Hybrid Rebreathers

Stephane

I'm not relying on the electronic as a parachute system. I'm using the controller whenever I wnt during my dive. And I'm aware of any change of PpO2 with the HUD.

__________________
Stéphane
Hammer-rEvo powered!

henckell

A recreational unit wouldn't need twin O2 tanks or regs. Normally the fixed IP on a manual Rebreather allows depths down to around 100 meters, well outside the recreational boundaries. If one O2 delivery system fails for some reason, it could have failed anyway using either only manual or only electronic control. The only reason for using twin O2 tanks/regs would be redundancy, which is usually not standard on any rig. You check your PO2 now and then and it's always possible to fly manually without any "O2-addition-aid".

I have used a HH-KISS for many years and I like the combined benefits of the two systems, but I've come across people who seem concerned about having two systems and who for some reason think that these systems (technically) would have a higher likelyhood of individual failure when used together?

I have no problem relying on a "parachute" functionality in a stressful situation and if it woulnd't work, then it´s not worse than not having it in the first place. It's like having ABS brakes in your car. They might fail without you noticing it, but if they don't they're still good to have when you need them, and it's not an added problem unless you drive around anticipating that it will save your life one day. Then you need to change your mindset!

I can understand the comment that an electronic system might make you complacent over time, but depending on how you see it you have a manual Rebreather with a "parachute" or an electronic unit with a "battery saver". Anyway, YOU are still responsible for knowing your PO2.

__________________
http://www.rekodeko.se

Ben Field

[quote=henckell;182930]A recreational unit wouldn't need twin O2 tanks or regs. Normally the fixed IP on a manual Rebreather allows depths down to around 100 meters, well outside the recreational boundaries. If one O2 delivery system fails for some reason, it could have failed anyway using either only manual or only electronic control. The only reason for using twin O2 tanks/regs would be redundancy, which is usually not standard on any rig. You check your PO2 now and then and it's always possible to fly manually without any "O2-addition-aid".[/quote

I think your missed my point- I was saying that two tanks is unecessary but I don't see how you can supply 11-12.5bar fixed IP for a Orifice and 7-8bar balanced for solenoid without complication or >insert magical new device<

The fixed IP might allow 100mtrs+ but I (and others I assume) need that flow rate shallower for the KISS principle to work, so I can't reduce it to allow for a solenoid...

__________________

Beware Fridge Suck

Stephane

Correct me if I'm wrong but the important point for the solenoid is the differential pressure.
In a Kiss style system, the IP delivered is constant and set to around 10 bar. So as depth increases (and ambient pressure), the differential pressure will decrease.
At 20m, we have 3 bar of ambient pressure resulting in a differential pressure of 7 bar, just what is recommended.

Am I missing something ?

__________________
Stéphane
Hammer-rEvo powered!

lizardland

It wouldn't be that hard. One reg supplies the solenoid with a line coming off the HP port to a second fixed IP 1st stage.

Or an h-valve.

Or an attenuator like on the Mk15 so that the solenoid is only getting a minimal exposure to the higher pressure. You could even put a remote meter valve so that if the solenoid did jam open then you could run it as a constant flow KISS style unit.

Or just use one reg with a varying IP supplying the solenoid, an adjustable meter valve and a bypass. Accept that you'll have to adjust O2 flow on the fly or manually add more frequently in parts of the dive.

It's "without complication" that comes subjective in any solution. I dived with the meter valve/varying IP solution for years (albeit without the solenoid), it's a great system. I've been tempted to re-fit a valve on to my CK.

Cheers,

Stuart

__________________
Can you imagine drifting along in the sea with your mouth open and a load of f***ing plankton going in? You'd like it, would you?

www.westons-cider.co.uk

Azerbaijani Association of Technical Divers Publicity Officer and Goat Wrangler

AntoineD

Hello,
this interesting discussion about the hybrid configuration makes me think about a similar situation with sky diving:

-Everybody opens his or her own parachute manually, looking at the altitude, (...mCCR)
-In addition each chute has a safety device that opens it automatically (actually the reserve parachute) when at a free fall speed below some low altitude threshold (...eCCR). But interestingly, it has never been used as routine (notably in training).
People are not proud when it opens: they have to replace a small rope loop, repack their reserve parachute, it shows they have crossed a limit, and it is way more stylish to open it manually.

So it looks like a mCCR mindset, with the electronics as back up.

If (when?) I had a hybrid CCR, I would look at it this way:
-a mental seal (or game) about not using the solenoid (low SP), thinking about the beauty to be all over the ppO2 with orifice+manually.
- the peace of mind of knowing the electronics are there (low chance that they fail when I happen to need them, as long as proper checking is done in a way or another at every dive)
- not thinking about any mental switch to eCCR mode explained above until I really feel a need (task loading, depth...) if any.

Antoine

divelermentov

[quote=Ben Field;182937] Mounting a second o2 tank isn't actually so difficult,
and as I see it it would give you the advantage that you can shut one system down without effecting the other, in particular with a stuck open solenoide.

This would even make the configuration change between mCCr, eCCr and hCCR not even a matter of 5 minutes, but just seconds ( turning tank on /off), this would mean that if you want to go deeper you could descent past the mCCR limitation as well, the eCCR would take over.

As i see it the eCCR is not the parachute to the mCCR, but the other way around. eCCRs are comfortable to dive, but they fail, you do have to monitor them constantly, just listening for the solenoide to kick in is i think not enough.


On another note a second tank would mean you get away with lower pressure o2 fills as well. and as i am really really tight and dont want to pay for a booster pump, nor the LDS for boosting my tanks this could allow me to suck my g of O2 empty to a lower pressure. Did I mention that I am really tight - dont like to retunr half empty 02 tanks to BOC.


So for me a hybrid would make sense, as a electronic failure wouldn't ground me form diving,
I still have to monitor the systems closely, therefore a po2 meter whcih is not part of teh eCCR would be my preference ( this woudl keep the monitoring between mCCR and eCCR seperat) - so truly two systems.
I could get away with less pressure in my 02 tanks, and at the end wouldn't have the mCCR limitations.

But these are only my .02

__________________
May The Sorb Be With You

Brainx3

Hi,


I find the idea of running mCCR primarily and eCCR as secondary does make better redundancy, and I think it's a very nice idea. Just wondering how the hybrid system could be implemented effectively to work in parallel mode on the Inspiration units?


Would appreciate any constructive ideas.


Best Regards. Wael

osiris

Huh? Why does running mCCR as primary and eCCR as secondary make for better redundnacy than eCCR as primary and mCCR as secondary? Sounds like this thread headed very quickly into "i AM therefore, I AM" territory. Surely, if you want your Inspo to work as a hybrid, you'd just shovel a KISS valve onto it - wouldn't you? Or are we duty bound to make this is more complicated than it need be?

Brainx3

Hi,


It's simply because eCCR have more failing points. Even though I have a 4th cell which is connected to my VR3, but I can't be cautious enough. I should probably re-phrase what I meant to say, which is hybrid system generally makes a better redundancy but it happens to be my personal opinion that running mCCR as primary and having the controllers as backup does make a better way of diving CCR. I'm not familiar with Kiss parts or any other units parts as I only dive inspiration. But as I said, I would appreciate some tips.


Best Regards. Wael