Valve Drill Logistics

[TSandM]

So, what we're really talking about is the procedure for "unable to locate failure".

In dealing with that, I think you have to think about what's likely to fail. Tank o-rings and manifold o-rings are in sites with little movement, that aren't assembled at the beginning of the dive. Failures here are relatively rare. On the other hand, failures of DIN o-rings, first stages, or hoses are relatively common. So, if I'm COMPLETELY at sea on what's failed, going for a post first seems to make sense to me as addressing the odds. If I close the right post and the bubbles don't stop, I isolate because now I'm in more trouble. If I were completely alone at that point, I'd likely turn the right post back on, turn the left post off and see what happened. If the bubbles still don't stop, I've got an unfixable failure at the very least, and I need to get the you-know-what out of Dodge. But if I've got a manifold failure AND BOTH OF MY TEAMMATES HAVE MYSTERIOUSLY DISAPPEARED, I'm having a really bad day.

Discussing what to do when diving solo isn't pertinent to any critique of the GUE approach to failures, because the system is based on having a team. Being alone in the water, for a GUE diver, means you've already had one major failure. Losing a valve at that point means you've got a second one . . .

 

[Rick Inman]

(piggy-backing)...and one of the great things about solid team diving is that your buddy is NOT going to be unaware that you are having an issue. Between your light signal and their awareness, I would guess that your buddy would be assessing where the failure is before you finish shutting down your own first guess - whichever valve - and letting you know if you are on the right track or not.

The idea that "always shut down the isolator first" cannot be an absolute, don't think about it axiom. Obviously if you know that you're gassing off from the failed BC inflator hose, you're going to shut off the right post. If you don't know where it's coming from, you're going to start shutting off something, and find out soon enough from your guess and your buddy. If you're all alone, and you can't quickly start shutting stuff down to find the problem, the isolator might be a good temporary stop gap.. I'm just saying that there is no "always" in the real world, only in drills.

Then, when you turn everything off and find out the bubbles were coming from your tail stage, won't you be surprised.

Nice thread, Easy.

 

[AndrewJD]

I say we run a simulation to determine the best "Policy".

To do that we need a list of failures and their conditional (given a failure) probabilities, some decision rules for each policy and some measures of performance that every one can agree on. Then we can implement it, run 1,000,000,000 trials and see which one wins....

I propose the following failures.

O-rings
Left Tank
Right Tank
Left Manifold
Right Manifold
Left Post Face
Right Post Face
Right LP hose
Left LP hose
Right HP hose
Left HP hose

First Stages
Right 1st Stage HP Seat
Left 1st Stage HP Seat


J

 

[Dirkadiver]

The bottom line is if you shut down the right post first, then the isolator in the same stroke, you're going to have a few seconds to tell if shutting the right post stopped the escaping gas before your hand gets to the isolator & gets it shut down. If it did, you wouldn't bother shutting down the isolator. If it didn't, you would shut down isolator, then move to left post.

Trying to determine where sound is coming from underwater (in this case the bubbles) doesn't seem like a great idea to me.

 

[do it easy]

This has been quite informative. There does seem to be a widespread discrepancy between valve drills (for reaching and manipulating valves) and the procedure for unidentifiable failures (UFOs - unidentifiable fizzing orifice).

Regarding having a teammate or buddy help, this is probably the most efficient way to figure out where the problem is. However, I think there are situations where this might not work smoothly. For example, diving through a restriction or maybe no vis. Or perhaps diving with a new diver in OW, who isn't familiar with manifolded doubles.

I do think that most failures will be obvious, and that they can be fixed by turning off just one valve. However, I want to be prepared with a procedure that would work in the worse case scenario.

 

[do it easy]

I say we run a simulation to determine the best "Policy".

To do that we need a list of failures and their conditional (given a failure) probabilities, some decision rules for each policy and some measures of performance that every one can agree on. Then we can implement it, run 1,000,000,000 trials and see which one wins....

I propose the following failures.

O-rings
Left Tank
Right Tank
Left Manifold
Right Manifold
Left Post Face
Right Post Face
Right LP hose
Left LP hose
Right HP hose
Left HP hose

First Stages
Right 1st Stage HP Seat
Left 1st Stage HP Seat


J

When I service my regs and manifolds, the o-rings that look the worse are the ones that seal the valve stem. These only hold pressure when the valve is open. Incidentally, the only valve that is consistently open and under pressure is the isolator. I'm not saying this is the most likely failure, but those little o-rings sure do work overtime!

 

[texdiveguy]

This has been quite informative. There does seem to be a widespread discrepancy between valve drills (for reaching and manipulating valves) and the procedure for unidentifiable failures (UFOs - unidentifiable fizzing orifice).

........ However, I want to be prepared with a procedure that would work in the worse case scenario.

So are you better prepared now....and what will you do different if anything from your original plan?

 

[do it easy]

So are you better prepared now....and what will you do different if anything from your original plan?

At this point, I don't think that I would change anything. I think the one thing that I learned was that valve drill and valve failure procedure are two different things, although in my mind, they should be the same.

For the real world unidentified failures, I think there is a general consensus to re-open the isolator last. Right post first or isolator first varies. I suppose you could have the best of both worlds, and close both at the same time, but one of my parameters was only manipulate one valve at a time. Besides, how would you signal your buddy?

 

[texdiveguy]

At this point, I don't think that I would change anything. I think the one thing that I learned was that valve drill and valve failure procedure are two different things, although in my mind, they should be the same.

For the real world unidentified failures, I think there is a general consensus to re-open the isolator last. Right post first or isolator first varies. I suppose you could have the best of both worlds, and close both at the same time, but one of my parameters was only manipulate one valve at a time. Besides, how would you signal your buddy?

Good points you make....I shut down my isolator and then move my hand and shut down the R post all in one continuis sweep.

I am just glad these failures are not real common....

 

[grazie42]

To me it seems strange that people want to separate "the drill" from "response to bubbling"...
You can but to me it seems a waste not to "use" the drill to also build the muscle-memory of "response to bubbling"...

I have been taught by three different instructors (during OH-enviroment courses) to close the isolator first. The reasoning being that by saving half of your remaining gas you preserve the 1/3rd you need to exit the OH-enviroment (or your next gas switch). You don´t need any more gas than that because the dive is over as soon as you regain control of the situation, saving more than 1/3rds isn´t worth the risk of ending up with less than 1/3rds...

The way I see it that has nothing to do with "team diving", I think anyone would be hard-pressed to argue that exiting on your own gas-supply isn´t better than not doing so, a response that doesen´t prioritize that is suboptimal...IMO...also, in all other planning we plan for "worst case scenarios"(within reason) ie lost buddy/team...even GUE does this in cave-courses with lost-buddy drills so it´s clearly not outside the realm of possibility even for GUE-divers to be seperated or be unable to help even though close (because of restriction etc), why not assume the same with the valve-drill?

If you know where the bubbles are coming from then adress the known "offender" but if you don´t, go for the isolator...IMO...despite my rather limited diving experience I´ve seen at least three real failiures where the diver couldn´t identify the source of the leak...

ymmv...