SCR/VSC as a CCR Bailout Method

Mdemon · 31st December 2007, 23:18

Quote: (Originally Posted by Dave Sutton)

Man.... do something about that animated avitar and I'll answer you... it's scaring the kids.....

Dave

Pot and Kettle!

Happy New Year All!

**Dave Sutton** · 31st December 2007, 23:25

Quote: (Originally Posted by Dsix36)

It scares me too

No offense, man, but it's *really* distracting enough to be annoying, as in it makes me dizzy (literally). Be a good sport and get something else, *please*? Otherwise I'm going to make you "invisible" just to save my eyes. Maybe it's just me, but... sheesh!

Mark's points above are dead on. Ditto for almost always being solo as well. The skillful diver has *many* available tools to use, not just one. VSC as per Cedric's suggested scheme (which is hardly new, BTW) is a great way if you are more worried about deco than about being trapped. Being able to let your PP02 drop to 0.20 or so is another tool in case you get stuck. Both Mark and I carry "many moles of 02", he with a second 02 bottle and a second manual add valve, and me by using diluents that others might think are a "little" hot for the depth. We're both accomplishing the same thing... giving ourselves an edge. Marks notes are good. I write mine on a slate... it's all good. Things like being able to maintain a setpoint PP02 sans electronics by constant bouyancy on a deco stop is another advanced skill. And Mark's point of PRACTICING it is the best advice available: What seems so easy on the couch, or even in the quarry (or tropics for that matter) might be completely impossible in the cold North Atlantic 100 miles offshore in a 2 knot current while hanging on an anchor line....

Dave

**Dsix36** · 31st December 2007, 23:43

Since Dave asked soooo nicely and we can't have him getting any more dizzy than he already is, I have unanimated my avitar. I hope that this meets with everyone's approval.

**Dsix36** · 31st December 2007, 23:45

Quote: (Originally Posted by diverklondike)

I am that much more anal about it since much of my wreck diving is solo...

My reasoning also. I want to know every possible way to save my butt.

streamway_explorer · 1st January 2008, 01:24

Quote: (Originally Posted by undrh2o)

Found this in the web archive at (http://web.archive.org/web/200112061...wsletter3.html)

It's from the journal of the Australian Amateur Rebreather group. It gives some calculations behind the theory.

(Editors note: Authors procedures and calculations not checked by the AARG, use at your own risk)

Above link is for Journal #3 For the complete set of 5 journals by AARG
Trimix Divers

Always make for a good read.

steveharriss · 1st January 2008, 08:50

Would this be the method by any chance?

Semi closed mode
When running in semi closed mode at greater depth you should vent air through your nose less frequently. The reason for this is that you waste more gas at greater depth and the ppO2 is high enough to make the air fine to reuse a few more times. Instead of using the rule of venting every fourth breath the rule is dependant on your depth. To get the number of breaths before venting you divide your depth by 10 and add 5 (vent freq = 5 + depth / 10). That means that for instance you exhale through your nose every 13th breath at 80 meters (5 + 80/10 = 13).

This was learnt at the feet of the Master by one of his acolytes. A six year old might struggle with the division part though

PS Already published on the WWW

***jradomski*** · 1st January 2008, 09:42

Quote: (Originally Posted by HMC)

jiseson had already kindly "paraphrased" Cedric's exact mathematical formula in this thread, but it has thereafter disappeared (either removed by jiseson himself or the administrator for fear of breach of copyright). Maybe people should just buy the manual... (my personal opinion).

Thats not new.. If thats what he is teaching Its right out of the ANDI TRD procedures that I wrote back in 2003, Its not stated exactly that way in the procedures but thats what is required (its staed in the procedures by example) and he has a copy of (He's an ANDI instructor) .. The numbers were chosen for simplicty of planning and for keeping the po2 close to that of what the oc gas would be.. Feel free to publish it all you want..

Its also in a CCR techniques manual I wrote back in 2003 that was given to all our tech rebreather instructors.. Here is the original text..

The most common method to operate the unit is to expel all the gas from
the loop every 3 to 5 breaths and fill with fresh gas. In actuality as the depth
increases the time the loop can sustain life at a constant depth increases. A
reasonable rule of thumb is to start with a base of 5 breaths to each fresh
inhalation. One additional breath can be added for each atmosphere of pressure.
When increasing duration use common sense, 9msw (30 fsw) is close enough to
two atmospheres, 18msw (60 fsw) is close enough to three atmospheres. It is the
responsibility of the diver to adjust this rule based on the gas the diver is using to
flush the loop. If the diver has good technique, the loop PO2 drop should be less than .1 bar.

I guess I should be flattered.. I wonder what else has been adopted..

steveharriss · 1st January 2008, 10:20

It's as Dave posted earlier.....there's nothing new under the Sun, just rehashes!

Interesting as it's a nice simple method but it would appear Cedric had already plagiarised it from elsewhere. Hardly worth buying the manual for. (also my personal opinion)

Hanssing · 1st January 2008, 10:33

Quote: (Originally Posted by steveharriss)

To get the number of breaths before venting you divide your depth by 10 and add 5 (vent freq = 5 + depth / 10). That means that for instance you exhale through your nose every 13th breath at 80 meters (5 + 80/10 = 13).

OK, I'm now getting confused

Can people tell me if all the SCR-methods are full loop-purges or single breadth exhale? I naturally allways assumed single breath exhale.

Anyway, I then dont see the formula as providing constant FO2. It may provide an FO2 close to the used gas, but according to simple SCR-teory its not a "constant" FO2. In fact the FO2 will be dropping when depth descreases. SO I "kinda" call bullshit.....

I write kinda because noone have told me I'm wrong in my posts, and I have a hard time seeing where I'm wrong - but I have no reallife experience, so I'm not trusting my own logic completely......

Could someone please read my posts again and tell me what I am missing:
http://www.rebreatherworld.com/rebre...tml#post159529

To Dave S:
Based upon my no doubt flawed logic, and a SCR-methos thats NOT full loop purge, ie. oply normal exhale from loop. And uses the gas down to 0.16PPO
A simple 3-year old formula for how many breaths would be:
Figure out how many time you could rebreathe the gas at surface.
Normally the FO2 drops app. 4-5% pr. breath, and we can breathe 16%.
So air could be rebreathed 2 times at surface.
EAN26 could be rebreathed 3 times at surface.
etc.
Now scale that to absolute pressure, at do that SCR-rate:
So trapped at 30msw (4 ATM) with a HOT EAN30:
Max SCR-rate @ 4ATM = 4*4:1 = 16:1
Edit: If you can confirm rEvo (mCCR) addition is working, by shutting down O2 and watching O2-needle drop, and know that the O2-feed coveres say 2/3rds of your metabolic need (0.8l/min O2 out off 1.2l/min used), then you could safely extend the ratio by 3:
Max SCR-rate @ 4ATM = 3*4*4:1 = 48:1

Again based upon simple formulas from active-SCR theory we all know.

I'm must be so wrong it silly

I'm sadly looking out at snow falling, but this debate has really made me go out and do some SCr-training - and I'll use my own simplified formulas.....

Nicolai

PS: Attched the SCR-calculations I made the other day.

richie · 1st January 2008, 10:44

Quote: (Originally Posted by Hanssing)

OK, I'm now getting confused

Can people tell me if all the SCR-methods are full loop-purges or single breadth exhale? I naturally allways assumed single breath exhale.
Nicolai
.

if you are running minimum loop volume you should only have a single breath to exhale

31st December 2007, 23:18	#41 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,931	Re: SCR/VSC as a CCR Bailout Method Quote: (Originally Posted by Dave Sutton) Man.... do something about that animated avitar and I'll answer you... it's scaring the kids..... Dave Pot and Kettle! Happy New Year All! __________________ www.southwestmafia.com "small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!" The WRONG Attitude will get you killed. "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
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31st December 2007, 23:25	#42 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,689	Re: SCR/VSC as a CCR Bailout Method Quote: (Originally Posted by Dsix36) It scares me too No offense, man, but it's really distracting enough to be annoying, as in it makes me dizzy (literally). Be a good sport and get something else, please? Otherwise I'm going to make you "invisible" just to save my eyes. Maybe it's just me, but... sheesh! Mark's points above are dead on. Ditto for almost always being solo as well. The skillful diver has many available tools to use, not just one. VSC as per Cedric's suggested scheme (which is hardly new, BTW) is a great way if you are more worried about deco than about being trapped. Being able to let your PP02 drop to 0.20 or so is another tool in case you get stuck. Both Mark and I carry "many moles of 02", he with a second 02 bottle and a second manual add valve, and me by using diluents that others might think are a "little" hot for the depth. We're both accomplishing the same thing... giving ourselves an edge. Marks notes are good. I write mine on a slate... it's all good. Things like being able to maintain a setpoint PP02 sans electronics by constant bouyancy on a deco stop is another advanced skill. And Mark's point of PRACTICING it is the best advice available: What seems so easy on the couch, or even in the quarry (or tropics for that matter) might be completely impossible in the cold North Atlantic 100 miles offshore in a 2 knot current while hanging on an anchor line.... Dave __________________ "Changes in Lattitudes, Changes in Attitudes, Nothing remains quite the same".... www.nobubblediving.com
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31st December 2007, 23:43	#43 (permalink)
Dsix36 Going Down? Current Rebreather/s: Optima Other Rebreather/s: Join Date: Aug 2007 Location: Deerfield Beach, Florida Posts: 1,054	Re: SCR/VSC as a CCR Bailout Method Since Dave asked soooo nicely and we can't have him getting any more dizzy than he already is, I have unanimated my avitar. I hope that this meets with everyone's approval. __________________ THE MORE THAT I LEARN, THE MORE THAT I STILL NEED TO LEARN!!!!!!
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31st December 2007, 23:45	#44 (permalink)
Dsix36 Going Down? Current Rebreather/s: Optima Other Rebreather/s: Join Date: Aug 2007 Location: Deerfield Beach, Florida Posts: 1,054	Re: SCR/VSC as a CCR Bailout Method Quote: (Originally Posted by diverklondike) I am that much more anal about it since much of my wreck diving is solo... My reasoning also. I want to know every possible way to save my butt. __________________ THE MORE THAT I LEARN, THE MORE THAT I STILL NEED TO LEARN!!!!!!
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1st January 2008, 01:24	#45 (permalink)
streamway_explorer New Member Current Rebreather/s: MK 15.X Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Home Build Join Date: Aug 2007 Location: Australia Posts: 46	Re: CCR Trimix Simplified by Mel Clark question Quote: (Originally Posted by undrh2o) Found this in the web archive at (http://web.archive.org/web/200112061...wsletter3.html) It's from the journal of the Australian Amateur Rebreather group. It gives some calculations behind the theory. (Editors note: Authors procedures and calculations not checked by the AARG, use at your own risk) Above link is for Journal #3 For the complete set of 5 journals by AARG Trimix Divers Always make for a good read. __________________ Michael Collins www.trimixdivers.com
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1st January 2008, 08:50	#46 (permalink)
steveharriss Bubble free by choice Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2006 Location: North Yorkshire Posts: 165	Re: SCR/VSC as a CCR Bailout Method Would this be the method by any chance? Semi closed mode When running in semi closed mode at greater depth you should vent air through your nose less frequently. The reason for this is that you waste more gas at greater depth and the ppO2 is high enough to make the air fine to reuse a few more times. Instead of using the rule of venting every fourth breath the rule is dependant on your depth. To get the number of breaths before venting you divide your depth by 10 and add 5 (vent freq = 5 + depth / 10). That means that for instance you exhale through your nose every 13th breath at 80 meters (5 + 80/10 = 13). This was learnt at the feet of the Master by one of his acolytes. A six year old might struggle with the division part though PS Already published on the WWW Last edited by steveharriss : 1st January 2008 at 08:53.
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1st January 2008, 09:42	#47 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,000	Re: SCR/VSC as a CCR Bailout Method Quote: (Originally Posted by HMC) jiseson had already kindly "paraphrased" Cedric's exact mathematical formula in this thread, but it has thereafter disappeared (either removed by jiseson himself or the administrator for fear of breach of copyright). Maybe people should just buy the manual... (my personal opinion). Thats not new.. If thats what he is teaching Its right out of the ANDI TRD procedures that I wrote back in 2003, Its not stated exactly that way in the procedures but thats what is required (its staed in the procedures by example) and he has a copy of (He's an ANDI instructor) .. The numbers were chosen for simplicty of planning and for keeping the po2 close to that of what the oc gas would be.. Feel free to publish it all you want.. Its also in a CCR techniques manual I wrote back in 2003 that was given to all our tech rebreather instructors.. Here is the original text.. The most common method to operate the unit is to expel all the gas from the loop every 3 to 5 breaths and fill with fresh gas. In actuality as the depth increases the time the loop can sustain life at a constant depth increases. A reasonable rule of thumb is to start with a base of 5 breaths to each fresh inhalation. One additional breath can be added for each atmosphere of pressure. When increasing duration use common sense, 9msw (30 fsw) is close enough to two atmospheres, 18msw (60 fsw) is close enough to three atmospheres. It is the responsibility of the diver to adjust this rule based on the gas the diver is using to flush the loop. If the diver has good technique, the loop PO2 drop should be less than .1 bar. I guess I should be flattered.. I wonder what else has been adopted.. __________________ 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. Last edited by jradomski : 1st January 2008 at 10:16.
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1st January 2008, 10:20	#48 (permalink)
steveharriss Bubble free by choice Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2006 Location: North Yorkshire Posts: 165	Re: SCR/VSC as a CCR Bailout Method It's as Dave posted earlier.....there's nothing new under the Sun, just rehashes! Interesting as it's a nice simple method but it would appear Cedric had already plagiarised it from elsewhere. Hardly worth buying the manual for. (also my personal opinion)
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1st January 2008, 10:44	#50 (permalink)
richie New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Megalodon Join Date: Nov 2005 Location: ireland Posts: 86	Re: SCR/VSC as a CCR Bailout Method Quote: (Originally Posted by Hanssing) OK, I'm now getting confused Can people tell me if all the SCR-methods are full loop-purges or single breadth exhale? I naturally allways assumed single breath exhale. Nicolai . if you are running minimum loop volume you should only have a single breath to exhale __________________ assumption is mother of all **** ups
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