Fatality at Jersey Island

[HIGHwing]

"DSV (DIVE SURFACE VALVE)The Dive Surface Valve (Fig. 1.15) is a neutrally buoyant one-way loop
“shut down” valve with a water purge. The rotating barrel is made of
stainless steel. The exhalation mushroom valve is seated on the right side
of the valve housing." (from the HP2 current manual).

Now show us the photo of the inhalation lower loop hose. You'll see the mushroom valve is contained within the barrel. My theory, i.e Theory Number 2, is that she left the lower loop hoses connected to the counterlungs and mistakenly attached the inhalation counterlung to the exhalation side (right). See also: The picture you've provided. By doing this, she blocked circular airflow completely, and precisely to the right of the right knurled ring in your photo. She would have passed every test, with the exception of the stereo test. She either omitted the stereo test, or performed it improperly. Please look in the manual to see if the proper testing procedure is outlined for us.

What I will be testing first is if the DSV can be screwed down to the wrong lower loop hose. IF that happens to be possible, I have no doubt that is precisely how she did it. And further, I will complete a full assembly and prove the until will pass everything but the stereo test.

Note: Hollis has engraved the airflow direction on the DSV to help with the stereo test, clearly evident in the photo you provided.

 

[gianaameri]

The people follwing this thread want to know how it's possible to make this error, and how to *prevent* this error.

1. It is very easy to confuse one counterlung for another or reverse a DSV which looks the same either side (although in hindsight one can spot the differences).
2. To prevent the error the designer has to design the unit such that it cannot be incorrectly assembled or that if incorrectly assembled it fails safe.

I have assembled my rebreather thousands of times and each time I pick-up the counterlung I have to think which one is left and which one is right. They are both black and I have to consciously think which is which looking at the various port connections.

In my rebreather if I were to reverse the counterlungs, I would not be able to connect the hoses because the designer uses left-hand thread for one counterlung and right-hand thread for the other.

The HP2 of the deceased lacked such features or anything equivalent (as much the Coroner and HSL are telling us).

Simple.

 

[Douglas Ward]

That's the point. It was stated that the mushroom valves were in contact with each other. This isn't possible with the BOV. If the mushrooms valves were in contact she was definitely using a DSV. So it was HUMAN ERROR in a long chain of incorrect assembly steps.

 

[gianaameri]

She either omitted the stereo test, or performed it improperly.

I said so in a prior post.

It is possible she did the stereo test and marked it as PASS in the Checklist when it should have been a fail.

Usually you require a chain of errors to have a fatality and we are perfectly capable of doing that, if design allows.

 

[Douglas Ward]

The lower loops hoses are keyed to attach to the counterlungs Prism2 Manual Part 1 Section 2 Page 5

 

[HIGHwing]

I said so in a prior post.

It is possible she did the stereo test and marked it as PASS in the Checklist when it should have been a fail.

Usually you require a chain of errors to have a fatality and we are perfectly capable of doing that, if design allows.

Just wait a couple hours, and I'll let you know what I find out. She made an assembly error, this doesn't appear debatable. What we need to figure out with the P2 is what's possible, and the consequence of swapping the lower hoses left to right. I'm 99% confident the until will breathe linear versus in a closed circuit, but I'll be a scientist about it and go in with eyes wide open.

The lower loops hoses are keyed to attach to the counterlungs Prism2 Manual Part 1 Section 2 Page 5

Which precisely explains why the counterlungs were reversed. Once the lower hoses were on the wrong side, she couldn't attach the counterlungs any other way. This action on her part put both mushroom valves together establishing linear airflow and stopping the circuit. This single action appears to have taken away the scrubber and accounts for Hypercapnia as cause of death.

 

[gianaameri]

Just wait a couple hours, and I'll let you know what I find out. She made an assembly error, this doesn't appear debatable. What we need to figure out with the P2 is what's possible, and the consequence of swapping the lower hoses left to right. I'm 99% confident the until will breathe linear versus in a closed circuit, but I'll be a scientist about it and go in with eyes wide open.

Hopefully, with your unit it is not possible to assemble it as she did, if the problem has already been corrected by Hollis, at least in the latest version.

Hopefully, you cannot connect the counterlung in reverse and/or the DSV upside down, or if you can, the rebreather will fail safe.

Which precisely explains why the counterlungs were reversed. Once the lower hoses were on the wrong side, she couldn't attach the counterlungs any other way. This action on her part put both mushroom valves together establishing linear airflow and stopping the circuit. This single action appears to have taken away the scrubber and accounts for Hypercapnia diagnosis as cause of death.

Ya finally got it.

We have been saying this a few posts down the line, but you should not be able to do that on your unit because it is a later version than that of the deceased.

 

[HIGHwing]

We'll find out, but I think it is possible.

 

[tstormdiver]

What it is sounding like more & more is the counterlungs were reversed, the lower loop hoses were on the correct counterlungs (both in a a reversed position) & that the DSV was backwards to the loop (would have been correct if the counterlungs & lower loop were on the correct sides). That would cause the mushroom valves to be against each other on the exhalation side (rendering that side inoperable). The misses would have been with the stereo tests & the positive & negative pressure tests, as one or both would not hold, since the DSV is keyed to each hose & would not seal properly.

I have had an older unit (2-1/2 yrs old) & a newer unit (a few months old) & have seen even older units (4+ yrs old) inaction,... There have been no obvious changes that I am aware of.

 

[gianaameri]

...since the DSV is keyed to each hose & would not seal properly.

That is the key.

Maybe her unit would allow her to make the connections and seal.

Design error, affecting a few units, hopefully later corrected.