DIR Rebreather - Thoughts - Page 9

jerry.mobbs · February 6th, 2007, 02:26 PM

Quote: (Originally Posted by decoweenie)

I see that it has been a while since you last dived your ECCR...

i suppose you'll be telling me 'you were in baghdad when i was in my dads bag' next

its more a rhetorical question, i'd never have done this back in the old days

i know through my own experience that ccrs hold setpoint very closely, the inspo was rock steady when i had it, it never put a foot wrong

now when everything is working fine which is well over 99% of the time based on personal experience, this is all fine and well

its when things go wrong that having a set point of 1.0 gives you a wider margin of error than say running it at 1.3

this is more in line with the idea of reducing the risk

the aarg did some stuff on this eons ago and i wonder why it never caught on

Quote: (Originally Posted by decoweenie)

I will take a personal example of diving the KISS which could be the worst case scenario if someone doesn't keep SP correctly - when compared to an ECCR...

I dive SP of 1.2 so on the Innis (round to 70m), the fiO2 on bottom is 15%. In the last couple of years diving it, the max deviation in the loop was always in the range of, let's say, 1.1 to 1.3 which means fiO2 of 13.75 to 16.25%.

We are talking about ~1% fiO2 deviation. With a mCCR unit where the diver manually keeping set-point.

What is the typical O2 analyzer error range ? 3% full scale ?

On an ECCR, the SP is actually much closer when not changing depth.

On ascend, it is catching up initially but doesn't take long. Especially with experienced divers who understand the physics and help to stabilize the loop SP.

If you are worried about this "dynamic" fiO2 in the loop, know that PSCR (i.e. RB-80) will also have that in smaller degree since the gas is also being injected with each breath.

yup, agree with you here

any idea where my unit went?

i sold to to a couple in scuba dubai when i was in pakistan?

nskdrs · February 6th, 2007, 03:19 PM

Quote: (Originally Posted by decoweenie)

Remember that it is only my own personal opinion so take it as a grain of salt.

THX, thats your disclaimer for DIR-divers right?

Joke aside, I really enjoy how you've been able to change your web-personality ( most of the times ) since you became an instructor, hats off!

I concur with your statement there, sure it does not enlighten possible details, then again , with your web experience you might be tired to fight for details on boards.

Then again its strange to me how experienced CCR-divers could use that "its-stable...indeed!" for justification.

Never heard this from an RB80-diver...and damn sure not from Reinhard, quite the opposite.
I hear this from other pSCR-divers

Hope to meet you one day and you tell me what made you so anti-GUE/DIR. Believe it or not, I might be fully capable to get your point

Cheers,
Hoffi.

decoweenie · February 6th, 2007, 04:29 PM

Quote: (Originally Posted by jerry.mobbs)

any idea where my unit went?

You better ask Ali to ask ScubaDubai since he lives there. I have no clue...

decoweenie · February 6th, 2007, 04:41 PM

Quote: (Originally Posted by nskdrs)

Never heard this from an RB80-diver...and damn sure not from Reinhard, quite the opposite.I hear this from other pSCR-divers

You lost me a bit here...

If you are saying that PSCR divers claiming that CCR loop SP isn't stable, then I would ask if that observation was derived from personal experience or web-regurgitation ?

AFAIK, Reinhard and Micheal W. were and are not ever CCR divers, as well as most PSCR divers I read from on the Internet. Most of them come from either EKPP or WKPP groups, IIRC.

Quote:

Hope to meet you one day and you tell me what made you so anti-GUE/DIR.

I am ?

Some of my best friends are either gay, racist or DIR...

Mark Chase · February 6th, 2007, 07:38 PM

Quote: (Originally Posted by jerry.mobbs)

Ok, heres a Q to keep the brain juices flowing.

Why not run the setpoint at 1.0?

The big issue is not config or deco, its managing the fluctuating gas mix. That way any issues with the sensors and your in the middle (very roughly) of the range .21 to 1.6.

Take deco out of the equation, a bit of extra deco won't fatally hurt you, but hypoxic, or hyperoxia will certainly ruin your day.

If you apply the principle of trying to reduce the risk, then lowering your setpoint gives you pretty good leeway either side?

Discuss?

First of all, you can run the set point any where you like so 1.0 is as good a number as any. I know several divers who use 1.2. 1.3 is kind of standard but then most of us are not doing big enough dives for it to be an issue.

You can also change set point to any thing you like during the dive or the ascent decent so you could mimic OC or do your air/bottom mix breaks on loop.

However the key issue here is fallibility of the cells.

Early cells were subject to AP's amazing design blunder of putting a screw head directly opposite cell 2. Condensation built up on the head and dripped on to the face of the cell causing cell errors.

Cells these days have a hydrophobic membrane on them to prevent this problem however humidity and water droplets on cell faces is still an issue just not such a big one any more.

The galvanic cells work on a chemical reaction with 02 that creates electricity in millivolts. More 02 more reaction more millivolts.

It is not a programed device that can have programming errors and it has no moving parts it is JUST a chemical reaction.

When a cell become current limited it can no longer obtain a high enough reaction rate to produce over X millivolts. End result it it reads 1.3 when in fact the o2 level is such that it should read 1.8.

"Current limited cells were flagged up as a major issue in 2003 my a diver called Ann Marie. (Ammers) Ammers is a gob sh#te but she is also incredibly knowledgeable about CCR, a very experience diver and a great laugh when you meet her. She made big noise about current limited cells and these days no one on any unit who logs on to any Rebreather site, has any excuse for not knowing about it.

It is not taught in Mod1. You are recommended to change your cells every 12 months 18 at a push but no one mentioned they could be knackered from brand new.

Since the big news got out there have developed several steps to avoid the problems of cell error. Some people do some of them but sadly there are many who don't seem to bother.

So to avoid cell errors hers my 2p

1: Purchase cells from different batches they are marked C6 A7 etc. This is month and year so C6 is March 2006 and A7 is January 2007. Making sure you run cells from different batches avoids batch failure issues.

2: New cells should be soaked in02 overnight to wake them up before the first calibration. It takes a bit to kick start them and first calibrations can be a mile off.

3: Cells can be "Spiked" So on decent you can inject 02 and ensure that the cell reads above set point. I usually spike to 1.8 on decent.

4: Odd cell readings can be confirmed by emptying the loop and flushing with bottom mix. This will give a known PP02. So if i am at 60m on 14/65 and i do this flush (Dill Flush) I should see 1.00 pp02 on my hand sets. If i don't there is something wrong. I can also ad a bit of 02 to the loop and jack the PP02 up to 1.5 or 1.6 at max depth to ensure they can still read above set point.

At the end of the dive we are usually on 100% 02 at 6m and should be seeing between 1.5 and 1.6. It is normal to get less than 1.6 due to the water vapor in the gas mix.

So if you follow these simple precautions you can avoid cell errors. For all three cells from three different batches to fail simultaneously in a way that gives steady readings on all three cells?? Its hard to accept this is a serious possibility. SOME erratic behavior should be noted even if that odd behavior is a rock solid 1.3 set point across the cells. That would make me do a check.

Because the cells are basically batteries the chance of a properly checked cell just suddenly failing is small. Usually they drift off set point and a quick dill flush or spike can confirm the error. SO if its a little dive you may decide to fly home on the last two cells on a big dive you may decide to bailout to OC or go Semi closed Rebreather and switch the 02 supply off.

As a result the question of set point is not that relevant unless its a monster dive. (Mind you Jerome was running 1.4 to 1.5 on his 190m Heleox dive??).
Run 1.2 or 1.3 and if the cells are working you will be fine and if there not you should notice.

A properly managed cell will not catch the diver out.

Its a training issue not an equipment issue.

Nigel (a VISION diver,) Had his hand set freeze on a fixed set point. He noticed and he did something about it. He lived and he told others about it. This is what should happen every time but sadly some people are not following the training or the guidelines suggested.

ATB

Mark Chase

ATB

Rubis · February 6th, 2007, 07:55 PM

I did not see this until now

DIRrebreather - Rebreather DIR scuba diving philosophy for CCR (Closed Circuit) and SCR (Semi Closed Circuit) Rebreather divers

they have dared

***EBT*** · February 6th, 2007, 10:33 PM

Enough already.

CCR isnt DIR and can't be given the current limitations on sensor technology and monitoring in a team. Theres plenty of scope for discussing it on RBW, or even YD, both have active threads on this.

Lets leave the DIR board to the DIR folks, christ even Im feeling sympathy for them. This is as bad for them as it is when I have to read "which thickness/colour of line or type of knot do I use to tie a pencil into my wetnotes"

PS Mark, Galvanic cells DO NOT generate a voltage, its a small but crucial misunderstanding.... you might want to read/comment on RBW.

Mark Chase · February 7th, 2007, 10:21 AM

Quote: (Originally Posted by EBT)

Enough already.

CCR isnt DIR and can't be given the current limitations on sensor technology and monitoring in a team. Theres plenty of scope for discussing it on RBW, or even YD, both have active threads on this.

Lets leave the DIR board to the DIR folks, christ even Im feeling sympathy for them. This is as bad for them as it is when I have to read "which thickness/colour of line or type of knot do I use to tie a pencil into my wetnotes"

PS Mark, Galvanic cells DO NOT generate a voltage, its a small but crucial misunderstanding.... you might want to read/comment on RBW.

So why when i put an avo meter across a cell sitting on my table at home, do I get a 8-10Mv output form the cell? 10mv is electricity isn't it? its coming from the cell? cells are rated in Millivolts Output?

Are we splitting hairs here?

The questions were asked and answered, regardless of the forum i don't see a problem with this. At least is a conversation about diving.

ATB

Mark Chase

Mark Chase · February 7th, 2007, 10:22 AM

Quote: (Originally Posted by Rubis)

I did not see this until now

DIRrebreather - Rebreather DIR scuba diving philosophy for CCR (Closed Circuit) and SCR (Semi Closed Circuit) Rebreather divers

they have dared

And interestingly he is promoting using a set point of 1.0 ???

ATB

Mark Chase

***EBT*** · February 7th, 2007, 11:09 AM

Quote: (Originally Posted by Mark Chase)

So why when i put an avo meter across a cell sitting on my table at home, do I get a 8-10Mv output form the cell? 10mv is electricity isn't it? its coming from the cell? cells are rated in Millivolts Output?

and thats not the true reading sice the cell isnt loaded with the manufacturer recommended terminating resistance. Its a subtle difference, but the devils in the detail.

Quote: (Originally Posted by chasey)

Are we splitting hairs here?

I recommend gaffa tape, it works on gerbils.

Anyway, thread closed its a DIR board and as we've already established this isnt DIR and the fundamentals of diving are there for all to see....

February 6th, 2007, 02:26 PM	#81 (permalink)
jerry.mobbs(Offline) New Member Join Date: May 2006 Location: asia Posts: 294	Quote: (Originally Posted by decoweenie) I see that it has been a while since you last dived your ECCR... i suppose you'll be telling me 'you were in baghdad when i was in my dads bag' next its more a rhetorical question, i'd never have done this back in the old days i know through my own experience that ccrs hold setpoint very closely, the inspo was rock steady when i had it, it never put a foot wrong now when everything is working fine which is well over 99% of the time based on personal experience, this is all fine and well its when things go wrong that having a set point of 1.0 gives you a wider margin of error than say running it at 1.3 this is more in line with the idea of reducing the risk the aarg did some stuff on this eons ago and i wonder why it never caught on Quote: (Originally Posted by decoweenie) I will take a personal example of diving the KISS which could be the worst case scenario if someone doesn't keep SP correctly - when compared to an ECCR... I dive SP of 1.2 so on the Innis (round to 70m), the fiO2 on bottom is 15%. In the last couple of years diving it, the max deviation in the loop was always in the range of, let's say, 1.1 to 1.3 which means fiO2 of 13.75 to 16.25%. We are talking about ~1% fiO2 deviation. With a mCCR unit where the diver manually keeping set-point. What is the typical O2 analyzer error range ? 3% full scale ? On an ECCR, the SP is actually much closer when not changing depth. On ascend, it is catching up initially but doesn't take long. Especially with experienced divers who understand the physics and help to stabilize the loop SP. If you are worried about this "dynamic" fiO2 in the loop, know that PSCR (i.e. RB-80) will also have that in smaller degree since the gas is also being injected with each breath. yup, agree with you here any idea where my unit went? i sold to to a couple in scuba dubai when i was in pakistan? __________________ -------------------- www.crossfit.com The DIR of Fitness

February 6th, 2007, 07:38 PM	#85 (permalink)
Mark Chase(Offline) New Member Join Date: Nov 2005 Location: Kent England Posts: 1,069	Quote: (Originally Posted by jerry.mobbs) Ok, heres a Q to keep the brain juices flowing. Why not run the setpoint at 1.0? The big issue is not config or deco, its managing the fluctuating gas mix. That way any issues with the sensors and your in the middle (very roughly) of the range .21 to 1.6. Take deco out of the equation, a bit of extra deco won't fatally hurt you, but hypoxic, or hyperoxia will certainly ruin your day. If you apply the principle of trying to reduce the risk, then lowering your setpoint gives you pretty good leeway either side? Discuss? First of all, you can run the set point any where you like so 1.0 is as good a number as any. I know several divers who use 1.2. 1.3 is kind of standard but then most of us are not doing big enough dives for it to be an issue. You can also change set point to any thing you like during the dive or the ascent decent so you could mimic OC or do your air/bottom mix breaks on loop. However the key issue here is fallibility of the cells. Early cells were subject to AP's amazing design blunder of putting a screw head directly opposite cell 2. Condensation built up on the head and dripped on to the face of the cell causing cell errors. Cells these days have a hydrophobic membrane on them to prevent this problem however humidity and water droplets on cell faces is still an issue just not such a big one any more. The galvanic cells work on a chemical reaction with 02 that creates electricity in millivolts. More 02 more reaction more millivolts. It is not a programed device that can have programming errors and it has no moving parts it is JUST a chemical reaction. When a cell become current limited it can no longer obtain a high enough reaction rate to produce over X millivolts. End result it it reads 1.3 when in fact the o2 level is such that it should read 1.8. "Current limited cells were flagged up as a major issue in 2003 my a diver called Ann Marie. (Ammers) Ammers is a gob sh#te but she is also incredibly knowledgeable about CCR, a very experience diver and a great laugh when you meet her. She made big noise about current limited cells and these days no one on any unit who logs on to any Rebreather site, has any excuse for not knowing about it. It is not taught in Mod1. You are recommended to change your cells every 12 months 18 at a push but no one mentioned they could be knackered from brand new. Since the big news got out there have developed several steps to avoid the problems of cell error. Some people do some of them but sadly there are many who don't seem to bother. So to avoid cell errors hers my 2p 1: Purchase cells from different batches they are marked C6 A7 etc. This is month and year so C6 is March 2006 and A7 is January 2007. Making sure you run cells from different batches avoids batch failure issues. 2: New cells should be soaked in02 overnight to wake them up before the first calibration. It takes a bit to kick start them and first calibrations can be a mile off. 3: Cells can be "Spiked" So on decent you can inject 02 and ensure that the cell reads above set point. I usually spike to 1.8 on decent. 4: Odd cell readings can be confirmed by emptying the loop and flushing with bottom mix. This will give a known PP02. So if i am at 60m on 14/65 and i do this flush (Dill Flush) I should see 1.00 pp02 on my hand sets. If i don't there is something wrong. I can also ad a bit of 02 to the loop and jack the PP02 up to 1.5 or 1.6 at max depth to ensure they can still read above set point. At the end of the dive we are usually on 100% 02 at 6m and should be seeing between 1.5 and 1.6. It is normal to get less than 1.6 due to the water vapor in the gas mix. So if you follow these simple precautions you can avoid cell errors. For all three cells from three different batches to fail simultaneously in a way that gives steady readings on all three cells?? Its hard to accept this is a serious possibility. SOME erratic behavior should be noted even if that odd behavior is a rock solid 1.3 set point across the cells. That would make me do a check. Because the cells are basically batteries the chance of a properly checked cell just suddenly failing is small. Usually they drift off set point and a quick dill flush or spike can confirm the error. SO if its a little dive you may decide to fly home on the last two cells on a big dive you may decide to bailout to OC or go Semi closed Rebreather and switch the 02 supply off. As a result the question of set point is not that relevant unless its a monster dive. (Mind you Jerome was running 1.4 to 1.5 on his 190m Heleox dive??). Run 1.2 or 1.3 and if the cells are working you will be fine and if there not you should notice. A properly managed cell will not catch the diver out. Its a training issue not an equipment issue. Nigel (a VISION diver,) Had his hand set freeze on a fixed set point. He noticed and he did something about it. He lived and he told others about it. This is what should happen every time but sadly some people are not following the training or the guidelines suggested. ATB Mark Chase ATB __________________ The only DIR Inspiration/Hammer head/KISS/rEvo/JJ diver in the village www.ourturkishvilla.co.uk Last edited by Mark Chase; February 6th, 2007 at 07:41 PM..

February 6th, 2007, 07:55 PM	#86 (permalink)
Rubis(Offline) cave deprived and Kissed Join Date: Nov 2005 Location: Broadway, (lost in Central NC, USA far far way from Caves SIGH !!!) Posts: 322	I did not see this until now DIRrebreather - Rebreather DIR scuba diving philosophy for CCR (Closed Circuit) and SCR (Semi Closed Circuit) Rebreather divers they have dared __________________ Petition against M26

February 6th, 2007, 10:33 PM	#87 (permalink)
*EBT*(Offline) Just another crouton... Join Date: Nov 2005 Location: Brighton Posts: 505	Enough already. CCR isnt DIR and can't be given the current limitations on sensor technology and monitoring in a team. Theres plenty of scope for discussing it on RBW, or even YD, both have active threads on this. Lets leave the DIR board to the DIR folks, christ even Im feeling sympathy for them. This is as bad for them as it is when I have to read "which thickness/colour of line or type of knot do I use to tie a pencil into my wetnotes" PS Mark, Galvanic cells DO NOT generate a voltage, its a small but crucial misunderstanding.... you might want to read/comment on RBW. Last edited by EBT; February 6th, 2007 at 10:42 PM..

February 7th, 2007, 10:21 AM	#88 (permalink)
Mark Chase(Offline) New Member Join Date: Nov 2005 Location: Kent England Posts: 1,069	Quote: (Originally Posted by EBT) Enough already. CCR isnt DIR and can't be given the current limitations on sensor technology and monitoring in a team. Theres plenty of scope for discussing it on RBW, or even YD, both have active threads on this. Lets leave the DIR board to the DIR folks, christ even Im feeling sympathy for them. This is as bad for them as it is when I have to read "which thickness/colour of line or type of knot do I use to tie a pencil into my wetnotes" PS Mark, Galvanic cells DO NOT generate a voltage, its a small but crucial misunderstanding.... you might want to read/comment on RBW. So why when i put an avo meter across a cell sitting on my table at home, do I get a 8-10Mv output form the cell? 10mv is electricity isn't it? its coming from the cell? cells are rated in Millivolts Output? Are we splitting hairs here? The questions were asked and answered, regardless of the forum i don't see a problem with this. At least is a conversation about diving. ATB Mark Chase __________________ The only DIR Inspiration/Hammer head/KISS/rEvo/JJ diver in the village www.ourturkishvilla.co.uk

February 6th, 2007, 03:19 PM	#82 (permalink)
nskdrs(Offline) Towboy Join Date: Nov 2006 Location: Berlin Posts: 467	Quote: (Originally Posted by decoweenie) Remember that it is only my own personal opinion so take it as a grain of salt. THX, thats your disclaimer for DIR-divers right? Joke aside, I really enjoy how you've been able to change your web-personality ( most of the times ) since you became an instructor, hats off! I concur with your statement there, sure it does not enlighten possible details, then again , with your web experience you might be tired to fight for details on boards. Then again its strange to me how experienced CCR-divers could use that "its-stable...indeed!" for justification. Never heard this from an RB80-diver...and damn sure not from Reinhard, quite the opposite. I hear this from other pSCR-divers Hope to meet you one day and you tell me what made you so anti-GUE/DIR. Believe it or not, I might be fully capable to get your point Cheers, Hoffi.

February 6th, 2007, 04:29 PM	#83 (permalink)
decoweenie(Offline) New Member Join Date: Mar 2006 Location: - Posts: 154	Quote: (Originally Posted by jerry.mobbs) any idea where my unit went? You better ask Ali to ask ScubaDubai since he lives there. I have no clue...

February 6th, 2007, 04:41 PM	#84 (permalink)
decoweenie(Offline) New Member Join Date: Mar 2006 Location: - Posts: 154	Quote: (Originally Posted by nskdrs) Never heard this from an RB80-diver...and damn sure not from Reinhard, quite the opposite.I hear this from other pSCR-divers You lost me a bit here... If you are saying that PSCR divers claiming that CCR loop SP isn't stable, then I would ask if that observation was derived from personal experience or web-regurgitation ? AFAIK, Reinhard and Micheal W. were and are not ever CCR divers, as well as most PSCR divers I read from on the Internet. Most of them come from either EKPP or WKPP groups, IIRC. Quote: Hope to meet you one day and you tell me what made you so anti-GUE/DIR. I am ? Some of my best friends are either gay, racist or DIR...

February 7th, 2007, 10:22 AM	#89 (permalink)
Mark Chase(Offline) New Member Join Date: Nov 2005 Location: Kent England Posts: 1,069	Quote: (Originally Posted by Rubis) I did not see this until now DIRrebreather - Rebreather DIR scuba diving philosophy for CCR (Closed Circuit) and SCR (Semi Closed Circuit) Rebreather divers they have dared And interestingly he is promoting using a set point of 1.0 ??? ATB Mark Chase __________________ The only DIR Inspiration/Hammer head/KISS/rEvo/JJ diver in the village www.ourturkishvilla.co.uk

February 7th, 2007, 11:09 AM	#90 (permalink)
*EBT*(Offline) Just another crouton... Join Date: Nov 2005 Location: Brighton Posts: 505	Quote: (Originally Posted by Mark Chase) So why when i put an avo meter across a cell sitting on my table at home, do I get a 8-10Mv output form the cell? 10mv is electricity isn't it? its coming from the cell? cells are rated in Millivolts Output? and thats not the true reading sice the cell isnt loaded with the manufacturer recommended terminating resistance. Its a subtle difference, but the devils in the detail. Quote: (Originally Posted by chasey) Are we splitting hairs here? I recommend gaffa tape, it works on gerbils. Anyway, thread closed its a DIR board and as we've already established this isnt DIR and the fundamentals of diving are there for all to see.... Last edited by EBT; February 7th, 2007 at 11:12 AM..