Diving with rebreathers means use the latest technology, diving Tec with rebreathers including Helium dives it’s the edge. You can't avoid all risks , but if you use an equipment that reduces overload tasking with automatic procedures and alarms will make your life easier underwater!
Dive Safe, No bubbles!

 

[ajduplessis]

Interesting first post on SB ......