OOA after only a few minutes with a full tank at 17m

[tursiops]

Old wives tale. The check might work, depending on the valve, but will never tell you if he valve is open, only that it is not shut.

My experience and testing says you are wrong. Perhaps I've been lucky with all the valves I've seen?

 

[Doc]

My experience and testing says you are wrong. Perhaps I've been lucky with all the valves I've seen?

I'm with you, I'm one of them "old wife story types", like 5k times over.

Watch gauge. Suck thrice. ANY bobbling movement? Valve not fully open. (I said any.)

Needle drops and stays dropped? Valve off.

At least in my so far limited life experience. And the way it was done at NBL, Bikonaur, strokes like them.

I, too, am amazed at how this is accepted as a "no precise answer" mystery.

BEWARE: Remote reading / linked digital Buck Rogers stuff? You're on your own.

The OP's situation is/was easily diagnosed.

 

[Bob DBF]

The needle should wobble if the valve is not fully open.

Watch gauge. Suck thrice. ANY bobbling movement? Valve not fully open. (I said any.)

Yes if there is a wobble the valve is not fully open, however because the SPG does not wobble does not mean the valve is fully open. It only means the valve is open enough so the flow rate is sufficient to meet the air demand with out affecting the HP reading.

Since words are not enough, go try and experiment for yourself. I did and found out what I am relating, as I did not want to just repeat what I remembered.

The OP's situation is/was easily diagnosed.

After the fact, the SPG did not bobble and the valve was not fully open when checked on the surface. At depth when one needs a higher flow rate the issue of a partially opened valve restricting the flow asserted itself. Someone who has been told that the SPG/breath check means the tank valve is open, cannot properly diagnose the problem quickly, and will be treated as an OOA, so no one is in danger unless they panic.


My assertion is that the check lets you know if the valve is closed or nearly closed, it does not tell you the valve is fully open, only a physical check can do that.



Bob

 

[Marie13]

This happens more often that most people would like to admit. Be it from “help” or “forgot” it amounts to the same. A visual check is a good thing.

Products

I love my Vindicator knobs for an extra visual check. Others here poo-poo them. YMMV.

 

[Bob DBF]

I love my Vindicator knobs for an extra visual check. Others here poo-poo them. YMMV.

I'm with you, however I only need one, and use it on my "boat tank", since SoCal dive boats are the only place I take a tank that someone might try to help me with my valve position.



Bob

 

[tursiops]

Yes if there is a wobble the valve is not fully open, however because the SPG does not wobble does not mean the valve is fully open. It only means the valve is open enough so the flow rate is sufficient to meet the air demand with out affecting the HP reading.

Since words are not enough, go try and experiment for yourself. I did and found out what I am relating, as I did not want to just repeat what I remembered.



After the fact, the SPG did not bobble and the valve was not fully open when checked on the surface. At depth when one needs a higher flow rate the issue of a partially opened valve restricting the flow asserted itself. Someone who has been told that the SPG/breath check means the tank valve is open, cannot properly diagnose the problem quickly, and will be treated as an OOA, so no one is in danger unless they panic.


My assertion is that the check lets you know if the valve is closed or nearly closed, it does not tell you the valve is fully open, only a physical check can do that.



Bob

I hate to quibble, especially with you, but it is a bit simplistic to demand the valve be fully open if indeed it is open enough so that the flow rate is sufficient to meet the air demand. This does not necessarily mean that it must be fully open. Three hard sucks on the reg at the surface is not a bad test....and -- as we agree -- will immediately tell you if the valve is closed (needles goes down, stays down) or only open mid-way (needle drops but recovers).

I guess there are five-valve positions: (1) closed; (2) open but not much and the SPG needle drops and recovers slowly; (3) open a bit more and the SPG needle drops but recovers quickly; (4) open sufficiently to allow the diver's air demands to be met (needle does not move even on very hard breaths); and (5) fully open.

The three-hard-breaths test avoids diving with 1-3, and forces the diver to be in situation 4 or 5. Turning the knob back a bit (1/4, 1/2, whatever) after opening it is by definition not situation 5, so hopefully is in situation 4. and not 3 or worse 2. The three-hard-breaths test forces situation 4 or 5.

The caveat to this approach would be that the boundary between situation 3 (not enough flow) and 4 (sufficient flow) shifts with depth, so at 4 or 5 atmospheres there could be some flow restriction that is gas density-dependent.

At this point you should ask, "so what do YOU do, Tursiops?" I open the valve all the way, and then use the three quick breaths tests just before jumping, to make sure no jerk has touched my valves. Redundancy.

 

[BlueTrin]

My experience and testing says you are wrong. Perhaps I've been lucky with all the valves I've seen?

It happened to me.

It was fine during buddy check and SPG needle didn’t move but it became much harder to breathe at around 17m, I could still get air but the airflow was limited.

I told my buddy to check my cylinder after I got to his octo, he checked and it wasn’t fully open. Once he opened it, everything was ok.

I think someone must have touched my kit but I will never know 100% sure.

 

[johndiver999]

Yes if there is a wobble the valve is not fully open, however because the SPG does not wobble does not mean the valve is fully open. It only means the valve is open enough so the flow rate is sufficient to meet the air demand with out affecting the HP reading.

Since words are not enough, go try and experiment for yourself. I did and found out what I am relating, as I did not want to just repeat what I remembered.



After the fact, the SPG did not bobble and the valve was not fully open when checked on the surface. At depth when one needs a higher flow rate the issue of a partially opened valve restricting the flow asserted itself. Someone who has been told that the SPG/breath check means the tank valve is open, cannot properly diagnose the problem quickly, and will be treated as an OOA, so no one is in danger unless they panic.


My assertion is that the check lets you know if the valve is closed or nearly closed, it does not tell you the valve is fully open, only a physical check can do that.



Bob

This is all exactly right

 

[rsingler]

...it is a bit simplistic to demand the valve be fully open if indeed it is open enough so that the flow rate is sufficient to meet the air demand. This does not necessarily mean that it must be fully open.

It must seem like a quibbling, but it's really not. A hard inhale (or three) at the surface with a partially open valve may demonstrate adequate air flow by good performance and NO needle deflection on the SPG.
But depending upon how "cracked" it is, you MAY find that at 4 atmospheres/100 feet, the air is dense enough that the restriction of that cracked valve now becomes a significant restriction to flow.
In other words, a surface test is not definitive. The proof? What happened to the OP.

Now the reg will likely do fine with a 50% open valve or more. But why open the valve anything but all the way (the turn back 1/8 turn issue notwithstanding)?
The OP's issue points out that "opening" it, even with testing at the surface, may not prevent a developing flow restriction with denser air at depth. Only opening the valve all the way, with or without a small turn back, is the only safe position.
So, to put the quibble to rest...

...it is a bit simplistic to demand the valve be fully open if indeed it is open enough so that the flow rate is sufficient to meet the air demand. This does not necessarily mean that it must be fully open.

...This is technically a correct statement. But it is important to dispel the myth that an unwavering SPG needle at the surface is enough of a test. The test is physically opening the valve all the way, and then breathing on it (just in case someone had trouble with the lefty loosey thing).

 

[tursiops]

The test is physically opening the valve all the way, and then breathing on it (just in case someone had trouble with the lefty loosey thing).

Agree completely. See my last paragraph in post #36.