The Isolation Manifold, lessons not learned and a small defence of the IUCRR

[cerich]

Many of us are critical of the lack of accident analysis that comes out of the IUCRR. I feel we need accident analysis to spot patterns systemically so that as a community and industry we can learn, mitigate and make it safer.
BUT... let's talk about something, that in my almost 3 decades teaching technical diving I have observed as well, the dual isolation manifold. It IMHO has killed and hurt more people than it has saved. It sounds logical, so much so that virtually every agency requires the use of them in standards when teaching in doubles. However, what it solves is exceptionally rare, while people diving with it shut and thinking they ran out of air and doing rocket assents, drownings etc. and also filling mistakes that has also killed and hurt people is not unheard of at all (I have witnessed a couple) and dives where the diver ran out of gas yet recognized the problem and did the isolator open and "squeal of shame" is not uncommon.

So, what does this have to do with the IUCRR?

Ok, we want accident reports for safety, they have moved away from for worry over lawsuits and also a oft cited philosophy that the rules of cave diving are known, people die when they break the rules so nothing is to be learned anyhow (strongly disagree).

So, let's connect the IUCRR and manifolds, they posted this back in 2005 manifolds article 1, and manifold article 2 , they are correct.
In the passing 17 years, no agency had a serious look at it that I am aware (and heck, I tried at one when on BOD), they remain a required standard, they are still so much accepted that you virtually never see a non isolating crossover and accidents continue to happen.

Given that, why would the IUCRR believe that accident analysis will change anything?
This is one of those situations where even if you show the data, even if you convince folks (agencies/instructors/manufs) that they are not safer, there will be an unwillingness to advocate a change because it means they were "wrong" and have to admit it, plus fight an uphill battle over with industry stakeholders and instructors/divers that having been taught are safer, will resist a change or re-thinking of the issue.


Just some food for thought

 

[Celt]

Not much chance of changing the dogma of agencies. With some divers its like religion there brainwashed.

 

[boulderjohn]

I am one who believes the analysis of dive accidents is a great help to the community.

As for manifolds, I have never heard of a closed manifold problem among the people with whom I have dived, but I do have a story that might be telling if I could only figure out what it was telling.

Years ago, when I was finishing my trimix training, I took the final exam. The instructor downloaded the exam in MS Word format from the agency website. IIRC, the exam was about 10 years old. One question had me baffled. I don't remember the exact wording, but it set up a scenario in which a diver is in a dive that seems to be going normally, but when he checks his SPG, he sees that he is going through his gas about twice as fast as expected. I was supposed to suggest a reason.

My instructor explained that the correct answer was that the isolator was closed, so all the gas was coming out of one cylinder. I pointed out that in a normal gear configuration, if the manifold was closed, the diver would not see that I was going through gas too quickly, the diver I would see that he was not going through gas at all. The SPG usually comes off the left post, and the diver usually breathes off the right post. The question would only make sense of the diver had made the highly unusual decision to run the SPG off the right post. My instructor, quite surprised, admitted that I was right and he had never thought of that before. Evidently, neither had any of his students.

So for at least 10 years, people from that agency had been taking that exam. If anyone in that entire agency had noticed this, they either had not notified the agency or the agency had not felt like taking the 5 minutes it would have required to change the MS Word exam and post the new version to the website.

So let's say that in real life a diver with an isolation manifold suddenly has an OOA response during an inhale because of a closed isolator. That means that the diver had not yet checked the SPG at any point in the dive.

 

[Marie13]

DGX recommends use of a Vindicator knob (red, closed; green, open) for the isolator. I’ve had people poo-poo it.

Does the Vindicator knob make sense for experienced divers? | Dive Gear Express®

Does the Vindicator knob make sense for experienced divers? The Vindicator seems a somewhat recreational diver product that appeals to entry level divers. With experience, divers develop a gearing up ...

www.divegearexpress.com

 

[Alaskan Scuba Dude]

My instructor explained that the correct answer was that the isolator was closed, so all the gas was coming out of one cylinder. I pointed out that in a normal gear configuration, if the manifold was closed, the diver would not see that I was going through gas too quickly, the diver I would see that he was not going through gas at all. The SPG usually comes off the left post, and the diver usually breathes off the right post. The question would only make sense of the diver had made the highly unusual decision to run the SPG off the right post. My instructor, quite surprised, admitted that I was right and he had never thought of that before. Evidently, neither had any of his students.

Your instructor is definitely right and to my knowledge was appeasing you. Anyone who is, or has been technical diving should have been trained or should have experienced a shut isolation valve and know to switch to backup. Monitoring turn pressure is crucial at depth.

 

[KenGordon]

You don’t have freeflows due to cold water or poor regulator setup? That is the main real world failure we get.

I agree you should capture accidents for bulk analysis.

 

[KenGordon]

Your instructor is definitely right and to my knowledge was appeasing you. Anyone who is, or has been technical diving should have been trained or should have experienced a shut isolation valve and know to switch to backup. Monitoring turn pressure is crucial at depth.

You should read that post again more carefully.

 

[Raphus]

I am one who believes the analysis of dive accidents is a great help to the community.

As for manifolds, I have never heard of a closed manifold problem among the people with whom I have dived, but I do have a story that might be telling if I could only figure out what it was telling.

Years ago, when I was finishing my trimix training, I took the final exam. The instructor downloaded the exam in MS Word format from the agency website. IIRC, the exam was about 10 years old. One question had me baffled. I don't remember the exact wording, but it set up a scenario in which a diver is in a dive that seems to be going normally, but when he checks his SPG, he sees that he is going through his gas about twice as fast as expected. I was supposed to suggest a reason.

My instructor explained that the correct answer was that the isolator was closed, so all the gas was coming out of one cylinder. I pointed out that in a normal gear configuration, if the manifold was closed, the diver would not see that I was going through gas too quickly, the diver I would see that he was not going through gas at all. The SPG usually comes off the left post, and the diver usually breathes off the right post. The question would only make sense of the diver had made the highly unusual decision to run the SPG off the right post. My instructor, quite surprised, admitted that I was right and he had never thought of that before. Evidently, neither had any of his students.

So for at least 10 years, people from that agency had been taking that exam. If anyone in that entire agency had noticed this, they either had not notified the agency or the agency had not felt like taking the 5 minutes it would have required to change the MS Word exam and post the new version to the website.

So let's say that in real life a diver with an isolation manifold suddenly has an OOA response during an inhale because of a closed isolator. That means that the diver had not yet checked the SPG at any point in the dive.

Absolutely!


If in DIR configuration a closed manifold would be visible fairly easy. 10min into the dive and still a full tank? There is something wrong..


I think manifolds are good and i would not dive without them.
Its well known, that tech diving requires more care and preparation.
And that includes checking the valves before i dive.the manifold always stays open, if the dive is uneventful. So i dont see, how it can happen, that a manifold is closed. Its checked before the dive. Its open during the dive and open after the dive. Its not like you open and close it all the time.


I dont know anyone, who had his manifold closed by accident and if that happens i would be very cautious to dive with this diver, because there might be more fundamentals missing.

 

[Vicko]

That sound of shame you hear on the surface when someone checks if it's open is really to much.
Plus the only time I saw a problem with the valves underwater in a tec diver was when the actual manifold was the one leaking, meaning it actually caused the guy to not have access to one of his tanks.
Here in Eu we don't even have burst disks...

 

[Celt]

Absolutely!


If in DIR configuration a closed manifold would be visible fairly easy. 10min into the dive and still a full tank? There is something wrong..


I think manifolds are good and i would not dive without them.
Its well known, that tech diving requires more care and preparation.
And that includes checking the valves before i dive.the manifold always stays open, if the dive is uneventful. So i dont see, how it can happen, that a manifold is closed. Its checked before the dive. Its open during the dive and open after the dive. Its not like you open and close it all the time.


I dont know anyone, who had his manifold closed by accident and if that happens i would be very cautious to dive with this diver, because there might be more fundamentals missing.

There's nothing wrong with manifolds there needed with multiple tanks, the isolator is useless and creates problems. It introduces more potential leaks and in the time it takes to close the isolator the valve could be closed. I've never used an isolator the minute I saw one I thought why would I add that to my tanks, what will it do for me?