How deep, how long on mCCR?

jkromelow

I have just finished my KISS conversion (started almost a year ago, using Gordon's latest valve) of my Dolphin and am starting my tests in the water tomorrow. I have survived the couch!

I am interested in everyones current experience about depths and durations they feel
comfortable with their converted units. How deep and how long? Are
there conditions or circumstances you don't dive your conversion?
Ideas on using it or not using it in an overhead (wrecks/caves)
environment? What has been your experience on dive boats with your
unit?

All feedback appreciated. If you have specific questions about my conversion, ask.

__________________
Justin Kromelow
TDI Instructor
PADI MSDT

Scuba_Vixen

Maybe if you gave us some particulars; where the O2 injects, your O2 monitoring setup, how many cells, is there a VR3 or Explorer connected to a cell, what you plan to use for dil, what you have set up for bailout, what OC level of training (ie trimix), any ccr experience, this kind of information might be helpfull to keep in mind when offering suggestions.

There's a lot of CCR Dolphins on the board here, as I recall some of them have been in the 100m range, a few to about 70m to 80m, but most are owned by less experienced CCR Rebreather'ers and we are still learning the units and keeping in the 30m to 40m range, with short forays to somewhat deeper depths.

As to durations: I think you have look at where you're diving, temps, currents, comfort and task loading, all conspire to shorten scrubber life.

Depth and whether you have deco planning and sufficient OC bailout under control weigh into the duration planning as well.

From my recent experiences, I'd suggest some time in the pool to get weighting and trim spot on and then a little "get aquainted" time in open water at rec depths and run times.

Without more to work with, I can't offer anything more specific.


Welcome to Rebreather World,


Darlene

caveseeker7

Welcome to Rebreather World, Justin.

The KISS valve should be good to 100 msw, give or take a few depnding on your IP.

The main issue will be the scrubber which is tested to and rated to recreational depths only.
You've probably read Dräger's document detailing scrubber duration in stock SCR mode.

Now take into consideration that no CO2 is vented in CCR mode, the uninsulated scrubber and the effect of ambient pressure on duration (Martin Parker made an excellent post regarding pCO2 and duration ).
Be carefull and conservative. Make sure you have someone watching back (even in the pool).

As Darlene pointed out, several converted Dolphins have been past 70 msw.
But for a large part it's uncharted territory.

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Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
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decoweenie

If you set the IP as close to the maximum value where the spring will become solid (~12.5 bar) like mine, depth will be around ~110m take a few meters depending on part tolerances (already tested).

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wrecked

The duration for the dolphin 2.2kg scrubber is 4hrs, thats what I learned in my training for the Dolphin. It would be interesting to see if anyone could put together a tried and tested alogrithm for duration of sorb, though I imagine the design of the Rebreather also play's a big part in the life of the sorb.

jradomski

Being Used as A CCR, I would expect about half of that (probably less to be on the safe side, especially in colder water).. Its not a great scrubber design, it really depends on alot of the gas being vented to be useful for more than a short period of time..

Another thing to remember about the dolphin scrubber, it has almost no water tolerance at all.. so you must carry enough bailout to cover your full ascent ( and enough gas to get you back to an ascent point like an anchor line if its needed) to the surface and decompression..

I know of one person who got a caustic cocktail at 100m and is lucky he made it back..

__________________
Joe Radomski
CCR Trimix Instructor Trainer
ANDI Instructor Trainer Director #10

All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

wedivebc

When you screw up it's bad luck, when you survive that it's skill

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Dave....

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jkromelow

Here are some of the details:

O2 injects in the inhale lung. I have attached it to the mass flow controller. I am using 2 sensors, right now one is VR3 and the other is my OxyGuage. I will replace the OxyGuage with one of Mark Munro's kits shortly for 2 or 3 sensors. For dil I will use air on shallow dives (<30m or so) and will probably use something like 10/50 for everything else. My OC training is through Trimix, and I do probably about 25-50 dives of 50m to 70m a year. (everything else is shallower, teaching, SCR for a few years now...) I will get some CCR training from a fellow instructor in the upcoming weeks.

I will use sling bottles for my bail out to provide maximum flexibilty in gas and volume selections. I typically dive in Monterey, CA. About 50-55 F.

I posed my question from the perspective of understanding where the practical limits of the unit would be based on peoples experiences. I am wondering if my mCCR will be my only CCR, or if I will eventually end up with a few based on its constraints.

Thanks for your input.

Mark Munro's

__________________
Justin Kromelow
TDI Instructor
PADI MSDT

wizbang

Hi jkromelow, welcome aboard. Sounds like you have been hard at it.
I am diving a mCCR using a Gordon Smith KISS valve. I use it for all my diving (a few exceptions) shallow or deep.

I am happy with the unit design and the scrubber for all my diving so far. No problems or floods. (A handset or two and a HID but that is another story)

I find the scrubber duration no problem but then again I don't muck about trying to make it last. I am happy to toss it early and stay in the safe zone. For deeper dives the work will be done in the first hour of a fresh scrubber and the rest will be deco. My usual diving area is much warmer 17 - 24c.

the unti has its limitation I hope to be working within them.
Hope that helps.
www.kissthedolphin.com I hope to update it soon.

E-man

12.5 bar = 12.3 ATA = 113msw = 373fsw