Hybrid Rebreathers

bgpartri

I just changed Lynn's rebreather to a hybrid again and noticed the interesting comments from Dave and Mike about hybrid rebreathers.

I should mention that Lynn had a hybrid system on her Classic KISS for several years. The first version of a Shearwater controller was a bolt-on for the KISS, and we left the orifice in place.

Now it looks like there will be more hybrids on the market, I would like to offer the opportunity to hear peoples opinions about operational procedures.

For example, should you dive manually and use the solenoid for a backup, or should you let the solenoid control the dive and have the orifice for backup?

What does the pre-breath test look like?

Obviously, I have my ideas on the subject, but it's clear that there are a variety of opinions and arguements for different strategies.

Bruce

__________________
http://www.rebreather.ca

Good judgement comes from experience, and experience comes from bad judgement.

paulraymaekers

Hi Bruce, i suppose you know my opinion, but just for the readers :-)

For me there is no absolute truth: i use the hybrid system in different ways:
one day i fly manually and have the solenoid as back-up (mostly in relaxed diving, looking at a reef or fishes :-), when there is more task-loading (filming, sometimes teaching) i have the unit fly on high set-point..

the point is the hybrid system leaves all the options open, and the user chooses what he likes at the given moment

regards
paul

__________________
www.rEvo-rebreathers.com

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

RAL

Dove with a fellow last year that was using a hybrid Meg. He added the manual bits (hydrogom I think) & set the E controler to his desired setpoint. I think he called it a buffered electric. Claimed it was way more stable than the stock Meg & his batteries lasted much longer. He was quite happy with it but indicated he took a bit of flack from Meg purists.

RAL

__________________
The sea does not care about you.

ForTheFight

Its certainly interesting, I personally would like the option to move my KISS over to hybrid from time to time.

__________________
This post may be up to 80% accurate...

dave t

One of the "weak" points of a manual system is you have to add a fair bit of o2 on the ascent if you want to maintain a good po2. If you or your buddy are in trouble and you have your hands full doing other stuff a manual system could put you in danger(its very difficult to do a controlled bouyant lift on an unconcious diver and maintain your po2 manually) For me this is where the parachute system comes into play.......so

run the unit on the orifice and have the electronics as a back-up

slightly off thread but my belief is that the reason why MCCr's have a good safety record is the "mindset" they instill in the diver. Adding auto functions may deteriorate that mindset!

Dave

Stephane

Hello Bruce,

Sorry, I have a Hammerhead, can I still play with you?

I fly the unit mostly manual and when there is task loading or when I feel lazy, I switch to the high set point. Even for ascent.
The solenoid fires at a low rate and with the HUDs, I control every time my PpO2. From time to time I compare the displays, all say the same value, incredible!
When in manual mode, the HH is mostly set to OC mode, the parachute opens at 0,19. That is for shallow dives (40m). Deeper, I will set it to a low set point (0,5).
I haven't had any issue with the controller yet (battery, solenoid stuck opened), I cross my fingers.
The hybrid system is very very pleasant to dive.

__________________
Stéphane
Hammer-rEvo powered!

gerstl_ossi

Hi Bruce,
My brother and I use our homemade rebreathers in hybrid mode. Kiss style orifice with 0,7 l flow and a GF controller on the unit from my brother and a pursuit on my unit. In normal use the controller had to add not many oxygen to hold the exactly pPO2. If there is a problem with the solenoid I can isolate it and use the rebreather in Kiss style mode only. We use two O2 tank, one with normal first stage set on 7 bar for the solenoid and one set on 13-14 bar (isolated) for the orifice.
Works fine
Cheers Oswald

bgpartri

What do you do for a pre-dive check to ensure that both systems are working?

Everybody pre-breaths now right?

Bruce

__________________
http://www.rebreather.ca

Good judgement comes from experience, and experience comes from bad judgement.

gerstl_ossi

I put the pursuit from 0.19 to 0,50 and watch the display to see the ppO2 raising to 0.50 and list the solenoid firing (O2 flow on orifice is off) . I prebreathe a few minutes. Than put the pursuit back to 0.19 and open the kiss system continuing my breathing for the rest of the prebreathe time. The ppO2 should stay in the 0,50 range as the flow rate is my metabolic consumption in rest situation.
I use the rebreather in eCCR mode with the flow always on. So the solenoid works normally, only that he has to fire not so much. I think it has no sens to fly a eCCR manually as the only problem a eCCR can have vs. a mCCR is the malfunction of the solenoid (problems on sensors are the same on both systems and make no difference) . And if the solenoid work, the eCCR work if not (stay in off or on position, low battery, malfunction of the controller electronic) I would have the same problem if i fly it manually and use the electronic only as a parachute (a parachute that would not work in in this case) . The KISS system on my unit is more for bailout situation where the controller electronic or the solenoid would not work. Or if I lost the oxygen of the tank for the solenoid. I can fly the unit in KISS style on a separate O2 tank and a separate HUD-Electronic (like Shearwaterhud with - different battery, different electronic, different electronic housing ec.)

Stephane

Nothing. If the solenoid does not fire, this is not a problem, I will drive the system manually.
For the orifice, I open the O2 valve while I put on the rig so at the end I have a PpO2 of 1,02. Anyway, diving with a clogged orifice is not difficult, I've done it.

Oh, yes, I should do it every time ...

__________________
Stéphane
Hammer-rEvo powered!