needle valves

Dave Sutton

Uhh...... err..... well.... since ya'll asked:

Perhaps sufficient *practical* experience with mCCR's to make a differentiation between theory and practice? . If you would get just a *little* experience with a basic no-flow mCCR, and then a little experience with an orifice flow mCCR, you would realize how low the workload is and how absolutely pointless this debate is.


"The difference between theory and practice is that in theory they are the same, but in practice they are diffferent"....


Smile.,

Dave

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Gill Envy

Hey Andy, this is a good question. I suspect that the difference between just monitoring and injecting manually and seeing what the difference is, is really at the heart of the matter. I think that one of the main material difference between mCCR's and eCCR's is the way that one is engaged more consciously. If a needle valve were adjusted as intended, as you point out, there would be little difference between it and a fixed orifice, but I can see how making it so that it is adjustible on the fly would temp the diver to become more adept at closely matching their metabolic consumption rate of o2 and gradually playing out the amount of times that o2 needs to be manually injected...more and more closely resembling the habits of an eCCR diver who mostly monitors. There is compelling evidence at this point that simply monitoring leads eventually to a level of complacency that can be fatal if, after many years of functioning failure free, a major mal***tion occurs or the right fatal cocktail of circumstances overwhelmes the diver. The question that matters to me centers around weather this difference (the difference in habit tendency with a needle valve) is enough to truly lead to complacency. If you could identify what the optimal interval for po2 injection and monitoring of it's effect is and you had the self discipline to adjust accordingly, it seems that it would be a great system.

Your point about symplicity is well taken... if looking at an eCCR compared to an mCCR with a needle valve (weather adjusted with the intent of regular interval manual o2 injection or even "too closely" tuned to one's Vo2) mCCR's with needle valves still have a lot fewer mechanical and electronic failure points.

but to refer back to the mCCR vs eCCR thread a while back, I think Dave S. has the right goal: Whatever system, it should "work 100% of the time, every time, with reliability to the 4th decimal place of 9's." At this point all the numbers point to mCCR's for that level of reliability and from what I can tell that is mCCR's without needle valves.

If needle valves become popular enough, eventually we will have something to compare to, but for now "on the fly" needle valves are rare and from purely a statistical point of view we have very little to go on.

That said, the pelagian has a very nice combination of desired attributes other than the needle valve...designed to give you po2 primarily from two monitors with an option for a fully independent 3rd cell for in-lining a po2/deco computer. I like it. Time will tell how this period of exploration "Evolves".

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Gill Envy

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silent running

Or an ECCR which can always function as an MCCR...

Is 100% still 100% if the back-up is always there ready to go and never used?

And how exactly would a needle valve be less reliable than any other version of MCCR? It can easily be unblocked/cleaned and it can be dialed down if IP creep occurs. What are we discussing, habit or mechanics?

At this point, this seems to be a people vs. equipment issue... -Andy

silent running

Dave, you already know that I've spent a few hrs on a CK and many more on a CMF SCR. And FWIW, I've gone hypoxic on a CMF SCR and had to BO, so lack of attention to my PO2/flow is something I understand first hand.

You already know that good friends and dive buddies of mine have used needle valves with plenty of success. So instead of diving with/watching those people and listening to my friends, should I drop everything and start experimenting more myself before I'm allowed to assert the following?

"For some people, in certain situations, needle valves are a viable way of controlling PO2 with minimal physical effort".

Again, what are me and my friends/dive buddies missing?



BTW, where is Mr. Rebreather Lab, Andy? I really have no big stake in this, I'm an ECCR guy...

Dave Sutton

I'll state it again, and this time in more detail:

You are missing *Sufficient experience with straight mCCR's and orifice mCCR's to learn that there's no extra effort involved*.


Long version:

The human factor issue that is here is the exact same issue that I see when training pilots: The human animal, once working "well" with any technical system, is programmed by nature to wish to stick to that method once it's been fully internalized as an "acceptable workload" and an "acceptable method". It's just the way human response is programmed. An individual using a certain system will tend to defend it *if it works*. They will tend to not wish to make a temporary increase in work in order to learn that a new method has validity. This is as predictable as the sun rising tomorrow morning. This is such a well know "barrier to learning" that it's something that we conciously address in the flight training environment. It's no different here. In flight training we actually do a formal assessment of candidates, and we use a formal method of determining their "receptiveness to learning". Some are well adapted to being able to take a "stand back and see" approach to a new method, and others are so stuck in the mud that we simply acknowlage that they are not trainable to a new level. We give our best efforts to the former, and we only offer the basics to the latter. You can be offered all the knowlage in the world, but if this barrier to learning is something that an individual really cannot put aside, they will be stuck at one level for the balance of their involvement with the subject. Don't be that guy.

I have zero doubt that the users of "in water adjustable needle valves" believe completely in their use, as they *work*. And to an outsider it also appears to be "just fine". The issue is that it's not *optimal*, and if the users would simply hold their present belief system in "idle" for a few dives, would try "System B", and would then re-evaluate the relative workload, my bet is that they would see that there is no practical advantage to their old way, and that the new way is easier and results in increased situational awareness.

Back to the first statement: People who want to *compare* methods as opposed to defending an existing method are only in a position to do so when they have sufficient experience with *every* method being compared. Without this experience, gained in an open and engaged manner without a predefined bias for or against a method, all anyone can do is to defend the status quo, and will use normal human rationalization to justify a belief system that may or may not be accurately perceived as being "best".

If you understand and work with these normal human factors, which are perfectly predictable, it'll decrease the learning curve tremendously. Back to the flight training analogy: We have HUGE issues in pilot training trying to get pilots to accept new methods that are different than what they have been using for years, even if the alternative methods are OBVIOUSLY better. This is just part and parcel of working with people. NOBODY likes to have their belief system challenged: To fully accept that improvement is possible, one must also acknowlage that the old way was not perfect. Ego often interferes with this. All of us have that response: We defend what we are doing because we believe it to be right. Human response is predictable, just the way we all are programmed. The first step to working with these issues is understanding that they are true, and then to try to identify when each of us (yes, me too...) are falling into that normal response.


One of our matras in flight training is:

"Resist the temption to make an immediate decision and then to support it with facts"....

Back to this discussion: You have made the decison that a needle valve is somehow "better" than other alternatives, and are now attempting to support it with facts. You *believe strongly* that a needle valve mCCR has less workload than a straight mCCR or an orifice mCCR. Your fairly low level of experience with the three systems does not preclude you from holding that strong belief system. The issue is that you have made decision not based on strong experience, but with "a little" personal experience and observation of others. That's not an adequate level of interaction for you to be in a position to be advocating or minimizing the advantages or to discuss the disadvantages of the the alternatives. Don't take this the wrong way. Be curious... curious enough to suspend a belief system until you have adequate experience to hold that opinion. That's exactly what we do in flight test: We propose hypotheticals, we design tests, and we try *everything* until we have it sorted out. You're close to me: I have rigs here with all three systems available. Feel free to spend a day with me *experimenting*. I'll set up several "problems" of high workload, surface swims, no hands-available drill, etc., and after a full day of *testing your belief system* we can hold further discussions of the methods available. I'd charge a pilot $1500 for a day of my time to do this in an airplane. I'll offer it as a favor if you want to come play.

In industry, the organizational barrier to improvement is called the "Not Invented Here" syndrome. In another era, groups would essentially say "We have sacrificed a virgin every Sunday and the Sun has always come up Monday, and since that has always worked before, we're not gonna take the chance that it might fail". Strong belief systems only have value when the alternatives have been FULLY experimented with. Knowlage of one way has little value, but the holder of that belief system will not generally distinguish the difference. Personally, in my neck of the woods, it's hard to find a good virgin these days... so we're not gonna sacrifice any...

Would anyone like me to write down a longer version of the "Apropriate Level of Automation" lecture that I give at the Test Pilots School? It's a discussion on the balance of Technical and Human factors when selecting "appropriate" levels of automation. It might have some interest to the group. If so, we ought to start a new thread. Might actually be worth an article.



Dave

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aknelson

Would anyone like me to write down a longer version of the "Apropriate Level of Automation" lecture that I give at the Test Pilots School? It's a discussion on the balance of Technical and Human factors when selecting "appropriate" levels of automation. It might have some interest to the group. If so, we ought to start a new thread. Might actually be worth an article.

Dave, It would be worthwhile to see what you have to say about the above.
I see the same symptoms in the industrie and have not figured a way around.
Sometime it is just lazy minds that braces thinking differently.

To the needle valves; I have done experiments with those setups and say it works with reservations. There are too many variables making it not working correctly and reliable. Therefore Automation has its place.

Andreas

Rebreatherlab

I am here from time to time, inbetween manufacturing Rebreather's with NEEDLE VALVES.

I think a valid point is that there are less "needle" MCCR's about than orifice, so track record is on the orifice side.

Personally i have seen much more problems with orifice Rebreather's both SCR's and CCR's than with needle RB's. Maybe needlevalve diving is so dangerous so you never allow yourself to go slack? Sort of, like crossing a highway blindfolded! -Hmm, did I bounce the valve half a turn open or did I not? - -Better check...

It is interesting accepting CCR divers in a Pelagian Class looking to hone their general CCR skills. In the next class we have total rookies without ability to compare between units.

The result is still the same: A diver who is aware of what is happening. A diver who can pick a dying cell from the rest before it packs in. A diver who can hold a set point better than most setpoint controllers (with some extra dives ok!), and knows when its pointless to chase the setpoint.

Many of the above items could be achived with any CCR, but it seems like the combination of needle, depth compensating 1st and the right mind set foster a special awareness.

How about closing the needle thread accepting that personal preference varies?

Coffee break's over. Back to making more needles!

Andy

silent running

Dave, I've not made any firm decisions beyond the one that led me to buy an ECCR, one which as it happens is as close to being 1/2M and 1/2E as you can get. One fact that I've neglected to mention thus far is that I have lots of experience flying my ECCR in pure manual mode, enough experience to say with confidence that I reguard it as being more work than I like when I'm seriously taxed. And I didn't need 1000's of hrs to figure this out.

If it seems that I believe anything strongly, it's because others have voiced opinions that conflict with things I know to be true, true from experience and observation. I "believe" only that the needle valves work well for those who I've dived with and learned from and who themselves have lots of experience with both fixed and adjustable O2 flow, that's all.

I understand the notion that people are resistant to change and the unfamiliar and that people don't know what they don't know. Thanks for the invitations to dive and I'm plenty curious about all the different rigs you have and of course, curious in general. And I'll give you the benefit of the doubt when you tell me not to take it the wrong way that I'm not "in a position to be advocating or minimizing the advantages or to discuss the disadvantages of the the alternatives." But I have plenty of practical experince from which to express an opinion and in this instance I don't really think you should be calling my experience level in to question. Not because I resent it, but because it's beside the point. Either I've made valid points and expressed some things which ring true or I haven't and you should address them in kind. I would appreciate it if we can talk about specifics instead of your perception of my mindset as I'm more likely to learn something that way. -Andy

silent running

Hi Andy, thanks for the response. Do you mind expanding on the knowing when it's pointless to chase the SP issue? And do you believe that an inline computer to monitor real time PO2 is important when diving a needled unit?

Also, I'm interested to know more about your experience in teaching MCCR needle vavles. What's the learning curve like for most people, how long does it take for people to reach the level of awareness necessary to dive one and how does this awareness differ from other types of MCCR diving?

Thanks, -Andy

Dave Sutton

With all respect, and no disrespect meant:

You haven't made any points that I believe ring true, I've addressed the subject *in detail* based on many years of trying all of the modes mentioned, and it's obvious that you have an opinion that is not going to change. Not a worry to me, just another data point for human factors. If you ever want to come to the quarry for a day with an open mind, I'll set forth a series of experiments that will be convincing. Cannot offer more. You have experience with eCCR, and mCCR, and have watched others work with needle valves. I'd have you do a series of events with both a needle valve rig and a fixed orifice rig, and I am *certain*, because we've done this before, that I could get you to loose situational awareness with the needle valve far faster than with an orifice, and that either is far easier to use than straight mCCR.






Best,

Dave

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"Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com