Doing Tech+Cave on a RB?

[rjack321]

Several are working on CO2 monitors and at least one manufacturer has a O2 injection if the loop PO2 falls below .19. But more importantly, where does the error-proofing stop? At what point do we say there are some requirements of the diver? I personally prefer to have my unit provide information and let me decide what to do. There are safety protocols built in but ultimately it is my job to run the rebreather, not vice-versa.

To this I say...

Its not error proofing as much as its designing a system which stays on the road by itself. Can't cross the double yellow or the white shoulder lines.

But if you say left it goes that way. You do control all the various manipulations to get the ppO2 to rise or use off-board gas as a SCR whatever. But then there are some inherent rules of the road which limit your abilities. Tough - its for your own good.

In the new stealth fighter (F22 I think its called) the plane can pull an enormous turn, 20gs whatever. But the onboard computer limits the turn capability to make sure the pilot doesn't pass out in the process.

There seems to be a general attitude that most divers want to control their own RB using the info provided. But if you foolishly tell it to pull 20gs and pass out (e.g. by using the dilutant button when you should be using the O2 button on a mCCR is wheer I think this happened) That's a design flaw IMO.

The Cis seems to be an exception to this information but not that much computer control concept. The Kiss being one unit on the other end of the spectrum (as far as I can tell).

Am I way off base here? We can talk about internal fault correction next

 

[rjack321]

As you comsume the O2, the recirculated gas volume shrinks making the inhale smaller and smaller

This is exactly what I was wondering (although I really didn't know how to ask) - how they did gas injection, thanks

 

[webhead]

I was thinking if there was a "door" to seperate a sensor from the loop. Then you could recal with a known mass of dilutant and O2. Via a seperate injection system or something like two simple constant flow orifices. wouldn't be much gas.

Nice idea. Can't say if anyone has tried this or not. My reaction is that this would add weight, complexity and cost to address something that I can monitor in other ways (i.e. dil flush, cell tests and monitoring loop volume while diving). And getting a bad cal u/w seems more dangerous to me than a cell that is drifting. One of the reasons you have 3 cells w/ most eCCRs.

I wondered if you could protect against scubber failure the same way - have 2 scrubbers isolated w/ a valve that you can turn u/w thus switching to a "good" scrubber if one fails.

When you do a dilutant flush what do you try to drive the pp02s down to?

Something lower than 1.4, I hope, if you are diving trimix. Intially, RB divers use air. This is part of gas planning and I try to mix a dil gas w/ a PO2 of less than 1.2 at max depth. It might be lower depending on if there is sand at the bottom or not. My bailout is usually higher PO2 at max depth mainly because if I'm using it, I'm not staying at max depth longer than I have to and I want higher PO2 to help w/ deco since I'm no longer at optimal PO2 for the whole ascent.

I was watching a nice show on PBS last night about aircraft design. They were talking about the original flying wing, 1950 plane. Which inherently had a lot of yaw to it - not having a rudder and all. It took too much pilot attention to be an effective bomber and was scrapped as a concept for years. So the new B2 is the same basic design regurgitated but its computer controlled fly by wire.

Pieces of wing have fallen off and the plane still flys - straight and level despite the inherent instability of a rudderless design. In fact the test pilot at the time didn't even realize it, the transition was that seamless. The chase plane saw the pieces come off and alerted the test pilot.

So extrapolating this concept to RBs. (and this is stolen partly from Cedrics pdf posted earlier [at least I think he's part author])

Why are their design elements which allow for diver error at all? I know you can always design a better idiot. But these deaths seem preventable to me via better engineering. CO2 sensors triggering loop flushes, and low ppO2 bailout injection regardless of diver action being the 2 most obvious that come to mind.

Easy answer is cost. Look at all the great features Kevin has added to the Ouroboros. Nice gear for 8250GBP (British pounds). And there is also the development curve. Think of flying in the 1920's. Don't think the Wright brothers were sharing their successes and failures w/ Curtis so they could all make a better plane back then. At DEMA, seemed like every manufacturer was touting a better CCR or upgrade but no one would give details. I think the RB industry has more vaporware than any software company I've seen... which is were we got the term from in the 1st place. Not being a manufacturer and just an end user, I can be ignorant of their issues and bad mouth them for delays and high prices.

Something tells me the Navy has these features in their RBs but us recreational folks are stuck reinventing/redesigning the wheel.

I'm not sure I agree w/ that. But hearing/seeing things like the Oceanic HUD makes me think they might have some cool toys over there. Problem I see w/ the military is that most stuff is classified or restricted use. And when the Navy pays a company to develop something, they usually don't like the maker selling to the public too. I'm still waiting for the F16 to be sold commercially. Or the 007 pen RB developed by the Oceanic skunkworks.

But the Navy dive gear that I've seen and read about seem to me to be a little behind the curve. Might have a lot to do w/ how they dive compared to the civilian world.

 

[limeyx]

Some additional comments.... and acronyms.

As for recent surface fatalities, I don't think I've heard about a death on the surface that occured on the surface. That is, the last couple incidents described a RB diver surfacing in trouble and slipping back underwater. The descriptions indicate that the diver had an issue underwater and surfaced in distress, possible w/ DCS. Years ago, there were reports of people that passed out walking to the swim platform from lack of O2. That is what I consider a surface accident.
...

I'm also advised that a 60 year old man died up north at Pt. Sur on Saturday. The initial information was another rebreather, but then a 2nd person told me it was open circuit. Any of you guys up north have any 1st hand information?


Hi Mike,

I was unfortunate enough to be on the boat. It's not clear what happened.

I can confirm that the missing diver was using a Prism rebreather. He exited the boat and was seen to swim to the float marking the downline to the pinnacle. Shortly thereafter his teammates called over to the boat and asked where he was. He had made it clear that nobody was to be solo diving so it is very unlikely he started the dive without his team. Surface conditions were good with relatively flat seas, light winds and no surface current (though there was a significant current at depth). It was determined that he was not on the surface. One of his teammates descended far enough to see the top of the pinnacle and didn't see him on the line. We called the CG and began search and rescue efforts. Several attempts were made locate him on the bottom including search patterns with scooters but the bottom under the boat was 170 feet so there was a limit to what we could do.



I think there was an SB thread about this one also.

 

[rjack321]

Think of flying in the 1920's. Don't think the Wright brothers were sharing their successes and failures w/ Curtis so they could all make a better plane back then. At DEMA, seemed like every manufacturer was touting a better CCR or upgrade but no one would give details. I think the RB industry has more vaporware than any software company I've seen... which is were we got the term from in the 1st place.

Good point. Its hard to tell when a gizmo is "mature" though. Since there don't appear (to my dumb outside eyes) too many commonalities between units beside the loop, counterlung an O2 sensors.

I mean there have got to be loads of RB versions of the Mares HUB out there. What kind of stupid gimicks should an interested diver steer away from?

 

[rjack321]

Hi Mike,

I was unfortunate enough to be on the boat. It's not clear what happened.

I can confirm that the missing diver was using a Prism rebreather. He exited the boat and was seen to swim to the float marking the downline to the pinnacle. Shortly thereafter his teammates called over to the boat and asked where he was. He had made it clear that nobody was to be solo diving so it is very unlikely he started the dive without his team. Surface conditions were good with relatively flat seas, light winds and no surface current (though there was a significant current at depth). It was determined that he was not on the surface. One of his teammates descended far enough to see the top of the pinnacle and didn't see him on the line. We called the CG and began search and rescue efforts. Several attempts were made locate him on the bottom including search patterns with scooters but the bottom under the boat was 170 feet so there was a limit to what we could do.

This was the surface incident that sticks in my mind as preventable with better engineering

 

[PacketSniffer]

Something tells me the Navy has these features in their RBs but us recreational folks are stuck reinventing/redesigning the wheel.

Actually, I spoke directly to someone from the Navy at DEMA that would know this information. I asked him if the Navy was using CO2 sensors in their rebreathers. The answer, today anyway, is no.

 

[trob09]

To this I say...

Its not error proofing as much as its designing a system which stays on the road by itself. Can't cross the double yellow or the white shoulder lines.

But if you say left it goes that way. You do control all the various manipulations to get the ppO2 to rise or use off-board gas as a SCR whatever. But then there are some inherent rules of the road which limit your abilities. Tough - its for your own good.

In the new stealth fighter (F22 I think its called) the plane can pull an enormous turn, 20gs whatever. But the onboard computer limits the turn capability to make sure the pilot doesn't pass out in the process.

There seems to be a general attitude that most divers want to control their own RB using the info provided. But if you foolishly tell it to pull 20gs and pass out (e.g. by using the dilutant button when you should be using the O2 button on a mCCR is wheer I think this happened) That's a design flaw IMO.

The Cis seems to be an exception to this information but not that much computer control concept. The Kiss being one unit on the other end of the spectrum (as far as I can tell).

Am I way off base here? We can talk about internal fault correction next

Well there are no cars that prevent the driver from:
- veering off the road or into oncoming traffic
- exceeding or dropping under the posted speed limits
- careening into people/buildings/lakes/trees
- putting Coke in the gas tank instead of fuel
- Drinking and driving (although there are individual, court-ordered cases of this)
- Driving without the lights
- Driving while some critical piece is broken
- Etc... you get the idea

I wouldn't want a car that does all of the things above any more than I want a rebreather that does the dive for me with me sort of steering it around. Safety features that are being built into cars are there to make accidents more survivable, not take the decision away from the driver.

I don't think you'll find a rebreather diver who doesn't want to see increased safety protocol and features. I think you will find a large percentage of rebreather divers prefer to keep themselves in control and not abdicate that control to the machine.

The Cis is an interesting and very well thought-out unit. It is also a beast (I've not dove one, but I have looked one over very closely). The KISS is also an attractive unit but not without drawbacks. I dive a heavily modified Meg that meets my current dive needs which includes caves and wrecks

 

[rjack321]

- Drinking and driving (although there are individual, court-ordered cases of this)
- Driving without the lights
- Driving while some critical piece is broken

To some extent yes, except there are more and more 'rain sensing' windshield wipers, daytime running lights, and breathalyzer interlock like devices.

But RB divers seem to shun the concept of the RB itself prohibiting a ppO2 of 2.5 Or a WOB (heat?) sensor which triggers a loop flush.

Is that because the technology hasn't been reliable enough to really trust to "drive" for you? I.e. your brain is the only fault free peice of equipment you take on the dive?

 

[trob09]

This was the surface incident that sticks in my mind as preventable with better engineering

Without body recovery (sorry to be morbid) there is no way to determine the cause of the fatality. By extension, there is no way to determine if better engineering was needed or if it would have prevented this accident.