What SAC-rate are you planning for from bailout to first stop?
- Thread starter Mr Walker
- Start date
iamyourgasman
Member
I still state that it is entirely possible to maintain "unrealistic" SAC eg 45lpm in a CO2 scenario for a prolonged period of time. This means it can carry on well into deco.
I also can't plan for lower working SAC than 17lpm as I have repeatedly measured this on OC.
I looked at the 45lpm gas volumes and decided that I can't carry that much gas especially if I want a deeper dive than 45m.
I plan for 25lpm until the first stop then drop it to 17lpm. As I'm unlikely to "work" on deco it has some in-built reserve.
As I have said before I do everything I can to avoid CO2 issues, utilising the experience of others and the technology available on my RB.
I also can't plan for lower working SAC than 17lpm as I have repeatedly measured this on OC.
I looked at the 45lpm gas volumes and decided that I can't carry that much gas especially if I want a deeper dive than 45m.
I plan for 25lpm until the first stop then drop it to 17lpm. As I'm unlikely to "work" on deco it has some in-built reserve.
As I have said before I do everything I can to avoid CO2 issues, utilising the experience of others and the technology available on my RB.
Mark Chase
ATB=AlwaysTalkingBollocks
And what physical exetrion is related to a stressed situation and how do you maintian it for 2.5 hours deco?
I keep saying it but it dosen't seem to regester. Just sit there in your chair and breath at 45lpm for as long as you can manage.
I reckon youd do amazingly well to last 5mins.
ATB
Mark
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Mark Chase
ATB=AlwaysTalkingBollocks
Exactly
That is the reality of the situation. 30lpm is the absolute max its worth planning for if your diving 50m+ and even then it results in stupidly short bottom times.
ATB
Mark
iamyourgasman
Member
Chris's point is that this decision has to be conscious, informed one. I see too many divers who don't appreciate the possibility of a prolonged high SAC in a bailout situation and dive "unknowingly alpinist" with a false sense of security.
Again, if your strategy is to meticulously mitigate the CO2 risk and only plan for flood etc, that is fine, but do not fool yourself that it will be adequate in the event of a CO2 hit.
Again, if your strategy is to meticulously mitigate the CO2 risk and only plan for flood etc, that is fine, but do not fool yourself that it will be adequate in the event of a CO2 hit.
Chris Brown
Official CAMRA ale tester
Thanks tamas, that's exactly what I was trying to say, but you put it better
Mark - I hear what you are saying but the vast majority of tech dives aren't 2.5 hours of required ascent / deco after getting a co2 hit.
Tamas is saying that these breathing rates are sustainable, someone else on another thread (can't recall exactly) was pointing out a possible error in your calculations or assumptions. It's not me that seems not to get it, perhaps the other way around?
Or perhaps we are all actually in the same ballpark but it's the usual Internet translTion???
We all agree 45lpm or more is not realistic volume calc level for deep long dives, (but I maintain it is ok for vast majority of mod1 /2 non overhead dives)
I wouldn't use 45 for a 100m dive, as you say, it's undoable and I agree
As tamas says, you have to pick your strategy and perhaps mitigate onset of c02 hits in the first place
Sent from my iPhone using Tapatalk
Mark - I hear what you are saying but the vast majority of tech dives aren't 2.5 hours of required ascent / deco after getting a co2 hit.
Tamas is saying that these breathing rates are sustainable, someone else on another thread (can't recall exactly) was pointing out a possible error in your calculations or assumptions. It's not me that seems not to get it, perhaps the other way around?
Or perhaps we are all actually in the same ballpark but it's the usual Internet translTion???
We all agree 45lpm or more is not realistic volume calc level for deep long dives, (but I maintain it is ok for vast majority of mod1 /2 non overhead dives)
I wouldn't use 45 for a 100m dive, as you say, it's undoable and I agree
As tamas says, you have to pick your strategy and perhaps mitigate onset of c02 hits in the first place
Sent from my iPhone using Tapatalk
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Mark Chase
ATB=AlwaysTalkingBollocks
Thanks tamas, that's exactly what I was trying to say, but you put it better
Mark - I hear what you are saying but the vast majority of tech dives aren't 2.5 hours of required ascent / deco after getting a co2 hit.
Tamas is saying that these breathing rates are sustainable, someone else on another thread (can't recall exactly) was pointing out a possible error in your calculations or assumptions. It's not me that seems not to get it, perhaps the other way around?
Or perhaps we are all actually in the same ballpark but it's the usual Internet translTion???
We all agree 45lpm or more is not realistic volume calc level for deep long dives, (but I maintain it is ok for vast majority of mod1 /2 non overhead dives)
I wouldn't use 45 for a 100m dive, as you say, it's undoable and I agree
As tamas says, you have to pick your strategy and perhaps mitigate onset of c02 hits in the first place
Sent from my iPhone using Tapatalk
Massive SACs (and 45 is massive) may be sustainable in a high physical exertion situation but in a little or no physical exertion situation like deco? they wont fly
QED if your hanging on the deco line breathing 45lpm your seriously screwed. Planning a bailout on such numbers is pointless as running out of gas is hardly your biggest problem.
Get your breathing under control or die
It either is or it is not acceptable to plan a dive on 25 or 30 LPM.
I dont see any justification for saying plan a bailout on 45lpm but then saying obviously for a 70, 80, 90, 100m dive it wont work.
If its OK to plan a 100m dive on 25, its sure as hell OK to plan a 45m dive on 25 because its the 100m dive your really going to need the gas on.
ATB
Mark
alexasigno
Member
Just came across this from the commercial sector, they plan for umbilical failure bailout with either OC or CCR at 62.5L/min.
The Norwegian sector of the North Sea recognises this as a significant risk, and stipulates that a diver must have a minimum of 10 minutes of emergency breathing gas, calculated at a breathing rate of 62.5l/min.
The Norwegian sector of the North Sea recognises this as a significant risk, and stipulates that a diver must have a minimum of 10 minutes of emergency breathing gas, calculated at a breathing rate of 62.5l/min.
Mark Chase
ATB=AlwaysTalkingBollocks
Is any one actualy reading whats been writen down.
We are talking about planning bailout over a period of decompresion which for a 60/70/80/90/100m dive I'd offer would be slightly longer than 10 mins
62.5lpm for 10mins? whats that a 100% safety margin over realistic figures. (And I am talking about realistic that can be maintained for 10 mins)
APD quote 40lpm SAC 4c water @ 40m and a .6lpm C02 flow to calculate their scrubber duration at something like 2.5 hours.
Having done severl hundred dives on my CCR I should be dead now as most of them were 3hours plus some substantialy more and there are divers out there geting close on 10 hours out of their scrubber.
What does this tell us?
It tells us that figures people are prepaired to put down as safety limits can be massivly distant from the realiaty
using a 2.5 hour scrubber limit for CCR is about as usefull a line in the sand as gas planning a dive on 45LPM+
EXCEPT FOR ONE BIG DIFERANCE
Running a scrubber fro a max duration of 2.5 hours is just adding a massive safety margin to your dive
Gas planning on 40/50/60 lpm is adding equipment stress and is adding gas safety for an event which is unlikley to hapen but in doing so adding kit stress which is significantly increasing the possabuility of issues during EVERY dive.
I find it totaly and utterly ridicilious to be told plan for 45lpm because you can manage to carry that much gas with a 20min bottom time at 60m????
We are diving CCR and thats not the sort of diving CCR was chosen for.
You lot need to think cairfulley about the impact of your unqualified statements.
1: It could encourage new divers to overlaod them selves with bailout cylinders and expose them selves to unnessary risk
2: It could be seen as expert testomany showing that somone planning a 80/90/100m dive on a 25 SAC bailout was being reckless
Your sugestions for gas planning should have caviets with them for longer decompresion dives where you explain that past novice level CCR diving it is impractical and is possably adding to the danger to plan on such high SACs to the point the risk benifit calculation doesn't add up.
ATB
Mark
alexasigno
Member
Mark I agree with you. My BO planning is 30lpm until my first stop as in previous post. I feel that's a fair balance of risk. I thought it would be interesting to share other philosophies.
Mark Chase
ATB=AlwaysTalkingBollocks
No problem but they need to be qualified so people who dont fully understand can read them in context
If somone new reads this threrad and starts planning on a 60lpm SAC to be "safe" then goes out doing 50m dives with three AL80 tanks full of gas, I dont think we have acheived any improvement in safety.
In fact i feer we may have made things worse
ATB
Mark
Mr Walker
Relax /Frankie
The question in my poll was (is) about sac-rate from bailing out on an incident to first stop. What sac-rate people use for planning their entire ascent including deco is a completley different question and bringing it up in this thread might be confusing for some as you say. But then your'e the one who keeps bringing it up...
Maybe another poll about sac-rate during ascent/deco is in order. But I'd love to see what someone like S Mitchell has to say on the subject.
/nils
Mark Chase
ATB=AlwaysTalkingBollocks
The question in my poll was (is) about sac-rate from bailing out on an incident to first stop. What sac-rate people use for planning their entire ascent including deco is a completley different question and bringing it up in this thread might be confusing for some as you say. But then your'e the one who keeps bringing it up...
Maybe another poll about sac-rate during ascent/deco is in order. But I'd love to see what someone like S Mitchell has to say on the subject.
/nils
Its one and the same question
There is only one reasion why you would suffer sustained increased SAC and that is a C02 hit
Even on a long deep dive you will not be spending much time on deep bailout so you will still be suffering C02 at the gas switch and still be suffering high SACs
The people I know who have survived C02 hits which cause big SACs all maintain they emptied every available tank
Initial panic induced elevated monster SAC shouldent be more than a few mins before you get it together. If it is then perhaps the issue is with the diver rather than the dive planning
Stress related elevated SAC should be acounted for but thats a totaly diferent matter and I would sugest I have covered that in the gas planing calculations I have offered in every post
ATB
Mark
Mr Walker
Relax /Frankie
No, it's not. I wrote the question and it's clearly defined "from bailout to first stop".
There are other reasons to elevated SAC, not finding shot line, getting caught in a current, loss of power on DPV, flooded unit resulting in loss of bouyancy to name a few.
/nils
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Mark Chase
ATB=AlwaysTalkingBollocks
OK I think thats getting a little silly as except for caught in a current those are all events that should be planned for and shouldent result is silly SACs. If they do I be looking at the divers build up to that level of diving rather than gas planning considerations. As for a current? If its so bad its going to significantly affect gas planing, then dont fight it and just go up.
If its in a cave? then you already planned for it right?
But ill back out of the discssion now as I have made my points on the risks of equipment loading as clearley as I can and I cant see how to improve upon what I have writen so far.
ATB
Mark
uwxplorer
rEvo carrier
Found in the discussion following Dan Warkander's presentation in the DAN Technical Diving Conference Proceedings, Jan 2008 (p 217):
"BRUCE PARTRIDGE: Did you come up with any sort of limits for the maximum ventilation under water? Can people ventilate at that rate under water, and did you come up with any maximum consumptions under water? How much oxygen is the most you'd ever need to add to maintain oxygen in the Rebreather?
DAN WARKANDER: The first question is this: How hard can you breathe under water.
We had one of our subjects at 57 meters; he did maintain more than 70 liters a minute throughout the 25 minute period, and he was always in good shape. But 70 liters a minute is probably more than most people can do, but testing and decision making is at 62 and a half. So 70 sounds like a lot, but it can be done even at such a great density."
"BRUCE PARTRIDGE: Did you come up with any sort of limits for the maximum ventilation under water? Can people ventilate at that rate under water, and did you come up with any maximum consumptions under water? How much oxygen is the most you'd ever need to add to maintain oxygen in the Rebreather?
DAN WARKANDER: The first question is this: How hard can you breathe under water.
We had one of our subjects at 57 meters; he did maintain more than 70 liters a minute throughout the 25 minute period, and he was always in good shape. But 70 liters a minute is probably more than most people can do, but testing and decision making is at 62 and a half. So 70 sounds like a lot, but it can be done even at such a great density."
Chris Brown
Official CAMRA ale tester
Thank you. Yet more evidence that these rates ARE ACHIEVABLE
Nitrogenius
oppinionated ;)
I know.. That's what I always say, because I experienced it myself but nobody seem to believe or listen..
