Depth limit of mCCR Dolphin?

**jmurba** · 20th March 2008, 22:10

sorry the photos were not added to the post

**Freef** · 21st March 2008, 08:30

The CO2 absorbing properties of the scrubber may be the limitation as there may not be sufficent dwell time.

As long as the CMF doesn't drop below it's critical value and go subsonic the gas flow should be mantained regardless of depth.

**jmurba** · 21st March 2008, 09:26

[quote=Freef;175985]The CO2 absorbing properties of the scrubber may be the limitation as there may not be sufficent dwell time.
quote]

Hello,

I he no technical information regarding the dolphin scrubber dwelling time, but I think it is pretty good, the dolphin has an exhalation conter lung that slows the gas flow,

however I would not dive it lower then 80m but it is just my choise , anyway I rarely exceed 65m

regards jean mi

**jmurba** · 21st March 2008, 14:44

Quote: (Originally Posted by caveseeker7)

For what it's worth, Dräger had originally planned an 80 meter version of the Dolphin, and IIRC ANDI actually trained a couple of the Dräger guys that were to develop and test the unit.

I also vaguely remember them helping out someone modifying Dolphins for some deeper diving, reviewing the changes and pitching in a few parts in the process. There was an article in a German dive mag some time back about it, I believe the units were still SC but had gas switching hardware.

Personally I don't like the idea of diving RBs without reasonable draining ability into overhead environs (I include substancial deco here), but that's me.

yes the prototype has been showned in paris in a equippement diving show.
there were very few mods in fact.
what is very funny is that the dolphin scr could be dived to 80m as it was only using a bigger tanks and a ray dsv to inject deco gas on the surface way back.
I've dived it scr trimix a lot without a shadows of a problem
the dolphin has so many differents orifices that it was easy to find the good one to bleed the correct gas flow in the bag.
this rebreather has proven to be really flexible, versatile.
the only stupid things were the fragile plastic shell and the small wing, otherwise the dolphin could have officially extended to normoxic trimix
it is a petty to see that they dropped the towel with this rebreather.

regards

jean mi

OceanOpportunity · 21st March 2008, 22:28

I've been experimenting with a ccr-dolphin for some time now, and find it to be an excellent platform. very simple, easy to modify, its small and lightweight. A great way to dive it...use onboard O2 at the bottom of the rig, and use offboard dil (as a stage) feeding the rig and your BOV. Talk about a tight package!

regarding the scrubber...Drager has it rated at 3 hours for hard work, 4 hours for warmer water/easy work. There is no reason why this changes from scr to ccr, as scrubber tests are done with a constant flow of CO2 through the scrubber and defined conditions. Granted, this is a smaller scrubber than some of the units out there right now, but for all intents and purposes, 3-4 hours is more than adequate. Of course we want to be considerate of scrubber duration reduction with depth, but this is true for any unit.

My hangup is that the rig is not flood tolerant. I'm going to play with a few ideas to evacuate water from the exhale side of the scrubber soon and see what I come up with...there ought to be simple enough solution. Anyone try anything?

**Freef** · 22nd March 2008, 08:01

My comments on the scrubber were based on the fact that it is meant for an SCR loop, meaning that a percentage of CO2 is lost before it gets to the scrubber, and that it is designed for a shallower dive than 120m!

The figures I have seen for the scrubber life [very cold water, very high vO2] show that it has a lot more life than most of us would use it to, and my own goes with colour changing absorbent showed that after 2-3 hours at 20-35m in 10C water there is still plenty of unused sorb to go.

21st March 2008, 08:30	#12 (permalink)
Freef Custom Title Disallowed! Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Jan 2006 Location: Land of the Freef, UK. Posts: 1,427	Re: Depth limit of mCCR Dolphin? The CO2 absorbing properties of the scrubber may be the limitation as there may not be sufficent dwell time. As long as the CMF doesn't drop below it's critical value and go subsonic the gas flow should be mantained regardless of depth. __________________ David. Diving the mahogany rebreather.
(Offline)

21st March 2008, 09:26	#13 (permalink)
jmurba wet bear Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: May 2006 Location: cannes france Posts: 920	Re: Depth limit of mCCR Dolphin? [quote=Freef;175985]The CO2 absorbing properties of the scrubber may be the limitation as there may not be sufficent dwell time. quote] Hello, I he no technical information regarding the dolphin scrubber dwelling time, but I think it is pretty good, the dolphin has an exhalation conter lung that slows the gas flow, however I would not dive it lower then 80m but it is just my choise , anyway I rarely exceed 65m regards jean mi __________________ when will I be able to think about something else then spending hours underwater, when will I be normal ? http://web.mac.com/jmurba/Site_2/home.html http://web.mac.com/jmurba/Site_3/home.html
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21st March 2008, 14:44	#14 (permalink)
jmurba wet bear Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: May 2006 Location: cannes france Posts: 920	Re: Depth limit of mCCR Dolphin? Quote: (Originally Posted by caveseeker7) For what it's worth, Dräger had originally planned an 80 meter version of the Dolphin, and IIRC ANDI actually trained a couple of the Dräger guys that were to develop and test the unit. I also vaguely remember them helping out someone modifying Dolphins for some deeper diving, reviewing the changes and pitching in a few parts in the process. There was an article in a German dive mag some time back about it, I believe the units were still SC but had gas switching hardware. Personally I don't like the idea of diving RBs without reasonable draining ability into overhead environs (I include substancial deco here), but that's me. yes the prototype has been showned in paris in a equippement diving show. there were very few mods in fact. what is very funny is that the dolphin scr could be dived to 80m as it was only using a bigger tanks and a ray dsv to inject deco gas on the surface way back. I've dived it scr trimix a lot without a shadows of a problem the dolphin has so many differents orifices that it was easy to find the good one to bleed the correct gas flow in the bag. this rebreather has proven to be really flexible, versatile. the only stupid things were the fragile plastic shell and the small wing, otherwise the dolphin could have officially extended to normoxic trimix it is a petty to see that they dropped the towel with this rebreather. regards jean mi __________________ when will I be able to think about something else then spending hours underwater, when will I be normal ? http://web.mac.com/jmurba/Site_2/home.html http://web.mac.com/jmurba/Site_3/home.html
(Offline)

21st March 2008, 22:28	#15 (permalink)
OceanOpportunity for a world of water Current Rebreather/s: Other CCR Dolphin Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Other CCR Dolphin Home Build Join Date: Nov 2006 Location: Providence, RI USA Posts: 596	Re: Depth limit of mCCR Dolphin? I've been experimenting with a ccr-dolphin for some time now, and find it to be an excellent platform. very simple, easy to modify, its small and lightweight. A great way to dive it...use onboard O2 at the bottom of the rig, and use offboard dil (as a stage) feeding the rig and your BOV. Talk about a tight package! regarding the scrubber...Drager has it rated at 3 hours for hard work, 4 hours for warmer water/easy work. There is no reason why this changes from scr to ccr, as scrubber tests are done with a constant flow of CO2 through the scrubber and defined conditions. Granted, this is a smaller scrubber than some of the units out there right now, but for all intents and purposes, 3-4 hours is more than adequate. Of course we want to be considerate of scrubber duration reduction with depth, but this is true for any unit. My hangup is that the rig is not flood tolerant. I'm going to play with a few ideas to evacuate water from the exhale side of the scrubber soon and see what I come up with...there ought to be simple enough solution. Anyone try anything? __________________ Michael Lombardi Oceans of Opportunity www.oceanopportunity.com Elected Director, Society for Human Performance in Extreme Environments MN'07, The Explorers Club Project Manager, Diving a Dream
(Offline)

22nd March 2008, 08:01	#16 (permalink)
Freef Custom Title Disallowed! Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Jan 2006 Location: Land of the Freef, UK. Posts: 1,427	Re: Depth limit of mCCR Dolphin? My comments on the scrubber were based on the fact that it is meant for an SCR loop, meaning that a percentage of CO2 is lost before it gets to the scrubber, and that it is designed for a shallower dive than 120m! The figures I have seen for the scrubber life [very cold water, very high vO2] show that it has a lot more life than most of us would use it to, and my own goes with colour changing absorbent showed that after 2-3 hours at 20-35m in 10C water there is still plenty of unused sorb to go. __________________ David. Diving the mahogany rebreather.
(Offline)

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