a whole new dimension and opinion on Rebreather diving

wannabe

maybe I will when I see him. Only talked to him over the phone. I learnt diving from him in 1984 and since then did not meet up with him since except when he was in the TDI setup in the mid 90s.

I only contacted him when someone directed me to him to service an O2 cleaned scubapro MK2 regulator.

Still your suggestion on current limited O2 cell is interesting.

nskdrs

Also,

Talk to people who have been using Rebreather's ( be it eCCR and/or O2CCR ) outside the "sparetime-activity-market", ex-commercial-divers, ex-forces ( the real ones ), you may find this enlightning for your very own risk assessments.
Talk to people who design O2-sensors, the engineers not the marketing people.
The words you chose to headline this thread do make me feel like I want to propose this,
hard to collect green blobs on it though

no hard feelings pls.
cheers,
hoffi

P.S. Good to see Mr. Mike is back.

decoweenie

No, me too since I agree.

Most new people getting into the new sport are usually very optimistic and only look at the good side. But everything has a negative side, and it is as important to be aware of it as well since you are in the timeframe where mistakes are easily made.

Having met said-MK-15 diver twice spanned over a period of 2 years after the incident, he is making good recovery but still far from fully recovered. Whenever I want to cut corners, I just think about him. He is a strong individual to have bounced back so far, not everyone could do the same...

__________________
"...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

webhead

Two comment on the original discussion....

I look at Rebreather diving like flying in the early 1900's. People called them death traps and even tried to make them illegal. But there was value in them and people pushed the technology and now the products today are past any desires the original inventors had. If this sport continues to grow, imagine what diving will be like in 100 years.

Second, I can't go back to OC because according to all the nay sayers, I'm doing OC wrong too and will kill myself. So according to the "people that know better" I'm doomed either way.

__________________
"These are not the droids you are looking for.... move along" - Obi-Wan Kenobi

Genesis

Well, CCRs - or OC for that matter - IS a deathtrap if you don't pay attention.

Run out of gas on OC at 200' with an hour-long deco obligation and tell me what your odds are.

How's this really different than a CCR? The risks are different, but they're still there in either format.

Fact is, much of what we consider an "everyday thing" is in fact a deathtrap if one is inattentive. You can quite easily kill yourself cleaning your gutters!

So what's reality here? IMHO its "complacency kills" - more than anything else. Its when you stop thinking that what you're doing is dangerous, and thus needs your full attention, that you get into trouble.

__________________
"A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American."
http://www.denninger.net
http://www.diversunion.org/liability.htm - Fix the Diving Cert racket

Yann A.

[quote=nskdrs;77848]Also,

Talk to people who design O2-sensors, the engineers not the marketing people.

Agree with you on that one.

For me the Eccr versus Mccr is silly.
What difference does it make to have a human brain or a Rebreather “brain” deciding on the O2 injection/ non-injection when it shouldn’t/should? You’d go Hyperoxic/Hypoxic the same way. Low output cells, poor calibration of cells would fool both divers due to incorrect information passed on to the injection-controlling unit.
The thread on different cells readings in dry and humid environment started by Sabgia and that went dead (unfortunately) pinpoint what is probable the weakest part in a Rebreather your cells. So it’s not Eccr against Mccr, it’s deciding whether you can/want to trust your cells.

Rgds,

Yann.

Gilles

[quote=Drmike;77799]I am yet to find a rebreather that I would trust with my life.
[quote]

I would call that wisdom!

Likewise applies to the car my wife and children drive in, the luxury coach my daughter travels in every weekend from boarding school, and the mountain bike I like to use for commutung to work every day.

This morning at dawn I stepped out with a cup of coffee in my garden and noticed that my cats were acting strange. I then noticed a small 30cm long black cobra standing with its hood out. I must of stepped within cm's of it.

Cannot trust my life to my own garden.

__________________
Gilles
http://www.dirrebreather.com

bgpartri

I think a lot of people underestimate the problems with cells. I've had various different rebreathers try to kill me in many ingenious ways, but the scariest one for me is bad sensors.

A lot of the other problems were pretty easy to spot. But if I hadn't had a lot of experience the first time my sensors got current limited, I probably wouldn't have noticed that the solenoid was firing too often. Scary.

Addition: What happened was all three sensors were old. I had decided to dive a rebreather that I hadn't used for a while. I didn't really think about how long it had been sitting in the dive room. At 100 feet, the solenoid kept firing every 5 seconds with no breaks. What was happening is that my ppo2 was getting higher and higher, while the average the computer was seeing was about 1.25. I might have been on a 2.0 before I noticed it. I have no way of knowing.

__________________
http://www.shearwaterresearch.com

Good judgment comes from experience. Experience comes from bad judgment.

rdmmdr

Guys:
Cell checkers are a cheap piece of kit that everyone should use and this just proves it once again. what i dont believe is the number of stupid things that have been done in the name of penny pinching. using expired sorb, flooded sorb, diving electronics that are known bad, and reusing sorb. this said from a home builder might sound strange like an oxymoron, but i will risk it. cell checkers should be a manditory peice of kit period.

rick

Genesis

This exact failure is why the K1 has the design feature in it that it does to attempt to prevent this.

You calibrate it on air.
You can then verify with an O2 loop flush on the surface, that all is ok in terms of cell linearity and operation.

HOWEVER, by default the maximum setpoint is 0.5! If you want higher, you must validate that the cells are capable of delivering the PO2 you're asking for.

On the surface, you can run the PO2 up to 1.0 (pure O2) and hit VALIDATE off the cal menu. For validation to succeed ALL THREE sensors must be in agreement (that is, none can be voted out); the computer then takes the PO2 you are showing and sets the maximum allowed setpoint to 0.1 under that.

So if you validate at 1.0, you may then run a PO2 on setpoint of up to 0.9.

If you validate at 20' and run it up to 1.6, you may run a setpoint up to 1.5.

The "high/low" setpoint switch happens at 10'.

Calibration is only good for 24 hours; validation is good for seven days, after which the system reverts back to 0.5. You can always "reset the clock" any time you'd like (by validating again), but if you don't, after a week it says "no more high PO2 for you until you PROVE the sensors are still able to read it."

While this doesn't prevent a sudden "oh $hit" situation with all three sensors, it absolutely DOES prevent what happened to you Bruce, in that after a significant layoff you can't use a high PO2 setpoint until you first prove that the PO2 you wish to run at can be achieved by the unit, AND that all three sensors are within linearity limits at that setpoint.

It is NOT hard to add this to a setpoint controller, and IMHO they all ought to have this feature in there. Its the ONLY way the computer can have any rational assurance that the cells can actually read a hyperbaric PO2.

__________________
"A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American."
http://www.denninger.net
http://www.diversunion.org/liability.htm - Fix the Diving Cert racket