oxygen ccr conversions

cstmwrks · 26th November 2006, 03:22

Quote: (Originally Posted by Lure_Angler)

By the way, I have a little question here and it goes like that:

What will happen to the diver if he dives a pendulum pure O2 rebreather without purging out the nitrogen and air that got in the loop before diving it? Does it mean he can dive slightly deeper than the 20 feet limit? Let's assume this diver here has got ppO2 meter.

Thank you all, God Bless

TC

TC,
Are you a scuba diver?... I know you directed your question to Dave but the question itself makes me wonder. I have NO idea what they put in modern dive text books these days as I have not looked at one in decades. You should not need to ask Dave or anyone else that question to get an answer. It *should* be as close as looking at a few pages of gas laws that almost always had a cool graphic in there that helps one visualize what is going on. And it does not need to be a rebreather book either.
Do a little book study and you should be able to tell all of us the answer to your own question.

Lure_Angler · 26th November 2006, 03:54

Dear all,

Yes, I am a scuba diver, albeit a very novice one. I do not remember my training saying anything about my question.

In fact, I have a possible answer to my own question in my mind but what I always like to do is to check with people with more experience to see just how close my own answer is to the correct one.

In this case, I've done readings on possibly all websites on rebreathers. Either the details are not there or it is in some language I cannot comprehend. Some did mention the need to purge the loop beforehand BUT they didn't mention what consequences to the diver will occur if you don't. All I know is since the gas in the loop is not 100% oxygen, he should be able to go slightly deeper since that would make the ppO2 more favourable. I learnt physics Equation of State (a combination of the 3 fundamental gas laws) but I don't see how I can use that know how to answer my own question.

I know how it feels, I guess. I'm reasonably skilled at lure fishing and whenever some noob comes around the fishing forums asking obvious questions, I get pissed a little too. But I'm trying my best to find all that I can, with as little hassle to others.

As for books, there is none in Singapore that talks about rebreathers. Libraries, bookshops, 2nd hand bookshops, dive shops, I've searched them all. Hell, I even tried to look for pirated copies. Even the pirates don't have it.

TC

cstmwrks · 26th November 2006, 04:01

Quote: (Originally Posted by Lure_Angler)

I know how it feels, I guess. I'm reasonably skilled at lure fishing and whenever some noob comes around the fishing forums asking obvious questions, I get pissed a little too. But I'm trying my best to find all that I can, with as little hassle to others.

TC

TC
Fer what its worth I'm not pissed at all. And to give you the answer is not a big hassle. Still, what dive text books do you have?
Bill

cstmwrks · 26th November 2006, 04:14

Quote: (Originally Posted by Lure_Angler)

In fact, I have a possible answer to my own question in my mind but what I always like to do is to check with people with more experience to see just how close my own answer is to the correct one.

TC

Are you willing to tell us your possible answer? If your line of thinking is correct no doubt some one will let you know. If your close but a little off course I'm pretty sure some one will get you on track without hacking you into hamburger!

Bill

Lure_Angler · 26th November 2006, 04:54

Quote: (Originally Posted by Lure_Angler)

All I know is since the gas in the loop is not 100% oxygen, he should be able to go slightly deeper since that would make the ppO2 more favourable. I learnt physics Equation of State (a combination of the 3 fundamental gas laws) but I don't see how I can use that know how to answer my own question.

I feel, by not purging, the pendulum would be able to emulate a mixed gas CCR system. Thus, the system could be used to dive slightly deeper, say maybe between 10 to 15 meters.

However, because there wouldn't be a diluent tank, there is no way to control ppO2. It would then be very dangerous to bring it to deeper depths like 20 over meters should the ppO2 go haywire. Oxygen toxicity would then result.

If I go along this line of thinking, wouldn't it be safe not to purge instead, since the diluted oxygen in the loop gives a wider safety margin? Assuming we respect the 20 feet limit.

TC

**Dave Sutton** · 26th November 2006, 12:29

Quote: (Originally Posted by Lure_Angler)

Dear Dave,

Let's see if I can beat your age of 21 for a first time, and still come out alive.

By the way, I have a little question here and it goes like that:

What will happen to the diver if he dives a pendulum pure O2 rebreather without purging out the nitrogen and air that got in the loop before diving it? TC

He will die.

Seriously, he *may* die.... especially on a rig with a large counterlung. What you don't want to have happen is to have a respirable volume of inert gas available in the loop. Leaving "some" air in the loop to essentialy make a "nitrox" rebreather out of an 02 one is the way that Hans and Lotte Hass did it back in the 30's when they were writing about the red sea. The issue is hypoxia on ascent.... so the technique is to do a FULL loop purge at perhaps 20 feet on ascent.

Frankly, doing this blind is stupid. doing it with PP02 monitoring is "less than stupid" but is "not mainstream". Watching me carry an 02 rig and a spare air so I can breath in a breath of air, and exhale it into the counterlung every atmosphere or so and then diving with a smile to 150 feet? Insane.. ;-) (I do have dual PP02 meters in the loop)

Don't try this stuff until you have lots of experience...

A couple of other things: On a pure 02 rig you need to really urge your lungs as well as the counterlung. The other thing is to re-purge at about the 30 minute mark, as you will be offgassing nitrogen raidly as you go onto pure 02 and that nitrogen which is expired into the bag can lower the fraqction 02 in the gas so much that it can cause hypoxia on ascent. These are all the reasons that these rigs feel out of favor in the 50's for sport diving use. 0 rigs seem simple, but a little knowlage can be very dangerous. They are not as simple as they seem.

Dave

***Decodiver*** · 26th November 2006, 12:45

I have many hundreds of hours on O2 CCR.

If you get your prebreathing protocols wrong and do not flush enough you are into a world of hurt!

As Dave Sutton says you can easily die on an O2 rig, perhaps even easier than on a standard CCR/SCR.

Be warned because when an O2 rig bites you, it leaves you mauled.

Cheers,

Dave Cooper.

Lure_Angler · 26th November 2006, 13:00

Dear Dave and all,

Don't worry, I won't die that easily. I asked that question firmly believing that purging is of utmost importance.

But it seems, the more you 'curse', the better are my chances of survival...

Thanks a lot anyway.

TC

DepthCharge · 26th November 2006, 16:14

Quote: (Originally Posted by Dave Sutton)

The gas flow is the same for both the old one and the pro, just the scrubber size is different. The system is a simple one, exhale thru the scrubber, into the bag, and inhale outta the bag.
Dave

Dave,
On the C-96 is the scrubber a radial or axial design? Just see some possible problems with a radial design.

cstmwrks · 26th November 2006, 20:01

Quote: (Originally Posted by Lure_Angler)

However, because there wouldn't be a diluent tank, there is no way to control ppO2. It would then be very dangerous to bring it to deeper depths like 20 over meters should the ppO2 go haywire. Oxygen toxicity would then result.

TC

Well I'm going to say that your thinking inside of a box. To say that without a diluent tank there is no way to control the PP02 is not true. You are correct that you do not have a widget, gidget, valve, button, slide or horn to blow. But it does not mean that you do not have a control method.
Just for example, your at 30 feet and the pp02 is now at .6 and you were keeping .8 as your goal for the dive. Were going with sensors so you know whats going on in the bag. Well if your not bottoming out the lung you vent gas out your nose and add 02.. your back at .8.... If you are bottoming out the lung just add 02.
If the PP02 is high and you need to bring it down that is another story.
If your already bottoming out the lung you just go up so the gas volume in the bag expands to keep the breathing volume comfortable. The PP02 will go down as you matabilize the 02.
There are a bunch more points I could make. Each action has a consequence to it and can effect your dive profile. I'm not going to go into them.

Bill

26th November 2006, 03:22	#31 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	Re: oxygen ccr conversions Quote: (Originally Posted by Lure_Angler) By the way, I have a little question here and it goes like that: What will happen to the diver if he dives a pendulum pure O2 rebreather without purging out the nitrogen and air that got in the loop before diving it? Does it mean he can dive slightly deeper than the 20 feet limit? Let's assume this diver here has got ppO2 meter. Thank you all, God Bless TC TC, Are you a scuba diver?... I know you directed your question to Dave but the question itself makes me wonder. I have NO idea what they put in modern dive text books these days as I have not looked at one in decades. You should not need to ask Dave or anyone else that question to get an answer. It should be as close as looking at a few pages of gas laws that almost always had a cool graphic in there that helps one visualize what is going on. And it does not need to be a rebreather book either. Do a little book study and you should be able to tell all of us the answer to your own question.
(Offline)

26th November 2006, 03:54	#32 (permalink)
Lure_Angler New Member Current Rebreather/s: Home Build Not Bought Yet Other Rebreather/s: Home Build Not Bought Yet Join Date: Nov 2006 Location: Singapore Posts: 68	Re: oxygen ccr conversions Dear all, Yes, I am a scuba diver, albeit a very novice one. I do not remember my training saying anything about my question. In fact, I have a possible answer to my own question in my mind but what I always like to do is to check with people with more experience to see just how close my own answer is to the correct one. In this case, I've done readings on possibly all websites on rebreathers. Either the details are not there or it is in some language I cannot comprehend. Some did mention the need to purge the loop beforehand BUT they didn't mention what consequences to the diver will occur if you don't. All I know is since the gas in the loop is not 100% oxygen, he should be able to go slightly deeper since that would make the ppO2 more favourable. I learnt physics Equation of State (a combination of the 3 fundamental gas laws) but I don't see how I can use that know how to answer my own question. I know how it feels, I guess. I'm reasonably skilled at lure fishing and whenever some noob comes around the fishing forums asking obvious questions, I get pissed a little too. But I'm trying my best to find all that I can, with as little hassle to others. As for books, there is none in Singapore that talks about rebreathers. Libraries, bookshops, 2nd hand bookshops, dive shops, I've searched them all. Hell, I even tried to look for pirated copies. Even the pirates don't have it. TC
(Offline)

26th November 2006, 04:01	#33 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	Re: oxygen ccr conversions Quote: (Originally Posted by Lure_Angler) I know how it feels, I guess. I'm reasonably skilled at lure fishing and whenever some noob comes around the fishing forums asking obvious questions, I get pissed a little too. But I'm trying my best to find all that I can, with as little hassle to others. TC TC Fer what its worth I'm not pissed at all. And to give you the answer is not a big hassle. Still, what dive text books do you have? Bill
(Offline)

26th November 2006, 04:14	#34 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	Re: oxygen ccr conversions Quote: (Originally Posted by Lure_Angler) In fact, I have a possible answer to my own question in my mind but what I always like to do is to check with people with more experience to see just how close my own answer is to the correct one. TC Are you willing to tell us your possible answer? If your line of thinking is correct no doubt some one will let you know. If your close but a little off course I'm pretty sure some one will get you on track without hacking you into hamburger! Bill
(Offline)

26th November 2006, 04:54	#35 (permalink)
Lure_Angler New Member Current Rebreather/s: Home Build Not Bought Yet Other Rebreather/s: Home Build Not Bought Yet Join Date: Nov 2006 Location: Singapore Posts: 68	Re: oxygen ccr conversions Quote: (Originally Posted by Lure_Angler) All I know is since the gas in the loop is not 100% oxygen, he should be able to go slightly deeper since that would make the ppO2 more favourable. I learnt physics Equation of State (a combination of the 3 fundamental gas laws) but I don't see how I can use that know how to answer my own question. I feel, by not purging, the pendulum would be able to emulate a mixed gas CCR system. Thus, the system could be used to dive slightly deeper, say maybe between 10 to 15 meters. However, because there wouldn't be a diluent tank, there is no way to control ppO2. It would then be very dangerous to bring it to deeper depths like 20 over meters should the ppO2 go haywire. Oxygen toxicity would then result. If I go along this line of thinking, wouldn't it be safe not to purge instead, since the diluted oxygen in the loop gives a wider safety margin? Assuming we respect the 20 feet limit. TC
(Offline)

26th November 2006, 12:29	#36 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Evolution Megalodon rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,913	Re: oxygen ccr conversions Quote: (Originally Posted by Lure_Angler) Dear Dave, Let's see if I can beat your age of 21 for a first time, and still come out alive. By the way, I have a little question here and it goes like that: What will happen to the diver if he dives a pendulum pure O2 rebreather without purging out the nitrogen and air that got in the loop before diving it? TC He will die. Seriously, he may die.... especially on a rig with a large counterlung. What you don't want to have happen is to have a respirable volume of inert gas available in the loop. Leaving "some" air in the loop to essentialy make a "nitrox" rebreather out of an 02 one is the way that Hans and Lotte Hass did it back in the 30's when they were writing about the red sea. The issue is hypoxia on ascent.... so the technique is to do a FULL loop purge at perhaps 20 feet on ascent. Frankly, doing this blind is stupid. doing it with PP02 monitoring is "less than stupid" but is "not mainstream". Watching me carry an 02 rig and a spare air so I can breath in a breath of air, and exhale it into the counterlung every atmosphere or so and then diving with a smile to 150 feet? Insane.. ;-) (I do have dual PP02 meters in the loop) Don't try this stuff until you have lots of experience... A couple of other things: On a pure 02 rig you need to really urge your lungs as well as the counterlung. The other thing is to re-purge at about the 30 minute mark, as you will be offgassing nitrogen raidly as you go onto pure 02 and that nitrogen which is expired into the bag can lower the fraqction 02 in the gas so much that it can cause hypoxia on ascent. These are all the reasons that these rigs feel out of favor in the 50's for sport diving use. 0 rigs seem simple, but a little knowlage can be very dangerous. They are not as simple as they seem. Dave __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com Last edited by Dave Sutton : 26th November 2006 at 12:34.
(Online)

26th November 2006, 12:45	#37 (permalink)
*Decodiver* Administrator Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jan 2005 Location: Geneva Posts: 2,194	Re: oxygen ccr conversions I have many hundreds of hours on O2 CCR. If you get your prebreathing protocols wrong and do not flush enough you are into a world of hurt! As Dave Sutton says you can easily die on an O2 rig, perhaps even easier than on a standard CCR/SCR. Be warned because when an O2 rig bites you, it leaves you mauled. Cheers, Dave Cooper. __________________ CCR/OC Trimix Instructor Trainer CCR Training to Mixed Gas in Switzerland, France, UK & Germany on Megalodon/COPIS-Megalodon/KISS/Sport KISS/Ouroboros/rEvo/Inspiration/Evolution/Sentinel www.zerogravitydiving.com Rebreather World Terms & Conditions
(Offline)

26th November 2006, 13:00	#38 (permalink)
Lure_Angler New Member Current Rebreather/s: Home Build Not Bought Yet Other Rebreather/s: Home Build Not Bought Yet Join Date: Nov 2006 Location: Singapore Posts: 68	Re: oxygen ccr conversions Dear Dave and all, Don't worry, I won't die that easily. I asked that question firmly believing that purging is of utmost importance. But it seems, the more you 'curse', the better are my chances of survival... Thanks a lot anyway. TC
(Offline)

26th November 2006, 16:14	#39 (permalink)
DepthCharge New Member Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Home Build Join Date: Mar 2005 Location: upstate NY Posts: 234	Re: oxygen ccr conversions Quote: (Originally Posted by Dave Sutton) The gas flow is the same for both the old one and the pro, just the scrubber size is different. The system is a simple one, exhale thru the scrubber, into the bag, and inhale outta the bag. Dave Dave, On the C-96 is the scrubber a radial or axial design? Just see some possible problems with a radial design. __________________ Later, John It's better to beg forgiveness than ask permission
(Offline)

26th November 2006, 20:01	#40 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	Re: oxygen ccr conversions Quote: (Originally Posted by Lure_Angler) However, because there wouldn't be a diluent tank, there is no way to control ppO2. It would then be very dangerous to bring it to deeper depths like 20 over meters should the ppO2 go haywire. Oxygen toxicity would then result. TC Well I'm going to say that your thinking inside of a box. To say that without a diluent tank there is no way to control the PP02 is not true. You are correct that you do not have a widget, gidget, valve, button, slide or horn to blow. But it does not mean that you do not have a control method. Just for example, your at 30 feet and the pp02 is now at .6 and you were keeping .8 as your goal for the dive. Were going with sensors so you know whats going on in the bag. Well if your not bottoming out the lung you vent gas out your nose and add 02.. your back at .8.... If you are bottoming out the lung just add 02. If the PP02 is high and you need to bring it down that is another story. If your already bottoming out the lung you just go up so the gas volume in the bag expands to keep the breathing volume comfortable. The PP02 will go down as you matabilize the 02. There are a bunch more points I could make. Each action has a consequence to it and can effect your dive profile. I'm not going to go into them. Bill
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