Hybrid Rebreathers

Drmike

Hi Paul, I am not very familar with your unit, but truth be told I dont need to change anything with any of my rebreathers if the controller or o2 inject fails - I just run manually of the independant display.


I have a deeply unpopular theory;
if someone isnt comfortable doing a dive by manual injections only (no solenoid, no kiss or needle) then they shouldnt do the dive on a fully functioning eccr or KISS

why? because if they are not comfortable its because they dont believe they can monitor their handsets enough on that dive to be safe....in which case they shouldnt be diving a Rebreather as electronics can fail at anytime and they need to monitor freq enough to negate that risk

[runs away and hides]

__________________
Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you

johnv

No, but I have enough experience with ECCR, CMF and needle valve systems to know that I don't need both on a single loop at the same time.

regards,
John

Brainx3

Hi guys,


Thanks for the feedback guys. All points have been taken. I personally have never dived hybrid before so I wouldn't be able to know the exact practical difference while diving. Although I spoke today with Dave Thompson and he told me that diving hybrid gives a more stable PPO2. In addition, theoratically speaking, hybrid system does provide a more controlled mCCR rather than pressing the O2 extensively upon ascend as we currently do on the Inspiration and Evolution units without having the possibility to have a constant O2 flow in case the controllers were down for any reason. In my opinion having such settings as follow would offer a better redundancy to the eCCR in general.

- Having eCCR with dual controllers (As we have in the Inspiration/Evolution)
- Additional HUD
- Additional O2 monitor with additional O2 Cell (As VR3 connected to the unit and/or Shearwater suit)
- Having O2 orifice with constant O2 flow connected to the loop and to a second O2 cylinder (Then the diver can control opening the extra cylinder in case the primary system failed and/or if the diver prefers to dive mCCR primarily and have the controllers as backup).


Best Regards. Wael

__________________
The depth of life cannot be measured in Bars, nor can the sea of lies, that lies within.

I don't take crap for an answer...

paulraymaekers

well that's part of the 'trip saver': on the rEvo you have 3 independant systems, is one fails, you have 2 left, and you continue your trip
with only one left, hmm, you end the dive correctly, but you don't do more dives with only one system

I fully agree!

__________________
www.rEvo-rebreathers.com

.... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...

Drmike

better redundancy doesnt automatically mean the system is overall safer (if that redundancy adds additional risk and complexity for little reward)

none of the above is needed IF you are monitoring your handsets enough

and if you arent monitioring your handsets enough you better not add a 2nd O2 system in parallel as it may save your some deco if one system fails to give you enough O2, but, with that insuficient monitoring, it could kill you if one system gives you too much

__________________
Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you

Brainx3

Hi,


Mike, you need to read again what I wrote in the brackets as it seems that you are focusing only on one point which is the complexity of the system. Rebreathers generally can kill if the diver doesn't know what's he/she is doing. Others have already implemented such hybrid systems and diving them without any problem.


Best Regards. Wael

__________________
The depth of life cannot be measured in Bars, nor can the sea of lies, that lies within.

I don't take crap for an answer...

Dave Sutton

How can the TRUTH be unpopular?
I always thought this was self evident.

You are lucky in your rig choices (wise, actually), as both the 'Boris and the Mark-xx's have the isolated secondary displays so they can be run mCCR. Most rigs are not as redundant and a pod fry = a dead rig witn no recovery. Right now the three 'most failure tolerant' expedition rigs (eCCR's) are the Mark-xx, 'Boris, and Shearwater-rEvo. The rEvo actually takes it to a new level, with essentially 2 secondaries (the dual rEvodreams) and the Shearwater controller acting as the "Primary". Loss of any two still gives a divable rig. Of the three rigs cited, the rEvo is by far the lowest workload to continue with after a failure, hands down.



Dave

.

__________________
.

"All animals are equal, but some animals are more equal than others"


Professional Small Boy: Never Successfully Cubicled.

Dave Sutton

I think it's all really a matter of how you view it: On the hybrid rEvo, it's dived as "Just an eCCR" and you never even THINK about the orifice. In fact, deep? The plug is outta the first stage, the orifice is blanked with a little plug, and it *is* a straight eCCR. It's all just plug and play. Toss the pod? Unblock the orifice, stick the plug back into the first stage and press on. For sub 80 meter stuff? Just leave the plug in the first stage, let the orifice flow, and it's not hurting a thing. The idea of a "parachute" system to me is nonsensical: Why bother? For me having the choice is just about saving the expedition, not the dive. With that said, it takes nothing away either in day to day use (in the case of the rEvo anyhow).

Going to be hosting a good mutual friend aboard EXPLORER this week... . "The Local Pinnicle Wreck" calls us to come and visit.


Dave


.

__________________
.

"All animals are equal, but some animals are more equal than others"


Professional Small Boy: Never Successfully Cubicled.

Drmike

may I sugest its you thats not reading. I am focusing on the additional risk of having a redundant 02 feed system-your only focusing on the percieved and/or min benefits

The risk includes more complexity and higher risk of o2 leaking into system
the latter you dont apear to recognise.


Let me ask you this question.

What problem are you trying to solve by adding a parachute 2nd o2 feed system?

Risk of hypoxia?

Ok lets investigate that.

Your at 50m loop is 1.3 and you only o2 feed systems stops injecting.

If your not monitoring how long swiming at that depth will it take for your loop to become hypoxic?

answer= a very long time (havent done maths but its ages). I suspect even the worst diver checks handsets far far more freq than the time req for loop to become hypoxic at depth

Your at 50m with 1.3 and your O2 feed system stops and for some strange reason you do direct ascent to surface, will you go hypoxic? answer = no


The only real risk of hypoxia on an Rebreather is if your bouncing up and down in shallows or surface swimming (esp with hypoxic dil) and even then risk is small esp on a deco dive

So your additional o2 feed system is in fact only solving one problem (risk of hypoxia inshallows or surface)
That risk can easily be negated by practicing o2 Rebreather in shallows as many do

That shallows benefit needs to be weighed against the risk of adding a 2nd o2 feed system.


That risk being the increased risk of o2 leak causing hyperoxia and the additional complexity (id perhaps go further and suggest a parachute may also encourage a more relaxed and complacent attitude towards monitoring) and perhaps a CMF system has a better safety record compared to eccr for just that reason.

So my 3rd question is if your at 50m with a loop of 1,3 diving cmf and the o2 solenoid sticks open ,or your cmf valve leaks- how long would it take for the loop to go hyperoxic? damng fast!

So we have 2 risks = hypoxia and hyperoxia
the former takes far far longer and is only a risk in shallows
the latter can happen very fast at any depth below 6m.


your parachute system may solve the former but it adds risk to the latter.


If I was diving a system with 1 or 10 o2 feed systems Id still be checking my handsets at an interval comencerate with the possible rate of change of my ppo2 at that time - this is survival Rebreather 101. If your doing that then you dont need more than 1 o2 feed system or associated additional complexity cost and risk.


Others have sex without condoms too without any problems.

I have effectively donemany many dives in hybrid mode (something manymk15 series divers are forced to do fromtime totime ) and I did find the solenoid (if its not in freq use) would jam up. so im not sure Id be confident it would work when needed anyway. Frankly your monitoring would have to be terrible to go hypoxic on a dive

__________________
Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you

Drmike

Hi Dave, so if i undestand you right on the revo the orifice is blocked off and only opened if the electronic injection fails? Thats fine (and neat)- but then its a very different thing to a parachute (parallel) system and doesnt share the associated risk of 2 simultaneous feed systems in operation at same time.
really? who might that be?...is she cute?

__________________
Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you