mCCR and zero viz exit

Meng_Tze · 31st March 2008, 19:17

Quote: (Originally Posted by Gill Envy)

Relying entirely on a setp point controller or entirely on a HUD and manual injection are both high risk scenarios, IMHO.

g

Thanks for the offer. Sounds like we will see a HUD put against a mask in mud soon....

You are right about above statement, but we are talking about an extreme situation here. Once you clear the zero vis silt out, one would go back to relying on the normal operating options to verify PO2.

Meng_Tze · 31st March 2008, 19:22

Quote: (Originally Posted by PCDiver)

Never been in a wreck with a total silt out? The dust in some of the wrecks has a very fine structure. It is very easy to reduce vis to almost nothing with only couple of wrong fin kicks. Been there, done that.

No I have not been in a wreck silt out, but have been in cave (fine clay) siltouts where vis went to 'zero'.... I could still see the glow of my lights and gauges......but could not read them. That is what we are talking about here.

We are not talking about reading screens/gauges, but being able to see the HUD or at least the glow thereof to discern what it is telling you.

I do not believe that, short of physically blocking the HUD, one would not be able to see the glow and thus make out PO2 status in a zero vis situation.

caverkevin · 31st March 2008, 19:32

Spot on buddy!! I agree. I have been in enough zero vis in wrecks, caves, muck inland lakes and black rivers to have a high degree of certainty that I could see my HUD. The only place I doubt I could see my HUD would be in the bottom of Breavort lake in Michigan. Doing salvage type work like that in not a place for a CCR.

Cheers!!

Kevin

Quote: (Originally Posted by Meng_Tze)

No I have not been in a wreck silt out, but have been in cave (fine clay) siltouts where vis went to 'zero'.... I could still see the glow of my lights and gauges......but could not read them. That is what we are talking about here.

We are not talking about reading screens/gauges, but being able to see the HUD or at least the glow thereof to discern what it is telling you.

I do not believe that, short of physically blocking the HUD, one would not be able to see the glow and thus make out PO2 status in a zero vis situation.

Mark Chase · 31st March 2008, 20:35

Quote: (Originally Posted by Gill Envy)

Relying entirely on a setp point controller or entirely on a HUD and manual injection are both high risk scenarios, IMHO.
g

I find that odd because I dive my HUD and manual injection all the time. Often for long dives. I only use my wrist display on decent and ascent. I have never considerd it risky??

ATB

Mark

Janos · 31st March 2008, 20:38

Quote: (Originally Posted by Mark Chase)

I did put it on hear as well

http://www.rebreatherworld.com/trip-...co-protec.html

And my version is HERE

Captain Spanky's Little Yellow Naughty Book is HERE

Janos

Janos · 31st March 2008, 20:44

Doing the same drill as Mark I managed to keep my ppO2 up by running minimum loop volume and injecting O2 before the ADV kicked in. The caves were very much at a constant level, so going hypoxic didn't really concern me. And at 8m it would have been hard to go hyperoxic.

When I first got the HUD, [url=http://www.rebreatherworld.com/rebreather-dive-computers-rebreather-electronics/7088-janos-dives-shearwater-electronics-his-kiss.html#post68860](Report HERE for those interested) I dived it without a mask on, and then I stirred up the silt as much as I could and put my head inside the resulting cloud. I could see the HUD fine. I am reasonably confident I would always be able to see the HUD in any diving conditions.

However, it's always useful to experience events such as Mark's as it shakes the confidence and reading about it on Rebreather World is of course the next best thing.

Janos

AM · 31st March 2008, 21:05

Quote: (Originally Posted by PCDiver)

If you don't hear the solenoid for a while, then it's time to bailout because the solenoid firing is the only way to find out whether the controller is working or not without a visual reference.

There is a way to tell whether or not a solenoid is putting oxygen into a loop at the appropriate intervals without being able to hear OR see any displays or solenoids. That way is by monitoring your O2 metabolism and loop volume. As you metabolise the oxygen from the loop and it is not replaced, you will feel the breathing bags go tighter.

The alternative, if constant depth is in your favour, on a mCCR, is a diluent flush. You should know from the diluent PPO2 x depth+1 what your expected PPO2 will be from a flush. Oxygen becomes critical upon ascent, I would not attempt SCR on an ascent on any rebreather with no monitoring (unless absolutely no choice) and first choice for ascent would be to switch to OC.

Skills can be learned to mitigate not being able to see PPO2 for short periods but they are not recommended for really newbie CCR divers, where the underpinning rules should be "if in doubt, bail out" and "always know your PO2".

Regards
AnneMarie

osiris · 31st March 2008, 21:52

Quote: (Originally Posted by lizardland)

If you can't see your gauges then why does it matter?

Go to your bail out tables (you do have a bail out table, don't you?

) and modify based on what you think happened.

Any idea how you see your tables if you can't see your gauges?

**Gill Envy** · 31st March 2008, 22:26

Quote: (Originally Posted by Mark Chase)

I find that odd because I dive my HUD and manual injection all the time. Often for long dives. I only use my wrist display on decent and ascent. I have never considerd it risky??

ATB

Mark

My risk assessment comfort zone involves cross checking two independent po2 monitoring systems fairly regularly. My HUD has basically become my primary too, but I check my handset about as regularly as I did when I was diving the evolution, I just monitor the HUD nearly all the time in between. As I'm sure you know it's easy to learn to read it in one's peripheral vision while I stay focussed on the dive. Maybe my paranoia will wear off eventually (I hope not!) but for now i'm being pretty anal in my protocals.

mattmexico · 31st March 2008, 22:48

Quote: (Originally Posted by Mark Chase)

I find that odd because I dive my HUD and manual injection all the time. Often for long dives. I only use my wrist display on decent and ascent. I have never considerd it risky??

ATB

Mark

yo

I have to agree. I am using almost entirely my HUD when diving eCCR and doing so foa long time. I mind you that I am using factors such as tank pressure, bag volume, solenoid sound and resulting bag volume increase to complete the picture. Almost entirely means I am looking at my primary handset every 10 minutes or so.

greetings
Matt

31st March 2008, 19:17	#41 (permalink)
Meng_Tze 246 Bubbleless Cove Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jan 2007 Location: FL, USA Posts: 105	Re: mCCR and zero viz exit Quote: (Originally Posted by Gill Envy) Relying entirely on a setp point controller or entirely on a HUD and manual injection are both high risk scenarios, IMHO. g Thanks for the offer. Sounds like we will see a HUD put against a mask in mud soon.... You are right about above statement, but we are talking about an extreme situation here. Once you clear the zero vis silt out, one would go back to relying on the normal operating options to verify PO2. __________________ Homo Bonae Voluntatis
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31st March 2008, 19:22	#42 (permalink)
Meng_Tze 246 Bubbleless Cove Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jan 2007 Location: FL, USA Posts: 105	Re: mCCR and zero viz exit Quote: (Originally Posted by PCDiver) Never been in a wreck with a total silt out? The dust in some of the wrecks has a very fine structure. It is very easy to reduce vis to almost nothing with only couple of wrong fin kicks. Been there, done that. No I have not been in a wreck silt out, but have been in cave (fine clay) siltouts where vis went to 'zero'.... I could still see the glow of my lights and gauges......but could not read them. That is what we are talking about here. We are not talking about reading screens/gauges, but being able to see the HUD or at least the glow thereof to discern what it is telling you. I do not believe that, short of physically blocking the HUD, one would not be able to see the glow and thus make out PO2 status in a zero vis situation. __________________ Homo Bonae Voluntatis Last edited by Meng_Tze : 31st March 2008 at 19:24.
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31st March 2008, 19:32	#43 (permalink)
caverkevin CK #159 Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Apr 2005 Location: Broadway NC Posts: 90	Re: mCCR and zero viz exit Spot on buddy!! I agree. I have been in enough zero vis in wrecks, caves, muck inland lakes and black rivers to have a high degree of certainty that I could see my HUD. The only place I doubt I could see my HUD would be in the bottom of Breavort lake in Michigan. Doing salvage type work like that in not a place for a CCR. Cheers!! Kevin Quote: (Originally Posted by Meng_Tze) No I have not been in a wreck silt out, but have been in cave (fine clay) siltouts where vis went to 'zero'.... I could still see the glow of my lights and gauges......but could not read them. That is what we are talking about here. We are not talking about reading screens/gauges, but being able to see the HUD or at least the glow thereof to discern what it is telling you. I do not believe that, short of physically blocking the HUD, one would not be able to see the glow and thus make out PO2 status in a zero vis situation.
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31st March 2008, 20:35	#44 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,470	Re: mCCR and zero viz exit Quote: (Originally Posted by Gill Envy) Relying entirely on a setp point controller or entirely on a HUD and manual injection are both high risk scenarios, IMHO. g I find that odd because I dive my HUD and manual injection all the time. Often for long dives. I only use my wrist display on decent and ascent. I have never considerd it risky?? ATB Mark __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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31st March 2008, 20:38	#45 (permalink)
Janos "Two Sheds" Current Rebreather/s: Classic Kiss Other Rebreather/s: Classic Kiss Join Date: Feb 2005 Location: East Surrey Posts: 581	Re: mCCR and zero viz exit Quote: (Originally Posted by Mark Chase) I did put it on hear as well http://www.rebreatherworld.com/trip-...co-protec.html And my version is HERE Captain Spanky's Little Yellow Naughty Book is HERE Janos __________________ You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves www.hellfins.com/shed
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31st March 2008, 20:44	#46 (permalink)
Janos "Two Sheds" Current Rebreather/s: Classic Kiss Other Rebreather/s: Classic Kiss Join Date: Feb 2005 Location: East Surrey Posts: 581	Re: mCCR and zero viz exit Doing the same drill as Mark I managed to keep my ppO2 up by running minimum loop volume and injecting O2 before the ADV kicked in. The caves were very much at a constant level, so going hypoxic didn't really concern me. And at 8m it would have been hard to go hyperoxic. When I first got the HUD, [url=http://www.rebreatherworld.com/rebreather-dive-computers-rebreather-electronics/7088-janos-dives-shearwater-electronics-his-kiss.html#post68860](Report HERE for those interested) I dived it without a mask on, and then I stirred up the silt as much as I could and put my head inside the resulting cloud. I could see the HUD fine. I am reasonably confident I would always be able to see the HUD in any diving conditions. However, it's always useful to experience events such as Mark's as it shakes the confidence and reading about it on Rebreather World is of course the next best thing. Janos __________________ You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves www.hellfins.com/shed
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31st March 2008, 21:05	#47 (permalink)
AM Gone diving!! Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Inside my cage Posts: 485	Re: mCCR and zero viz exit Quote: (Originally Posted by PCDiver) If you don't hear the solenoid for a while, then it's time to bailout because the solenoid firing is the only way to find out whether the controller is working or not without a visual reference. There is a way to tell whether or not a solenoid is putting oxygen into a loop at the appropriate intervals without being able to hear OR see any displays or solenoids. That way is by monitoring your O2 metabolism and loop volume. As you metabolise the oxygen from the loop and it is not replaced, you will feel the breathing bags go tighter. The alternative, if constant depth is in your favour, on a mCCR, is a diluent flush. You should know from the diluent PPO2 x depth+1 what your expected PPO2 will be from a flush. Oxygen becomes critical upon ascent, I would not attempt SCR on an ascent on any rebreather with no monitoring (unless absolutely no choice) and first choice for ascent would be to switch to OC. Skills can be learned to mitigate not being able to see PPO2 for short periods but they are not recommended for really newbie CCR divers, where the underpinning rules should be "if in doubt, bail out" and "always know your PO2". Regards AnneMarie __________________ Attitude keeps you alive
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31st March 2008, 21:52	#48 (permalink)
osiris Custom Title Allowed! Current Rebreather/s: Inspiration Classic Sport Kiss Home Build Other Rebreather/s: Home Build Join Date: Feb 2006 Location: Auckland Posts: 230	Re: mCCR and zero viz exit Quote: (Originally Posted by lizardland) If you can't see your gauges then why does it matter? Go to your bail out tables (you do have a bail out table, don't you?) and modify based on what you think happened. Any idea how you see your tables if you can't see your gauges?
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31st March 2008, 22:26	#49 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,253	Re: mCCR and zero viz exit Quote: (Originally Posted by Mark Chase) I find that odd because I dive my HUD and manual injection all the time. Often for long dives. I only use my wrist display on decent and ascent. I have never considerd it risky?? ATB Mark My risk assessment comfort zone involves cross checking two independent po2 monitoring systems fairly regularly. My HUD has basically become my primary too, but I check my handset about as regularly as I did when I was diving the evolution, I just monitor the HUD nearly all the time in between. As I'm sure you know it's easy to learn to read it in one's peripheral vision while I stay focussed on the dive. Maybe my paranoia will wear off eventually (I hope not!) but for now i'm being pretty anal in my protocals. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
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31st March 2008, 22:48	#50 (permalink)
mattmexico Rebreather World Writer Current Rebreather/s: Megalodon Classic Kiss Optima RB80 / Clone Other Rebreather/s: Inspiration Classic Evolution Prism Topaz Sport Kiss RB80 / Clone Join Date: Aug 2005 Location: Mexico, Q.Roo, Playa del Carmen Posts: 752	Re: mCCR and zero viz exit Quote: (Originally Posted by Mark Chase) I find that odd because I dive my HUD and manual injection all the time. Often for long dives. I only use my wrist display on decent and ascent. I have never considerd it risky?? ATB Mark yo I have to agree. I am using almost entirely my HUD when diving eCCR and doing so foa long time. I mind you that I am using factors such as tank pressure, bag volume, solenoid sound and resulting bag volume increase to complete the picture. Almost entirely means I am looking at my primary handset every 10 minutes or so. greetings Matt __________________ N 20' 37.617' W 87' 04.693' www.andreaswmatthes.com
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