Passive Scr Superiority?

trob09

It is entirely possible that my suspicion is incorrect. I eagerly await facts to develop a position that is stronger than a suspicion, but at this point in time, that is all I have. It is heavily influenced by the thought that I am the weak link in my diving and that it is my responsibility to ensure that my equipment is operating correctly and I am as prepared as I can be for the time when it stops working correctly.

I am not certain that all of the factors that drive accidents are in the "know your PO2" thread or can be limited to "rebreather faults".

I agree that every effort should be made to remove know failure points from the unit - on that we clearly agree. I am also not trying to sweep everything under the "diver error" rug.

I am saying that the choices and practices that a diver makes should definitely be considered when analyzing accidents. To chalk it all up to "rebreather faults" does a disservice to the term analysis.

I am also saying that no one has done a _serious_ analysis of all the factors that drive rebreather accidents and deaths. Until this analysis is done (as it was for aircraft), any use of a statistic to support a claim or position on one model or brand over another should not be considered gospel.

tim

jmurba

[quote=nigelh;72595]"Safest" cannot be determined theoretically and even when you start counting incidents Passive SCRs are so rare

no they are not rare, they are dived every day in French army for 50 years

AD_ward9

[quote=jmurba;73443] Exactly.

Draeger Dolphins and Rays account for as many rebreathers as all the eCCRs put together except the Inspos, and for many years they exceeded Inspos.

Commercial rebreathers are all passive SCRs. A commercial rebreather (ie one for commercial umbilical dive use), clocks up vastly more hours than a sports unit.

PSCRs are pretty safe. Adding a decent monitoring package makes them much safer still. In my opinion, all eCCRs should also be PSCRs. That is, unplug the power, and they operate instantly as a PSCR. Using variable orifice valves, it can be done.

Cheers

Alex

decoweenie

AFAIK, this is COMPLETELY wrong.

There has been no fatality on a KISS unit supplied from Jetsam.

MANY people added a component of the KISS unit to their unit, and that does not make the unit a KISS unit.

If you are referring to the incident where someone added an orifice valve to the YBOD, that is not a KISS incident since I have received different versions of the report. And it didn't sound like the diver knew what was the right thing to do.

As far as the rest of your statistic, I have no glue where you are getting your numbers...

__________________
"...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..."

- Rebreather World PM

O.C.Diver

This statistical BS is all rather pointless. The only real way to make any meaningful comparison of deaths relative to specific models is to compare number of deaths per 10,000 dives on each model. When the sample number gets large enough percentages can more realistically be determined. Unfortunately, nobody has any idea what the number of deaths per 10,000 dives is for any of these units.

Ted

__________________
Consider this my opinion.......sometimes I'm even right, but remember.........YMMV.

Ted Green
Charter Boat "OC Diver"
http://www.ocdiver.com

AD_ward9

Let us keep goal posts in one place.

I left out the KISS. You challenged me, pointing out there are lots of different types of KISS that make up that KISS population implying the population is big enough to use. I took your definition and pointed out there is one fatality. It was not a Jetsam KISS. There is nothing to argue about: I am not including KISSes because I do not have useful data on how many and what type there are in use. It is below my worry horizon. It is either in with the Draeger Dolphins in safety, or close behind: IMHO the latter, but without data there is no point arguing about it. A KISS is for sure a lot safer than a March 2000 YBOD.

As a moderator, can you answer the question I posed: "Can RBW publish how many users it has, for each type of rebreather? We can then do a poll and find out what propertion of rebreather users are on RBW, by contacting one of the dive training agencies to see how many XYZ agency rebreather divers are here, compared to how many have cert cards. That would be a useful thing to do. Given the population size is large, this would give a fairly precise confirmation of numbers. Is RBW able to do this, or is this Data Mining and prohibited?"

As to OC diver,who says, "This statistical BS is all rather pointless. The only real way to make any meaningful comparison of deaths relative to specific models is to compare number of deaths per 10,000 dives on each model." You do not live in an ideal world. This means we must gather the data that can be obtained, and try and cross check it from different sources, rather than wait for something we will never get. When the data we gather comes up each time with the same number, it is probably right. The numbers have to be out by a factor of a hundred for my conclusion to be worthless, and I can state with 100% confidence that there are not 165,000 active YBOD users! Nor are there just 16.5. Wakey, wakey

The abysmal safety record of some manufacturers is giving the whole rebreather industry a bad name, damaging everyone on this board.

Anyway back to thread, we agree PSCRs are pretty safe. My tuppence worth is that IMHO eCCRs should always fail to leave a PSCR. Dolphins and KISSes have an accident rate below our worry horizon, while eCCRs with solendoid valves have both more failure modes and a grim accident record. We should eliminate solenoid valves from eCCRs, as it then does not need the electronics to be active and working properly all the time, for the user to stay alive.

Alex

decoweenie

Just for clarification once again, I merely guessed some number of units in used divided into groups predefined by someone else.

One of those predefined groups is mCCR, thus I justified the number given by listing what I know/think of the units could be classified as mCCR-unit.

You kept referring to this group as "KISS units". They are not!

Anyway, all of this playing with statistics is pointless really other than for those who are pursuing their own commercial agendas. So I am outtahere...

PS: Not sure if you addressed 2nd part of the post to me or not, but I am not a moderator.

__________________
"...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..."

- Rebreather World PM

steevke

Hear hear!

steven

gtzavelas

I think this should very interesting info, apart from this thread.
Just one note: pSCR fall in the category of "other SCR" in the Rebreather combo selection.

silent running

Hi Alex, you know that I have to disagree with you here. IMHO, the solenoid is not the problem. It's the fact that you can't isolate the high current side-controller, solenoid, displays-on most ECCRs from the low current side-sensors, wiring harness. Neither the Prism or MK15.5 need any power to be flown manually as both have a 2dry driven directly by the sensors. And both allow you to properly trouble shoot and be sure you know when it's a sensor problem or a hardware/power problem. I know, I'm a broken record. But what difference does it make if it has a solenoid or not? As long as the unit can be flown without power, nothing short of 3 totally crapped out sensors or a total loop flood will cause BO. Of course I agree that ECCRs have more failure modes, that's why I have come to think an ECCR should be as simple as possible. Is an SP only ECCR with a passive 2dry really more complicated than an MCCR with 3 battery driven displays and a mass flow orifice? Not to me it isn't. On both units the mechanical means of O2 delivery can fail, and both can then be flown manually, by injecting O2 on demand via add button or feathering the tank valve. What's the big deal?

RMV keyed SCRs are certainly ingenious, but they are also more mechanically complicated, less effcient and less accurate than any CCR that can be flown without power. And they apparently breathe poorly, no contest for me. -Andy