Doing Tech+Cave on a RB?

[limeyx]

1) I person, 6ish pages ago, said to not not do the tech or cave route on a RB. Its wasn't me, and it seems like its time to get over it.
...

Ps. I know the RB80 doesn't have a "setpoint". "Changing" it by changing supply cylinders was a joke.

Although that's essentially what the EKPP are doing in that weird cave of theirs that wont stay at one reasonable depth for more than 100 feet. Maybe not ideal, but seems to "work"

 

[rjack321]

Glad you're back thought I was the only bubblehead here...

 

[JeffG]

Although that's essentially what the EKPP are doing in that weird cave of theirs that wont stay at one reasonable depth for more than 100 feet. Maybe not ideal, but seems to "work"

I thought (and I could be wrong...not like that would be the first time) is that the WKPP were using stages with quick disconnects to drive the RB80 and keeping the backgas tanks as the reserve. I'm sure that's what Casey was doing on their last run.

 

[CCRDolphinDiver]

Ooooh....I can hear the chest thumping from here. (or..I'll drop some names, and maybe somebody will be impressed)

You're the man.

Right, so dam--ed if I do and the same if I dont... how does one give out correct information, debunk the bunk and set the record straight without saying where you come from and without sounding like you are thumping your chest. I have had enough of guys who state "THIS IS THE TRUTH" but just expect folks to read and believe with no background, no experience and under thier names it reads 50-99 dives. But when I give some info, back it up with references, Im beating my chest or dropping names. Well done jeff, Im sure everyone is chanting your name and bowing down :bow:

 

[rjack321]

Here are some real questions...

1) I have experienced quite a bit of sensor drift with my continuous blending fill station. Do any of the current commercially available units (CCAU) allow you to take a sensor "off-line" and recalibrate it during a dive? (seperate from the loop)

2) Do any CCAUs have a a Cis like membrane or some other waterproofing to keep caustic crap out of your lungs in event excess water gets in the loop?

3) Do any CCAUs other than the RB80/clones allow you to basically dive OC gases "straight-up"

4) How did the old time early 1900s O2 rebreathers work?

5) Is there a CO2 sensor of any type incorporated into any commercial unit? Canary in the loop??

6) Seems like there have been a number of surface fatalities lately - fairly experienced folks too. Has anyone a low pp02 backup injection system or is this considered to dangerous to have "armed"?

7) I have some LED tail lights on my boat trailer. They are fully potted, but in less than a year a whole bunch of them have failed. What kind of electronics leakage safeguards exist and which units have them? aka "redundant potting"

 

[limeyx]

I thought (and I could be wrong...not like that would be the first time) is that the WKPP were using stages with quick disconnects to drive the RB80 and keeping the backgas tanks as the reserve. I'm sure that's what Casey was doing on their last run.

Yes, that's my understanding too, but the dive I was talking about was EKPP not WKPP

Profile is on this page:

I think the depth variations are so great that they need drive bottles with different MOD's and have to switch between them.

http://www.ekpp.org/projects/gourneyrou06_03/push.html

 

[CCRDolphinDiver]

Here are some real questions...

1) I have experienced quite a bit of sensor drift with my continuous blending fill station. Do any of the current commercially available units (CCAU) allow you to take a sensor "off-line" and recalibrate it during a dive? (seperate from the loop)

2) Do any CCAUs have a a Cis like membrane or some other waterproofing to keep caustic crap out of your lungs in event excess water gets in the loop?

3) Do any CCAUs other than the RB80/clones allow you to basically dive OC gases "straight-up"

4) How did the old time early 1900s O2 rebreathers work?

5) Is there a CO2 sensor of any type incorporated into any commercial unit? Canary in the loop??

6) Seems like there have been a number of surface fatalities lately - fairly experienced folks too. Has anyone a low pp02 backup injection system or is this considered to dangerous to have "armed"?

7) I have some LED tail lights on my boat trailer. They are fully potted, but in less than a year a whole bunch of them have failed. What kind of electronics leakage safeguards exist and which units have them? aka "redundant potting"

1) no, that would be very dangerous to do, however you can purge the loop with a known gas (diluent at depth and O2 at <20) at any depth and determine for yourself which sensors are correct.
2)no, however the Cis-lunar canister (if you can find one) can be dropped into a meg with no mods. ISC has purchased the rights to build the water tolerant version of the radial scrubber similar to the original cis scrubber, they will begin production of the non water tolerant version this month.
3)some units allow off board gas to be plummed into the loop and these can be breathed "open Loop" or SCR (Meg, inspio/evo, boris, Optima, prism), user courses teach carrying sufficient OC bailout to reach the surface as a slung cylinder. the Jetsam KISS CCR's have a BOV or bail out valve as part of the DSV or dive surface valve (boy we love our acronyms) but it basically the thing you put in your mouth, on the kiss units you turn a valve and are breathing OC off the same mouthpeice that you were breathing the loop off of.
4)they didnt mostly you were just breathing down the gas trapped in the helmet, with some potash to absorb the CO2.
5) there are at least 4 companies working on it, that have functioning prototypes
6)diver error is a quantity that has plauged the industry and will continue to do so, just like driver error, there will always be those who insist on racing on the streets, driving under the influence and such, just as soon as you build something idiot proof, they will design better idiots.
7) I cant comment on your lights, maybe the reason they failed wasnt potting?? Meg electronics are fully potted and there was one run that failed, but since then great results and very few failures. Inspio stuff is in the handsets and sealed,(occasional failures, Prisim electronics are in the head and potted, then sealed with an o ring cap, I dont know how CCR tech does the boris elect, the optima HH is sealed in the handset by O rings but not potted.

 

[rjack321]

1) no, that would be very dangerous to do, however you can purge the loop with a known gas (diluent at depth and O2 at <20) at any depth and determine for yourself which sensors are correct.

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.

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

6)diver error is a quantity that has plauged the industry and will continue to do so, just like driver error, there will always be those who insist on racing on the streets, driving under the influence and such, just as soon as you build something idiot proof, they will design better idiots.

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.

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

 

[trob09]

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.

Increased unit complexity and increased risk of failure. What if the "doors" get stuck shut? what if you accidentally re-calibrate at depth with an inaccurate calibration. I'd prefer to flush the loop with a known gas and read the cell reaction. At that point I'll decide if the cells can be trusted or not. If they can't, the dive is over. This may mean SCR or OC bail-out depending on the circumstances.

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

Depends on the particular philosophy, but for me Diluent should have a PO2 of 1.0 or less at the deepest depth of the dive.

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.

I saw that too, great show. A lot of people are trying to build that sort of control into rebreathers, others prefer to keep the diver in greater control. There is always a risk of a 'safety feature' becoming an additional complexity/failure point

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.

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.

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

Much like few of us have weapons mounts on our cars or personal planes capable of Mach 2.

 

[webhead]

Some additional comments.... and acronyms.

2) Most rebreathers are designed to collect outside water from the most likely source, the mouth piece. That is, if water enters the mouthpiece, water ends up in the exhale counterlung (CL) where it stays for the dive or can be expelled out thru an over pressure valve (OPV) on the CL. Some designs are better than others in this regard.

3) Like every product, there are more and more upgrades and mods for units to add things like this. That is, while a unit may not come w/ the BOV from the factory, there are several people making parts that can be added later - things like the BOV, an auto diluent valve (ADV) and 4th cell holder are the most common.

And to expand on Ron's comment on training, RB classes teach the use of off board gases, diving a full electronic CCR (eCCR) in semi closed (SCR) mode and manual mode, loop flush for PO2 check, etc. They also teach signs and solutions to all problems you can think of including low or high PO2 (hyeroxia and hyperoxia), too much CO2 (hypercapnia) and O2 exposure (CNS, etc.)

4) This might not be what you asked but the first "big" use of rebreathers were O2 only units. They are about as simple as they come if used in 20 feet of water or less. You don't need to monitor PO2 because your PO2 is always between 1.0 and 1.6 (surface and 20 fsw). As you comsume the O2, the recirculated gas volume shrinks making the inhale smaller and smaller. One either presses a manual addition valve (MAV) to add O2 and increase the loop volume or there was/is a mechanical valve like an ADV that adds O2 for you. And your bailout was to swim 20 feet or less up.

5) One unit, the APD Inspiration and Evolution w/ Vision electronics has developed a tempeture or temp stick. It does not measure CO2 but it does monitor the scrubber usage by changes in the "hot" areas in the scrubber bed. This aides the diver with tracking scrubber usage.

6) While I agree w/ Ron. I think that the diver just needs to be vigilante that if they are breathing the loop, they need to be working - everything on, tested and working. If this is done then the unit (thinking specifically of the Meg and Inspo/Evo) will maintain a breathable PO2 (i.e. inject O2). Many of the eCCRs have "auto-on" controllers. They turn on automatically when wet or they sense a pressure increase. Not a fix for proper pre dive procedures but an attempt to protect the forgetful and foolish.

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.

7) Different companies do different and similar things to protect the electronics from water. Some divers will tell you there are 2 types of u/w electronics - those that have flooded and those that will. I think there have been major advancements in this field especially w/ all the dive computers for recreational use. But I also think there is work to be done. A common problem there is how do you make something 100% waterproof when the user is likely sealing it? I can seal the main PCB but if the battery compartment leaks after a user changes the battery, what can you do as a manufacturer? Not the most common RB failure but maybe the most common electronics failure next to O2 cell issues.